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ABSTACT Rennet milk curds were prepared under 4 different temperature and acidity conditions. The development of different types of inter-protein chemical bonds (disulfide, hydrophobic, electrostatic, hydrogen, and calcium bridges) was monitored for 60 min after curd cutting. Hydrophobic inter-protein interactions originally present in casein micelles in milk were substituted by electrostatic, hydrogen, and calcium bonds throughout the curd curing period. Disulfide bonds were not disturbed by the experimental conditions employed in the study, remaining at a constant level in all studied treatments. Acidification of curds increased the availability of soluble ionic calcium, increasing the relative proportion of calcium bridges at the expense of electrostatic-hydrogen bonds. Although pH defined the nature of the interactions established among proteins in curd, temperature modified the rate at which such bonds were formed.

Sucrose detection and discrimination thresholds were determined by conducting two alternative forced-choice tests with aqueous solutions. The standard models probit and logit, and non-linear were fitted to the empirical psychometric functions. 0, 7 and 15 g/L sucrose solutions were used as standard stimuli in the detection and discrimination experiments (two levels) respectively. Comparison stimuli consisted of aqueous sucrose solutions with concentrations from 0.5 to 25 g/L. Observed absolute threshold was around 2.96 g/L and the difference limen for 7 and 15 g/L standard stimuli was around 2.98 g/L and 5.29 g/L, respectively. Calculated Weber fractions for 7 and 15 g/L standard stimuli were 0.42 and 0.35, respectively. Judges' performance in the discrimination experiment was similar to that observed in the detection experiment. Goodness of fit for probit and logit models was similar. The non-linear model showed a lower average error and demonstrated an excellent predictive ability.

En el presente trabajo se estudió el efecto del uso de métodos tradicionales para la cocción del frijol: remojo, cocción en olla de barro o de presión, y adición de especias (laurel o epazote). Con respecto al ácido fítico, los resultados muestran que la cocción en olla de presión con previo remojo, es el método que disminuye en mayor proporción la concentración de este factor antinutricional. Para la disminución de α-oligosacáridos rafinosa y estaquiosa, el remojo es el tratamiento que da una mejor respuesta para disminuir los α-galactosacáridos. La cocción en olla de barro disminuye considerablemente estos compuestos en comparación con el uso de olla a presión. El uso de hojas de epazote y de laurel fue muy efectivo para disminuir la concentración de oligosacáridos, además de inhibir el crecimiento microbiano. Por otro lado el uso de presión en la cocción fue el más efectivo para la disminución de la actividad de los inhibidores de tripsina. Una combinación de cocina tradicional mexicana (uso de especias) y cocina moderna (olla a presión) es la mejor manera de disminuir los compuestos antinutricionales y preservar la calidad microbiana de los frijoles cocidos. Estos resultados muestran la importancia de estudiar y preservar la cocina tradicional mexicana.

This study aimed to characterize the quality and bioactive compounds from five cultivars grown in Mexico´s northern region: Heritage, Summit, Harvest, and red and yellow Autumn. The physicochemical characteristics, DPPH anti-radical capacity, total phenolics, flavonoid and anthocyanins, polyphenolic profile, and ascorbic acid levels of the raspberries were assessed. The Harvest cultivar presented the highest weight and firmness and the lowest yield, total phenolics, and flavonoids. The yellow Autumn Bliss contained higher concentrations of polyphenols and ascorbic acid, and the red Autumn Bliss contained higher concentrations of flavonoids and anthocyanins and possessed a greater antioxidant capacity. The polyphenol profile indicated the presence of seven phenolic acids, namely, ellagic, gallic, caffeic, chlorogenic, p-coumaric, hydroxybenzoic, and protocatechuic acids; and four flavonoids, namely, catechin, quercetin-3-β-D-glucoside, quercetin-3-glucuronide, and rutin; these compounds were present in all the varieties, except for rutin, in yellow Autumn Bliss. The results of this study highlight the most valuable raspberry cultivars in terms of weight and firmness (Harvest), yield (Heritage), polyphenols and ascorbic acid (yellow Autumn Bliss), and anthocyanins and antioxidant capacity (red Autumn Bliss) in raspberries grown in northern Mexico.

Cotton (Gossypium hirsutum L.) is an important fibre crop of global significance. It is mainly utilised for the textile industry, and its seeds as cattle feed and to re-harvest fields. However, an important amount of the cottonseed obtained during processing is discarded. Some reports indicate that cottonseed contains high-quality protein and important lipid content. The aim of the present study was to compare different extraction methods (Soxhlet, mechanical and ultrasound-assisted) in order to achieve the highest extraction yield of cottonseed oil (CSO). The extraction efficiency was measured based on the effects of temperature, organic solvent (OS), extraction time and solvent:seed (s:s) ratio, using a Box-Behnken 34 experimental design. From our results, ultrasound-assisted extraction had the highest extraction yield (38.25%) at 45 oC, after 1 h for a 10:1 ratio using Folch mixture as OS. Palmitic, oleic and linoleic acids were the main residues in the characterised CSO, and this oil can be utilized for biodiesel production. This research intends to promote the use of this agroindustrial by-product to add value to cottonseed.

Background Phages are ubiquitous in the environment and have been used successfully as biological control agents against pathogenic microorganisms in some food systems. However, the use of phages for biocontrol strategies at a commercial scale in the food industry as a whole still faces some challenges. Scope and approach Better strategies to address interference by food matrices and environmental conditions still need to be found. The basic mechanisms involved in the phage infection process in complex systems such as milk and dairy products still need to be clarified. It is well known that receptors of the bacterial cell wall play a key role in the infection process. In the present paper, several criteria were proposed regarding the way in which the interactions between the phage-host system and food may occur and how these interactions could affect the treatment effectiveness. Key findings and conclusions According to the current knowledge in the field, we identify two key interfering principles, namely, food structure and milk compounds with binding or bioactive capacity. Food structure is related to phage diffusion, and gel dairy products are the main foods that limit the encounter between phages and bacteria. Milk compounds, such as proteins, lipids, carbohydrates and bioactive compounds can compete with binding sites in phage-host systems, leading to a decrease in treatment effectiveness.

