Edam干酪加工工艺研究

对Edam加工关键因素进行了研究。通过实验得出Edam干酪的最佳工艺条件为发酵剂添加量为0.01%,CaCl2添加量为0.015%(均为质量分数),热缩温度为38℃,可得到较高的干酪得率及较好的产品品质。     

Subject: Novel cheeses and cheese-making processes

Cheese substitutes can be produced in many forms, but most are made by blending the individual constituents, including non-dairy fats or proteins, to produce a cheese-like product to meet specific requirements. A substantial market has developed in the United States, particularly for industrial food uses: of these, pizza manufacture and the school meals programme are the most important. A small market has been established in Britain, mostly replacing imported cheese in formulated foods. It is suggested that cheese substitutes, or cheese analogues prepared entirely from dairy components, could be developed as useful additions to processing ranges and would be unlikely to reduce natural cheese consumption.     

预处理在羊毛MTG酶处理工艺中的应用

为解决单独用蛋白酶处理羊毛织物时防缩效果不明显的问题,文章在谷氨酰胺转胺酶(MTG酶)处理前对比了H2O2、等离子体、超声波预处理对羊毛织物防缩等性能的作用效果,选择最佳的预处理方法.讨论了在最佳预处理条件下,MTG酶浓度、处理温度和时间的改变对羊毛织物防缩性能的影响,并借助电镜扫描照片观察处理前后羊毛纤维的微观结构.结果表明:采用等离子预处理效果比较好,最佳工艺条件为,MTG酶浓度3%,30℃,处理50 min.     

Acceleration of Edam cheese ripening using acid fungal protease

Edam cheese was made from a mixture of cow/goat milk (1:1, v/v). The mixture of both milks was standardized to have 3.2% fat and a casein/fat ratio of 0.7, heated at 72 °C for 15 s, immediately cooled to 40 °C and divided into four portions. Acid fungal protease (Formase 200) was added at levels of 0.5, 1.0 and 2.0 g/kg of curd to the first three portions, and the last one was manufactured without the addition of acid fungal protease to serve as a control sample. The samples of control as well as those of different treatments were analysed for chemical and organoleptic properties when fresh and after 1, 2 and 3 months of storage at 12 ± 1 °C. The obtained results pointed out that the samples of Formase-treated-cheese exhibited higher values of soluble nitrogen/total nitrogen ratio (SN/TN), total volatile fatty acids (TVFA), titratable acidity (TA), and the flavour was developed faster as compared with the samples of control. A good quality Edam cheese could be produced with a high acceptability when Formase 200 was used at level of 1.0 and 2.0 g/kg of curd and the cheese was ripened for 2 months only.     

Edam牦牛干酪成熟过程中品质变化及蛋白质降解

为研究Edam牦牛半硬质干酪成熟机理,分别测定成熟0、20、40、60、80 d Edam牦牛干酪的感官、理化、物性、蛋白质和脂肪分解指标,采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳和傅里叶变换红外光谱等方法研究酪蛋白降解情况,通过Pearson相关性分析成熟时间与各指标间的相关性。结果表明：随着成熟时间延长,感官评分先下降后上升;水分含量、pH值下降;亮度值（L*）下降,红度值（a*）和黄度值（b*）值上升;硬度、弹性、胶黏性均上升,凝聚性逐渐下降;储能模量和损耗模量升高,损耗角正切值始终小于1;成熟时间与总氮含量、pH 4.6和12%三氯乙酸条件下干酪中可溶性氮含量等呈极显著正相关（P<0.01）;脂肪含量先升高后降低,游离脂肪酸含量和硫代巴比妥酸值逐渐增加。酪蛋白（casein,CN）降解研究结果表明：αs1-CN、αs2-CN、β-CN及κ-CN均随成熟时间延长而不断降解,成熟80 d时大分子蛋白降解明显;成熟过程中β-折叠、α-螺旋逐渐向无规卷曲转化;成熟时间与羰基含量、表面疏水性呈极显著正相关（P<0.01）,与总巯基含量呈显著负相关（P<0.05）。     

Salt reduction in film‐ripened,semihard Edam cheese

As a potential measure to improve public health, this study aimed to reduce the sodium (Na) content of film‐ripened, semihard Edam cheese to ≤0.4 g Na/100 g (≤1 g NaCl/100 g), while retaining typical quality and safety characteristics. For this, mineral salt substitutions containing potassium (K) were compared with simple NaCl reduction in brine, alongside an adjustment of starter cultures in an effort to enhance taste. Desired Na and K values were achieved, and microbial quality was not compromised in Na‐reduced Edam after six weeks of ripening. However, all Na‐reduced cheeses tasted bitter and were therefore organoleptically unsatisfactory.     

