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Gas production in cheese making is becoming increasingly prevalent in the dairy industry. This gas is produced by microbes that are naturally found in the cheese, and when they metabolize sugar or other sources of energy, they can produce gas. This gas causes slits and cracks in the cheese, which causes the cheese to be worth less and causes issues during slicing and shredding. There are many microbes that cause unwanted gas in cheese, this research focuses on four know gas producers and five other protective microbes that use the same energy sources or have the ability to inhibit the gas producers in some way. Each protective microbe was challenged with all four of the gas producing microbes. The BUILD Dairy program of the Western Dairy Center granted the funding, so that this research could take place. This funding was used to support graduate students as well as for laboratory and manufacturing expenses. The Information that this study yielded data about how the use of protective adjunct cultures can be used to reduce gas production caused by gas producing microbes has been presented at national dairy and cheese industry conferences.

Cheddar cheese proteolysis were accelerated employing Penicillium candidum PCA1/TT031 protease into cheese curd. In the present study, several of the significant factors such as protease purification factor (PF), protease concentration and ripening time were optimized via the response surface methodology (RSM). The ideal accelerated Cheddar cheese environment consisted of 3.12 PF, 0.01% (v/v) protease concentration and 0.6/3 months ripening time at 10 °C. The RSM models was verified to be the most proper methodology for the maintain of chosen Cheddar cheese. Under this experimental environment, the pH, acid degree value (ADV), moisture, water activity (aw), soluble nitrogen (SN)%, fat and overall acceptability were found to be 5.4, 6.6, 35%, 0.9348, 18.8%, 34% and 13.6, respectively of ideal Cheddar cheese. Furthermore, the predicted and experimental results were in significant agreement, which confirmed the validity and reliability of the suggested method. In spite of the difference between the ideal and commercial Cheddar cheese in the concentration of some of amino acids and free fatty acids, the sensory evaluation did not show any significant difference in aroma profile between them. Supplementary Information The online version contains supplementary material available at 10.1186/s13568-021-01205-9.

Each cheese type has a unique flavor. A variety of compounds of various concentrations and different chemical classes contribute to this flavor. In the present study, the effect of processing techniques (ultrasonication (US), high pressure processing (HPP), microwave (MW)) on the flavors and sensory properties of milk and cheese was investigated. Samples of treated and untreated milk and cheese were analyzed for volatile compounds (including aldehydes, ketones, alcohols, fatty acids, and hydrocarbons). Significant variation was observed, and the results of sensory evaluation showed that cheese prepared from HPP and US-1 (21 J/g) secured higher sensory scores when compared to cheese prepared from US-2 (41 J/g), MW treatment, and the control. Variations in volatile profiles of milk and cheese were also evident according to the treatment process i.e., dodecanoic acid, octanoic acid, heptanoic acid, and nonanoic acid. Valeric acid was present only in US-1- (21 J/g) and US-2- (41 J/g) treated cheese, which is responsible for burnt and metallic flavors in milk and cheese. Butanoic acid, heptanal, heptanone, and butanediol were present in HPP, while ethyl butanoate, decanone, and 2,3-butanedione were present in microwave-treated milk. In a nutshell, the results of volatile compounds and sensory scores of cheeses are analogous, which shows that ultrasonication with high power output has some drawback because of the burnt and metallic flavor.

peer-reviewed The objective of this study was to investigate the effect of adding different levels of a thermoresistant protease produced by a Pseudomonas fluorescens strain to milk on the manufacture and quality of Cheddar cheese. Fresh raw milk was collected, standardized, and pasteurized at 72°C for 15 s, and the enzyme was added to give a protease activity of 0.15 or 0.60 U/L (treatments P1 and P4, respectively), while one sample had no enzyme added (control). Milk was stored at 4°C for 48 h and Cheddar cheese was manufactured after 0 and 48 h of storage. Results indicated that the protease was active in milk during 48 h of storage; however, its effect on milk composition was minimal. The protein that was preferentially hydrolyzed by the protease over storage was β-casein, followed by κ-casein. The mean cheese yield and recovery of fat and protein obtained for all cheeses were not affected by protease activity. The protease showed low activity during cheese manufacture, possibly because of unfavorable conditions, including low pH. One of the factors that might have influenced protease activity was the pH of the curd (approximately 6.55 after acidification and 5.35 at milling), which was lower than that at which the enzyme would have optimum activity (pH 7 to 9). Consequently, the composition, pH, patterns of proteolysis, and hardness of all cheeses produced were similar and in accordance with values expected for that type of cheese, independently of the protease activity level. However, slight increases in proteolysis were observed in P4 cheeses and produced using milk stored for 48 h. Both the P1 and P4 cheeses had higher concentrations of free amino acids (FAA) compared with the control, whereas urea-PAGE electrophoretograms indicated a greater breakdown of caseins in the P4 cheese samples, which may be related to possible increases in numbers of proteolytic bacteria in milk during storage. Therefore, the thermoresistant psychrotrophic bacterial protease(s) tested in this study may affect the manufacture or quality of Cheddar cheese during ripening to a relatively limited extent. However, controlling initial levels of proteolytic bacteria in raw milk remains essential, because proteolysis affects the development of flavor and texture in cheese.

Ripening is a crucial step to guarantee the high commercial value of cheddar cheese, one of the dairy products the European Union exports the most. Although several methods have lately been proposed to assess its ageing process from a chemical point of view, the majority of them is not particularly time-efficient and implies destructive analytical tests, thus, exhibiting limitations for, e.g., industrial applications. Here, a fast approach based on combining Raman and Mid-InfraRed (MIR) spectroscopy with ANOVA-Simultaneous Component Analysis (ASCA) is proposed in a low-level data fusion framework. This approach allowed to evaluate how storage temperature and time (as well as their interaction) influence cheddar ripening in a relatively cheap, rapid and green fashion.

The current study was conducted to elucidate the impact of encapsulation on the stability and viability of probiotic bacteria (Bifidobacterium bifidum) in cheddar cheese and in vitro gastrointestinal conditions. Purposely, probiotics were encapsulated in two hydrogel materials (kepa carrageenan and sodium alginate) by using an internal gelation method. Cheddar cheese was supplemented with unencapsulated/free and encapsulated probiotics. The product was subjected to physicochemical (pH, titrable acidity, moisture, and protein) and microbiological analysis for a period of 35 days of storage. Furthermore, the probiotics (free and encapsulated) were subjected to simulated gastrointestinal conditions. The initial probiotic count in cheese containing encapsulated probiotic was 9.13 log CFU/g and 9.15 log CFU/g which decreased to 8.10 log CFU/g and 7.67 log CFU/g while cheese containing unencapsulated probiotic initially 9.18 log CFU/g decreased to 6.58 log CFU/g over a period of 35 days of storage. The incorporation of unencapsulated and encapsulated probiotic affected the physicochemical, microbiological, and sensory attributes of the cheese. The encapsulated probiotic bacteria exhibited better survival as compared to unencapsulated probiotic. A 2.60 CFU/g log reduction in unencapsulated cells while just 1.03 CFU/g and 1.48 CFU/g log reduction in case of sodium alginate and K‐carrageenan, respectively, was recorded. In short, encapsulation showed protection and stability to probiotic in hostile conditions.

