Search

The enzymatic repertoire of starter cultures belonging to the Lactococcus genus determines various important characteristics of fermented dairy products but might change in response to the substantial environmental changes in the manufacturing process. Assessing bacterial proteome adaptation in dairy and other food environments is challenging due to the high matrix-protein concentration and is even further complicated in particularly cheese by the high fat concentrations, the semi-solid state of that matrix, and the non-growing state of the bacteria. Here, we present bacterial harvesting and processing procedures that enable reproducible, high-resolution proteome determination in lactococcal cultures harvested from laboratory media, milk, and miniature Gouda cheese. Comparative proteome analysis of Lactococcus cremoris NCDO712 grown in laboratory medium and milk revealed proteome adaptations that predominantly reflect the differential (micro-)nutrient availability in these two environments. Additionally, the drastic environmental changes during cheese manufacturing only elicited subtle changes in the L. cremoris NCDO712 proteome, including modified expression levels of enzymes involved in flavour formation. The technical advances we describe offer novel opportunities to evaluate bacterial proteomes in relation to their performance in complex, protein- and/or fat-rich food matrices and highlight the potential of steering starter culture performance by preculture condition adjustments.

The noninvasive, longitudinal study of products and food processing is of interest for the dairy industry. Here, we demonstrated that single-sided nuclear magnetic resonance (NMR) can be used for noninvasive monitoring of the cheese ripening process. The maturation of soft-ripened Camembert-like molded cheese samples was monitored for 20 d measuring 1-dimensional and 2-dimensional NMR relaxation and diffusion data at various depths, ranging from the hard surface layer to the soft center. Gelation and gel shrinkage were observed throughout ripening, and a complete loss of free water signal was observed at the cheese rind. Transversal (T₂) relaxation distributions include 3 components that evolve with ripening time and position, corresponding to water inside the casein gel network, water trapped in casein, and fat. Two-dimensional T₁-T₂ relaxation experiments provided enhanced resolution of the 3 components, allowing quantification of the relative proportions of each phase. Furthermore, diffusion (D)-T₂ relaxation correlation experiments revealed the bimodal size distribution of fat globules. The study demonstrated that single-sided NMR can provide spatially resolved signal intensity, relaxation, and diffusion parameters that reflect structural changes during the ripening process and can be exploited to understand and monitor the ripening of cheeses.

This study reports for the first time the relationship between bacterial succession, characterized by high-throughput sequencing (sequencing of V3–V4 16S rRNA regions), and the evolution of gross composition, free fatty acids (FFAs) and biogenic amines (BAs) during cheese ripening. Specifically, Idiazabal PDO cheese, a raw ewe milk-derived semi-hard o hard cheese, was analysed. Altogether, 8 gross parameters were monitored (pH, dry matter, protein, fat, Ca, Mg, P and NaCl) and 21 FFAs and 8 BAs were detected. The ripening time influenced the concentration of most physico-chemical parameters, whereas the producer mainly affected the gross composition and FFAs. Through an O2PLS approach, the non-starter lactic acid bacteria Lactobacillus, Enterococcus and Streptococcus were reported as positively related to the evolution of gross composition and FFAs release, while only Lactobacillus was positively related to BAs production. Several environmental or non-desirable bacteria showed negative correlations, which could indicate the negative impact of gross composition on their growth, the antimicrobial effect of FFAs and/or the metabolic use of FFAs by these genera, and their ability to degrade BAs. Nonetheless, Obesumbacterium and Chromohalobacter were positively associated with the synthesis of FFAs and BAs, respectively. This research work provides novel information that may contribute to the understanding of possible functional relationships between bacterial communities and the evolution of several cheese quality and safety parameters.

The aldehyde 3-methylbutanal is a key aroma compound for many types of cheeses. Intracellular enzymes of cheese starter cultures are predominantly responsible for the conversion of leucine into 3-methylbutanal. Environmental conditions during cheese manufacturing also play a role in the production of 3-methylbutanal. Our work shows that salting has a detrimental effect on the capacity of Lactococcus lactis subsp. lactis DS84445 to produce 3-methylbutanal. In that respect, a promising way to control the concentration of 3-methylbutanal is by using a cheese starter culture that produces the aimed level of 3-methylbutanal before salting starts and preferably when lactose is still available.

The fatty acid (FA) composition of milk from six European areas, as well as the alteration in the FA profile during cheese production, was studied using both a targeted GC-FID and an untargeted GC-MS approach. By applying principal component, partial least square discriminant and chemical similarity enrichment analysis, a discrimination of the geographical areas could be achieved highlighting important FA classes such as odd‐ and branched‐chain FAs for the differentiation. The FA profile remained constant during cheese production, and aroma compounds have been identified as biomarkers for the ripening methods used, namely foil and smear ripening.

Flavour compounds in cheese are formed by metabolism of residual lactose, lactate and citrate, proteolysis and lipolysis through the activity of e.g., starter bacteria. Generally identified aroma components in cheese are fatty acids, esters, alcohols, ketones, lactones, aldehydes, and sulphur compounds. Various compounds contribute to specific flavours reviewed in this study. In propionic acid cheeses (e.g. Emmenthaler, Maasdamer, Grevé), lactate fermentation with products of propionic and acetic acids, and CO2 is important for the characteristic sweet, nutty flavour and eye-formation of these cheeses. The variation of aroma components in cheese is influenced by many factors; type of starter culture and strain, milk quality and composition, pH, temperature, salt, moisture content and ripening conditions. To control the flavour and predetermined characteristic of a cheese variety, sensory evaluation is conducted. Methods for sensory analysis include discrimination methods, descriptive sensory method, affective consumer tests and grading methods. Depending on the objective of the analysis, methods are used to evaluate cheese quality and defects, in product development or after replacement of an ingredient, for research purposes, marketing, shelf-life evaluation and to investigate consumer acceptability. The objectives of the literature review are to examine aroma compounds in cheese, with focus on propionic acid cheeses. The variation and origin of aroma components as well as their contribution to flavour in cheese are investigated. In addition, methods for sensory evaluation of cheese are reviewed., Smakämnen i ost bildas via metabolism av resterande laktos, laktat och citrat, proteolys och lipolys, med hjälp av bland annat starterkulturens bakterier. Fettsyror, estrar, alkoholer, ketoner, laktoner, aldehyder och svavelföreningar är generella grupper av ämnen som bidrar till ostens smak. Olika grupper av ämnen bidrar till specifika smaker som kommer att tas upp i rapporten. I propionsyraostar (exempelvis Emmentaler, Maasdamer och Grevé) är fermentering av laktat grundläggande eftersom det bidrar med ostarnas karaktäristiska hål och söta, nötaktiga smak från fermenteringsprodukterna propionsyra, ättiksyra, och CO2. Variationen av smakämnen i ost beror på många faktorer; typ av starterkultur, mjölkkvalité, mjölkegenskaper och tillverkningsprocesser så som pH, temperatur, salt- och vätskehalt och lagringsförhållanden. En osts smak och karaktär utvärderas med hjälp av olika metoder för sensorisk analys, till exempel skillnadsmetoder, beskrivande metod av en tränad sensorisk panel och konsumenttester. Metoderna används för att utvärdera ostens kvalité vid produktutveckling, i forskningssyften, för marknadsföring, i studier av förändringar som sker under den förväntade hållbarhetstiden och för utvärdering av konsumenters acceptans. Syftet med litteraturstudien är att undersöka smakämnen i ost, med fokus på propionsyraostar. Variationen i smakämnen i ost samt hur de har bildats, liksom deras bidrag till smak, kommer att analyseras. Dessutom ska olika metoder för sensorisk utvärdering av ostens smak undersökas.