The effect of milk homogenization conditions, including speed (17,400 rpm; 20,600 rpm; and 24,000 rpm) and time (5–25 min) on phage affinity in milk fractions was investigated. A broad host-range Listeria phage (A511) was inoculated. Milk fractions separation was carried out and phage enumeration was expressed as percentage of added phages. A maximum quantifiable phage of 42.6% was obtained in unhomogenized milk. Homogenization (5 min, at any speed) further reduced quantifiable phages (15.9–20.6%), but this percentage increased as homogenization time increased. Phage distribution in unhomogenized milk showed preference for fat followed by caseins. Milk homogenization caused milk fat to lose its ability to bind phages, inducing phages to bind to caseins preferentially. Whey was the milk fraction with the lowest affinity for phage. The effect of homogenization speed and time on phage affinity was only observed in caseins. A correlation between phages bound to caseins, fat surface area and fraction Φ was observed.

The effect of water content on the flow factor of pectin powder was investigated. Water content was expressed either as water activity or as moisture content. A new methodology intended to vary independently water activity and moisture content was proposed in this study. The proposed methodology allowed to generate powders with similar moisture content but different water activity values. As expected flow factor decreased as water content increased. Powder water activity showed to be a better descriptor of the effect of water content on flow factor than powder moisture content.

It has been reported that polysaccharides like carrageenan can change the crystallization of lactose. However, it is still unclear whether changes in lactose mutarotation, solubility, and super-solubility are involved in carrageenans' effect on lactose crystallization. It has been established that the conversion of α- to β-lactose forms (mutarotation) in an aqueous solution has a significant impact on lactose crystallization. Similarly, lactose solubility changes lead to changes in the metastable zone (MZ), a region between the solubility and super-solubility of lactose. The width of this MZ determines the temperature drop necessary to induce lactose nucleation. This work aimed to study the effect of carrageenans on lactose mutarotation and solubility. For this purpose, lactose solutions were added with ι and κ- carrageenan at two concentrations: 50 and 100 mg L−1. Optical rotation measurements estimated the proportion of β/α isomers in lactose solutions. Besides, solubility and super- solubility was determined to build the MZ. The presence of carrageenans changed both the time to reach the mutarotation balance and the proportion of β/α isomers at mutarotation equilibrium. Carrageenans decreased the solubility of lactose in a range of temperatures between 10 and 60 °C and reduced the metastable zone width (MZW).

Cotton (Gossypium hirsutum L.) is an important fibre crop of global significance. It is grown and harvested in tropical and subtropical regions of more than 80 countries. The state of Chihuahua, in Mexico, is the leader in the production of cotton covering 70% of national production. According to statistics reported in 2016, 488,000 metric tons were obtained and utilized as follows: 93% for textile industry, 2.28% as cattle feed, 1.1% was re-harvested, and the other 3.56% was discharged, and in consequence an environmental impact occurs. That remaining cottonseed constitutes a potential agroindustry residue with biotechnological applications due to its chemical composition: fibre, proteins (as well as essential amino acids such as lysine, methionine, tryptophan, and other amino acids) carbohydrates, and lipids (it is important to highlight gossypol and the fatty acids profile). In this chapter, food and bioenergy applications of cottonseed in terms of bioactive compounds (phenolic content), bioactivity (antioxidant activity), and lipid content (production of biodiesel) are reviewed, as well as the chemical compounds responsible of such applications, different types of extraction methods and analytical protocols for their identification, purification, and quantification.

The influence of environmental factors such as glycerol concentration, time of production, presence of Escherichia coli, and two different strains of Lactobacillus reuteri (ATCC 55730 and ATCC 53608) on 3-hydroxypropionaldehyde (3-HPA) production was analyzed. Additionally, the influence of those factors on gene expression in the 3-HPA production pathway was evaluated. The genes studied were GldC, cbiP, and Lreu_1734. The results of this study showed that the principal environmental factors that influence 3-HPA production are glycerol concentration and Lactobacillus reuteri strain. As glycerol concentration increased, 3-HPA content increased. The greatest 3-HPA concentration (56.6 mM ±5.99) was achieved by L. reuteri ATCC 55730. Gene expression was also affected by environmental factors. Factor that showed the greatest influence were also strain and glycerol concentration. The genes cbiP, GldC, and Lreu_1734 had basal gene expression in glycerol absence; however, glycerol regulated its expression. Glycerol induced overexpression of cbiP and GldC genes (Strain ATCC 53608), probably to ensure its efficient utilization. On the contrary, glycerol concentration suppressed Lre_1734 expression in both analyzed strains, as a mechanism for 3-HPA accumulation. Down-regulation was observed in all the genes tested in strain ATCC 55730, probably due to feedback inhibition by 3-HPA.

Melissococcus plutonius is a pathogenic bacterium that affects honeybee brood triggering colony collapse in severe cases. The bacterium causes a European foulbrood (EFB) disease in the honeybee populations, impacting beekeeping and agricultural industries. The pathogenesis, epidemiology, and variants of M. plutonius have been studied, but the virulence factors involved in larval infection are still unknown. Recently, an in-silico study suggested putative genes that might play a role in the pathogenesis of EFB. However, studies are required to determine their function as virulence factors. In addition, the few studies of clonal complexes (CCs), virulence factors, and variation in the honeybee larvae mortality have interfered with the development of more efficient control methods. The research, development, and differences in virulence between genetic variants (CCs) of M. plutonius and potential virulence factors implicated in honeybee larval mortality are discussed in this review.

Bacterial cell surface hydrophobicity is a relevant property in determining the ability of bacteria to adhere to inert surfaces. This property has been measured using the microbial adhesion to hydrocarbon (MATH) test. Several reports in the literature establish the percentage of adhesion to hydrocarbons (PoAtH) value produced by the MATH test for a broad variety of bacteria. Discrepancies in PoAtH values reported for the same strain of a specific microorganism suggest that some method-induced variation may exist, as different research teams employ different versions of the assay. The objective of the present study was to compare the performance of different versions of the MATH test as reported in the literature, to quantify the magnitude of the method-induced variation on PoAtH values. The study demonstrated that PoAtH values are influenced twice as much by variations in the employed assay than by actual differences in cell surface composition or architecture. The two L. reuteri strains studied responded differently to changes in assay conditions showing 40 and 70% method-dependent variation for strain ATCC 53609 and 55730, respectively. These results highlight the need to properly standardize the MATH test to enable comparison of PoAtH values produced by independent research teams.

