Objective assessment of cheddar cheese quality

Chemical and physical analyses of cheese are required to objectively assess cheese ripening. Statistical Multivariate Analysis of HPLC and free amino acid data for each of 60 Cheddar cheeses, varying in age and quality, were used to objectively classify the cheeses according to maturity, flavour quality (defective or not) and texture. Additional information was obtained from compositional analysis and gel electrophoresis. The total concentration of free amio acids was more effective than HPLC analysis for discriminating between mild, mature and extra-mature Cheddar cheeses whereas HPLC discriminated more effectively between defective and non-defective.     

Measurement of the oxidation-reduction potential of cheddar cheese

ABSTRACT:  The objective of this study was to develop a method to measure the oxidation–reduction (redox) potential of hard cheeses such as cheddar and to investigate the impact on this parameter of measurement temperature, and factors associated with electrochemical cell design such as distance between reference and working electrodes and depth into the cheese of the platinum electrodes. For this purpose, a novel, self-sealing, platinum working electrode was constructed which was thin and flexible enough to be inserted directly into the cheese sample. A calomel electrode was used as the reference electrode and the circuit was completed with a 3 M KCl salt bridge. The physical orientation of electrodes, such as distance between reference electrode and working electrode, had a substantial effect on equilibrium time for redox potential measurement. The time required for redox potential to reach equilibrium was 2 d in cheddar cheese and the optimum distance between the platinum and calomel electrodes was 2.5 cm. The fastest equilibration time was obtained when the working electrode was inserted 5 or 6 cm into the cheese. Temperature also had an important effect on redox potential. The shortest time to reach equilibrium of potential was at room temperature (20 °C), but it was not practical to keep cheese at this temperature for a period of 2 d. Therefore, redox measurement at 12 °C was recommended in spite of the longer equilibration time compared with room temperature. The results of this study suggest that the novel platinum working electrode allows reproducible measurement of the oxidation–reduction potential of cheddar cheese.     

Enhanced nutty flavor formation in cheddar cheese made with a malty Lactococcus lactis adjunct culture

Nutty flavor in Cheddar cheese is desirable, and recent research demonstrated that 2- and 3-methyl butanal and 2-methyl propanal were primary sources of nutty flavors in Cheddar. Because malty strains of Lac-tococcus lactis (formerly Streptococcus lactis var. malti-genes) are characterized by the efficient production of these and other Strecker aldehydes during growth, this study investigated the influence of a malty L. lactis adjunct culture on nutty flavor development in Cheddar cheese. Cheeses made with different adjunct levels (0, 10⁴ cfu/mL, and 10⁵ cfu/mL) were ripened at 5 or 13°C and analyzed after 1 wk, 4 mo, and 8 mo by a combination of instrumental and sensory methods to characterize nutty flavor development. Cheeses ripened at 13°C developed aged flavors (brothy, sulfur, and nutty fla-vors) more rapidly than cheeses held at 5°C. Additionally, cheeses made with the adjunct culture showed more rapid and more intense nutty flavor development than control cheeses. Cheeses that had higher intensities of nutty flavors also had a higher concentration of 2/3-methyl butanal and 2-methyl propanal compared with control cheeses, which again confirmed that these compounds are a source of nutty flavor in Cheddar cheese. Results from this study provide a simple methodology for cheese manufacturers to obtain consistent nutty flavor in Cheddar cheese.     