Estimation of genetic parameters for cheese-making traits in Spanish Churra sheep

The global production of sheep milk is growing, and the main industrial use of sheep milk is cheese making. The Spanish Churra sheep breed is one of the most important native dairy breeds in Spain. The present study aimed to estimate genetic parameters for a wide range of traits influencing the cheese-making ability of Churra sheep milk. Using a total of 1,049 Churra ewes, we studied the following cheese-making traits: 4 traits related to milk coagulation properties (rennet coagulation time, curd-firming time, and curd firmness at 30 and 60 min after addition of rennet), 2 traits related to cheese yield (individual laboratory cheese yield and individual laboratory dried curd yield), and 3 traits measuring curd firmness over time (maximum curd firmness, time to attain maximum curd firmness, and syneresis). In addition, a list of milk traits, including the native pH of the milk and several milk production and composition traits (milk yield; the fat, protein, and dried extract percentages; and the somatic cell count), were also analyzed for the studied animals. After discarding the noncoagulating samples (only 3.7%), data of 1,010 ewes were analyzed with multiple-trait animal models by using the restricted maximum likelihood method to estimate (co)variance components, heritabilities, and genetic correlations. In general, the heritability estimates were low to moderate, ranging from 0.08 (for the individual laboratory dried curd yield trait) to 0.42 (for the fat percentage trait). High genetic correlations were found within pairs of related traits (i.e., 0.93 between fat and dried extract percentages, ?0.93 between the log of the curd-firming time and curd firmness at 30 min, 0.70 between individual laboratory cheese yield and individual laboratory dried curd yield, and ?0.94 between time to attain maximum curd firmness and syneresis). Considering all the information provided here, we suggest that in addition to the current consideration of the protein percentage trait for improving cheese yield traits, the inclusion of the pH of milk as a measured trait in the Churra dairy breeding program would represent an efficient strategy for improving the cheese-making ability of milk from this breed.     

干酪用牛凝乳酶替代品的研究进展

牛凝乳酶具有高凝乳活性和低非特异蛋白水解活性而广泛用于干酪制备。随着干酪市场的逐年增长,牛凝乳酶出现供不应求,其替代品应运而生,包括其他动物凝乳酶、植物凝乳酶、微生物凝乳酶、重组凝乳酶。在这些替代品中,重组牛凝乳酶显示出与天然牛凝乳酶相似的酶学特性,并且纯度更高,制作的干酪品质更好。目前已经有重组牛凝乳酶上市出售,成功替代了天然牛凝乳酶,但关于提高重组牛凝乳酶表达量与催化活性的研究远未止步。文中主要综述了凝乳酶结构、牛凝乳酶的替代品和重组凝乳酶的研究进展,详细综述了一些提高重组牛凝乳酶的表达方法,为外源蛋白在宿主中的高水平表达提供了有效参考。     

转谷氨酰胺酶对Cheddar干酪力学性质的影响

通过微流变仪分析凝乳的黏弹性及流动性,利用质构仪、流变仪和低场核磁技术跟踪发酵周期测定Cheddar干酪样品质构特性、流变性和水分分布的情况,明晰转谷氨酰胺酶对Cheddar干酪凝乳及发酵过程的影响规律。结果表明,添加TGase会降低凝乳的弹性因子,随凝乳时间延长,宏观黏度指数显著升高,流动性显著降低。TGase可以增加干酪硬度、咀嚼性和剪切力;TGase可以提高干酪弹性模量(G')),损耗模量(G'),增加了干酪的黏弹性。核磁分析表明,TGase对干酪自由水的影响显著,降低了结合水的弛豫时间。     

Genome-wide association study for selected cheese-making properties in Dual-Purpose Belgian Blue cows

