契达酶改性干酪的研制

选择中性蛋白酶、风味酶以及脂酶Lipase R,将其添加到新鲜干酪浆中,水解到一定程度以生产出具有契迭风味的酶改性干酪.首先添加中性蛋白酶和风味酶,根据蛋白水解程度和感官评价,确定出具有最佳风味的初级水解产品.之后向此初级产品中分别添加Lipase R进行脂解以获得最终的EMC.最后将生产出的EMCs产品与新鲜干酪、天然成熟契达干酪进行比较,比较内容包括理化成分、蛋白水解程度、感官评价等.     

EFFECT OF CALCIUM AND PHOSPHORUS, RESIDUAL LACTOSE AND SALT-TO-MOISTURE RATIO ON TEXTURAL PROPERTIES OF CHEDDAR CHEESE DURING RIPENING

The texture profile analysis (TPA) parameters and meltability of Cheddar cheeses with varying levels of calcium (Ca) and phosphorus (P) content, residual lactose content and salt‐to‐moisture (S/M) ratio were studied at 0, 1, 2, 4, 6 and 8 months of ripening. The TPA hardness had an inverse relationship with the meltability of Cheddar cheese and at any given ripening time, lower TPA hardness corresponded to higher meltability of Cheddar cheese. Higher Ca and P content (0.67% Ca and 0.53% P) in Cheddar cheese resulted in up to 22.8, 5.7, 14.6, 13.5 and 35.2% increase in hardness, springiness, cohesiveness, resilience and chewiness values, respectively, and up to 23.5 and 27.7% decrease in meltability and adhesiveness values during ripening compared to the Cheddar cheese prepared with lower Ca and P content (0.53% Ca and 0.39% P). Higher residual lactose content (1.4%) in Cheddar cheese resulted in up to 24.6, 8.8 and 20.0% increase in hardness, cohesiveness and chewiness values, respectively, and up to 12.7% decrease in meltability value in the Cheddar cheese during ripening compared to the lower lactose content (0.78%). High S/M ratio (6.4) resulted in up to 29.4, 30.3 and 29.4% increase in hardness, adhesiveness and chewiness values, respectively, and up to 7.3% decrease in meltability value in Cheddar cheese compared to low S/M ratio (4.8) during ripening.     

RHEOLOGICAL AND CHEMICAL PROPERTIES OF MOZZARELLA CHEESE

Dynamic viscoelastic parameters and chemical properties of Mozzarella cheese produced using a "no-brine" cheese making method with 3 different cooking temperatures (38, 41, and 44C) were determined. Samples were stored for 3 weeks at 4C before dynamic mechanical analysis at 22C. G', G" and tan δ were 5.8 – 6.4 × 10⁵ dyne/cm², 1.9 – 2.1 × 10⁵ dyne/cm², and 0.33 – 0.35, respectively, at 1% strain and 10 rad/s. The percentage of intact α_s-casein and β-casein were 38–40% and 33–35% of total protein in the cheese, respectively. The range of cooking temperatures used in this experiment had little effect on dynamic viscoelastic properties or the amount of intact protein for the cheese.     

PINK DISCOLORATION IN CHEDDAR CHEESE

Pink material isolated from defective Cheddar cheeses consisted of norbixin associated with phospholipid and casein. UV spectra and polyacrylamide gel electro-phoretic studies indicated that the associated casein fraction was mainly Beta casein with at least three additional unidentified peptide components. The presence of norbixin was confirmed by chromatographic and spectral studies. Evidence for the phospholipid part of the complex is circumstantial and needs further confirmation. Model system studies indicated that a localized production of hydrogen sulfide can cause a micro-fine precipitation of norbixin due to a decrease in pH. Phospholipid may act to prevent the resolubilization of norbixin which appears as pink zones in the cheese     

TEXTURE ANALYSIS OF CHEDDAR CHEESE MADE FROM ULTRAFILTERED MILK

The textural properties of Cheddar cheese made from ultrafiltered milk were assessed. Cheddar cheeses were prepared from 1.5- and 2.0-fold concentrated milk and ripened for three months. Textural characteristics of the UF cheeses were compared to control and commercial Cheddar cheeses by sensory and instrumental measures. The texture of cheese made from UF milk differed from the control commercial Cheddar cheeses. According to the trained sensory panel, the UF cheeses were harder and more rubbery, crumbly, chewy and grainy than the control and commercial Cheddar cheeses (P <0.01). The texture profile analysis (TPA), conducted using the Instron, did not correspond to the sensory measurements nor was it successful in discriminating among the cheese samples. Lack of agreement between the sensory and instrumental tests was attributed to differences in the testing conditions and procedures of the two methods. Instrumental tests should be validated against sensory measures in order to be useful as measures of palatability. Consumer preferences for the commercial, control and UF Cheddar cheeses were significantly different (P < 0.01), the UF cheeses being less preferred in terms of flavor, texture and overall acceptability.     