Hygroscopic powders adsorb water from air humidity, increasing their cohesion and decreasing their flowability. Maltodextrin, pectin and starch powders were used to evaluate the correlation between flow factor and water content expressed both, as absolute moisture, and as water activity. Powder water content was adjusted through exposition to high relative humidity atmospheres. Maltodextrin and starch powders did not change their flowing behavior within the studied range, remaining easy-flow and cohesive powders respectively. Pectin powder, on the other hand, adsorbed water up to 12% (w/w), modifying its flowability from free-flow, to easy-flow, to cohesive powder. Powders flow factor changed as water content increased in all tested conditions. However, flow factor showed to be better correlated to water activity than to absolute moisture content. These results suggest water activity may be a better parameter to describe the effect of water content on powder flowability than absolute moisture.

We assessed the antimicrobial activity of reuterin produced in vitro in glycerol aqueous solutions in situ by Lactobacillus reuteri ATCC 53608 as part of a fermented milk product against starter (Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus), spoilage (Penicillium expansum), pathogenic (Staphylococcus aureus Salmonella enterica ssp. enterica, and Listeria monocytogenes), and pathogen surrogate (Escherichia coli DH5α) microorganisms. We also assayed the influence of cold storage (28 d at 4°C) and reuterin on the color and rheology of the fermented milk product. We obtained maximum reuterin concentrations of 107.5 and 33.97 mM in glycerol aqueous solution and fermented milk product, respectively. Reuterin was stable throughout its refrigerated shelf life. Gram-positive microorganisms were more resistant to reuterin than gram-negative microorganisms. Penicillium expansum and Lactobacillus reuteri ATCC 53608 survived at concentrations up to 10 and 8.5 mM, respectively. Escherichia coli DH5α was the most sensitive to reuterin (0.9 mM). The presence of reuterin did not cause relevant changes in the quality parameters of the fermented milk product, including pH, acidity, soluble solids, color, and rheological aspects (storage and loss moduli and viscosity). This study demonstrated the viability of using Lactobacillus reuteri ATCC 53608 as a biopreservative in a fermented milk product through reuterin synthesis, without drastically modifying its quality parameters.

Milk curds are a semisolid structure resulting from the enzymatic coagulation of milk, consisting mainly of paracasein micelles, fat globules, and whey. This gel undergoes a series of changes in its composition and structure during setting and curing, affecting curd density. The present study investigated the composition and density of inoculated and noninoculated milk curds during a 60-min curing period conducted at 30, 35, and 40°C. The purpose of the study was to determine the density changes occurring in the protein phase of curds during curing under different conditions of temperature and pH to understand the nature of the structural changes happening in the paracasein matrix. Noninoculated curd density values oscillated between 1.0247 and 1.0294 g/cm3 after 60 min of curing, whereas inoculated treatments showed values between 1.0222 and 1.0321 g/cm3. This small difference in density between the studied samples was surprising because the whey content of samples differed greatly. Density of the protein phase reached values of 1.8002 and 1.4388 g/cm3 for noninoculated and inoculated curds, respectively, after 60 min of curing. Two independent mechanisms involved in the development of the protein-based structure of curds were identified upon comparison of the development of protein phase density in inoculated and noninoculated curds. Although the larger increase in protein phase density observed in noninoculated curds was probably due to the concurrent action of calcium-mediated electrostatic bonds and temperature-dependent hydrophobic bonds, inoculated curds showed a lower protein phase density caused by calcium solubilization and by a decrease in the net charge of paracasein micelles induced by pH reduction.

Raspberries are important sources of bioactive compounds, whose synthesis is influenced by the fertilization system and the maturity stage. This study evaluated the effect of organic and conventional fertilization systems on raspberries at three maturity stages, pink, ripe, and overripe. Physicochemical characteristics, bioactive compounds (phenolic profile, vitamin C), antioxidant capacity (DPPH, FRAP, TEAC, and ORAC), phenolic-associated enzyme, phenylalanine ammonia lyase (PAL), and antioxidant enzymes (SOD, CAT, GPx, and APX) were evaluated. The physicochemical determination of the fruit did not reveal differences between fertilization systems. Regarding bioactive compounds, higher content of anthocyanins was found in organic raspberries at all maturity stages. Organic fertilization increased the content of ellagic acid and gallic acid at all stages of maturity. Higher content of caffeic, hydroxybenzoic, protocatechuic acid, and vitamin C was observed in organic raspberry at the overripe stage. Raspberries grown with organic fertilization exhibited higher values of antioxidant capacity by the DPPH, FRAP, and TEAC methods at all maturity stages. Raspberries under organic fertilization showed significantly greater activity of CAT, SOD, APX, GPX, and PAL. The present study suggests that organic fertilization induces oxidative stress causing an increase in antioxidant defense mechanisms, enhancing bioactive compound production, and improving antioxidant capacity in raspberries.

Apples have distinctive quality attributes that may be defined by environmental conditions of the geographical regions where fruits are cultivated, such as temperature, solar radiation, photoperiod, and photothermic units. A three-year study was conducted to compare ‘Golden Delicious’ and ‘Red Delicious’ apples from two different regions, Washington, USA (WA) and Chihuahua, Mexico (CHIH). Apple samples were harvested weekly from early August to late October (~120-180 days after full bloom - DAFB), and analysed for quality parameters. Geographic environmental data were obtained, and photoperiod, solar radiation, degree-days and photothermal units were calculated. Results show quality differences between CHIH and WA apples. WA shows a ~5-week delay in apple bloom, possibly due to the lower temperatures presented in WA. Apples from both regions required the same photoperiod, ~ 2,222 h, to attain the beginning of the ripening stage, which took more days (three weeks) for CHIH apples, most likely attributed to the higher elevation of CHIH orchards (2,062 vs. 763 masl). The main distinctive quality differences found between WA and CHIH apples were firmness and aroma volatile compounds. CHIH apples presented substantially higher amounts of aroma compounds. WA apples showed greater firmness, probably due to lower photothermal units. Using all firmness data (both varieties, both growing zones) a remarkable correlation was found between firmness and photothermal units (R=0.89), which may suggest firmness could be improved by the manipulation of degree days and photoperiod, that is, temperature and light.