The fatty acid (FA) composition of milk from six European areas, as well as the alteration in the FA profile during cheese production, was studied using both a targeted GC-FID and an untargeted GC-MS approach. By applying principal component, partial least square discriminant and chemical similarity enrichment analysis, a discrimination of the geographical areas could be achieved highlighting important FA classes such as odd‐ and branched‐chain FAs for the differentiation. The FA profile remained constant during cheese production, and aroma compounds have been identified as biomarkers for the ripening methods used, namely foil and smear ripening.

[EN] The aim of this study was to evaluate the transfer of the most widely used antibiotics in dairy goats from milk to cheese as well as their effect on the cheese-making process and cheese characteristics during ripening. Antibiotic-free milk was spiked individually with 7 veterinary drugs (amoxicillin, benzylpenicillin, cloxacillin, erythromycin, ciprofloxacin, enrofloxacin, and oxytetracycline) at an equivalent concentration of the European Union maximum residue limit. Spiked goat milk was used to make mature Tronchon cheeses, which were analyzed at 0, 30, and 60 d of maturation to determine pH, chemical composition, proteolytic and lipolytic activities, and color and textural properties. A sensory evaluation of 60-d ripened cheeses was carried out. Cheeses from raw antibiotic-free goat milk were made simultaneously to be used as reference. The cheese-making process was unaffected by the presence of most antibiotics evaluated. Only erythromycin and oxytetracycline significantly increased the time required for cheese production (122 +/- 29 and 108 +/- 25 min, respectively). However, variable amounts of antibiotics, ranging from 7.4 to 68%, were transferred from milk to cheese, with oxytetracycline and quinolones showing the highest retention rates. In general, antibiotic residues present in the cheeses at the beginning of maturation decrease significantly along time. Thus, beta-lactams and erythromycin residues were not detectable after 30 d of ripening. However, relatively high concentrations of enrofloxacin (148 +/- 12 mu g/kg) and ciprofloxacin (253 +/- 24 mu g/kg) residues were found in the cheeses after 60 d of maturation. The quality characteristics of the Tronchon cheeses were only slightly affected by such substances, with few significant differences in the free fatty acid concentration and color and textural properties of the cheeses. Results herein indicate that the use of goat milk containing antibiotics, such as quinolones, at the European Union maxim

The aim of this work was to observe chemical and physical changes in Dutch-type cheese during ripening depending on salt concentration. Ripening is one of the most important factors influencing the sensory quality of cheese and therefore the cheese production should be studied. Among the substances which are formed during ripening belong the biogenic amines which are produced by the decarboxylation of amino acids. These amino acids are created during proteolysis. The salt content largely affects the intensity of the ripening process, but also other cheese parameters such as dry matter content, hardness or content of biogenic amines. In the course of 3 months ripening of model cheeses with different cultures and with different salt content, the effect of the salt on pH, dry matter content, free amino acids and biogenic amines content and hardness was monitored. The concentration of NaCl affected the dry matter content and the hardness of the samples. The reduction in salt content contributes to the higher accumulation of biogenic amines during ripening. © 2019 Potravinarstvo Slovak Journal of Food Sciences.

[EN] The aim of this study was to evaluate the transfer of the most widely used antibiotics in dairy goats from milk to cheese as well as their effect on the cheese-making process and cheese characteristics during ripening. Antibiotic-free milk was spiked individually with 7 veterinary drugs (amoxicillin, benzylpenicillin, cloxacillin, erythromycin, ciprofloxacin, enrofloxacin, and oxytetracycline) at an equivalent concentration of the European Union maximum residue limit. Spiked goat milk was used to make mature Tronchon cheeses, which were analyzed at 0, 30, and 60 d of maturation to determine pH, chemical composition, proteolytic and lipolytic activities, and color and textural properties. A sensory evaluation of 60-d ripened cheeses was carried out. Cheeses from raw antibiotic-free goat milk were made simultaneously to be used as reference. The cheese-making process was unaffected by the presence of most antibiotics evaluated. Only erythromycin and oxytetracycline significantly increased the time required for cheese production (122 +/- 29 and 108 +/- 25 min, respectively). However, variable amounts of antibiotics, ranging from 7.4 to 68%, were transferred from milk to cheese, with oxytetracycline and quinolones showing the highest retention rates. In general, antibiotic residues present in the cheeses at the beginning of maturation decrease significantly along time. Thus, beta-lactams and erythromycin residues were not detectable after 30 d of ripening. However, relatively high concentrations of enrofloxacin (148 +/- 12 mu g/kg) and ciprofloxacin (253 +/- 24 mu g/kg) residues were found in the cheeses after 60 d of maturation. The quality characteristics of the Tronchon cheeses were only slightly affected by such substances, with few significant differences in the free fatty acid concentration and color and textural properties of the cheeses. Results herein indicate that the use of goat milk containing antibiotics, such as quinolones, at the European Union maxim

The aim of this work was to observe chemical and physical changes in Dutch-type cheese during ripening depending on salt concentration. Ripening is one of the most important factors influencing the sensory quality of cheese and therefore the cheese production should be studied. Among the substances which are formed during ripening belong the biogenic amines which are produced by the decarboxylation of amino acids. These amino acids are created during proteolysis. The salt content largely affects the intensity of the ripening process, but also other cheese parameters such as dry matter content, hardness or content of biogenic amines. In the course of 3 months ripening of model cheeses with different cultures and with different salt content, the effect of the salt on pH, dry matter content, free amino acids and biogenic amines content and hardness was monitored. The concentration of NaCl affected the dry matter content and the hardness of the samples. The reduction in salt content contributes to the higher accumulation of biogenic amines during ripening. © 2019 Potravinarstvo Slovak Journal of Food Sciences.

