Detection of Volatile Compounds of Cheese and Their Contribution to the Flavor Profile of Surface‐Ripened Cheese

The volatiles responsible for the typical aroma of cheese are produced mainly by lipolytic and proteolytic pathways and by the metabolism of lactose, lactate, and citrate. The volatile profile of cheese is determined by gas chromatography (GC), which includes the extraction, separation, and detection of volatiles. A wide range of extraction techniques is available, and technological improvements have been developed in GC separation and detection that enhance our understanding of the role of individual key volatiles to cheese flavor. To date, for surface‐ripened cheese, the main volatiles detected that contribute to flavor include acids, ketones, alcohols, and sulfur compounds. However, based on the limited number of studies undertaken and the approaches used, it appears that a significant degree of bias possibly exists that may have over‐ or underestimated the impact of specific chemical classes involved in the flavor of these types of cheese.     

Nutritional Evaluation of Accelerated Ripened Cheddar Processed Cheese

Accelerated ripened Cheddar cheese was prepared by blending two parts of shredded curd made from standardized cow's milk with one part of 5.2% NaCl solution and ripening at 30°C for 8 days. On a dry matter basis, protein and fat of accelerated ripened cheese were similar to that of conventionally ripened Cheddar cheese, while lactose and total ash were greater. Similar observation was made for processed cheese samples. No change in vitamin A or in riboflavin but a fourfold increase in folic acid was observed during accelerated ripening. Protein efficiency ratio, net protein utilization and digestibility coefficient by rat tests were slightly but significantly higher for conventionally ripened processed cheese. However, no difference in biological value was observed.     

Effect of Curd Healing Time on Stirred Curd Cheese Yield

Cheese was manufactured with variable heal times to determine the effect of curd healing time on stirred curd cheese yield. A randomized complete block design with three treatments (vat healing times from cut to cook) was replicated six and four times in studies 1 and 2, respectively, for a total of 30 vats of stirred curd cheese. In study 1, heal times of 15, 22, and 29 min were used in manufacturing cheese. Curd was not healed or healed 15 or 30 min in study 2. Cooking curd immediately after cutting resulted in significantly lower moisture content in cheese, lower raw cheese yields, and higher fat loss into whey. Healing cheese curd 15 min or longer decreased syneresis, resulting in higher moisture cheese and increased raw cheese yield. Heal time extended to 30 min resulted in a significantly smaller loss of fat into whey. Healing time had a significant effect on moisture retention, fat loss, and raw cheese yield.     

Cheddar Cheese Ripening and Flavor Characterization: A Review

Cheddar cheese is a biochemically dynamic product that undergoes significant changes during ripening. Freshly made curds of various cheese varieties have bland and largely similar flavors and aroma and, during ripening, flavoring compounds are produced that are characteristic of each variety. The biochemical changes occurring during ripening are grouped into primary events including glycolysis, lipolysis, and proteolysis followed by secondary biochemical changes such as metabolism of fatty acids and amino acids which are important for the production of secondary metabolites, including a number of compounds necessary for flavor development. A key feature of cheese manufacture is the metabolism of lactose to lactate by selected cultures of lactic acid bacteria. The rate and extent of acidification influence the initial texture of the curd by controlling the rate of demineralization. The degree of lipolysis in cheese depends on the variety of cheese and may vary from slight to extensive; however, proteolysis is the most complex of the primary events during cheese ripening, especially in Cheddar-type cheese.     

Ripening Changes in a Blue-Mold Surface Ripened Cheese from Goat's Milk

Samples of blue-mold surface ripened goat milk cheese were analyzed for fat and protein breakdown during ripening. After 2 wk, cheese had a pH of 4.96 and 9.13 micromoles of free fatty acids (F.F.A.)/g fat. After 6 wk, the pH increased to 6.43 and F.F.A. were 160.85 micromoles/g fat. At this time, the cheese rind pH was 7.18 with 253.81 micromoles FFA/g fat. Water soluble protein in the cheese increased from 20.47% at 2 wk of ripening to 26.62% after 4 wk of ripening.     