Introduction. The use of hail nets to protect apples during development and maturation on the tree is very common in Mexico. This practice can cause changes in fruit quality and aroma composition. The effects of the hail net color on the quality and aroma volatile production of apple cultivated in Chihuahua, Mexico, were evaluated. Materials and methods. ‘Golden Delicious’ apple trees were covered with white or black hail nets. Apple samples were harvested weekly from August to early October, and analyzed for weight, axial and equatorial diameters, color (°Hue), firmness, total soluble solids (TSS), acidity, ethylene production (EC), and aroma volatile composition. The photosynthetically available radiation (PAR) was measured every ten days under each hail net and outside. Results and discussion. Apple quality was affected by hail net color. Black hail nets delayed maturation and quality development of apples by one week when compared with white hail nets. The PAR values were 18% lower under black nets than under white nets. Quality parameters at commercial harvest (162 days after full bloom) showed that white-net apples presented 7% lower firmness, 11.1% less acidity, 8.3% higher TSS and a more developed yellow color, when compared with black-net apples. In addition, white-net apples presented higher contents of the main aroma compounds (in μg L-1 ) 1-hexanol (8.09 vs. 4.38), 2-methyl-1-butanol (6.24 vs. 2.65), and 2-methyl-butyl acetate (0.47 vs. 0.16). At the same maturity stage (beginning of the climacteric rise), no difference was found between white- and black-net apples in TSS, acidity, firmness and aromatic compounds. Conclusion. Hail net functionality goes beyond protecting orchards from hail damage; hail net color affects the apple maturation rate, quality and aroma volatile production.

There is great interest in the dairy industry to find new ingredients or technologies that improve the textural and rheological properties of cream cheese. In this work, it was assessed the use of high-energy ultrasound as an alternative to modify the textural and rheological properties of cream cheese. Cream cheeses were made with milk sonicated at varying combinations of ultrasound power (0–100 W), temperatures (4–63 °C) and times (0–30 min). The main results showed that thermosonication (TS) of the milk reduced the size of milk-fat globules and increased the fat content and yield of cream cheese. Furthermore, the TS of the milk improved the thermostability of the cream cheese significantly. The best textural and rheological properties of cream cheeses were observed in those cheeses made with milk TS at 50 W for long times (⩽30 min) and applying temperatures between 35 and 50 °C.

The growing demand for natural and minimally processed products, is influencing the use of natural antimicrobials such as bacteriophages. However, their application has presented some challenges regarding to their stability into the food. This has forced the food industry to look for alternatives. One possible alternative has been the combination of bacteriophages with emerging technologies, which offers a synergistic effect for bacterial reduction. Either alone or in combination with other technologies, bacteriophages have had a variable response in each food. A detailed knowledge regarding the influence of food and emerging technologies on phage stability is not available yet. This review will give an overview over the effect of both the emerging technologies itself and the impact of food matrix on phage stability, also it will discuss on the possible mechanisms by which bacteriophages are not stable in food systems.

Raw milk and milk fractions were analysed for their activity against the bacteriophage A511. The whole milk was separated into fat, casein and whey. Fat was fractionated further into butter serum, butter oil, butter milk and milk fat globule membrane. Bacteriophage was inoculated and was enumerated at different time periods (0, 24, 48, 72 and 96 h). Results (plaque-forming units, PFU) showed that raw milk reduced phage counts 2.4 log10 PFU mL−1. Among milk fractions, fat and whey were the most active fractions, reducing the phage titre 2.6 and 2.1 log10 PFU mL−1, respectively, compared with 0.8 log10 PFU mL−1 in casein. Fat fractions also influenced phage stability. The main effect was attributed to the milk fat globule membrane (2.1 log10 PFU mL−1 reduction) followed by butter milk and butter serum (1.0 log10 PFU mL−1 reduction). Butter oil showed no effect on phage stability.

One of the main quality parameters in apples is aroma, its main precursors are fatty acids (FA) and amino acids (AA). In this study, alginate edible coatings were used as carriers of linoleic acid or isoleucine to serve as precursors for the production of aroma in cut apples. Apple wedges were immersed in a CaCl2 solution and coated with one of the following formulations: alginate solution (Alg-Ca), Alg-Ca-low-level linoleic acid (0.61 g/Lt), (LFA), Alg-Ca-high-level linoleic acid (2.44 g/L; HFA), Alg-Ca-low-level isoleucine (0.61 g/L; LAA), and Alg-Ca-high-level isoleucine (2.44 g/L; HAA). Apple wedges were stored at 3 °C and 85% relative humidity for 21 d and key volatiles were studied during storage. Addition of precursors, mainly isoleucine, showed to increase the production of some key volatiles on coated fresh-cut apples during storage. The concentration of 2-methyl-1-butanol was 4 times higher from day 12 to day 21 in HAA, while 2-methyl butyl acetate increased from day 12 to day 21 in HAA. After 21 d, HAA-apples presented a 40-fold value of 2-methyl-butyl acetate, compared to Alg-Ca cut apples. Values of hexanal increased during cut apple storage when the coating carried linoleic acid, mainly on HFA, from 3 to 12 d. The ability of apples to metabolize AA and FA depends on the concentration of precursors, but also depends on key enzymes, previous apple storage, among others. Further studies should be done to better clarify the behavior of fresh-cut apples as living tissue to metabolize precursors contained in edible coatings for the production of volatiles.

