TORSION ANALYSIS OF FRESH AND AGED CHEESES1

Six cheese varieties encompassing a wide compositional and age range were analyzed fresh and after aging to determine correlations between casein proteolysis products, fat content, moisture content, and torsion results. Shear stress, a measure of the strength of the casein matrix, was dependent on the amount of intact α_sl‐casein. Shear strain, a measure of the cohesiveness of a structure, exhibited a negative correlation with fat content and a positive correlation with moisture content. Shear strain was also correlated with the ratio of moisture to protein, an indication of the interaction between casein particles. Torsion tests provide information on the level of degradation of the casein network in cheese, which can be used by manufacturers to alter storage conditions to optimize the quality of their aged cheese., April 10, 2003     

Queso Chihuahua: manufacturing procedures, composition, protein profiles, and microbiology

A survey of fresh commercial Queso Chihuahua made from raw or pasteurized cow's milk was undertaken to determine the impact of cheesemaking parameters on composition, protein breakdown and microbial counts. Despite variations in the manufacturing procedure, the composition and casein breakdown of the cheeses fell within a comparatively tight range. Pathogens were not detected in any of the cheeses, but total aerobic plate counts exceeded the recommended limit for this variety. Differences in Mexican Queso Chihuahua manufacturing procedures did not substantially alter the final product, the quality of which could be improved by reduction of bacteria present.     

Qualitative and Quantitative Determination of Caseins with Reverse-Phase and Anion-Exchange HPLC

Whole native caseinate (WNC) and casein (CN) fractions from preparative DE-52 cellulose urea columns were chromatographed using C-8 reverse-phase (RP) and DEAE-type anion-exchange (AEx) HPLC systems. With RP, α_S2-CN and κ-CN eluted first as several small peaks; α_S1-CN eluted later as two peaks, followed by β-CN peaks. With AEx, κ-CN eluted early as a group of peaks, β-CN eluted next, and α_S1-CN and α_S2-CN coeluted last. Standard curves were prepared for α_S1-CN and β-CN using RP-PHLC and showed correlation coefficients of 0.99 and 0.98, respectively. The caseins in WNC, nonfat dry milk casein, commercial casein(ates) and caseins from milks of individual cows were determined.     

Stability of β-Galactosidase from Aspergillus oryzae and Khyveromyces lactis in Dry Milk Powders

A milk-based beverage powder with 2% vegetable fat and reduced levels of lactose is needed by some segments of the consumer market as well as military units. To provide such, two commercial β-galactosidases were dry-blended into milk powders made with coconut, cottonseed, canola or sunflower oils and stored at ?20, 4, 25, and 45°C. Enzyme activity was measured monthly by reconstituting the powders and measuring freezing point depression after incubation at 32°C (optimum for P-galactosidase from Kluyveromyces luctis) and incubation at 50°C with pH adjusted to 5.0 (for activity of Aspergillus oryzae enzyme). Both enzymes retained >95% of original activity at ?20 and 4°C. Activity of K. Zuctis enzyme declined moderately at room temperature (～23°C) and rapidly at 45°C. The A. oryrae enzyme retained 93.4% of original activity after 6 mo at 45°C.     

Queso Chihuahua: effects of seasonality of cheesemilk on rheology†

Fresh semihard raw milk (RM) and pasteurized milk (PM) cheeses made by Mennonite communities in Chihuahua, Mexico were sampled in early winter, mid‐spring and late summer and evaluated during storage to determine if rheological properties were affected by the season the cheese was produced. Seasonal effects were observed in the rheology of the RM cheeses, which underwent more extensive proteolysis than the PM cheeses. The rheological properties of the PM cheeses and the composition of all cheeses were consistent throughout the year. The texture of the RM cheese is affected by season, whereas the variability in texture and composition of PM cheese is minimal, allowing for the manufacture of a uniform product.     

Mexican Queso Chihuahua: rheology of fresh cheese†

Rheological properties of fresh Queso Chihuahua made from raw milk (RM) or pasteurized milk (PM) were characterized using texture profile, torsion and small amplitude oscillatory shear analyses. Although the rheological properties varied significantly among the different brands with overlapping ranges for the individual RM and PM cheese brands, overall the PM cheeses were harder, chewier and more cohesive but had lower viscoelastic values than the RM cheeses. Establishing the rheological properties of Mexican Queso Chihuahua increases our understanding of the quality traits of Hispanic‐style cheeses and provides a foundation for maintaining the traditional texture of the cheese.