In the study, the microencapsulation method was applied in the production of white cheese from goat milk to prevent the loss of viability of Lactobacillus paracasei and Bifidobacterium longum due to environmental factors during their storage period. For this purpose, the cheese was obtained using three types of microcapsules -symbiotic microcapsules containing probiotic bacteria and probiotic + fructooligosaccharide, probiotic + inulin. In addition, probiotics, fructooligosaccharide and inulin have been added to cheese in free form, and a total of 7 different cheeses have been produced with the control sample. In the microencapsulation, 1% sodium alginate was used as coating material and the extrusion method was applied. The cheese samples have been stored at +4 0C for 180 days. It has been determined that the viability of L. paracasei and B.longum has been preserved with the microencapsulation technique, while the viability of probiotic bacteria is preserved at a higher level in cheese samples obtained with the addition of prebiotics to microencapsules. It has been concluded that probiotic microorganisms are available above the minimum therapeutic effect value in grams of cheese samples containing microcapsules and these cheese could be considered as probiotic., Scientific and Technological Research Council of Turkey (TUBITAK) [TUBITAK TOVAG 108O039], This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK), Grant No: TUBITAK TOVAG 108O039.

Microfiltration (MF) removed 53.60 ‒ 70.29 % of native whey protein from pasteurized skim milk to permeate, and retained micellar casein concentrate (MCC) (89.64 - 93.64 % of casein expressed as percentage of total protein) in the retentate. The objective of this thesis was to formulate cheesemilk of desired composition by using MF and to study how each component affect cheese quality. In this thesis, (1) the influence of temperature, number of diafiltration (DF) steps, composition of DF media as well as type of MF membrane on the composition of MCC was examined; (2) the effect of levels of total casein, β-casein or whey protein in cheesemilk on the qualities of semi-hard cheese (Cheddar or Emmental) made therefrom were evaluated and (3) as casein micelles is more heat stable than whey protein, the heat stability of MCC and its impact on resultant cheesemilk was also analysed. Compared to MF without a DF step, DF with water increased the removal of whey protein and small molecules, such as lactose and soluble salts, from feed milk to permeate and the depletion of solutes present in the serum phase of milk increased with an increasing number of DF steps. The rennet coagulability of cheesemilk in addition to the composition, pH, texture, yield, flowability and colour in resultant cheeses were not affected by the whey protein content of the cheesemilk. However, removing whey protein from milk increased the plasmin activity of the cheesemilk formulated therefrom and also increased the level of primary proteolysis (as measured by urea-PAGE and HPLC) in the resultant Emmental cheeses. Increasing the casein content in cheesemilk led to an increased gel firming rate in milk and an increase in hardness, pH and plasmin activity as well as a decrease in moisture content and primary proteolysis in the resultant Cheddar cheese. Reducing β-casein levels from milk by 4.25 % neither affected the rennet coagulation properties of cheesemilk nor influenced the composition, pH, plasmin activity, primary proteolysis, texture profile, flowability and colour in the resultant Emmental cheese. Depletion of milk whey protein content in milk by either 53.60 % or 70.29 % largely increased milk heat stability as measured by rennet coagulation, plasmin activity and cheese quality. Subjecting MCC with 70.29 % whey protein depletion to 90 °C for 15 s neither impaired the rennet coagulation properties of cheese milk prepared therefrom nor altered the composition, texture profile, meltability and volatile profile of resultant Cheddar cheese. However for whey protein reduced-milk (53.60 %) heated at 120 °C for 15 s, the rennet coagulability and plasmin activity in the resultant cheesemilk were significantly reduced, with the flowability in the resultant Emmental cheese decreased and redness increased. Overall, the results generated from this research will help cheesemakers to formulate cheesemilk of desired composition and milk with superior heat stability by using MF and micellar casein concentrates. This research also generated new knowledge on the interactions between cheesemilk components and processes to which the milk is subjected to and how this influences the quality of semi-hard cheeses produced therefrom.

Cheesemaking is a process susceptible to defects caused by microbes not purposefully added by the manufacturer. While these bacteria are not a health concern, they can cause problems such as producing carbon dioxide inside the cheese. This can cause slits and cracks in cheese making cheese unsuitable for slicing. One such bacteria identified by cheese researchers at Utah State University and Weber State University is Paucilactobacillus wasatchensis. When present in cheese, it can cause gas formation by using galactose to supply its energy. In doing so, it takes this six-carbon sugar and converts it into a five-carbon sugar and at the same time releasing carbon dioxide. The research team proposed a two-year project to develop a model system for studying this unwanted gas formation. This also involved investigation of other bacteria that could be added which use up these sugars and prevent Plb. wasatchensis from producing the unwanted gas. The BUILD Dairy program of the Western Dairy Center provided $85,000 for graduate student support and laboratory expenses for this project as a way to increase student investigations to solve problems faced by the dairy industry. Information on the successful use of protective cultures to metabolize galactose before Lb. wasatchensis could use it to make carbon dioxide has been disseminated through presentations at regional and national microbiology, dairy, and cheese industry conferences.

Citrus reticulata Blanco crude flowers extracts (CFE) at four different concentrations (1, 2, 3 and 4%, v/v) were used as natural milk coagulant instead of rennet to apply for Cheddar cheese making from buffalo milk. The physicochemical properties of Cheddar cheeses were compared with cheese made with 0.002% (v/v) rennet (control cheese). Physicochemical properties of Cheddar cheese showed that cheese made with 1% and 2% of CFE had a crumbly and slightly softer texture/appearance. While cheeses containing 3 and 4% crude flowers extracts had semi-hard texture/appearance of curd similar to rennet added cheese. Protein analysis shows that crude flowers extracts made cheese had significantly higher protein content than control. The Cheddar cheese with 3% and 4% CFE were preferred by panelists instead of 1% and 2% CFE for their taste, texture/appearance and overall acceptability. Conclusively, crude flowers extracts coagulated Cheddar cheese fulfills the compositional requirement with acceptable organoleptic characteristics and at the same time provides nutritional health benefits.

The purpose of our study was to evaluate the effect of the addition of Lactobacillus casei and Lactobacillus plantarum to Cheddar cheese on the antioxidant properties during its ripening time and after simulated gastrointestinal conditions. During the whole ripening time, the scavenging of DPPH and hydroxyl radicals both reached their maximum activity at the 16th week, while reducing power activity was reached at the 20th week. The antioxidant values of probiotics cheese were significantly higher than that of control (p< 0.05). Similar results were found after simulated gastrointestinal conditions. The simulated gastric digestion can significantly reduce the activity of DPPH radicals-scavenging (p< 0.05), but after intestinal condition, the values came back to the same level compared with that before digestion. The electrophoretic patterns indicated that adding probiotic to cheese could promote the hydrolysis of protein to enhance the antioxidant activity, especially with mixed probiotics. The addition of probiotic bacteria to Cheddar cheese had nearly no effect on its composition, texture profile analysis, and sensory analysis.