Chihuahua cheese or Mennonite cheese is one of the most popular and consumed cheeses in Mexico and by the Hispanic community in the United States. According to local producers the yield of Chihuahua cheese ranges from 9 to 9.5 kg of cheese from 100 kg of milk. Cheese yield is a crucial determinant of profitability in cheese-manufacturing plants; therefore, different methods have been developed to increase it. In this work, a miniature Chihuahua-type cheese model was used to assess the effect of a phospholipase A1 (PL-A1) and exopolysaccharide (EPS)-producing bacteria (separately and in combination) on the yield, microstructure, and texture of cheese. Four different cheeses were manufactured: cheese made with PL-A1, cheese made with EPS-producing bacteria, cheese with both PL-A1 and EPS-producing bacteria, and a cheese control without PL-A1 or EPS-producing bacteria. The compositional analysis of cheese was carried out using methods of AOAC International (Washington, DC). The actual yield and moisture-adjusted yield were calculated for all cheese treatments. Texture profile analyses of cheeses were performed using a texture analyzer. Micrographs were obtained by electron scanning microscopy. Fifty panelists carried out sensorial analysis using ranking tests. Incorporation of EPS-producing bacteria in the manufacture of cheese increased the moisture content and water activity. In contrast, the addition of PL-A1 did not increase fat retention or cheese yield. The use of EPS alone improved the cheese yield by increasing water and fat retention, but also caused a negative effect on the texture and flavor of Chihuahua cheese. The use of EPS-producing bacteria in combination with PL-A1 improved the cheese yield and increased the moisture and fat content. The cheeses with the best flavor and texture were those manufactured with PL-A1 and the cheeses manufactured with the combination of PL-A1 and EPS-producing culture.

This study investigated the effect of high hydrostatic pressure treatments on mycelial development, spore viability, and total proteolytic and lipolytic activity of Penicillium roqueforti PV-LYO 10 D. Fungus growing in liquid medium was pressure-treated at 300, 400, and 500 MPa for 10 min at 20 °C following seven days of incubation at 25 °C and analyzed periodically up to day 9 after treatments to evaluate the effect on fungal growth. Mycelial mass of P. roqueforti was significantly affected at all pressure treatments evaluated, being 15.48%, 22.28%, 30.03%, and 12.53% lower than controls on day 1, 3, 6, and 9 after 300 MPa treatment, respectively. In a similar way, at 400 and 500 MPa, mycelial mass was 31.08% and 60.34% lower than controls one day after treatments and 49.74% and 80.85% lower on day 9, respectively. The viability of P. roqueforti spores decreased by 36.53% at 300 MPa, and complete inactivation took place at ≥ 400 MPa from an initial count of 7 log cfu/mL. Total proteolytic activity was not significantly affected at 300 MPa but was reduced by 18.22% at 400 MPa and by 43.18% at 500 MPa. Total lipolytic activity also decreased as the intensity of the pressure treatments increased. 21.69%, 39.12%, and 56.26% activity reductions were observed when treatments of 300, 400 and 500 MPa were applied, respectively. The results from this study show that pressure treatments are able to control growth, inactivate spores, and alter enzyme activity of P. roqueforti, which could be of interest in extending the shelf-life of blue-veined cheeses and other food products.

Raw and heat-treated (boiled and grilled) pungent and non-pungent peppers (poblano, bell, chilaca, caribe, jalapeno, serrano, habanero and manzano) were evaluated for their content of some bioactive compounds and free radical-scavenging activity. Boiling and grilling were performed under household conditions. Ascorbic acid content in raw peppers varied from 306 to 3438 μg/g. This content was reduced 15–87% by heat treatments. Total carotenoids content in raw peppers ranged between 1 and 156 μg/g. β-Carotene represented 3–78% of total carotenoids in raw peppers. β-Carotene content was reduced (1–45%) by heat treatments. Free radical-scavenging activity varied widely (7–101 μmol TE/g) in raw peppers. Boiling and grilling reduced (6–93%) sequentially the antiradical activity of pungent peppers. In contrast, gradual increases of antiradical activity in non-pungent peppers were induced by boiling and grilling. Household heat treatment altered highly the content of bioactive/antioxidant compounds in tested peppers.

Natural bioactive compounds include a broad diversity of structures and functionalities that provide an excellent pool of molecules for the production of nutraceuticals, functional foods, and food additives. Some of those compounds can be found in nature at high concentration such as polyphenols but others can only be found at very low levels, so that massive harvesting is needed to obtain sufficient amounts, and their structural diversity and complexity make chemical synthesis unprofitable. The inherent difficulties in screening and producing these compounds have led to the development of advanced technologies. The commonly used methods for their extraction are the conventional liquid–liquid or solid–liquid extraction and the advanced include pressurized-liquid extraction, subcritical and supercritical extractions, and microwave- and ultrasound-assisted extractions. In addition, these extraction techniques have been improved with previous steps (enzyme-and instant controlled pressure drop-assisted extractions) which help to release the compounds from the matrix. These technologies could provide in the next few years an innovative approach to increase the production of specific compounds for use as nutraceuticals or as ingredients in the design of functional foods.

Codon optimization of the Bos taurus Chymosin gene (CYM) for its expression in Pichia pastoris was performed in this study. A synthetic CYM gene was designed in silico by replacing codons rarely used by P. pastoris with equivalent nucleotide combinations that codify for the same amino acid but that are more frequently encountered in the genome of P. pastoris. A total of 332 nucleotides were modified to optimize 289 codons. The synthetic CYM gene was cloned into the expression vector pPICZαA and transformed into P. pastoris. The transformed strains were grown in artificial media supplemented with glycerol as a carbon source to increase biomass and then cultured in a similar medium replacing glycerol with methanol as a carbon source to initiate gene induction. Raw extracts of the growth media exhibited milk-clotting activity of 146.11 SU/mL. Produced recombinant chymosin showed coagulant activity from 25 to 50 °C, and within a pH range of 5-6.9, having optimum activity at 35-40 °C, and pH 5.0. These results show that codon optimization is a viable strategy to improve CYM gene expression levels in P. pastoris for the production of recombinant chymosin.

Flavour is a key quality att ribute of apples defined by volatile aroma compounds. Biosynthesis of aroma compounds involves metabolic pathways in which the main precursors are fatty and amino acids, and the main products are aldehydes, alcohols and esters. Some enzymes are crucial in the production of volatile compounds, such as lipoxygenase, alcohol dehydrogenase, and alcohol acyltransferase. Composition and concentration of volatiles in apples may be altered by pre- and postharvest factors that cause a decline in Apple flavour. Addition of biosynthetic precursors of volatile compounds may be a strategy to promote aroma production in apples. The present manuscript compiles information regarding the biosynthesis of volatile aroma compounds, including metabolic pathways, enzymes and substrates involved, factors that may affect their production and also includes a wide number of studies focused on the addition of biosynthetic precursors in their production.

ulveda Abstract: High hydrostatic pressure (HHP) is a cutting-edge processing technology attracting research and industrial interest in the food sector due to its potential to produce microbiologically safe products, modify the functional properties of proteins and polysaccharides, and alter biochemical reactions without significantly affecting the nutritional and sensory properties of food. Currently, there are only a limited number of pressure-treated cheese products available in the market. Nevertheless, results from numerous research studies on various cheese varieties seem promising, especially since HHP technology is today more cost-effective than in the past. Considering the progress made in the application of HHP on cheese during the past 15 years, this paper reviews the direct application of HHP treatments to cheese and the effects it has on its microbiology and ripening process, as well as on quality parameters such as physicochemical, rheological, and sensory properties. Detailed information of published studies is presented with the aim of providing a clear picture of the use of this technology on cheese processing. Areas of research in need of more attention are also identified.