The objective of the study was to assess the development of the biogenic amine content in model cheese samples individually inoculated with two biogenic amine producing non-starter lactic acid bacteria strains of Lactobacillus curvatus subsp. curvatus (DEPE T3 and DEPE T36) and two biogenic amine producing non-starter lactic acid bacteria strains of Lactobacillus paracasei (DEPE T51 and DEPE T52) over the course of a 90 day storage period (10 ± 1 °C). During the entire ripening period, the dominant biogenic amine was tyramine. After just two months of ripening, tyramine concentration 167 mg/kg was detected in the model cheeses with the DEPE T3 strain (moreover a total biogenic amine concentration was 220 mg/kg), whilst in the case of the DEPE T36 strain it was even 211 mg/kg of tyramine (sum of biogenic amine was 302 mg/kg). In the samples with the added DEPE T51 and DEPE T52 strains, tyramine concentration after 90 days of ripening almost reached the level of 50 mg/kg. © 2018 Elsevier Ltd

The objective of the study was to assess the development of the biogenic amine content in model cheese samples individually inoculated with two biogenic amine producing non-starter lactic acid bacteria strains of Lactobacillus curvatus subsp. curvatus (DEPE T3 and DEPE T36) and two biogenic amine producing non-starter lactic acid bacteria strains of Lactobacillus paracasei (DEPE T51 and DEPE T52) over the course of a 90 day storage period (10 ± 1 °C). During the entire ripening period, the dominant biogenic amine was tyramine. After just two months of ripening, tyramine concentration 167 mg/kg was detected in the model cheeses with the DEPE T3 strain (moreover a total biogenic amine concentration was 220 mg/kg), whilst in the case of the DEPE T36 strain it was even 211 mg/kg of tyramine (sum of biogenic amine was 302 mg/kg). In the samples with the added DEPE T51 and DEPE T52 strains, tyramine concentration after 90 days of ripening almost reached the level of 50 mg/kg. © 2018 Elsevier Ltd

Dairy products from goat's milk are characterized by their distinctive aroma and their specific taste. However, the strong aroma can discourage some consumers. Properties of cheese can be modified by the combination of goat's and cow's milk. On the other hand, chemical diversity from different milk origin may affect the changes during ripening. The aim of the study was to compare the intensity of changes during ripening of model cheese samples produced with various ratios of goat's and cow's milk. The combinations 100:0 (100% goat's milk), 75:25, 50:50, 25:75 and 0:100 (100% cow's milk) were used for the manufacture of Dutch-type cheeses, which were ripened during a period of 84 days. Protein profile, free amino acid content and biogenic amine content were used for the description of cheese properties during storage. Cluster analysis showed different changes in the protein matrix of the examined samples. The results indicated that even low addition of cow's milk significantly affected the protein profile. However, the homology of protein profiles rose with the increasing ripening time. More intensive proteolysis occured in the samples with predominance of goat's milk. Moreover, cheese samples produced only from goat's milk presented a significant increase inthe amount of free amino acids after 14 days of ripening. The effect of milk origin on the production of biogenic amines was also examined. However, higher concentrations of biogenic amines were detected in samples manufactured from goat's milk. Tyramine, putrescine, histamine and phenylethylamine were detected during the storage of the samples. The total biogenic amine content exceeded 100 mg/kg in samples with predominance of goat's milk. © 2017 Potravinarstvo Slovak Journal of Food Sciences.

Dairy products from goat's milk are characterized by their distinctive aroma and their specific taste. However, the strong aroma can discourage some consumers. Properties of cheese can be modified by the combination of goat's and cow's milk. On the other hand, chemical diversity from different milk origin may affect the changes during ripening. The aim of the study was to compare the intensity of changes during ripening of model cheese samples produced with various ratios of goat's and cow's milk. The combinations 100:0 (100% goat's milk), 75:25, 50:50, 25:75 and 0:100 (100% cow's milk) were used for the manufacture of Dutch-type cheeses, which were ripened during a period of 84 days. Protein profile, free amino acid content and biogenic amine content were used for the description of cheese properties during storage. Cluster analysis showed different changes in the protein matrix of the examined samples. The results indicated that even low addition of cow's milk significantly affected the protein profile. However, the homology of protein profiles rose with the increasing ripening time. More intensive proteolysis occured in the samples with predominance of goat's milk. Moreover, cheese samples produced only from goat's milk presented a significant increase inthe amount of free amino acids after 14 days of ripening. The effect of milk origin on the production of biogenic amines was also examined. However, higher concentrations of biogenic amines were detected in samples manufactured from goat's milk. Tyramine, putrescine, histamine and phenylethylamine were detected during the storage of the samples. The total biogenic amine content exceeded 100 mg/kg in samples with predominance of goat's milk. © 2017 Potravinarstvo Slovak Journal of Food Sciences.

Stremmen is een belangrijke stap in het kaasbereidingsproces. Wat gebeurt er eigenlijk tijdens het stremmen? Welke rol speelt stremsel hierbij? En welke soorten stremsel zijn er? In dit artikel meer over dit wezenlijke ingrediënt voor de kaasbereiding.

Op boerderij De Groote Voort in Lunteren wordt alleen nog kaas met een natuurkorst gemaakt. De oude kaasopslag was niet geschikt voor de rijping van deze kaas. Daarom werd er een nieuwe kaasopslag gerealiseerd die als proeftuin dient voor het op een natuurlijke manier laten rijpen van kaas met een natuurkorst.