Egyptian cheeses are considered an important part of the Egyptian diet. This study aimed to examine 60 random samples of different types of commercial cheeses in Egypt, including soft cheeses (Domiati and Tallaga) and hard cheeses (Cheddar and Ras). The samples were subjected to chemical and microbial examination. Biogenic amines (BAs) are nitrogenous compounds found in a variety of foods; their presence is undesirable and related to spoilage, and can result in toxicological effects in humans. Thus, BAs were determined by using a high-performance liquid chromatography (HPLC) analysis. Moreover, the ability of Bacillus polymyxa D05-1 to reduce levels of experimentally added biogenic amines during the manufacturing of Tallaga cheese was investigated. The obtained results revealed variations in the chemical composition between the investigated samples. Furthermore, many cheese samples contained high levels of BAs, including histamine, tyramine and putrescine. Domiati cheese had the highest levels of BAs, followed by Tallaga and Cheddar, whereas Ras cheese had the lowest levels. The existence of yeasts, molds, coliforms and the high levels of BAs in cheese samples indicate the unsanitary conditions in which they were made and stored. Furthermore, addition of B. polymyxa D05-1 during Tallaga cheese manufacturing resulted in a reduction in BA levels.

Spore forming bacteria continue to be a source of concern for dairy processors mostly for their spoilage and less frequently for their pathogenic attributes. This research investigated the bacterial spore forming population in a Cheddar cheese making system from raw milk reception at the plant through the cheese making stages until ripening. Although the raw milk samples met regulatory requirements at the time of processing, at least 100 aerobic spores per ml were present which soon concentrated to 1,000 spores/g along with the milk into the cheese matrix. However, thermoduric bacteria were 1 log higher than aerobic spores in both milk and cheese curds. Bacillus, the most prominent genus, consisted mostly of B. licheniformis species which had a high diversity with only seven of the 23 subtypes present in curds traceable to raw milk. Upon screening the B. licheniformis collection with two new B. paralicheniformis specific markers, four isolates of B. paralicheniformis were obtained. Bacillus was also resident in the plant which could have been introduced by the raw milk. Paenibacillus was another important group isolated from the dairy samples which dominated in the aged cheeses up to 20 months of age in the absence of Bacillus. A wide diversity of Paenibacillus species were obtained including some (P. azoreducens, P. barengoltzii, P. woosongensis, P. pabuli and P. phoenicis) which have not been reported in cheese. The most prominent Paenibacillus was P. macerans which produced acid, gas and off-odours. An easy-to-use groEL gene-based detection qPCR assay for P. macerans with a detection limit of 100 CFU/ml was developed. Given the right conditions, there is a possibility for the low level Paenibacillus spores occurring in raw milk to concentrate into cheese, increase in number, germinate, produce unwanted gas and cause undesirable odour. The newly developed markers can be used to improve raw milk characterization prior to milk processing. Spore levels in raw milk need to be monitored in Canada. We propose that it should be used in communicating milk quality similar to somatic cells and total bacterial count, since their levels have been shown to increase significantly in cheese where they can cause problems. Genome Canada (Genomic Applications Partnership Program (GAPP) Round 7) NSERC/Dairy Farmers of Ontario Industrial Research Chair in Dairy Microbiology held by G. LaPointe 2021-11-30

To evaluate the contributions of 3-methylbutanal, 2-methylbutanal, 2-methylpropanal, and benzaldehyde in cheddar cheese models, the threshold values, optimal concentration ranges, and perceptual actions of these compounds were determined at various concentrations. The thresholds for 3-methylbutanal, 2-methylbutanal, 2-methylpropanal, and benzaldehyde in the cheese matrix were 150.31, 175.39, 150.66, and 500.21 &mu, g/kg, respectively, which were significantly higher than the corresponding values in water. The optimal concentration ranges of these aldehydes were determined as 150&ndash, 300, 175&ndash, 325, 150&ndash, 350, and 500&ndash, 1500 &mu, g/kg, respectively. Based on the results of the threshold method and Feller&rsquo, s model, five binary mixtures were found to have synergistic effects, and only the pair of 2-methylpropanal and benzaldehyde was determined to have a masking effect. In addition, the synergistic olfactory effects between the four ternary mixtures and the quaternary mixture of these aldehydes were also assesSsed using Feller&rsquo, s model. In a &sigma, &tau, plot analysis, synergism was usually observed when these odor pairs were at their threshold levels. In summary, the results suggested that perceptual interactions among these aldehydes exist in a cheese model variably with different concentrations and threshold ratios. This study will be helpful to a further understanding of the nutty aroma and improving the aroma quality of cheddar cheese.

The aim of this research is to substantiate the possibility of using crushed activated carbon (hereinafter referred to as activated carbon) as a food additive in the production of Cheddar cheese in order to expand the range of this type of cheese on the market. The studied samples of Cheddar cheese, produced in accordance with the technological instructions approved in the prescribed manner, in compliance with the state sanitary regulations for dairy enterprises in accordance with GSP 4.4.4.011. According to the research results, all physicochemical, microbiological and toxicological indicators comply with the requirements of DSTU 6003:2008. It is proved that the introduction of activated carbon helps to reduce the amount of moisture without increasing the level of acidity in the finished product. Thus, ensuring the compliance of physico-chemical and microbiological indicators with the requirements of the standard. In the process of laboratory studies, the presence of carbohydrates in the control and experimental samples is revealed, which indicates the incomplete ripening of cheese in the process of cheddarization. It is established that the introduction of activated carbon during the ripening of cheese helps to reduce the amount of carbohydrates by 2.8%. The introduction of activated carbon helps to reduce the moisture content by 0.4%, in comparison with the sample without its use. The influence of activated carbon on the indicators of active and triturated acidity, which affect the safety indicators of cheddar cheese during storage for 30 days, is analyzed. As a result of the study, lower pH values of a sample of cheddar cheese with activated carbon are obtained, which helps to suppress the growth of conditionally pathogenic microflora of cheese and stabilizes microbiological parameters during storage of Cheddar cheese with activated carbon. It is proved that cheddar cheese with activated carbon maintains high quality indicators throughout the entire storage period

To investigate the notion that starter cultures can be a reservoir of bacteriophages (phages) in the dairy environment, strains of three DL-starters (undefined mesophilic mixed-strain starters containing Lactococcus lactis subsp. lactis biovar. diacetylactis and Leuconostoc species) were selected and induced by mitomycin C, and the whole starters were induced spontaneously as well as by mitomycin C. Frequency of induction of 17%, 26% and 12% was estimated among the isolates of the three starters, with majority of the induced phages mostly showing morphological similarity to known P335 phages, and with a fraction of them showing atypical features. Sequences of P335 quasi-species phages were found to be the most frequent entities in almost all metaviromes derived from the induced lysates. However, sequences of Slavirus phages (previously 936 phages) were emerged as the predominant entities following spontaneous induction of one of the starters, suggesting a phage-carrier state. Sequences of other phages such as 949,1706, C2virus (previously c2 phages) and Leuconostoc species could also be observed but with a lower relative frequency. Taken together, the majority of the P335 quasi-species phages could represent the induced viral community of the starters and the remaining phase groups mainly represent the background ambient viral community.