市售切达奶酪的风味特性

对来自4个国家、不同成熟时间的市售切达奶酪进行描述性感官评定与挥发性风味物质分析,通过主成分分析和聚类分析解析市售切达奶酪的风味特征和不同国家对切达奶酪风味感官评定的文化差异性,并采用偏最小二乘法探究挥发性风味物质与风味感官属性之间的关系。实验结果表明:切达奶酪的风味特征主要有奶香味、奶油味、硫味、酸味、鲜味、坚果味、肉汤味、成熟度、滋味强度等;不同国家感官评定使用的描述词存在差异,与美国感官评价员使用的描述词相比,我国感官评价员使用的描述词缺少乳清味、水果味、牛膻味,增加了腐臭味、不洁味、刺激性、成熟度等风味描述词;不同国家感官评定组区分不同切达奶酪依据的风味属性存在差异性,我国感官评价员主要通过奶香味、奶油味、硫味、酸味、鲜味、成熟度、滋味强度来区分切达奶酪。     

Bioavailability of iron-milk-protein complexes and fortified cheddar cheese

Iron fortification is used to increase dietary iron intake. Dairy products are widely consumed but contain almost no iron. Cheddar cheese was fortified with ferric chloride or iron-casein, ferripolyphosphate-whey protein, and iron-whey protein complexes. Hemoglobin regeneration efficiency was determined to evaluate iron bioavailability. Maximal and basal iron bioavailabilities were measured in anemic weanling rats fed low iron diets (about 22 mg iron/kg) and normal adult rats fed high iron diets (about 145 mg iron/kg) of iron density (32 mg iron/1000 kcal) found in some high iron human diets. Maximal iron bioavailabilities for ferric chloride or iron-casein, ferripolyphosphate-whey protein, and iron-whey protein complexes were 85, 71, 73, and 72%, respectively, and for the respective iron-fortified cheeses they were 75, 66, 74, and 67%. Differences were not significant in maximal iron bioavailabilities among iron sources and between fortified cheeses and fortification iron sources. Basal iron bioavailabilities for 10-d feeding of the respective fortification iron sources were 5, 8, 6 and 7%, respectively, and 4, 4, 3, and 3% for 14 d feeding; the differences among the iron sources were not significant. Maximal and basal iron bioavailabilities of ferrous sulfate were 85 and 5%, respectively. Practical implications of these observations are discussed.     

Tryptophan catabolism in Brevibacterium linens as a potential cheese flavor adjunct

Attempts to develop a desirable reduced fat Cheddar cheese are impeded by a propensity for flavor defects such as meaty-brothy, putrid, fecal, and unclean off-flavors in these products. Recent studies suggest aromatic amino acid catabolism of starter, adjunct, and nonstarter lactic acid bacteria significantly impact off-flavor development. The objective of this study was to delineate pathways for catabolism of tryptophan (Trp) in Brevibacterium linens, a cheese flavor adjunct, and to determine the potential for this organism to contribute to this defect. Growth and production of aromatic compounds from Trp by B. linens BL2 were compared in two incubated conditions (laboratory and a cheese-like environment). A chemically defined medium was used to determine the cellular enzymes and metabolites involved in Trp catabolism. Trp was converted to kynurenine, anthranilic acid, and three unknown compounds in laboratory conditions. The accumulation of other unknown compounds in the culture supernatant in laboratory conditions indicated that B. linens BL2 degraded Trp by various routes. Up to 65% of Trp was converted to anthranilic acid via the anthranilic acid pathway. To assess this potential before cheese making, the cells were incubated in cheese-like conditions (15 degrees C, pH 5.2, no sugar source, 4% NaCl). Trp was not utilized by BL2 incubated in this condition. Enzyme studies using cell-free extracts of cells incubated in laboratory conditions and assayed at optimal and nonoptimal enzyme assay conditions revealed Trp transaminase (EC 2.6.1.27) was active before enzymes of the anthranilic acid pathway were detected. The products of Trp transaminase activity were not, however, found in the culture supernatant, indicating these intermediates were not exported nor accumulated by the cells. Enzymes assayed in nonoptimal conditions had considerably lower enzyme activities than found in laboratory incubation conditions. Based on these results, we hypothesize that these enzymes are not likely to be involved in the formation of compounds associated with off-flavors in Cheddar cheese.     