Heat treatments (HT) modify the renneting properties of raw milk, hence nonthermal technologies seem to be a good option to ensure the microbial quality of milk without modifying its renneting properties. The effect of pulsed electric fields (PEF) and high hydrostatic pressure (HHP) on the rennet coagulation properties of milk was compared with the effect caused by HT. Milk was processed by HHP (400 and 500 MPa from 0 to 20 min) and PEF (36 and 42 kV/cm for up to 64 pulses). HHP reduced the rennet coagulation time (RCT) of milk to ∼60% of the RCT of raw milk. Contrarily, PEF and HT increased RCT in ∼10%. Gels made from HHP milk presented G′ values of 170 Pa after 20 min, raw milk reached only 50 Pa after 60 min, and PEF and HT showed lower G′ values. HHP increases rennet coagulation efficiency, whereas PEF milk behaves similarly than raw milk. PRACTICAL APPLICATIONS Nonthermal technologies have been suggested as a means to ensure the microbiological safety of milk without modifying its nutritional and technical attributes, and as a way to enhance its various functional properties. High hydrostatic pressure and pulsed electric field treatments applied in this study modified the renneting properties of milk, providing as a useful tool for the redesigning of cheese-making processes. Rheological data presented in this paper clearly characterize the formation of curds out of milk treated with nonthermal treatments over milk proteins might result in the development of novel cheeses with different textures, flavors and nutritional content.

A water-based sucrose solution at subthreshold concentration (1 g/L) and pure water were used to evaluate the discriminative ability of nontrained judges to perform a two-alternative forced-choice (2AFC) test after the use of chewing gum for different periods of time. Three types of chewing gum were evaluated: CF, fruit-flavored caloric (sweetened with sucrose/dextrose); NF, fruit-flavored noncaloric (sweetened with Sorbitol/Xylitol); and NC, unsweetened, unflavored, unsoftened gum base. Two fixed times and four time classes were selected for the chewing times studied at 2, 5, 10–19, 20–29, 30–39 and ≥40 min. While the control group (no gum) was not able to consistently identify the sweet solution, judges chewing NC, NF and CF were able to do so (α = 0.05) after 5, 10 and 30 min of chewing, respectively. An increase in salivary flow rate, salivary pH and perceptive memory elicited by the gustatory and mechanical stimulation involved in the act of chewing are suggested as possible mechanisms behind the observed effect. PRACTICAL APPLICATIONS Discriminative sensory analytical methods must be able to reliably detect and quantify differences between samples. Any new test protocol or addition to it, which is able to improve the performance and sensitivity of sensory judges as individuals or as a group, helps in reaching this goal. From a practical point of view, ensuring that a test protocol renders results comparable with those produced by the most sensitive individuals in a given population guarantees the validity and usefulness of the conducted tests and their results. The proposed use of chewing gum as a preparative step in discriminative sensory test protocols is an attempt to finding a method able to increase the discriminative ability of sensory taste panels composed of nontrained judges.

The effect of AVG application on the quality and volatile production of ‘Golden Delicious’ apples, grown in Chihuahua Mexico, was evaluated. AVG (125 g AVG/ha) was applied on apple trees four weeks before harvesting. Apples were harvested 176 days after full bloom and stored at 8 °C for 35 d. Quality parameters and volatile compounds were periodically evaluated. AVG application retarded color changes, and preserved acidity of apples during storage. Ethylene synthesis was also delayed by AVG. Control apples presented higher total soluble solids content than AVG-treated apples at the end of cold storage. Volatile production was affected by AVG application, especially in the case of esters and alcohols, which presented 59% and 33% lower values in AVG-treated apples at the end of storage. A higher concentration of aldehydes was observed at harvest time in AVG-treated apples; however, no difference was observed between treatments during storage. Higher correlations between ethylene production and aldehydes and alcohols were found in control apples (0.98, and 0.98, respectively), than in AVG-treated apples (0.6 and 0.90, respectively). AVG application on ‘Golden Delicious’ apples conferred a variety of benefits, such as delaying maturation, maintaining color, and reducing changes in acidity and total soluble solids. However, AVG treatment negatively affects the production of some volatile compounds.

Whole milk was processed using selected combinations of pulsed electric fields (PEF) and thermal treatments to inactivate Listeria innocua . Electric field intensities of 30 and 40 kV/cm were applied at selected number of pulses (1–30) and temperatures (20–72 °C) for less than 10 s. A maximum microbial reduction of 4.3 log cycles was achieved using 10, 17.5, 20 and 25 pulses, when processing milk at 30 kV/cm and initial temperatures of 43, 33, 23 and 13 °C, respectively. Around 4.3 log cycles of L. innocua was observed when treating milk at 40 kV/cm using 3, 10, 12.5, 15, and 20 pulses and 53, 33, 23, 15, and 3 °C, respectively. Milk treated with 40 kV/cm of electric field intensity, few pulses, and initial temperature close to 55 °C showed the best balance between L. innocua inactivation and energy-consumption. An energy expenditure of around 244 J/mL was achieved, which can be further reduced to 44 J/mL using a thermal regeneration system.