Kaasspecialist Zijerveld wilde een smaakvolle geitenkaas met slechts 30 procent vet in het assortiment. Met ambachtelijke technieken lukte dat niet. Wageningen UR Food & Biobased Research vond een nieuwe receptuur voor het kaasje. Gezonder en net zo lekker.

Het Presidium Boeren Goudse Oplegkaas (BGO) bestaat nu ruim 10 jaar. De bijzondere kwaliteit van deze meer dan 20 kilo wegende kaas, die gemaakt wordt van rauwe melk met behulp van houten vaten en linnen doeken, wordt niet alleen door de kaasmaker bereikt maar ook door de affineur. In gesprek met affineurs Arie Blok en Kees Remijn.

In Veenhuizen, bij velen bekend als het gevangenisdorp, maken Martin Schyns en Jan Craens kaas in een ruim honderd jaar oude zuivelfabriek. Martin maakt het liefst kaas met een natuurkorst. “Dat is puur natuur en de korst geeft een speciale smaak.”

Kaasspecialist Zijerveld wilde een smaakvolle geitenkaas met slechts 30 procent vet in het assortiment. Met ambachtelijke technieken lukte dat niet. Wageningen UR Food & Biobased Research vond een nieuwe receptuur voor het kaasje. Gezonder en net zo lekker.

© 2014 American Dairy Science Association. Lactobacillus plantarum is a lactic acid bacterium that can be found during cheese ripening. Lipolysis of milk triacylglycerols to free fatty acids during cheese ripening has fundamental consequences on cheese flavor. In the present study, the gene lp_1760, encoding a putative esterase or lipase, was cloned and expressed in Escherichia coli BL21 (DE3) and the overproduced Lp_1760 protein was biochemically characterized. Lp_1760 hydrolyzed p-nitrophenyl esters of fatty acids from C2 to C16, with a preference for p-nitrophenyl butyrate. On triglycerides, Lp_1760 showed higher activity on tributyrin than on triacetin. Although optimal conditions for activity were 45°C and pH 7, Lp_1760 retains activity under conditions commonly found during cheese making and ripening. The Lp_1760 showed more than 50% activity at 5°C and exhibited thermal stability at high temperatures. Enzymatic activity was strongly inhibited by sodium dodecyl sulfate and phenylmethylsulfonyl fluoride. The Lp_1760 tributyrin esterase showed high activity in the presence of NaCl, lactic acid, and calcium chloride. The results suggest that Lp_1760 might be a useful tributyrin esterase to be used in cheese manufacturing.

The objective of our study was to compare the effect of addition of decarboxylase positive strain of Lactococcus lactis subsp. lactis on biogenic amine production, intensity of proteolysis and changes of hardness during ripening of white brined cheese. Model samples were kept under 10 degrees C for 56 days. The FAA content of cheese and hardness of samples were increasing during ripening. Significant differences in FAA content and also hardness were not found between control samples and samples with decarboxylase positive lactococci (P >= 0.05). Production of biogenic amine was more intense in sample with addition of decarboxylase positive lactococci (especially during first 28 days of ripening) and depends on initial micro flora during first stage of ripening. However, environmental conditions and ripening time are important factors which play major role in biogenic amine production through the microorganism growth in following ripening phases.

The objective of our study was to compare the effect of addition of decarboxylase positive strain of Lactococcus lactis subsp. lactis on biogenic amine production, intensity of proteolysis and changes of hardness during ripening of white brined cheese. Model samples were kept under 10 degrees C for 56 days. The FAA content of cheese and hardness of samples were increasing during ripening. Significant differences in FAA content and also hardness were not found between control samples and samples with decarboxylase positive lactococci (P >= 0.05). Production of biogenic amine was more intense in sample with addition of decarboxylase positive lactococci (especially during first 28 days of ripening) and depends on initial micro flora during first stage of ripening. However, environmental conditions and ripening time are important factors which play major role in biogenic amine production through the microorganism growth in following ripening phases.

The study deals with the effects of the origin of milk (cow, ewe, goat, at different proportions), seasonality, and ripen- ing time on the contents of conjugated linoleic acid (CLA) in 224 samples of cheese. The sum of the cis 9, trans 11 and trans 10, cis 12 isomers was determined by GC-FID, after the extraction and methylation of the fatty acids of the samples, observing that the mean amount of CLA was 2.22, 2.72, and 3.54 mg/g of cheese, depending on the proportions of cow’s, goat’s, or ewe’s milks, respectively. The contents in cow’s, ewe’s, and goat’s milk, together with the ripening time and seasonality, were seen to have significant effects ( P < 0.05) on the concentration of CLA. The Pearson correlation re- vealed an inverse correlation between the content of CLA and the % of cow’s milk ( r = –0.269, P < 0.01) and seasonality ( r = –0.290, P < 0.01), and a direct correlation between CLA content and the % of ewe’s milk ( r = 0.312, P < 0.01) and the month of ripening ( r = 0.188, P < 0.01)

The study deals with the effects of the origin of milk (cow, ewe, goat, at different proportions), seasonality, and ripen- ing time on the contents of conjugated linoleic acid (CLA) in 224 samples of cheese. The sum of the cis 9, trans 11 and trans 10, cis 12 isomers was determined by GC-FID, after the extraction and methylation of the fatty acids of the samples, observing that the mean amount of CLA was 2.22, 2.72, and 3.54 mg/g of cheese, depending on the proportions of cow’s, goat’s, or ewe’s milks, respectively. The contents in cow’s, ewe’s, and goat’s milk, together with the ripening time and seasonality, were seen to have significant effects ( P < 0.05) on the concentration of CLA. The Pearson correlation re- vealed an inverse correlation between the content of CLA and the % of cow’s milk ( r = –0.269, P < 0.01) and seasonality ( r = –0.290, P < 0.01), and a direct correlation between CLA content and the % of ewe’s milk ( r = 0.312, P < 0.01) and the month of ripening ( r = 0.188, P < 0.01)