Background Ripening of cheddar cheese is a time taking process, duration of the ripening may be as long as one year. Long ripening time is a big hindrance in the popularity of cheese in developing countries. Further, energy resources in these countries are either insufficient or very expensive. Therefore, those methods of cheese ripening should be discovered which can significantly reduce the ripening time without compromising the quality characteristics of cheddar cheese. In accelerated ripening, cheese is usually ripened at higher temperature than traditional ripening temperatures. Ripening of cheddar cheese at high temperature with the addition of vitamin E and selenium is not previously studied. This investigation aimed to study the antioxidant activity of selenium and vitamin E in accelerated ripening using cheddar cheese as an oxidation substrate. Methods The ripening of cheddar cheese was performed at 18 °C and to prevent lipid oxidation, vitamin E and selenium were used alone and in combination. The treatments were as: cheddar cheese without any addition of vitamin E and selenium (T1), cheddar cheese added with 100 mg/kg vitamin E (T2), 200 mg/kg vitamin E (T3), 800 μg/kg selenium (T4), 1200 μg/kg selenium (T5), vitamin E 100 mg/kg + 800 μg/kg selenium (T6) and vitamin E 200 mg/kg + 1200 μg/kg selenium (T7). Traditional cheddar cheese ripne ripened at 4-6 °C for 9 months was used as positive control. Cheese samples were ripened at 18 °C for a period of 12 weeks and analyzed for chemical and oxidative stability characteristics at 0, 6 and 12 weeks of storage. All these treatments were compared with a cheddar cheese without vitamin E, selenium and ripened at 4 °C or 12 weeks. Vacuum packaged cheddar cheese was ripened 18 °C for a period of 12 weeks and analyzed for chemical and oxidative stability characteristics at 0, 4 and 8 weeks of storage period. Results Addition of Vitamin E and selenium did not have any effect on moisture, fat and protein content of cheddar cheese. After 6 weeks of ripening, total antioxidant capacity of T1, T2, T3, T4, T5, T6, T7 and standard cheese were 29.61%, 44.7%, 53.6%, 42.5%, 41.4%, 64.1%, 85.1% and 25.4%. After 6 weeks of ripening, reducing power of T1, T2, T3, T4, T5, T6, T7 and SC cheese were 14.7%, 18.1%, 26.3%, 19.2%, 25.3%, 33.4%, 40.3% and 11.6%. After 6 weeks of ripening, 1, 1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity of T6 and T7 were 54.2% and 66.9%. While, DPPH free radical scavenging activity of T1 and standard cheese after 6 weeks of ripening were, 19.1 and 18.5%, respectively. Free fatty acids of vitamin E and selenium supplemented, non-supplemented and standard cheese were not significantly influenced from each other in 0, 6 and 12 weeks old cheddar cheese. Peroxide values of T1, T2, T3, T4, T5, T6, T7 and standard cheese after 6 weeks of accelerated ripening were 1.19, 1.05, 0.88, 1.25, 0.29, 0.25, 0.24 and 0.28 (MeqO2/kg). After 6 weeks of ripening, anisidine value of T6 and T7 were 6.55 and 6.14. Conjugated dienes of T1, T2, T3, T4, T5, T6, T7 and standard cheese, after 6 weeks of accelerated ripening were 0.61, 0.55, 0.42, 0.77, 0.65, 0.17, 0.15 and 0.19. After 6 weeks of accelerated ripening, concentrations unsaturated fatty acids in T1, T2, T3, T4, T5, T6, T7 and standard cheese decreased by18.19%, 17.45%, 16.82%, 16.19%, 12.71%, 8.48%, 6.92% and 14.71%. After 12 weeks of accelerated ripening, concentration of unsaturated fatty acids in T1, T2, T3, T4, T5, T6 and T7 and standard cheese decreased by 26.2%, 21.2%, 18.7%, 14.2%, 10.4%, 4.84%, 1.03% and 6.78%. Cheddar cheese samples added with vitamin E, selenium and their combinations produced more organic acids during the ripening period of 12 weeks. After 6 and 12 weeks of ripening, flavor score of T6 and T7 was better than standard ripened cheddar cheese. Conclusions After 6 weeks of accelerated ripening, sensory characteristics of T6 and T7 were similar to cheddar cheese that was ripened at 4 °C for 9 months. Ripening time of cheddar cheese may be reduced to 6 weeks by elevated temperature (18 °C) using vitamin E and selenium as antioxidants at T6 and T7 levels.

This study was carried out to investigate the microbiological quality of cheddar cheese collected from markets and restaurants. A total of one hundred and fifty cheddar cheese samples were collected randomly in accordance with standard protocols from different markets and restaurants in Amman- Jordan. Pathogenic bacteria which include Salmonella, coliform bacteria, Staphylococcus aureus, and Listeria monocytogenes were considered as indicators of microbiological quality. All tests were performed according to official documented procedures. Listeria monocytogenes was found in 4% of market pre-sliced cheese and 8% pre-sliced restaurant samples. Packaged cheese samples that were sliced on request were free from Listeria monocytogenes. About 12% of pre-sliced restaurant cheese samples and about 8% of pre-sliced market samples were contaminated with S. aureus compared with only 4% of sliced on request cheese samples. Salmonella was not detected in packaged cheddar cheese that was sliced on request. However, about 10% of sliced cheddar cheese market samples and 8% of sliced cheddar cheese samples collected from restaurants were contaminated by Salmonella. About 10% of pre sliced market samples were polluted by coliform compared with 2% sliced on request cheddar cheese. The highest percentage of contaminated cheddar cheese by coliform was detected in restaurant samples (14%). The Jordanian food standards states that cheddar cheese samples must be free from pathogenic bacteria indicated above, therefore, a percentage of samples investigated herein are out of specifications. It is evident from the results presented above that the prevalence of different pathogenic organisms in the cheese samples studied was limited but mostly due to unhygienic handling of the product prior to presentation to the end customer.

The purpose of this study was to determine physicochemical and sensory properties, aroma-active compounds and number of lactic acid bacteria in goat cheeses. High variation was observed among the cheeses in terms of fat %(w/w) and salt %(w/w) contents and titratable acidities %(w/w). Average counts of lactococci lactobacilli and enterococci were 6.90, 6.43 and 5.26 log cfu (colony-forming unit)/g, respectively. The following compounds had high aroma intensity in the cheeses: acetic acid, butanoic acid, hexanoic acid, p-cresol and phenyl acetic acid. Cooked, whey, creamy, animal-like, waxy, salty and sour were the characteristic sensory descriptors. © 2017 Society of Dairy Technology

Cheddar cheese was made using control culture (Lactococcus lactis subsp. lactis), or with control culture plus a galactose-metabolising (Gal+) or galactose-non-metabolising (Gal−) Streptococcus thermophilus adjunct; for each culture type, the pH at whey drainage was either low (pH 6.15) or high (pH 6.45). S. thermophilus affected the levels of residual lactose and galactose, and the volatile compound profile and sensory properties of the mature cheese (270 d) to an extent dependent on the drain pH and phenotype (Gal+ or Gal−). For all culture systems, reducing drain pH resulted in lower levels of moisture and lactic acid, a higher concentration of free amino acids, and higher firmness. The results indicate that S. thermophilus may be used to diversify the sensory properties of Cheddar cheese, for example from a fruity buttery odour and creamy flavour to a more acid taste, rancid odour, and a sweaty cheese flavour at high drain pH.