Milk-fat globule membranes are susceptible to damage by mechanical and thermal processes. This damage is translated into alterations of milk fat structure and functionality of cheese-making milk. The objective of this work was to evaluate the effect of pulsed electrical fields (PEF), high hydrostatic pressure (HHP), and conventional thermal treatments on fat globule size distribution and ζ-potential. Milk was processed by HHP at 400 and 500 MPa for 0–20 min, and with PEF at 36 kV/cm and 42 kV/cm up to 64 pulses. The ζ-potential of HHP and PEF treated milk were − 15.47 mV and − 14.63 mV respectively. HHP treatments induced fat globules flocculation, increasing their mass moment mean diameter. Although PEF processing did not modify the true mean diameter of MFG, it induced small globules to clump together, causing an apparent increment in the population of larger milk-fat globules. Industrial relevance The market for traditional raw dairy products has increased in recent times in several regions of the world due to their unique flavor and texture attributes. However, the potential negative implications of consuming raw products limit the growth of this market segment. Manufacture of raw-like cheese from thermally pasteurized milk is not feasible, among other things, because of milk fat globule membrane damage caused by elevated temperatures. Nonthermal food preservation technologies offer the potential to produce milk technically suitable for the industrial manufacture of microbiologically safe raw-like dairy products.

Application of pulsed electric fields (PEF) in combination with mild thermal treatment was studied to extend the shelf life of whole milk. Five pulses with peak electric field strength of 35 kV/cm and pulse width of around 2.3 μs were applied to milk at 65 °C and sustained for less than 10 s. Shelf life of the milk was extended by a minimum of 24 days. A synergistic interaction between PEF and mild thermal treatment was found. Neither the severe PEF treatment applied at lower temperatures, nor the mild thermal treatment equivalent, including longer treatment times than used in this study, could significantly extend the shelf life of milk. However, the combination of both PEF and mild temperature extended milk's shelf life adequately. The use of a thermal regeneration system improved the energy efficiency of the studied preservation process making it highly competitive with pasteurization.

The inactivation of Listeria innocua ATCC 51742 by pulsed electric fields was investigated at 35, 40 and 45 kV/cm. Results indicate that at treatment times shorter than 37 μs at 40 and 45 kV/cm, and 49 μs at 35 kV/cm, there is a linear relationship between the logarithm of the survivor fraction and the treatment time. However, longer times result in an abrupt increase in the slope of the inactivation curve and in inactivation values greater than six logarithmic cycles. A model based on Weibull's survival function was used to describe microbial inactivation and then compared to a first-order kinetic model. Distribution parameters of Weibull's survival function and kinetic constant for the first-order kinetic model were calculated by fitting experimental data. Calculated mean times for microbial inactivation from Weibull's distribution were 11.55, 8.65 and 5.39 μs at 35, 40 and 45 kV/cm, respectively. The goodness-of-fit between experimental and predicted values was determined using an accuracy factor. The model based on the Weibull survival distribution provided better accuracy factors than first-order kinetics. The model based on Weibull's survival function seems promising for describing survival curves that exhibit concavity.

A procedure applying equivalent pulsed electric field (PEF) treatments of similar peak electric field intensity, total treatment time, and treatment temperature, while delivering different amounts of electric current, was successfully developed in this study. Listeria innocua suspended in McIllvaine buffer was subjected to five PEF treatments, each with a peak electric field intensity of 28.85 kV/cm applied for 60 μs at 44.3 °C, with peak electric currents of 1.94, 2.20, 2.76, 3.51, and 4.21 kA, respectively. To apply the described treatments, the charge voltage, pulsing frequency, and initial temperature and electrical conductivity of the treated media were adjusted, based on calculations made using pertinent fundamental mathematical models. Neither the amount of electric current flowing through the treated product, nor the amount of delivered electric energy or the electric conductivity of the studied media showed any influence on the bactericidal effectiveness of the applied treatments within the studied range.

The effect of treatment temperature on the bactericidal effectiveness of pulsed electric fields (PEF) applied on Listeria innocua suspended in McIllvaine buffer was investigated. Electric field intensity and number of applied pulses were applied in the ranges of 31–40 kV/cm and 5–35 pulses, respectively. Studied treatment temperatures were sustained for 10 s, and ranged between 19°C and 59°C depending on the amount of energy delivered by the PEF treatment. The application of PEF at higher temperatures proved to be more effective than either PEF at low temperatures or the applied thermal treatments by themselves. A maximum bacterial inactivation of 6-log cycles was obtained by applying either: 20 pulses of 40 kV/cm at 65°C, 25 pulses of 36 kV/cm at 61°C, or 31 pulses of 31 kV/cm at 56°C. On the other hand, a thermal treatment of 66°C sustained for 30 s reduced the bacterial population on its own by only 5-log cycles, and the application of 60 pulses of 31 kV/cm at 30°C caused only 3-log cycles of bacterial inactivation. The findings in this study suggest that PEF technology may be effectively used as an enhanced mild thermal preservation method.

Thermally pasteurized milk bulk-shipped to distant places is usually pasteurized for a second time after arrival at the point of consumption. Such double thermal treatment has the potential to reduce the sensory and nutritional quality of milk; hence the use of a nonthermal preservation method was investigated. High-temperature short-time (HTST) pasteurized milk was treated with five pulsed electric fields (PEF) having peak electric field of 35 kV/cm and 2.3 μs of pulse width, at a temperature of 65 °C for less than 10 s. PEF treatments were applied either immediately after thermal pasteurization to produce an extended-shelf life product, or eight days after thermal pasteurization to simulate processing after bulk-shipping. Application of PEF immediately after HTST pasteurization extended the milk’s shelf life to 60 d, while PEF-processing after eight days caused a shelf life extension of 78 d, both proving to be successful strategies to extend the shelf life of milk.

Black bean and rice burrito meal-ready-to-eat individual-size (MRE's) entrees were retorted in flexible pouches with four residual gas levels (10, 20, 30, 40 cm 3 ) and stored at three temperatures (4. 4, 26.7 and 37. 8C). Storage temperature was more influential upon quality than residual gas beyond one month of storage. Physicochemical and trained sensory analyses demonstrated that burritos stored at 37. 8C darkened over time, but burritos stored at 4.4 and 26. 7C did not. Untrained consumers gave lower scores to burritos stored at 37. 8C, which were dull, dark, dry, and compressed, than to burritos stored at 4.4C, which were glossy, light, sticky and moist throughout storage. Burrito shelf-life exceeded 6 months at 4.4C, but was limited to less than 3 months at 37. 8C. Residual gas levels in black bean and rice burrito MRE's need not be specified as long as levels are maintained between 10-40 cm 3 .