The study deals with the effects of the origin of milk (cow, ewe, goat, at different proportions), seasonality, and ripen- ing time on the contents of conjugated linoleic acid (CLA) in 224 samples of cheese. The sum of the cis 9, trans 11 and trans 10, cis 12 isomers was determined by GC-FID, after the extraction and methylation of the fatty acids of the samples, observing that the mean amount of CLA was 2.22, 2.72, and 3.54 mg/g of cheese, depending on the proportions of cow’s, goat’s, or ewe’s milks, respectively. The contents in cow’s, ewe’s, and goat’s milk, together with the ripening time and seasonality, were seen to have significant effects ( P < 0.05) on the concentration of CLA. The Pearson correlation re- vealed an inverse correlation between the content of CLA and the % of cow’s milk ( r = –0.269, P < 0.01) and seasonality ( r = –0.290, P < 0.01), and a direct correlation between CLA content and the % of ewe’s milk ( r = 0.312, P < 0.01) and the month of ripening ( r = 0.188, P < 0.01)

The study deals with the effects of the origin of milk (cow, ewe, goat, at different proportions), seasonality, and ripen- ing time on the contents of conjugated linoleic acid (CLA) in 224 samples of cheese. The sum of the cis 9, trans 11 and trans 10, cis 12 isomers was determined by GC-FID, after the extraction and methylation of the fatty acids of the samples, observing that the mean amount of CLA was 2.22, 2.72, and 3.54 mg/g of cheese, depending on the proportions of cow’s, goat’s, or ewe’s milks, respectively. The contents in cow’s, ewe’s, and goat’s milk, together with the ripening time and seasonality, were seen to have significant effects ( P < 0.05) on the concentration of CLA. The Pearson correlation re- vealed an inverse correlation between the content of CLA and the % of cow’s milk ( r = –0.269, P < 0.01) and seasonality ( r = –0.290, P < 0.01), and a direct correlation between CLA content and the % of ewe’s milk ( r = 0.312, P < 0.01) and the month of ripening ( r = 0.188, P < 0.01)

The study deals with the effects of the origin of milk (cow, ewe, goat, at different proportions), seasonality, and ripen- ing time on the contents of conjugated linoleic acid (CLA) in 224 samples of cheese. The sum of the cis 9, trans 11 and trans 10, cis 12 isomers was determined by GC-FID, after the extraction and methylation of the fatty acids of the samples, observing that the mean amount of CLA was 2.22, 2.72, and 3.54 mg/g of cheese, depending on the proportions of cow’s, goat’s, or ewe’s milks, respectively. The contents in cow’s, ewe’s, and goat’s milk, together with the ripening time and seasonality, were seen to have significant effects ( P < 0.05) on the concentration of CLA. The Pearson correlation re- vealed an inverse correlation between the content of CLA and the % of cow’s milk ( r = –0.269, P < 0.01) and seasonality ( r = –0.290, P < 0.01), and a direct correlation between CLA content and the % of ewe’s milk ( r = 0.312, P < 0.01) and the month of ripening ( r = 0.188, P < 0.01)

The aim of this paper was to investigate the role of two types of Penicillium roqueforti moulds (type esportazione and dolce) in the ripening of two Gorgonzola-type cheese varieties. Cheeses were analysed after 4, 14, 30 and 60 days of ripening. Microbiological analysis showed high numbers of total bacterial count, yeasts and moulds in both 60-day-old cheese varieties. The concentration of water-soluble N, nonprotein N and 5% phosphotungstic acid-soluble N increased significantly during ripening. Patterns of proteolysis by urea-polyacrylamide gel electrophoresis showed that rind-to-core gradients and age-related changes in moisture and salt content influenced mould and other enzyme activities, which are reflected in various rates of protein degradation. The hydrolysis of alpha s(1)- and beta-caseins was more extensive in the core than under the rind of both cheese varieties.

[EN] The effect of including artichoke silage in the rations of dairy ewes on milk characteristics and biochemical changes of ripened cheeses was evaluated. Four groups of lactating ewes were fed rations containing 0, 10, 20, or 30% artichoke silage on a dry matter basis. Bulk milk samples were collected 3 times during the feeding period, and semi-hard cheeses were manufactured and sampled during ripening. Milk composition and cheese yield were not affected by diet. Inclusion of 20 and 30% artichoke silage reduced the firmness of the curds at a level only detected by the Gelograph (Gelograph-NT, Gel-Instrumente, Thalwil, Switzerland) probe. Inclusion of artichoke silage in ewes' diet decreased fat and total free fatty acids content of these cheeses and increased total free amino acids content. Despite the effect of diet on cheese ripening characteristics, the overall sensory scores for cheeses corresponding to artichoke silage diets were statistically higher than those for the control cheeses.

[EN] The effect of including artichoke silage in the rations of dairy ewes on milk characteristics and biochemical changes of ripened cheeses was evaluated. Four groups of lactating ewes were fed rations containing 0, 10, 20, or 30% artichoke silage on a dry matter basis. Bulk milk samples were collected 3 times during the feeding period, and semi-hard cheeses were manufactured and sampled during ripening. Milk composition and cheese yield were not affected by diet. Inclusion of 20 and 30% artichoke silage reduced the firmness of the curds at a level only detected by the Gelograph (Gelograph-NT, Gel-Instrumente, Thalwil, Switzerland) probe. Inclusion of artichoke silage in ewes' diet decreased fat and total free fatty acids content of these cheeses and increased total free amino acids content. Despite the effect of diet on cheese ripening characteristics, the overall sensory scores for cheeses corresponding to artichoke silage diets were statistically higher than those for the control cheeses.

Messeklever is terug van weggeweest. De Noord-Hollandse streekkaas werd tijdens de nationale keuring van boerenkaas gekozen tot lekkerste kaas in de bijzondere klasse. Nu dingt de kaas mee naar de Smaakvol2009, de erkenning voor het beste authentieke product van Nederlandse bodem. Een verhaal over een oer-Hollandse kaas die niet als oer-Hollands oogt

Een internationaal kaashandelshuis dat zijn Boerenkazen nog in een origineel kaaspakhuis laat rijpen. In deze ‘snelle’ tijd lijkt het bijna onmogelijk. Toch bestaat het. Zijerveld in Bodegraven heeft zo’n kaaspakhuis in bezit en wil het niet meer kwijt. Een interview

Attempts to select lactic acid bacteria for use as adjuncts have been made, with the purpose of both controlling off-flavors in cheese and enhancing the development of good cheese flavor. A promising application of bacteriocin-producing LAB is a control of adventitious spoilage microorganisms and their use as cell-lysis inducing agents to increase proteolysis and flavor formation in cheese. It is also proposed that cheese could be an effective vehicle for delivery of probiotics to the consumer., Mikroorganizmi imaju ključnu ulogu u toku proizvodnje i zrenja sireva. U tim procesima velika pažnja se poklanja izboru starter kultura, ali se često zaboravlja aktivnost takozvane sekundarne mikroflore koja je specifično vezana za određena svojstva pojedinih vrsta sireva. Ta mikroflora može da posluži kao potencijalni izvor sojeva koji bi ulazili u sastav takozvanih "dopunskih" kultura čija je funkcija poboljšanje senzornih osobina i skraćenje zrenja sireva. U dopunske kulture mogle bi da spadaju i one koje sadrže sojeve koji sintetišu bakteriocine u cilju sprečavanja razvića neželjene mikroflore ili koji ubrzavaju proces liziranja ćelija čime se oslobađa veliki broj intracelularnih enzima bitnih za procese zrenja. Isto tako i primena probiotika u proizvodnji sireva privlači sve veću pažnju, jer su se sirevi pokazali kao dobri vektori za prenos probiotika.