Purification and Properties of Aminopeptidase I from Penicillium caseicolum

An extracellular aminopeptidase from Penicillium caseicolum was purified from the ammonium sulfate fraction using chromatography on DEAE-Sephacel and chromatofocusing on PBE-94 gel. The purified enzyme exhibited homogeneity upon electrophoresis. The enzyme was most active at pH 7.5 and was Stable within pH range of 6.0 to 7.5. The enzyme was most active at 40°C and was stable up to 50°C. The activity was inhibited by p-chloromercuribenzoic acid and was considerably inhibited by metal chelating reagents. It was highly activated by cobalt and slightly activated by zinc and manganese. The molecular weight of the enzyme was 120,000 by gel filtration on Sephadex G-200. The Michaelis constant for arginine-2-naphthylamide was estimated to be 1.0 × 10⁻⁴ M. Characterization studies indicated that the enzyme was capable of cleaving an aminoterminal leucine and phenylalanine residues. The enzyme showed a wide range of specificity against dipeptides and oligopeptides.     

仙人掌内酯豆腐的研制

以米邦塔食用仙人掌和大豆为主要原料研制仙人掌内酯豆腐，其最佳工艺参数为：以豆、水比为：1：4制成的豆乳，与仙人掌汁按6：2的比例调配，GDL（D-葡萄糖酸-δ-内酯）添加量为0．40％，成品呈淡绿色，质地细腻、弹性好．具纯正豆香味及仙人掌特有的清香。     

干酪风味影响因素的论述

本文对影响干酪风味的众多因素进行了论述,包括乳的来源、成分,干酪的盐含量、结构和酸度变化,干酪中的相变化带来的影响,以及基因和风味的联系,发酵剂和附属发酵剂的影响。从而为控制干酪的风味形成,获得稳定一致的风味物质,制作特征性风味的干酪奠定基础。     

Proteolysis of Fynbo Cheese Salted with NaCl/KCl and Ripened at Two Temperatures

Cheeses salted in solutions of 100g NaCl/L and 100g KCl/L and ripened for 90 days at 12°C and 16°C were compared with cheeses salted in brine of 190g NaCl/L and ripened at the same temperatures. Peptides of the water-soluble nitrogen (WSN) fraction were quantified by the Kjeldahl method and analyzed by reverse-phase HPLC. There were no differences (P>0.05) attributable to salt treatments; and the cheeses stored at 16°C showed higher levels of WSN/Total Nitrogen (TN) than cheeses ripened at 12°C. HPLC profiles of WSN extracts showed differences in the hydrophilic zone for cheeses ripened at different temperatures, but profiles were similar for cheeses salted with NaCl and with NaCl/KCl.     

High-Pressure Treatment and Freezing of Raw Goat Milk Curd for Cheese Manufacture: Effects on Cheese Characteristics

High-pressure treatment of raw goat milk curd was investigated as an alternative to thermal treatment of milk in cheese manufacture, and curd freezing as a procedure to surmount the seasonality of goat milk production. Experimental cheeses were made by mixing (70:30) fresh cow milk curd with frozen curd from pasteurized goat milk (PGC), frozen curd from raw goat milk (RGC), or frozen pressurized curd from raw goat milk (PRGC). Control cheese was made from a mixture (70:30) of pasteurized cow and goat milk. RGC cheese showed the highest counts of staphylococci, Gram-negative bacteria and coliforms, whereas PRGC cheese had maximum aminopeptidase activity, esterase activity, and overall proteolysis. Control cheese exhibited the highest dry matter content and peptide levels, the lowest concentration of free amino acids, the highest concentration of volatile compounds such as free fatty acids, alcohols and esters, and the firmest texture. Differences in sensory characteristics between experimental and control cheeses were of minor importance. High-pressure treatment of curd allowed the production of cheese of bacteriological quality similar to that of control cheese made using pasteurized milk, while curd freezing did not alter the sensory characteristics of experimental cheeses with respect to control cheese.     

Casein Degradation of Fynbo Cheese Salted with NaCl/KCl Brine and Ripened at Various Temperatures

ABSTRACT: Effect of temperature and salt substitution on casein degradation of Fynbo cheese was studied. Fynbo cheeses, salted in solutions of 190 g NaCl/L and of 100 g NaCl/L and 100 g KCl/L and ripened at 5, 12, and 16 °C, were sampled at 1, 5, 10, 20, 30, 60, and 90 d of ripening, at central and external zones. Samples were analyzed for moisture and chloride contents, maturation index, and casein degradation by urea‐polyacrylamide gel electrophoresis. NaCl replacement by KCl did not affect any of the parameters studied. Total salt concentration and ripening temperature affected proteolysis significantly. First‐order kinetics constants for α_s1‐casein degradation were in the range of 0.002 to 0.016 day^‐1 and the activation energy of the reaction was approximately 26 kcal/gmol.     