This study aimed to estimate genetic parameters and identify genomic region(s) associated with selected cheese-making properties (CMP) in Dual-Purpose Belgian Blue (DPBB) cows. Edited data were 46,301 test-day records of milk yield, fat percentage, protein percentage, casein percentage, milk calcium content (CC), coagulation time (CT), curd firmness after 30 min from rennet addition (a30), and milk titratable acidity (MTA) collected from 2014 to 2020 on 4,077 first-parity (26,027 test-day records), and 3,258 second-parity DPBB cows (20,274 test-day records) distributed in 124 herds in the Walloon Region of Belgium. Data of 28,266 SNP, located on 29 Bos taurus autosomes (BTA) of 1,699 animals were used. Random regression test-day models were used to estimate genetic parameters through the Bayesian Gibbs sampling method. The SNP solutions were estimated using a single-step genomic BLUP approach. The proportion of the total additive genetic variance explained by windows of 25 consecutive SNPs (with an average size of ～2 Mb) was calculated, and regions accounting for at least 1.0% of the total additive genetic variance were used to search for candidate genes. Heritability estimates for the included CMP ranged from 0.19 (CC) to 0.50 (MTA), and 0.24 (CC) to 0.41 (MTA) in the first and second parity, respectively. The genetic correlation estimated between CT and a30 varied from ?0.61 to ?0.41 and from ?0.55 to ?0.38 in the first and second lactations, respectively. Negative genetic correlations were found between CT and milk yield and composition, while those estimated between curd firmness and milk composition were positive. Genome-wide association analyses results identified 4 genomic regions (BTA1, BTA3, BTA7, and BTA11) associated with the considered CMP. The identified genomic regions showed contrasting results between parities and among the different stages of each parity. It suggests that different sets of candidate genes underlie the phenotypic expression of the considered CMP between parities and lactation stages of each parity. The findings of this study can be used for future implementation and use of genomic evaluation to improve the cheese-making traits in DPBB cows.     

Effect of water content on the hardness of Edam cheese

It is proposed that the physical properties of cheese, in particular hardness, depend on moisture content. A statistical analysis of the experimental data in support of the proposal has been carried out. Empirical equations describing the changes in physical properties with moisture content in Edam cheese after pressing, during ripening, and as marketed, have been developed. A transformed function is proposed that makes possible the control of Edam cheese hardness by regulation of the dehydration level during the pressing operation.     

Influence of transglutaminase treatment on some physico-chemical properties of milk

Transglutaminase (TGase) is an enzyme that cross-links many proteins, including milk proteins. In this study, the effects of TGase on some physico-chemical properties of milk were studied. TGase-treated milk was not coagulable by rennet, which was due to failure of the primary (enzymic) stage of rennet action rather than the non-enzymic secondary phase. Dissociation of TGase-treated casein micelles by urea or sodium citrate or removal of colloidal calcium phosphate by acidification and dialysis was reduced, presumably due to the formation of cross-links between the caseins. Casein micelles in TGase-treated milks were also resistant to high pressure treatment and to hydrolysis by plasmin. Results of the present study show that milk proteins are fundamentally modified by the action of TGase, which may have applications in the manufacture of functional proteins for use as novel food ingredients.     

Exo-metabolites of mycelial fungi isolated in production premises of cheese-making and meat-processing plants

Data were obtained on the species composition of mycelial fungi isolated from the air of workrooms and production premises in cheese-making and meat-processing plants. The strains studied were shown to be capable of producing various low molecular weight compounds. Many of them are mycotoxins such as α-cyclopiazonic acid (CPA), mycophenolic acid (MPA), citrinin, cladosporin, roquefortine and ergot alkaloids. The profiles of the secondary metabolites were used to elucidate the species’ names of the isolated strains.     

Effects of ultra-high pressure homogenization on the cheese-making properties of milk

The effects of single- or 2-stage ultra-high pressure homogenization (UHPH; 100 to 330 MPa) at an inlet temperature of 30°C on the cheese-making properties of bovine milk were investigated. Effects were compared with those from raw, heat-pasteurized (72°C for 15 s), and conventional homogenized-pasteurized (15 + 3 MPa, 72°C for 15 s) treatments. Rennet coagulation time, rate of curd firming, curd firmness, wet yield, and moisture content of curds were assessed. Results of particle size and distribution of milk, whey composition, and gel microstructure observed by confocal laser scanning microscopy were analyzed to understand the effect of UHPH. Single-stage UHPH at 200 and 300 MPa enhanced rennet coagulation properties. However, these properties were negatively affected by the use of the UHPH secondary stage. Increasing the pressure led to higher yields and moisture content of curds. The improvement in the cheese-making properties of milk by UHPH could be explained by changes to the protein-fat structures due to the combined effect of heat and homogenization.     