Attempts to select lactic acid bacteria for use as adjuncts have been made, with the purpose of both controlling off-flavors in cheese and enhancing the development of good cheese flavor. A promising application of bacteriocin-producing LAB is a control of adventitious spoilage microorganisms and their use as cell-lysis inducing agents to increase proteolysis and flavor formation in cheese. It is also proposed that cheese could be an effective vehicle for delivery of probiotics to the consumer., Mikroorganizmi imaju ključnu ulogu u toku proizvodnje i zrenja sireva. U tim procesima velika pažnja se poklanja izboru starter kultura, ali se često zaboravlja aktivnost takozvane sekundarne mikroflore koja je specifično vezana za određena svojstva pojedinih vrsta sireva. Ta mikroflora može da posluži kao potencijalni izvor sojeva koji bi ulazili u sastav takozvanih "dopunskih" kultura čija je funkcija poboljšanje senzornih osobina i skraćenje zrenja sireva. U dopunske kulture mogle bi da spadaju i one koje sadrže sojeve koji sintetišu bakteriocine u cilju sprečavanja razvića neželjene mikroflore ili koji ubrzavaju proces liziranja ćelija čime se oslobađa veliki broj intracelularnih enzima bitnih za procese zrenja. Isto tako i primena probiotika u proizvodnji sireva privlači sve veću pažnju, jer su se sirevi pokazali kao dobri vektori za prenos probiotika.

Cheese flavour is an important quality attribute, and is mainly formed during cheese ripening. Besides compounds that are formed from protein and carbohydrates, milk fat-derived compounds are essential for cheese flavour. Before, but mainly during ripening, free fatty acids, lactones, ketones, esters, alcohols and aldehydes can be formed from milk fat, compounds that all contribute their own special character to the final cheese flavour. The formation mechanisms that lead to these compounds are not completely understood, and therefore cheese flavour formation is not under full control.

Para-k-Casein entsteht durch Hydrolyse des kappa-Caseins nach Zugabe proteolytischer Enzyme zur Milch. Untersuchungen an selbst erstellten Modellen unter Bedingungen, die die Käsereifung simulieren, zeigen, dass die Proteolyse des für die Käsereifung bedeutenden para-k-Caseins stark vom Wassergehalt abhängt. Mit Hilfe geeigneter Methoden (SDS-Elektrophorese, IEF, GPC, RP-HPLC, ESI-MS u.a.) konnte der Abbau des para-k-Caseins durch die industriell relevanten Milchgerinnungsenzyme Chymosin, Fromase und Suparen bei unterschiedlichem Wasserangebot verfolgt werden. Para-k-Casein wird bei einem käseüblichen Wassergehalt von 60 % innerhalb von 15 Wochen über wenig höhermolekulare Spaltprodukte überwiegend zu Peptiden mit Molmassen im Bereich von 400-1400 Da abgebaut. Wie elektrophoretische Untersuchungen zeigen, wird para-k-Casein auch im Sauermilchkäse abgebaut. Allerdings ist die Detektion der in sehr geringer Menge entstandenen Hydrolyseprodukte problematisch., K-casein is one of the original casein components in milk. Model-experiments under cheese ripening conditions demonstrate the hydrolysis of para-k-Casein, which is the hydrophobic part of kappa-casein, by rennet and rennet substitutes fromase and suparen. Different water contents influences the dimension of hydrolysis of para-k-Casein. A water content of 60 % usual found in cheese results in a great number of hydrolysis products from para-k-Casein with molecular weights between 400-1400 Da. The hydrolyses was investigated for a time period of 15 weeks by several analytical methods (i.e RP-HPLC, ESI-MS, electrophoretic methods, and others). Investigations by electrophoresis of the ripening process of acid curd cheese demonstrated that para-k-Casein is also hydrolysed in this type of cheese, but the detection is quite difficult.

Para-k-Casein entsteht durch Hydrolyse des kappa-Caseins nach Zugabe proteolytischer Enzyme zur Milch. Untersuchungen an selbst erstellten Modellen unter Bedingungen, die die Käsereifung simulieren, zeigen, dass die Proteolyse des für die Käsereifung bedeutenden para-k-Caseins stark vom Wassergehalt abhängt. Mit Hilfe geeigneter Methoden (SDS-Elektrophorese, IEF, GPC, RP-HPLC, ESI-MS u.a.) konnte der Abbau des para-k-Caseins durch die industriell relevanten Milchgerinnungsenzyme Chymosin, Fromase und Suparen bei unterschiedlichem Wasserangebot verfolgt werden. Para-k-Casein wird bei einem käseüblichen Wassergehalt von 60 % innerhalb von 15 Wochen über wenig höhermolekulare Spaltprodukte überwiegend zu Peptiden mit Molmassen im Bereich von 400-1400 Da abgebaut. Wie elektrophoretische Untersuchungen zeigen, wird para-k-Casein auch im Sauermilchkäse abgebaut. Allerdings ist die Detektion der in sehr geringer Menge entstandenen Hydrolyseprodukte problematisch., K-casein is one of the original casein components in milk. Model-experiments under cheese ripening conditions demonstrate the hydrolysis of para-k-Casein, which is the hydrophobic part of kappa-casein, by rennet and rennet substitutes fromase and suparen. Different water contents influences the dimension of hydrolysis of para-k-Casein. A water content of 60 % usual found in cheese results in a great number of hydrolysis products from para-k-Casein with molecular weights between 400-1400 Da. The hydrolyses was investigated for a time period of 15 weeks by several analytical methods (i.e RP-HPLC, ESI-MS, electrophoretic methods, and others). Investigations by electrophoresis of the ripening process of acid curd cheese demonstrated that para-k-Casein is also hydrolysed in this type of cheese, but the detection is quite difficult.