Heat Transfer During the Washing of Small Curd Cottage Cheese

The heat transfer which occurs during the cooling of small curd cottage cheese during washing is mathematically modeled as a conduction process. The thermal diffusivity for curd was determined experimentally and shown to agree with predictions of correlations in the Literature. Heat transfer occurs rapidly in curd, and is a relatively less significant design basis for washing systems than mass transfer.     

Ripened Semihard Cheese Covered with Lard and Dehydrated Rosemary (Rosmarinus officinalis L.) Leaves: Processing,Characterization, and Quality Traits

This study aimed to establish a manufacturing protocol and to characterize semihard cheese covered with lard and rosemary during ripening. After the manufacturing protocol was defined, the cheeses were produced with pasteurized and raw milk from Holstein cows, with and without (control) coating, and then ripened for 60 d. During this period the physicochemical properties, color, proteolysis, texture profile, and sensory acceptance were performed. The early‐ripening cheeses differed from the others in terms of color and moisture content. Multivariate statistical analysis separated chesses in groups differentiated by the effects of heat treatment of milk and ripening period. The ripened cheeses obtained from raw milk were sensorially more preferred. The coating gave the final products higher moisture content and favored color and texture characteristics. Consumer testing showed that the cheese obtained from raw milk and coated with lard and rosemary was the most preferred (acceptance of 82%) due to the specific coating of rosemary (aroma and flavor). This product has potential to add value and to diversify the production of semihard cheeses.     

豆腐渣面包的研制

以面包专用粉、脱水豆腐渣粉为主要原料，配以白砂糖、酵母等辅料，经过调粉、发酵、烘烤精制而成。通过配方、工艺条件的确定，制成的面包具有普通面包的色、香、味、形，又含有特殊营养成分。     

Temperature Dependence of Effective Diffusion Coefficient for Total Solids During Washing of Cheese Curd

The temperature dependence of the effective diffusion coefficient of total solids from small curd cottage cheese was estimated by fitting batch washing data at several temperatures (25°C, 35°C, 50°C, and 58°C) to a previously developed mass transfer model. The model was based on spherical geometry of curd particles. The correlation for diffusivity was found to be D_effective= (0.0658T + 1.72) × 10^?6, where D_effective is in cm²/sec and T is in °C.     

Diacetyl as a Flavor Component in Full Fat Cottage Cheese

Diacetyl was detected at about 0.2 ppm using a two alternative forced choice procedure. Consumer acceptance for cottage cheese showed a small effect of added diacetyl, peaking at 1.0 ppm for aroma acceptance and flavor acceptance. Patterns of acceptance across diacetyl levels were similar for both frequent and infrequent consumers. Consumer acceptance tests conducted in a campus-based sensory testing facility gave similar results to tests conducted in a shopping mall, although the mall data were more variable.     

凝乳工艺对功能性低脂干酪中活菌数的影响

活菌数是功能性低脂干酪的重要指标,就凝乳工艺过程对功能性低脂干酪活菌数的影响进行了研究,旨在通过控制凝乳工艺过程参数而使干酪最终活菌数达到功能性食品的标准。通过对单因素试验和正交试验研究与分析,结果表明:凝乳酶添加量0.01%,凝乳温度35℃,凝乳pH 6.2,CaCl2添加量0.03%,干酪活菌数均能达到107CFU/mL,符合功能性低脂干酪的活菌数要求,能够获得较为理想的试验效果。     

发酵剂对双蛋白干酪理化特性及风味的影响

在牛乳和添加豆乳(质量分数10%)的牛乳中分别使用筛选发酵剂与商品发酵剂进行切达干酪生产,并对成熟干酪的理化成分、质地、风味成分和感官特性进行分析。结果表明,豆乳的添加对干酪的质地、风味和感官特性均无不良影响,而应用筛选发酵剂L. lactis subsp. cremoris QH27-1和L. lactis subsp. lactis XZ3303生产双蛋白切达干酪对干酪的品质有一定的改善作用,可将其应用于双蛋白干酪生产中。