BEHAVIOR OF MOZZARELLA, CHEDDAR AND PROCESSED CHEESE SPREAD IN LUBRICATED AND BONDED UNIAXIAL COMPRESSION

The response of a material under uniaxial compression depends both on the bulk material properties and on the frictional effects at the sample-platen interface. Three commercial cheeses (cheddar, mozzarella and processed cheese spread) were studied in uniaxial compression. Frictional effects at the sample surface were examined under three conditions: (1) lubrication of the sample-platen interface; (2) bonding of the sample to the instrument platens; (3) samples neither bonded nor lubricated. The forces required to deform the cylindrical sample to a given strain level were highest for the bonded cases and lowest under lubricated conditions. The stress in lubricated compression, ρ_L, was calculated from Fh(πR_ρ²h_ρ)     

SEASONAL VARIABILITY OF CHEDDAR CHEESE WHEY POWDER: A CASE STUDY

Cheddar whey powder from one plant was evaluated for variations in quality parameters over 12 months. Representative samples were analyzed monthly for microbiological, physicochemical and sensory properties. The seasonal variability in the physicochemical properties was minor. Fall samples were higher in Hunter Lab parameter L* (lightness) and pH but lower in solubility index. Summer samples were high in solubility index and titratable acidity but low in L*. May production was significantly higher in standard plate count (SPC) and free moisture than the rest of the year. February production was significantly lower in SPC and free moisture content. There were no significant differences in aroma and flavor across the seasons. The flavor was generally bland, with the most intense attribute rating 5 on the 15‐point intensity scale. The order of intensity of the most intense attributes was cooked flavor and aroma > sweetness > caramelized flavor and aroma.     

PROTEIN DEGRADATION IN CHEDDAR CHEESE SLURRIES

SUMMARY— Preferential degradation of caseins was noted in the ripening of Cheddar curd slurries, with the degradation generally being in the order of para-K, β-, α_s-caseins. The addition of reduced glutathione to the slurry caused an immediate release of peptides from the protein mass and decreased the initial rate of β-casein degradation. The peptides appeared to be preferentially utilized during the first 4 days of ripening; thereafter rapid degradation of β-casein occurred. In quiescent slurries, α_s-casein degradation exceeded that of β-casein, whereas periodic agitation reversed the degradation rate of the two caseins. The rate and extent of characteristic flavor development appeared to be related directly to β-casein degradation, but not to changes in concentration of pare-K or α_s-caseins.     

GC-MS法分析成熟切达干酪游离脂肪酸组分及含量

通过GC-MS联用,分析了成熟切达干酪游离脂肪酸组分及相对含量,得知成熟切达干酪中含游离脂肪酸12种,其中不饱合脂肪酸含量高达75.12%,其中以9-十八碳烯酸和十六烯酸含量较高.     

RETENTION OF FREE FATTY ACIDS DURING SPRAY DRYING OF CHEDDAR CHEESE

The effect of processing variables, such as total solids, atomization pressure and inlet drying air temperature, on the retention of free fatty acids (FFA) in Cheddar cheese during spray drying was investigated. A cheese homogenate was prepared with minimum heat treatment and spray dried at a feed temperature of approximately 43°C. The retention of FFA increased with molecular weight under all drying conditions. In the absence of emulsifying salts, a lower total solids content in the homogenate fed to the dryer increased the retention of FFA. For example, the maximum retention of butyric acid at 30% T.S. and at 4% T.S. was about 60% and 35%, respectively. In addition, higher atomization pressures and higher inlet drying air temperatures decreased the retention of FFA. Emulsifying salts were effective, especially at 40% T.S., in increasing the retention of FFA. These results could be predicted from the selective diffusion theory of the retention of volatile compounds.     

KINETICS OF NONENZYMATIC BROWNING IN CHEDDAR CHEESE POWDER DURING STORAGE

Nonenzymatic browning (NEB) in Cheddar cheese powder during storage was investigated in the water activity (a_w) and temperature ranges of 0.48–0.85 and 20–40C, respectively. The NEB obeyed zero-order reaction kinetics during storage. Activation energies and Q₁₀ values were in the range of 15.1–22.3 kcal/mole and 2.2–3.5, respectively. The NEB increased with increasing temperature and storage time. There was an a_w maxima at 0.63 for NEB at 20C. At 30 and 40C, NEB decreased with increasing a_w. A generalized NEB model for Cheddar cheese powder during storage was developed based on Arrhenius equation to describe NEB as a function of a_w and temperature. Powders stored at 20 and 30C were evaluated for quality aspects. Maximum storage stability was obtained in powders stored at a_w of 0.54 at 20C for five months based on an overall desirability score of 3.5 on a 7-point scale. The average score of fresh powders were 4.7 throughout the storage study 7.