Para-k-Casein entsteht durch Hydrolyse des kappa-Caseins nach Zugabe proteolytischer Enzyme zur Milch. Untersuchungen an selbst erstellten Modellen unter Bedingungen, die die Käsereifung simulieren, zeigen, dass die Proteolyse des für die Käsereifung bedeutenden para-k-Caseins stark vom Wassergehalt abhängt. Mit Hilfe geeigneter Methoden (SDS-Elektrophorese, IEF, GPC, RP-HPLC, ESI-MS u.a.) konnte der Abbau des para-k-Caseins durch die industriell relevanten Milchgerinnungsenzyme Chymosin, Fromase und Suparen bei unterschiedlichem Wasserangebot verfolgt werden. Para-k-Casein wird bei einem käseüblichen Wassergehalt von 60 % innerhalb von 15 Wochen über wenig höhermolekulare Spaltprodukte überwiegend zu Peptiden mit Molmassen im Bereich von 400-1400 Da abgebaut. Wie elektrophoretische Untersuchungen zeigen, wird para-k-Casein auch im Sauermilchkäse abgebaut. Allerdings ist die Detektion der in sehr geringer Menge entstandenen Hydrolyseprodukte problematisch., K-casein is one of the original casein components in milk. Model-experiments under cheese ripening conditions demonstrate the hydrolysis of para-k-Casein, which is the hydrophobic part of kappa-casein, by rennet and rennet substitutes fromase and suparen. Different water contents influences the dimension of hydrolysis of para-k-Casein. A water content of 60 % usual found in cheese results in a great number of hydrolysis products from para-k-Casein with molecular weights between 400-1400 Da. The hydrolyses was investigated for a time period of 15 weeks by several analytical methods (i.e RP-HPLC, ESI-MS, electrophoretic methods, and others). Investigations by electrophoresis of the ripening process of acid curd cheese demonstrated that para-k-Casein is also hydrolysed in this type of cheese, but the detection is quite difficult.

Para-k-Casein entsteht durch Hydrolyse des kappa-Caseins nach Zugabe proteolytischer Enzyme zur Milch. Untersuchungen an selbst erstellten Modellen unter Bedingungen, die die Käsereifung simulieren, zeigen, dass die Proteolyse des für die Käsereifung bedeutenden para-k-Caseins stark vom Wassergehalt abhängt. Mit Hilfe geeigneter Methoden (SDS-Elektrophorese, IEF, GPC, RP-HPLC, ESI-MS u.a.) konnte der Abbau des para-k-Caseins durch die industriell relevanten Milchgerinnungsenzyme Chymosin, Fromase und Suparen bei unterschiedlichem Wasserangebot verfolgt werden. Para-k-Casein wird bei einem käseüblichen Wassergehalt von 60 % innerhalb von 15 Wochen über wenig höhermolekulare Spaltprodukte überwiegend zu Peptiden mit Molmassen im Bereich von 400-1400 Da abgebaut. Wie elektrophoretische Untersuchungen zeigen, wird para-k-Casein auch im Sauermilchkäse abgebaut. Allerdings ist die Detektion der in sehr geringer Menge entstandenen Hydrolyseprodukte problematisch., K-casein is one of the original casein components in milk. Model-experiments under cheese ripening conditions demonstrate the hydrolysis of para-k-Casein, which is the hydrophobic part of kappa-casein, by rennet and rennet substitutes fromase and suparen. Different water contents influences the dimension of hydrolysis of para-k-Casein. A water content of 60 % usual found in cheese results in a great number of hydrolysis products from para-k-Casein with molecular weights between 400-1400 Da. The hydrolyses was investigated for a time period of 15 weeks by several analytical methods (i.e RP-HPLC, ESI-MS, electrophoretic methods, and others). Investigations by electrophoresis of the ripening process of acid curd cheese demonstrated that para-k-Casein is also hydrolysed in this type of cheese, but the detection is quite difficult.

The most significant issues that describe biochemical changes during cheeses ripening have been shown in this work. The changes that occur on carbohydrates, proteins and milk fat, contribute in development of aroma and texture, which are typical for particular group of cheese. The next enzymes participate in cheese ripening: clotting enzymes; indigenous milk en­zymes; starter cultures and their enzymes; enzymes from secondary starters; non-starter lactic acid bacteria (adjunct cultures); non-starter bacteria that either survive pasteurization or contaminate milk after pasteurization. Also, the content of whey proteins in cheese has very important influence on ripening. The reviewed issues are very important for science and practice. On the second hand, the way in which technological process is managed has the great influence on biochemical changes that occur during cheese ripening. ., U radu su razmotrena najznačajnija pitanja koja definišu biohemijske promene u toku zrenja sireva. Ove promene se dešavaju na ugljenim hidratima, proteinima i mlečnoj masti i doprinose formiranju arome i teksture karakteristične za određenu vrstu sira. U zrenju sireva učestvuju: koagulanti različitog porekla; nativni enzimi mleka; starter kulture i njihovi enzimi; enzimi sekundarnih startera; ne-starterske bakterije mlečne kiseline - dopunske kulture ('adjunct' culture) koje imaju primenu kod ubrzanog zrenja; ne-starterske bakterije, koje preživljavaju pasterizaciju mleka ili dospevaju u mleko nakon pasterizacije, kao i sadržaj serum proteina u siru. Sva ova pitanja su od izuzetnog značaja ne samo za nauku, već i za praksu. Biohemijske promene koje se dešavaju tokom zrenja sireva, rezultat su, pre svega, načina vođenja tehnološkog procesa prilikom izrade sireva. .