The current study was conducted to elucidate the impact of encapsulation on the stability and viability of probiotic bacteria (Bifidobacterium bifidum) in cheddar cheese and in vitro gastrointestinal conditions. Purposely, probiotics were encapsulated in two hydrogel materials (kepa carrageenan and sodium alginate) by using an internal gelation method. Cheddar cheese was supplemented with unencapsulated/free and encapsulated probiotics. The product was subjected to physicochemical (pH, titrable acidity, moisture, and protein) and microbiological analysis for a period of 35 days of storage. Furthermore, the probiotics (free and encapsulated) were subjected to simulated gastrointestinal conditions. The initial probiotic count in cheese containing encapsulated probiotic was 9.13 log CFU/g and 9.15 log CFU/g which decreased to 8.10 log CFU/g and 7.67 log CFU/g while cheese containing unencapsulated probiotic initially 9.18 log CFU/g decreased to 6.58 log CFU/g over a period of 35 days of storage. The incorporation of unencapsulated and encapsulated probiotic affected the physicochemical, microbiological, and sensory attributes of the cheese. The encapsulated probiotic bacteria exhibited better survival as compared to unencapsulated probiotic. A 2.60 CFU/g log reduction in unencapsulated cells while just 1.03 CFU/g and 1.48 CFU/g log reduction in case of sodium alginate and K‐carrageenan, respectively, was recorded. In short, encapsulation showed protection and stability to probiotic in hostile conditions., Microencapsulation technologies have wide application for the development of various functional foods, such as yoghurt, cheese, cultured cream, and frozen dairy desserts, and for biomass production encapsulation can be used for the target delivery of any sensitive ingredients. Encapsulation provides protection against pH changes, mechanical stress, temperature, enzymatic activity, time, and osmotic force.

Colored Cheddar cheeses are prepared by adding an aqueous annatto extract (norbixin) to cheese milk; however, a considerable proportion (∼20%) of such colorant is transferred to whey, which can limit the end use applications of whey products. Different geographical regions have adopted various strategies for handling whey derived from colored cheeses production. For example, in the United States, whey products are treated with oxidizing agents such as hydrogen peroxide and benzoyl peroxide to obtain white and colorless spray-dried products; however, chemical bleaching of whey is prohibited in Europe and China. Fundamental studies have focused on understanding the interactions between colorants molecules and various components of cheese. In addition, the selective delivery of colorants to the cheese curd through approaches such as encapsulated norbixin and microcapsules of bixin or use of alternative colorants, including fat-soluble/emulsified versions of annatto or beta-carotene, has been studied. This review provides a critical analysis of pertinent scientific and patent literature pertaining to colorant delivery in cheese and various types of colorant products on the market for cheese manufacture, and also considers interactions between colorant molecules and cheese components; various strategies for elimination of color transfer to whey during cheese manufacture are also discussed.

Cheddar cheese predicted to develop into different quality classes has been evaluated by time domain Nuclear Magnetic Resonance, Thermogravimetric analysis and quantitative sensory analysis. The water and fat proton signals in the transverse relaxation decay curves have been deconvoluted. Proton transverse relaxation values for both the water and fat fractions decrease and the relative %age of the proton peak area, predominantly from the fat increases over a 450-day ripening period. The thermodynamic free water percentage increases during maturation. Water and fat attributes can distinguish between Cheddar cheese batches after 56 days. Cheese batches which have lower transverse relaxation values for the water and fat proton fractions and a higher relative %age of the proton peak area predominantly from fat at 56 days, mature after 270 days to be more yellow, rubbery and smooth, have a less sour and lingering aftertaste and are also harder to form into a cheese ball.

The Irish dairy industry has expanded significantly over the last five years since the abolition of the milk quotas in 2015. The Food Harvest Programme predicted that the milk production would increase by 50% by 2020. The expansion opportunity for Irish dairying has the potential to contribute greatly to the national economy; however, the consistent production of high quality dairy products in accordance with specific international quality parameters is essential to hold market share. The aim of this thesis is to investigate how cold storage conditions at farms can influence the microbiological quality and processability of raw milk, as well as how the quality of raw milk can impact the quality of dairy products. The experimental chapters are divided into two parts; in the first part the studies focused on evaluating the relationship between raw milk cooling conditions on-farm and quality, while in the second part the relationship between raw milk quality, processability and effects on the quality of dairy products were investigated. The thesis was divided into six studies, the specific objectives of each were: (i) to determine the effect of storage temperature and time on the microbiological quality and composition of milk; (ii) to determine the effect of different pre-cooling rates on the microbiological load and composition of milk, as well as on energy requirements; (iii) to monitor the microbiological load of milk throughout the manufacturing process of low-heat skim milk powder, from farm bulk tanks to final product; (iv) to investigate the dynamics of levels of chlorate, perchlorate, trichloromethane, quaternary ammonium compounds and iodine throughout the manufacturing process of skim milk powder; (v and vi) and to determine the effect of different levels of a thermo-resistant protease, produced by a Pseudomonas fluorescens strain, on the cheese-making properties of milk and quality of Cheddar cheese.

The effects of dietary zinc supplementation on chemical composition, nutritional quality and volatile profile of Giuncata cheese were investigated. Dietary zinc addition did not influence milk yield and composition, but induced a marked reduction of somatic cell count. Both in milk and cheese the experimental samples were characterised by a lower concentration of saturated fatty acids and an increase in oleic, vaccenic and rumenic acids. The volatile profile of Giuncata cheese samples was also affected by dietary zinc intake, with an increase in concentration of butanoic acid, hexanoic acid and hexanal. The present results suggest a positive role of zinc in improving animal health and nutraceutical properties of milk and corresponding cheese. Such findings could contribute to the production of cheeses with interesting properties, although further evaluations should be performed to confirm the consumer acceptability of these changes.

In the present study, the characteristics of Allium sativum (AS) cheddar cheese was compared to plain cheese in the presence or absence of fish collagen (FC), in relation to acidity and proteolysis of milk protein during 0, 14, 30, and 60 days of ripening. Cadmium-ninhydrin method was used to determine the concentrations of free amino acids (FAAs) in cheese. In addition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS–PAGE) was used to study the casein hydrolysis and the type of proteolysis in all cheese types. Based on the present results, AS showed the ability to enhance the acid production of cheese (p 0.05) between AS- and plain- (control) cheese in the presence of FC on day 14 onwards. AS- cheese showed the highest (p

The production of Cheddar cheese using micellar casein concentrate (MCC), a novel milk ingredient powder with a high casein content (∼92%), was evaluated. Four types of Cheddar cheese were manufactured and ripened for 180 days from the following starting materials: standardised control milk (control), skim milk with cream (SC), reconstituted MCC with cream (MC) and reconstituted low-heat skim milk powder with cream (PC). Only minor differences were found in composition between treatments, but MC cheese showed higher levels of proteolysis compared with other treatments, linked to significantly higher plasmin and chymosin activities. No differences were observed in hardness between treatments (60, 120 and 180 days), but the springiness and cohesiveness of MC and PC cheeses were significantly higher than that of the control and SC cheeses at 60, 120 and 180 days. The use of casein-dominant dairy streams thus has the potential for production of Cheddar cheese with tailored functionality.