Changes in specific physico-chemical and sensory attributes as well as acceptability of beefsteak and beef stew Meal-Ready-to-Eat (MRE) components packed under different headspace levels (10, 20, 30 and 40 cm 3 ) and stored at selected temperatures of 4, 27 and 38C (40, 80 and 100F) were evaluated over a six month period. No significant changes in microbial counts, pH, residual oxygen, color, hardness and oxidation occurred in retort-packed beefsteak or beef stew. Unlike beefsteak, beef stew received acceptable scores by consumers during all six months of analysis. Consumers' lack of familiarity with beefsteak may have negatively influenced product acceptability. Beefsteak and beef stew acceptability and specific attributes, particularly moistness and firmness, were detrimentally affected by high storage temperatures. Headspace may be increased to 40 cm 3 without significant detrimental effects on product quality and acceptability of beefsteak or beef stew.

Wet pack pears in retort pouches were studied for six months. Four selected residual gas volumes [10, 15, 20 and 30 cubic centimeters (cc)] were used to determine the influence of residual gas volume on physicochemical and sensory attributes. Three storage temperatures (4.4, 26. 7and 37. 8C) were used to carry out an accelerated shew-life study. Residual gas of 30 cc promoted faster darkening and higher ascorbic acid degradation than the rest of the volumes studied (a ≤ 0.01). No significant effect of residual gas volume was found on any other attribute analyzed. Temperature accelerated the consumption of remaining oxygen in the pouches, degradation of ascorbic acid, formation of 5-hydroxymethyl-2-furaldehyde (HMF) and 2-furaldehyde, and softening of pears. Calculated activation energies (EJ for HMF and 2-furaldehyde formation, ascorbic acid, and color degradation were 35, 31.1, 29.8, and 10.4 kcal/mol, respectively. Residual gas volume of 20 cc was the maximum volume studied that accomplished the desired shelf-life for this product.

Industrial implementation of pulsed electric field electro-technology (PEF) for food preservation has been rather slow, despite its potential to produce safe, nutritious and high-quality products. Several research groups around the world are in a race to validate and optimize the operation of PEF systems. Insufficient kinetic studies and inaccurate treatment delivery assessment are some of the main obstacles to the implementation of this technology. Equivalency among PEF systems, treatment delivery and control variables need to be clearly defined before actual industrial implementation takes place. Limited commercial availability of PEF systems, mainly due to the complexity and high cost of pulsers, and to technical and economical limitations of the scaling-up process, reflects into high initial investment and operation costs. This paper reviews the state of the art on the above-mentioned issues, and also discusses engineering, biological, and regulatory aspects that should be considered for optimization and commercial implementation of PEF as a food preservation technology.

Diced pears packed in flexible retortable pouches were manufactured to obtain packages with 10, 15, 20 and 30 cm 3 residual gas, then stored at 4.4, 26.7 and 37.8 °C for six months. The 2-furaldehyde and 5-hydroxymethyl-2-furaldehyde values increased and pears turned darker, softer, more homogeneous in shape/size, less fruity in flavor and aroma, and less acceptable to consumers over time. Elevated temperatures and high residual gas levels were particularly detrimental to pear quality. Highest quality was maintained for 6 months when pears packaged at any residual gas level were stored at 4.4 °C. Acceptable quality was maintained for 6 months in pears packaged with less than 30 cm 3 residual gas, stored at 26.7 °C. Pear quality declined most rapidly at 37.8 °C, 30 cm 3 residual gas. Residual gas volume of 15 cm 3 should not be exceeded to maintain highest quality and acceptability of diced pears packed in flexible retortable pouches.

Absolute threshold and just noticeable difference (JND) were determined for the perception of pungency using chili pepper in aqueous solutions. Absolute threshold and JND were determined using 2 alternative forced-choice sensory tests tests. High-performance liquid chromatography technique was used to determine capsaicinoids concentration in samples used for sensory analysis. Sensory absolute threshold was 0.050 mg capsaicinoids/kg sample. Five JND values were determined using 5 reference solutions with different capsaicinoids concentration. JND values changed proportionally as capsaicinoids concentration of the reference sample solutions changed. Weber fraction remained stable for the first 4 reference capsaicinoid solutions (0.05, 0.11, 0.13, and 0.17 mg/kg) but changed when the most concentrated reference capsaicinoids solution was used (0.23 mg/kg). Quantification limit for instrumental analysis was 1.512 mg/kg capsaicinoids. Sensory methods employed in this study proved to be more sensitive than instrumental methods. Practical Application: A better understanding of the process involved in the sensory perception of pungency is currently required because "hot" foods are becoming more popular in western cuisine. Absolute thresholds and differential thresholds are useful tools in the formulation and development of new food products. These parameters may help in defining how much chili pepper is required in a formulated product to ensure a perceptible level of pungency, as well as in deciding how much more chili pepper is required in a product to produce a perceptible increase in its pungency.

La producción de frutos de tomate (Lycopersicon esculentum Mill.) con sabor agradable está recibiendo atención especial, porque este atributo se ha convertido en uno de los principales parámetros de calidad en la aceptación de frutas y hortalizas. Aquí se analiza cómo los compuestos volátiles influyen significativamente en el sabor del tomate, por ser responsables de su aroma. Los principales compuestos volátiles del tomate involucran a aldehídos, alcoholes, cetonas y ésteres insaturados de cadenas cortas, los cuales son producidos a partir de ácidos grasos, aminoácidos libres y carotenoides. Entre las principales enzimas involucradas se encuentran lipoxigenasa, hidroperoxidoliasa y alcohol deshidrogenasa para la biosíntesis de volátiles a partir de ácidos grasos; además están las enzimas aminotransferasa, descarboxilasa y alcohol deshidrogenasa, relacionadas con la biosíntesis de volátiles derivados de aminoácidos. La composición y concentración de los compuestos volátiles depende de factores genéticos, así como de las condiciones de cultivo y del almacenamiento. El presente manuscrito compila y analiza la información actual referente a la biosíntesis de los volátiles que definen el aroma del tomate, así como sus rutas metabólicas, enzimas y sustratos involucrados; así mismo analiza los principales factores precosecha, cosecha y poscosecha que afectan su biosíntesis.