Influence of adjunct cultures on volatile free fatty acids in reduced-fat Edam cheeses

The effects of the adjunct cultures Lactococcus lactis ssp. diacetylactis, Brevibacterium linens BL2, Lactobacillus helveticus LH212, and Lactobacillus reuteri ATCC 23272 on volatile free fatty acid production in reduced-fat Edam cheese were studied. Lipase activity evaluation using p-nitrophenyl fatty acid ester substrates indicated that L. lactis ssp. diacetylactis showed the highest activity among the 4 adjunct cultures. Full-fat and 33% reduced-fat control cheeses (no adjunct) were made along with 5 treatments of reduced-fat cheeses, which included individual, and a mixture of the adjunct cultures. Volatile free fatty acids of cheeses were analyzed using static headspace analysis with 4-bromofluorobenzene as an internal standard. Changes in volatile free fatty acid concentrations were found in headspace gas of cheeses after 3-and 6-mo ripening. Acetic acid was the most abundant acid detected throughout ripening. Full-fat cheese had the highest relative amount of propionic acid among the cheeses. Certain adjunct cultures had a definite role in lipolysis at particular times. Reduced-fat cheese with L. lactis ssp. diacetylactis at 3-mo showed the highest levels of butyric, isovaleric, n-valeric, iso-caproic, and n-caproic acid. Reduced-fat cheese with Lactobacillus reuteri at 6 mo produced the highest relative concentration of isocaproic, n-caproic, and heptanoic, and the highest relative concentration of total acids.     

Physical properties of pizza Mozzarella cheese manufactured under different cheese-making conditions

The effect of manufacturing factors on the shreddability and meltability of pizza Mozzarella cheese was studied. Four experimental cheeses were produced with 2 concentrations of denatured whey protein added to milk (0 or 0.25%) and 2 renneting pH values (6.4 or 6.5). The cheeses were aged 8, 22, or 36 d before testing. Shreddability was assessed by the presence of fines, size of the shreds, and adhesion to the blade after shredding at 4, 13, or 22°C. A semi-empirical method was developed to measure the matting behavior of shreds by simulating industrial bulk packaging. Rheological measurements were performed on cheeses with and without a premelting treatment to assess melt and postmelt cheese physical properties. Lowering the pH of milk at renneting and aging the cheeses generally decreased the fines production during shredding. Adding whey protein to the cheeses also altered the fines production, but the effect varied depending on the renneting and aging conditions. The shred size distribution, adhesion to the blade, and matting behavior of the cheeses were adversely affected by increased temperature at shredding. The melting profiles obtained by rheological measurements showed that better meltability can be achieved by lowering the pH of milk at renneting or aging the cheese. The premelted cheeses were found to be softer at low temperatures (<40°C) and harder at high temperatures (>50°C) compared with the cheeses that had not undergone the premelting treatment. Understanding and controlling milk standardization, curd acidification, and cheese aging are essential for the production of Mozzarella cheese with desirable shreddability and meltability.     

Oligomerization of β-lactoglobulin by microbial transglutaminase during high pressure treatment

High pressure treatment of solutions of #-lactoglobulin in the presence of microbial transglutaminase for 60 min at 40 °C resulted in an enzyme-induced oligomerization of the whey protein at pressures of 400 MPa and to a less extent at 600 MPa. The degree of crosslinking was lower when transglutaminase was added to solutions of #-lactoglobulin after high pressure treatment and no oligomerization was detectable when the protein was incubated with transglutaminase under atmospheric pressure. Thus, microbial transglutaminase in combination with high pressure treatment offers new perspectives for the modification of globular proteins, which usually are not affected by the enzyme under atmospheric conditions.     

Modulation of the thermal stability of β-lactoglobulin by transglutaminase treatment

The influence of microbial transglutaminase (MTGase) treatment in the presence and absence of dithiothreitol (DTT) on the thermal stability of β-lactoglobulin (β-LG) was investigated using size-exclusion chromatography (SEC) combined with on-line multiangle laser light scattering (MALLS) and UV detection. SEC–MALLS–UV analyses showed that moderate MTGase treatment (up to 6 or 9 h) led to the decline in thermal stability of β-LG, while excess treatment (e.g. 23 h) resulted in remarkable increase, irrespective of whether the reducing agent DTT was present or not. The modulation in thermal stability may be attributed to the partial unfolding of protein molecules and the subsequent re-arrangement of conformation.     

Edam干酪储存期组分变化对其质构的影响

研究了Edam干酪在不同储存期可溶性氮质量分数、游离脂肪酸质量分数变化与质构的关系,为了更好地评价干酪质量提供理论依据。