Background Buffalo milk is the second largest source of milk on the globe, it is highly suitable for the preparation of mozzarella cheese, however, it is not suitable for the preparation of cheddar cheese due to high buffering capacity, low acid development, excessive syneresis, lower lipolysis that lead to lower sensory score. Accelerated ripening can enhance lipolysis and improve sensory characteristics of cheddar cheese. Lipolysis and antioxidant capacity of buffalo cheddar cheese in conventional ripening is not previously studied. Optimization of ripening conditions can lead to better utilization of buffalo milk in cheese industry. Methods Effect of accelerated ripening on lipolysis and antioxidant properties of cow and buffalo cheddar cheese were investigated. Cheddar cheese prepared from standardized (3.5% fat) cow and buffalo milk was subjected to conventional and accelerated ripening (4 °C and 12 °C) for a period of 120 days. Fatty acid profile, organic acids, free fatty acids, cholesterol, antioxidant activity and sensory characteristics were studied at 0, 40, 80 and 120 days of ripening. Results Fatty acid profile of cow and buffalo cheddar in conventional (120 days old) and accelerated ripening were different from each other (p

During cheese manufacturing, on average 90% of the starter culture cells are believed to be entrapped in the curd, with the remainder lost in whey. This paper shows that plasmid-cured dairy strains of Lactococcus lactis show cell retention in the curd of 30-72%, whereas over-expression of pili on the lactococcal cell surface can increase cell retention to 99%. Exopolysaccharide production and cell clumping and chaining do not influence cell retention in cheese curd. L. lactis surface alteration also strongly affected the distribution of cells in the cheese matrix: clumping and over-expression of pili led to formation of large cell aggregates embedded in the protein matrix whereas exopolysaccharide expression resulted in cells being surrounding by small serum regions in the protein matrix of the cheese. These results suggest that surface properties of dairy starter cultures strongly determine retention and distribution of the bacteria in cheese curd. (C) 2018 The Authors. Published by Elsevier Ltd.

peer-reviewed Background Strains of Lactobacillus paracasei are present in many diverse environments, including dairy and plant materials and the intestinal tracts of humans and animals. Their adaptation to various niches is correlated to intra-species diversity at the genomic and metabolic level. In this study, we compared the genome sequences of three L. paracasei strains isolated from mature Cheddar cheeses, two of which (DPC4206 and DPC4536) shared the same genomic fingerprint by PFGE, but demonstrated varying metabolic capabilities. Results Genome sizes varied from 2.9 Mbp for DPC2071, to 3.09 Mbp for DPC4206 and 3.08 Mpb for DPC4536. The presence of plasmids was a distinguishing feature between the strains with strain DPC2071 possessing an unusually high number of plasmids (up to 11), while DPC4206 had one plasmid and DPC4536 harboured no plasmids. Each of the strains possessed specific genes not present in the other two analysed strains. The three strains differed in their abundance of sugar-converting genes, and in the types of sugars that could be used as energy sources. Genes involved in the metabolism of sugars not usually connected with the dairy niche, such as myo-inositol and pullulan were also detected, but strains did not utilise these sugars. The genetic content of the three strains differed in regard to specific genes for arginine and sulfur-containing amino acid metabolism and genes contributing to resistance to heavy metal ions. In addition, variability in the presence of phage remnants and phage protection systems was evident. Conclusions The findings presented in this study confirm a considerable level of heterogeneity of Lactobacillus paracasei strains, even between strains isolated from the same niche.

This chapter presents various hard cheeses, such as Allgau Mountain cheese, Berner Alpkase Protected Designation of Origin (PDO) and Berner Hobelkase PDO, and Cheddar and explores its types, method of manufacture and relevant research. Allgau mountain cheese is a traditional and popular cheese from the Allgau region in Germany and is manufactured from raw cow's milk. Berner Alpkase PDO is a full-fat hard cheese made from raw cow's milk. For the production of Berner Hobelkase PDO cheese wheels, Berner Alpkase cheeses with good storage quality are washed at the age of 6-8 months and further dry-ripened up to a minimum age of 18 months. Cantal cheese is the third Appellation d'Origine Controlee cheese in France, with a yearly production of 14,707 tonnes. Cheddar cheese is the most consumed cheese in the world, originating from Somerset around the late twelfth century. Cheshire cheese is mentioned in the Domesday Book at the end of the eleventh century. © 2018 John Wiley & Sons, Ltd. All rights reserved.

Despite being potentially highly useful for characterizing the biodiversity of phages, metagenomic studies are currently not available for dairy bacteriophages, partly due to the lack of a standard procedure for phage extraction. We optimized an extraction method that allows the removal of the bulk protein from whey and milk samples with losses of less than 50% of spiked phages. The protocol was applied to extract phages from whey in order to test the notion that members of Lactococcus lactis 936 (now Sk1virus ), P335, c2 (now C2virus ) and Leuconostoc phage groups are the most frequently encountered in the dairy environment. The relative abundance and diversity of phages in eight and four whey mixtures from dairies using undefined mesophilic mixed-strain cultures containing Lactococcus lactis subsp. lactis biovar diacetylactis and Leuconostoc species (i.e., DL starter cultures) and defined cultures, respectively, were assessed. Results obtained from transmission electron microscopy and high-throughput sequence analyses revealed the dominance of Lc. lactis 936 phages (order Caudovirales , family Siphoviridae ) in dairies using undefined DL starter cultures and Lc. lactis c2 phages (order Caudovirales , family Siphoviridae ) in dairies using defined cultures. The 936 and Leuconostoc phages demonstrated limited diversity. Possible coinduction of temperate P335 prophages and satellite phages in one of the whey mixtures was also observed. IMPORTANCE The method optimized in this study could provide an important basis for understanding the dynamics of the phage community (abundance, development, diversity, evolution, etc.) in dairies with different sizes, locations, and production strategies. It may also enable the discovery of previously unknown phages, which is crucial for the development of rapid molecular biology-based methods for phage burden surveillance systems. The dominance of only a few phage groups in the dairy environment signifies the depth of knowledge gained over the past decades, which served as the basis for designing current phage control strategies. The presence of a correlation between phages and the type of starter cultures being used in dairies might help to improve the selection and/or design of suitable, custom, and cost-efficient phage control strategies.

The draft genome sequence of Staphylococcus saprophyticus DPC5671, isolated from cheddar cheese, was determined. S. saprophyticus is a common Gram-positive bacterium detected on the surface of smear-ripened cheese and other fermented foods.

The strains Staphylococcus saprophyticus DPC5671 and Corynebacterium casei DPC5298 were applied in combination with Debaryomyces hansenii DPC6258 to the surface of young Cheddar cheese curd to obtain two different smear-ripened cheeses. A surface microbiota developed over the incubation period, comprising of both yeast and bacteria; pulsed field gel electrophoresis confirmed that the inoculated strains of S. saprophyticus DPC5671 or C. casei DPC5298 were the dominant bacterial strains on the surface of the cheese at the end of the ripening period. The smear cultures changed the appearance and aroma, which were significantly different from the control cheese. The approach presented in this study represents a method for the development of new cheese varieties with novel aromas within a short ripening time.