Storage stability of lutein during ripening of cheddar cheese

Lutein (3,3'-dihydroxy-alpha-carotene) has been identified as a dietary factor that can delay the onset of age-related macular degeneration (AMD). However, available food sources of lutein contain only modest amounts of the carotenoid. Food fortification with lutein extract has been identified as a low-budget approach to prevent the onset or progression of AMD. The objectives of this study were to 1) incorporate various amounts of lutein into Cheddar cheese; 2) examine the color, pH, microbiological, and sensory characteristics of the Cheddar cheese during storage; and 3) analyze the stability of lutein during the cheese maturation process. Lutein extracted from corn was added to Cheddar cheese in quantities of 1, 3, and 6 mg per serving size. Measurements of the lutein stability were carried out by HPLC using a YMC C30 carotenoid column. Microbiological analyses of cheese samples included aerobic plate count, coliform, and yeast/mold counts. The color attributes a* and b* were significantly different between the treatment and control groups; however, no significant difference was observed in L* value and pH. Significant differences among 1, 3, and 6 mg lutein-enriched cheeses were observed in the aerobic plate count and yeast/mold compared with the control. Cheese samples contained no detectable levels of coliforms (< 10 cfu/g). The HPLC data showed quantitative recovery of lutein during the storage period, and no lutein degradation products were identified. These results indicate that lutein, a functional additive with purported ability to prevent or reduce the onset of AMD, can be incorporated into cheese adding value to this product.     

规模化切达奶酪生产过程中质量控制点的研究

探讨了大规模切达奶酪生产过程中凝乳的酸度发展,水分控制,切达奶酪加盐量,切达奶酪成熟对程中若干工艺参数对切达奶酪质量的影响.     

Cheddar干酪附属发酵剂筛选及其应用

为了筛选能够促进Cheddar干酪成熟,从泡菜、腐乳及不同产地的Cheddar中筛选具有高肽酶活力和自溶度的乳杆菌作为Ched-dar干酪附属发酵剂,并应用于Cheddar干酪的制作中.结果表明,从美国Cheddar干酪中筛选出1株Lactobacillus plantarum OD具有较高的肽酶活力和自溶度,运用于Cheddar千酪的制作中能显著提高其游离氨基酸浓度,改善其风味,有利于加快干酪的成熟.     

Impact of liposome-encapsulated enzyme cocktails on cheddar cheese ripening

Cheddar cheese proteolysis and lipolysis were accelerated using liposome-encapsulated enzymatic cocktails. Flavourzyme, neutral bacterial protease, acid fungal protease and lipase (Palatase M) were individually entrapped in liposomes and added to cheese milk prior to renneting. Flavourzyme was tested alone at three concentrations (Z1, Z2 and Z3 cheeses). Enzyme cocktails consisted of lipase and bacterial protease (BP cheeses), lipase and fungal protease (FP cheeses) or lipase and Flavourzyme (ZP cheeses). The resulting cheeses were chemically, rheologically and organoleptically evaluated during 3 months of ripening at 8 °C. Levels of free fatty acids and appearance of bitter and astringent peptides were measured. Certain enzyme treatments (BP and ZP) resulted in cheeses with more mature texture and higher flavor intensity in a shorter time compared with control cheeses. No bitter defect was detected except in 90-day-old FP cheese. A full aged Cheddar flavor was developed in Z3 and ZP cheeses, while treatment BP led to strong typical Cheddar flavor by the second month and did not exhibit any off-flavor when ripening was extended for a further month.     

钙添加对切达奶酪品质的影响

研究了钙添加(100、200、500 mg/L)对切达奶酪成熟特性及感观品质的影响。测定了切达奶酪在成熟中不可溶钙、pH 4.6-可溶性氮、12%三氯乙酸(TCA)-可溶性氮、质构及挥发性风味物质的变化,对产品进行气味、滋味及质构的感观评价。结果表明:钙添加能显著降低蛋白质水解程度,增大奶酪硬度及弹性,降低切达奶酪苦味。0~200 mg/L钙添加对质构的感官无显著性影响,500 mg/L钙添加能显著降低奶酪粘性和凝聚性,并导致奶酪呈现易碎性和粉质特性。