Lactic acid bacteria are gram-positive bacteria that are widely used in a variety of dairy fermentation processes. Notably, strains of the lactic acid starter bacterium Lactococcus lactis are of great economic importance because of their world-wide use in cheese making. The characteristic aroma, flavor and texture of cheese develops during ripening of the cheese curd through the action of numerous enzymes derived from the cheese milk, the coagulant, and the starter and non-starter bacteria. Ripening is a slow and consequently an expensive process that is not fully predictable or controllable. Principal methods by which accelerated ripening may be achieved include: an elevated ripening temperature, use of modified or adjunct starters, addition of exogenous enzymes, and use of cheese slurries. The advantages, limitations, technical feasibility and commercial potential of these methods are discussed in Chapter 1 of this thesis.Since the growth of lactococci ceases at or shortly after the end of curd manufacture, their intracellular enzymes are ineffective until the cells die and lyse. It would be expected that the sooner starter enzymes are released through lysis, the sooner they can participate in flavor forming reactions and hence the faster the rate of cheese ripening could be. There is not a single compound or class of compounds which appears to be responsible for the full flavor of cheese. Several volatile components contribute to the flavor of cheese. In hard-type cheeses, such as Gouda and Cheddar, proteolytic enzymes from mesophilic lactococci play a crucial role in the formation of free amino acids during ripening. The enzymes from lactococci are also very important for the formation of flavor components from amino acids. However, to promote an adequate interaction between substrates and enzymes, lysis of cells leading to the release of intracellular enzymes into the cheese matrix, is considered to be essential.In order to improve the properties of fermented p

Semi-hard cheese types, such as Gouda, cannot be satisfactorily produced when using ultrafiltration technology. Although the cheese yield increases using this method, the higher financial return is completely lost by the (poor) quality of the cheese. The work described in this thesis is directed at improving, by microbiological methods, the quality of e.g. Gouda cheese made from ultrafiltered milk. In the course of the work, some fundamental questions were raised on growth behaviour of lactic acid bacteria in UF concentrated milk in relation to regular milk, on survival and stability of the bacteria in regular cheese and on the principles of flavour development during cheese ripening.Growth characteristics of starter bacteria in milk concentrated by ultrafiltration. Chapter 2 describes the growth behaviour of Lactococcus lactis in UF concentrated milk in relation to regular milk. The total amount of biomass of L. lactis subsp. cremoris E8 and the mixed strain starter culture Bos decreased gradually by 25 and 40%, respectively, when growing in UF-retentates with increasing concentration factors up to a factor 3.6 compared with the total growth reached in regular milk. The cause of the decreased outgrowth found in UFretentates is not precisely known, but it is clearly related to the increased concentration of whey proteins in the UF-retentate.Regulated production of proteolytic enzymes. The enzymes of the proteolytic system, composed of the extracellular serine proteinase and the intracellular peptidases, hydrolyse in concerted action the milk proteins into amino acids. The proteolytic activity of lactococci is crucial for growth in milk. In cheese milk the degradation of casein is hydrolysed by the combined activity of chymosin and proteolytic enzymes. During maturation of cheese the pool of amino acids contribute, either directly or as precursor for flavour compounds, to the final cheese flavour (8). In contrast to the wealth of knowledge on the biochemical and gene

Aandacht voor een onderzoek naar factoren die de produktie van proteolytische enzymen door melkzuurbacterien remmen

Model cheeses were developed to study the behaviour of proteolytic agents involved in cheese maturation under conditions that closely resemble those in normal cheese. The models were applied to study protein breakdown by Lactococcus lactis ssp. cremoris HP , as a function of various ripening variables. Proteolysis was monitored by several methods; amino acid-N determinations and amino acid analyses were best suited for quantitatively following protein breakdown. Amino acid production was enhanced at a higher pH, at a lower NaCl content and at a higher ripening temperature of cheese; much larger quantities of amino acids were produced from paracasein being predigested by rennet than from untreated paracasein. Ratios of paracasein to water of 1:2.5 or 1:3.5 did not significantly affect amino acid formation by the starter strain. Compared to intact cells, lysed cells drastically enhanced amino acid production; the results pointed to lysis of a (minor) part of the starter population. It is argued that the use of these model systems can produce unequivocal results.

[EN]: Eight wild-type strains belonging to lactococci, lactobacilli or leuconostoc species were tested as starter cultures in the production of semi-hard goat's milk cheese. The screening of the strains in cheesemaking was in a laboratory scale production. Eleven batches were produced using a combination of the strains in different proportions as starters. Two control batches were made, one from raw milk without starter and another from pasteurized milk with a commercial starter. The strains used in the cheeses that received the best scores in the laboratory scale production were assayed in a pilot scale cheesemaking process. The control batch was produced from raw milk without starter. The starter containing Lactococcus lacb's subsp lactis IFPL 359, Lactobacillus casei subsp casei IFPL 731, Lactobacillus plantarum IFPL 935, Leuconostoc mesenteroides subsp dextranicum IFPL 709 and Leuconostoc paramesenteroides IFPL 705 provided the cheeses with the best characteristics after 60 d of ripening. Lactococci were the most abundant flora in the cheeses, and lactobacilli attained high counts on conclusion of ripening. The cheeses presented nitrogen fractions higher than in the control. The experimental cheeses displayed small, evenly-distributed openings and were awarded maximum scores for flavor, texture and general acceptability., [FR]: Huit souches sauvages de lactocoques, de lactobacilles et de leuconostocs ont été testées en tant que levain pour la fabrication de fromages de chèvre à pâte semi-dure. L'étude des souches, dans un premier temps, a été réalisée au laboratoire. Onze levains, composés de différents mélanges des 8 souches, ont été utilisés pour la fabrication de fromages. Deux fabrications témoins, l'une à base de lait cru sans levain et l'autre à base de lait pasteurisé ensemencé avec un levain du commerce, ont aussi été réalisées. Après évaluation de la qualité des fromages obtenus, les meilleurs levains ont été testés à l'échelle pilote. Le levain contenant les souches Lactococcus lactis subps lactis IFPL 359, Lactobacillus casei subsp casei IFPL 731, Lactobacillus plantarum IFPL 935, Leuconostoc mesenteroides subsp dextranicum IFPL 709 et Leuconostoc paramesenteroides IFPL 705 a donné les meilleurs fromages, après 60 j d'affinage. À l'issue de la période d'affinage, la flore de ces fromages était composée en majorité de lactocoques. Les lactobacilles étaient aussi très abondants. La fraction azotée était plus importante dans les fromages expérimentaux que dans les fromages témoin. Les fromages obtenus avec ce levain avaient une ouverture petite et régulière, un goût et une texture optimales et, en général, étaient de qualité supérieure.