The putative citrate metabolic pathway in Lactobacillus casei ATCC 334 consists of the transporter CitH, a proton symporter of the citrate-divalent metal ion family of transporters CitMHS, citrate lyase, and the membrane-bound oxaloacetate decarboxylase complex OAD-ABDH. Resting cells of Lactobacillus casei ATCC 334 metabolized citrate in complex with Ca 2+ and not as free citrate or the Mg 2+ -citrate complex, thereby identifying Ca 2+ -citrate as the substrate of the transporter CitH. The pathway was induced in the presence of Ca 2+ and citrate during growth and repressed by the presence of glucose and of galactose, most likely by a carbon catabolite repression mechanism. The end products of Ca 2+ -citrate metabolism by resting cells of Lb. casei were pyruvate, acetate, and acetoin, demonstrating the activity of the membrane-bound oxaloacetate decarboxylase complex OAD-ABDH. Following pyruvate, the pathway splits into two branches. One branch is the classical citrate fermentation pathway producing acetoin by α-acetolactate synthase and α-acetolactate decarboxylase. The other branch yields acetate, for which the route is still obscure. Ca 2+ -citrate metabolism in a modified MRS medium lacking a carbohydrate did not significantly affect the growth characteristics, and generation of metabolic energy in the form of proton motive force (PMF) was not observed in resting cells. In contrast, carbohydrate/Ca 2+ -citrate cometabolism resulted in a higher biomass yield in batch culture. However, also with these cells, no generation of PMF was associated with Ca 2+ -citrate metabolism. It is concluded that citrate metabolism in Lb. casei is beneficial when it counteracts acidification by carbohydrate metabolism in later growth stages.

It has been known since the 1960s that lactic acid bacteria are essential for the development of cheese flavor. In the ensuing 50 years significant research has been directed at understanding the microbiology, genetics and biochemistry of this process. This review briefly covers the current status of cheese flavor development and then provides our vision for approaches which will enhance our understanding of this process. The long-term goal of this area of research is to enable technology (i.e. cultures and enzymes) that results in consistent rapid development of cheese variety-specific characteristic flavors.

It has been known since the 1960s that lactic acid bacteria are essential for the development of cheese flavor. In the ensuing 50 years significant research has been directed at understanding the microbiology, genetics and biochemistry of this process. This review briefly covers the current status of cheese flavor development and then provides our vision for approaches which will enhance our understanding of this process. The long-term goal of this area of research is to enable technology (i.e. cultures and enzymes) that results in consistent rapid development of cheese variety-specific characteristic flavors.

peer-reviewed A concentrated form of cell free extract (CFE) derived from attenuated Lactococcus lactis supsb. lactis 303 CFE was encapsulated in liposomes prepared from two different proliposome preparations (Prolipo Duo and Prolipo S) using microfluidization. Entrapment efficiencies of 19.7 % (Prolipo S) and 14.0 % (Prolipo Duo) were achieved and the preparations mixed in the ratio 4 (Prolipo Duo):1 (Prolipo S). Cheddar cheese trials were undertaken evaluating the performance of CFE entrapped in liposomes, empty liposomes and free CFE in comparison to a control cheese without any CFE or liposomes. Identical volumes of liposome and amounts of CFE were used in triplicate trials. The inclusion of liposomes did not adversely impact on cheese composition water activity, or microbiology. Entrapment of CFE in liposomes reduced loss of CFE to the whey. No significant differences were evident in proteolysis or expressed PepX activity during ripening in comparison to the cheeses containing free CFE, empty liposomes or the control, as the liposomes did not degrade during ripening. This result highlights the potential of liposomes to minimize losses of encapsulated enzymes into the whey during cheese production but also highlights the need to optimize the hydrophobicity, zeta potential, size and composition of the liposomes to maximize their use as vectors for enzyme addition in cheese to augment ripening. Department of Agriculture, Food and the Marine

A collection of 147 isolates obtained from 23 samples of traditional Azerbaijani dairy products was screened for the presence of proteolytic enzymes. Six Enterococcus faecalis strains obtained from three cheese samples have been identified as proteinase-producing strains, according to their ability to hydrolyze caseins. RAPD-PCR profiles of their total DNA showed different patterns for strains isolated from different cheese samples. The proteolytic activities of these strains were studied during their growth in milk and in non-proliferative cells system. Isolated strains were able to hydrolyze alpha(S1)-, alpha(S2)-, beta-caseins and BLG albeit to different extents, at optimal pH in the range 6.0-7.2 and optimal temperature in the range 37-45 A degrees C, depending on the strain. Proteolysis was strongly inhibited in the presence of EDTA-specific inhibitor of metalloproteases-but the presence of other types of proteases cannot be excluded. The potential pathogenicity of the strains was evaluated investigating the presence of the genes coding different virulence factors and their resistance to antibiotics. The obtained results yield new information about technological characteristics and safety of studied Enterococci strains from Azerbaijani artisanal dairy products. Many from the isolated strains contribute certainly to the differences in flavor, texture, and taste of Azerbaijani traditional cheeses and could represent new adjunct cultures for the dairy industry.

Grated Graviera cheese was stored for up to 9 weeks under both fluorescent light and in the dark, packaged aerobically and under modified atmosphere packaging (MAP) of (a) 100% CO2, (b) 100% N-2 and (c) 50% CO2/50% N-2. Cheese samples stored under fluorescent light showed a higher degree of lipid oxidation (P < 0.05) (ca. 3-4 times higher for MAP samples and 20 times higher for aerobically packaged samples) and suffered a gradual discolouration compared with samples stored in the dark. Chemical composition did not produce statistically significant changes (P > 0.05) as a function of storage time. Solid phase microextraction-gas chromatography/mass spectroscopy was used to determine volatile compounds produced under specific packaging treatments. Free fatty acids, esters, aldehydes, ketones and alcohols were recorded for all treatments, with aerobic packaging and exposure to light giving higher concentrations of volatile compounds compared with other treatments. Sensory analysis showed that light, gas composition and storage time significantly affected (P < 0.05) taste and odour attributes of grated Graviera cheese. The best sensory attributes were obtained using 100% N-2 or 50% N-2/50% CO2 and storage in the dark. That is, samples packaged in either 100% N-2 or 50% N-2/50% CO2 retained acceptable taste for 9 weeks stored in the dark vs. 4 weeks under light. For aerobically packaged samples, respective shelf life was 2.5 weeks vs. 2 weeks. International Dairy Journal

Recombined cream was formulated by high shear mixing of butter with denatured whey proteins. Size distributions of the resulting globules were similar to native fat globules which passively participate in milk gelation. Fat globules in traditional recombined cream are stabilized with caseins that actively participate in milk gelation resulting in cream with poor cheesemaking properties. Cheddar cheese was used as a model to evaluate cheesemaking properties of whey protein stabilized cream. Recombined milk cheese relative to whole milk cheese had similar composition, texture, sensory and structural properties. Incorporation of vitamin D3 or omega-3 into recombined cream did not affect the sensory properties of 3 month ripened cheese however levels of nutrients decreased during 6 months ripening. This research will offer the Canadian dairy industry greater flexibility for sourcing ingredients for cheese production; helping to mitigate economic impacts of seasonal variation in milk supply, and to enhance the nutritional properties of cheese. OMAFRA and Dairy Farmers of Ontario

Part B; International audience; Bio-preservation could be a valuable way to control Shigatoxin-producing Escherichia coli (STEC) in cheese. To this end, 41 strains were screened for their inhibitory potential on model cheese curd and on pasteurized and raw milk uncooked pressed cheeses. Strains of Lactococcus lactis, Lactococcus garvieae, Leuconostoc pseudomesenteroides, Leuconostoc citreum, Lactobacillus sp, Carnobacterium mobile, Enterococcus faecalis, Enterococcus faecium, Macrococcus caseolyticus and Hafnia alvei reduced STEC O26:H11 counts by 1.4-2.5 log cfu g(-1) and to a lesser extent STEC O157:H7 counts in pasteurized milk cheeses. Some strains can act in synergy to inhibit STEC in raw milk uncooked pressed cheeses. Inhibitory associations had no adverse effect on the sensory characteristics of these cheeses. The association of H. alvei, Lactobacillus plantarum and Lc. lactis was the most inhibitory: after inoculation of this consortium into milk, STEC O26:H11 and O157:H7, inoculated at 2 log cfu ml(-1), were reduced by up to 3 log cfu g(-1) in ripened cheese. Inhibition in cheese cannot be predicted from H2O2 production in BHI medium, decreased pH or milk reduction. It is not clear what role the rapid decrease in pH during the first 6 h may play in the inhibition. Further studies will be needed to determine the nature of the inhibition.

Texture perception results from a dynamic process induced by food oral processing during consumption. To go further in the understanding of cheese texture, the present study aims to investigate the role of composition, structure and texture of cheeses on the dynamics of bolus formation, in order to gain insight on the dynamics of texture perception. An integrative approach based on sensory, rheological, structural and physiological studies was used. It included the development or the adaptation of existing methods to characterize the dynamics of phenomena. One of the main outcomes was that the swallowing time seems to be the key parameter linking all experimental data sets. This parameter induced large modifications in physical properties of cheese boluses (rheology and hydration), in relation with the composition and the initial structural and physical properties of cheeses. Concerning sensory properties evaluated at the main steps of consumption, differences between cheeses were also observed, mainly due to different modifications of bolus properties depending on products, leading thus in different sensory trajectories in mouth.

Vector error correction models (VECM) are used to model price transmission when farm and retail prices are cointegrated. To allow for non-linearity in the cointegration process, researchers may specify thresholds to break the error correction process into regimes according to whether the retail price is above, below, or close to its equilibrium value given farm prices. However, because the coefficients in a VECM can change when there is movement from one regime to another, the model can be discontinuous. This implies sudden, “hard” regime changes. In this study, we extend the threshold VECM to include features of STAR models. Our approach allows for gradual, soft regime changes. An empirical application to retail cheese and farm milk price is presented.

Milk has a high nutritive value, not only For the new-born mammal and for the human consumer, but also for microbes. Raw milk kept at roam temperature will be liable to microbial spoilage. After some days, the milk will spontaneously become sour. This is generally due to the activity of lactic acid bacteria. A flora of these bacteria may develop, which can be transferred deliberately to fresh milk in order to maintain or even strengthen it. This principle is the basis for controlled acidification of milk towards products, sustainable and safe, with most often an attractive flavour. Various types of fermented milks and derived products have been developed in all parts of the world, each with its own characteristic history. Their nature depends very much on the type of milk used. on the pre-treatment of the milk, on the temperature (climate) and the conditions of fermentation and on the subsequent technological treatments. Most fermented dairy products contain lactic acid bacteria, but other bacteria, yeasts and moulds may be involved as well. In optimising the manufacturing processes, starter cultures for fermented dairy products have been developed. They are composed of selected microorganisms, propagated as multiple-strain starters consisting of a defined mixture of pure cultures or as mixed-strain starters consisting of an undefined mixture of different types of bacteria. The use of starters, on the one hand, has been tremendously positive with respect to the quality of the product, but, on the other hand, it has diminished the diversity of fermented dairy products. Since the dairy industry is keen to explore new possibilities for enhancing the diversity of its product range, there is a new interest nowadays in searching for potential starter organisms from the pool, which existed at the time of raw milk fermentation. This contribution reviews some potential opportunities and recent developments in this search. (C) 2002 Elsevier Science Ltd. All rights reserved.

BACKGROUND: Lactococcus lactis is a lactic acid bacterium that has been used for centuries in the production of a variety of cheeses, as these bacteria rapidly acidify milk and greatly contribute to the flavour of the fermentation end-products. After a short growth phase during cheese ripening L. lactis enters an extended non-growing state whilst still strongly contributing to amino acid-derived flavour formation. Here, a research approach is presented that allows investigation of strain- and amino acid-specific flavour formation during the non-growing state.RESULTS: Non-growing cells of five selected L. lactis strains were demonstrated to degrade amino acids into flavour compounds that are relevant in food fermentations and differs greatly from production of flavour compounds using growing cells. As observed earlier in other research set-ups and with other microorganisms, addition of NADH, α-ketoglutarate and pyridoxal-5-phosphate was demonstrated to be essential for optimal flavour formation, suggesting that intracellular pools of these substrates are too low for the significant production of the flavour compounds. Production of flavours during the non-growing phase strongly depends on the individual amino acids that were supplied, on the presence of other amino acids (mixtures versus single compounds), and on the strain used. Moreover, we observed that the plasmid-free model strains L. lactis MG1363 and IL1403 produce relatively low amounts of flavour components under the various conditions tested.CONCLUSIONS: By using this simplified and rapid approach to study flavour formation by non-growing lactic acid bacteria, lengthy ripening periods are no longer required to assess the capacity of strains to produce flavours in the long, non-growing state of dairy fermentation. In addition, this method also provides insight into the conversion of single amino acids versus the conversion of a mixture of amino acids as produced during protein degradation. The generated results are complementary to earlier generated datasets using growing cells, allowing assessment of the full flavour forming potential of strains used as starter cultures in industrial food fermentation processes.

The physicochemical properties of cheese and milk gels are greatly influenced by molecular interactions between the casein proteins involving calcium. Novel experiments were designed to investigate the relationship between insoluble caseinbound cations and rheological properties of Cheddar cheese and rennet-induced milk gels. Cheddar cheese and rennet-induced milk gels were supplemented with Mg2+ or Sr2+ to compare their effects on their rheological properties to those previously reported in literature for Ca2+ supplementation. Sr2+ displayed behaviour similar to Ca2+ as observed by its ability to increase the rigidity of cheese and rennet milk gels and also decrease cheese meltability. Mg+2 had no influence on cheese rheological properties and was greatly inferior to Ca2+ and Sr2+ in its ability to increase rennet milk gel elasticity. Cheddar cheese was supplemented with the calcium-chelating salts trisodium citrate, disodium hydrogen phosphate or disodium EDTA, in an attempt to reduce the CCP content of cheese and thereby modify its rheological and functional properties. TSC and EDTA were successful in decreasing cheese CCP, whereas DSP caused an initial increase in CCP content. Cheddar cheese was supplemented with chlorides of iron, copper and zinc at salting to investigate the effects of concentrations of these elements in excess of those found innately or commonly in fortification studies, with emphasis on mineral equilibria changes and resultant alteration of rheological properties. Zinc addition was the only added metal that significantly influenced cheese rheological properties, leading to an increase in cheese rigidity and decreased cheese melt at elevated temperatures. Gum tragacanth was used as a fat-replacer in the manufacture of reduced-fat Cheddar cheese, in an attempt to improve the rheological, functional and sensory properties of reduced-fat Cheddar. Overall, the experimental work reported in this thesis generated new knowledge and theories about how casein-mineral interactions influence rheological properties of casein systems.