乳品加工中重要热处理指示物的研究

乳品加工过程中,热处理是主要的加工方式,热处理对乳品的营养有很大的影响。为了控制乳品的质量,必须检测热处理过程中温度是否符合规定的要求,文中将就几种重要热处理指示物在乳品热处理质量控制中的研究与应用进行论述。     

高级杏仁酸乳的研制

本课题在酸奶技术的基础上,将杏仁乳与牛乳的混合液中加入乳酸菌发酵。采用正交实验,用保加利亚乳杆茵和嗜热链球菌混合发酵杏仁牛乳混合液,找出混合发酵的最佳工艺条件。苦杏仁经90℃热煮后迅速于冷水中冷却去皮,然后于0．1％HCl中浸泡10-12h,经浸泡漂洗,再经组织破碎机破碎,胶体磨处理,过滤等,添加牛奶、蔗糖于杏仁奶中,经均质杀菌、冷却后,接种1％-3％已驯化的嗜热链球菌和保加利亚乳杆菌发酵剂,发酵条件为40-42℃,恒温箱中培养,再经调配得成品。     

Dairy products and inflammation: A review of the clinical evidence

Inflammation is a major biological process regulating the interaction between organisms and the environment, including the diet. Because of the increase in chronic inflammatory diseases, and in light of the immune-regulatory properties of breastfeeding, the ability of dairy products to modulate inflammatory processes in humans is an important but unresolved issue. Here, we report a systematic review of 52 clinical trials investigating inflammatory markers in relation to the consumption of dairy products. An inflammatory score (IS) was defined to quantitatively evaluate this interaction. The IS was significantly positive for the entire data set, indicating an anti-inflammatory activity in humans. When the subjects were stratified according to their health status, the IS was strongly indicative of an anti-inflammatory activity in subjects with metabolic disorders and of a pro-inflammatory activity in subjects allergic to bovine milk. Stratifying the data by product categories associated both low-fat and high-fat products, as well as fermented products, with an anti-inflammatory activity. Remarkably, the literature is characterized by a large gap in knowledge on bioavailability of bioactive nutrients. Future research should thus better combine food and nutritional sciences to adequately follow the fate of these nutrients along the gastrointestinal and metabolic axes.     

凝固型鹰嘴豆酸乳的发酵工艺研究

以鹰嘴豆和复原乳为主要原料,通过保加利亚乳杆菌和嗜热链球菌发酵得到鹰嘴豆酸奶。结果表明:膨胀鹰嘴豆以6倍质量的水进行磨浆,再与复原乳以1∶1混合,通过保加利亚乳杆菌和嗜热链球菌1∶1混合发酵,接种量6%,加糖量5%,发酵温度42℃,发酵时间6～7 h。     

鹰嘴豆酸奶的发酵工艺优化

以鹰嘴豆、复原乳为主要原料,将保加利亚乳杆菌和嗜热链球菌作为发酵剂,对发酵剂接种量、加糖量及发酵时间进行优化,结果表明:将鹰嘴豆浆与复原乳1:1混合,接种量为7%,加糖量为5%,发酵时间为10 h,在42℃条件下进行发酵,可得到品质优良,口感良好的鹰嘴豆酸奶。     

Modeling of Camembert-type cheese mass loss in a ripening chamber: main biological and physical phenomena

A model of the mass loss of Camembert-type cheese was established with data obtained from 2 experimental ripening trials carried out in 2 pilot ripening chambers. During these experiments, a cheese was continuously weighed and the relative humidity, temperature, oxygen, and carbon dioxide concentrations in the ripening chamber were recorded online. The aim was to establish a simple but accurate model that would predict cheese mass changes according to available online measurements. The main hypotheses were that 1) the cheese water activity was constant during ripening, 2) the respiratory activity of the microflora played a major role by inducing heat production, combined with important water evaporation, 3) the temperature gradient existing inside the cheese was negligible, and the limiting phenomenon was the convective transfer. The water activity and the specific heat of the cheeses were assessed by offline measurements. The others parameters in the model were obtained from the literature. This dynamic model was built with 2 state variables: the cheese mass and the surface temperature of the cheese. In this way, only the heat transfer coefficient had to be fitted, and it was strongly determined by the airflow characteristics close to the cheeses. Model efficiency was illustrated by comparing the estimated and measured mass and the mass loss rate for the 2 studied runs; the relative errors were less than 1.9 and 3.2% for the mass loss and the mass loss rate, respectively. The dynamic effects of special events, such as room defrosting or changes in chamber relative humidity, were well described by the model, especially in terms of kinetics (mass loss rates).     

Kinetics of Casein Degradation during Ripening of Fynbo Cheese Salted with NaCl/KCl Brine

First-order kinetics with respect to the α_s1-casein concentration was used to study casein degradation during low-fat Fynbo cheese ripening. Effects of partial NaCl replacement by KCI during cheese salting were studied by statistical treatment of the casein degradation results. Four zones from cheeses at 1, 5, 10, 20, and 30 ripening days were analyzed by a polyacrylamide gel electrophoresis method. Similar kinetic parameters were obtained for a cheese salted with a NaCl/KCl brine and for a control cheese during ripening. Results were more affected by salt concentration than by salt substitution. KCl did not strongly influence kinetics of Fynbo cheese proteolysis.     

葛根酸奶的工艺研究

对具有营养保健功能的葛根酸奶的加工工艺进行了初步探讨.结果表明以鲜葛根为原料,用0.05%Vc+0.1%柠檬酸作为护色剂,可制得色泽洁白,质量良好的葛根汁;采用葛根汁鲜牛奶＝37的原料配比,将保加利亚乳杆菌和嗜热链球菌以11混合作为发酵剂进行发酵,采用接种量3%,加蔗糖量8%,发酵温度42℃,发酵时间5h等工艺条件,可得到品质风味优良的葛根酸奶.     

Conjugated Linoleic Acid Concentrations in Dairy Products as Affected by Processing and Storage

Total conjugated linoleic acid (CLA) concentrations increased 1.32 fold in salted and 1.27 in unsalted butter but did not alter the ratio of 9-cis 11-trans to total CLA. Nonfat yogurt showed an increase in CLA content with processing (5.25 mg total CLA/g fat) compared to unprocessed raw material (4.40 mg CLA/g fat). No changes in CLA content was observed in processed dairy products such as lowfat yogurt, regular yogurt, lowfat and regular ice cream, sour cream or cheeses such as Mozzarella, Gouda and Cheddar. Storage did not affect CLA concentration in any products suggesting that CLA is a stable component.     

Accumulation of Some Flavor Compounds in Full- and Reduced-fat Cheddar Cheese Under Different Ripening Conditions

Reduced-fat cheese showed higher levels of ethanol and lower acetoin than full-fat samples throughout ripening regardless of conditions. Total headspace volatiles, as well as butanoic and hexanoic acids, increased with ripening time and temperature. Full- and reduced-fat cheeses developed distinctly different headspace volatile profiles throughout ripening. The effects of ripening conditions were more notable in full-fat samples. Ripening reduced-fat Cheddar cheese at an elevated temperature for a limited time may enhance development of some desirable volatiles such as butanoic acid.     

Proteolysis in Mozzarella cheeses manufactured by different industrial processes

The objective of the present study was to investigate the influence of stretching temperature, fat content, and time of brining on proteolysis during ripening of Mozzarella cheeses. Seventeen cheese-making experiments (batches) were carried out on an industrial scale on successive days, following the standard procedure with some modifications. Fat content of cheese milk, temperature at the stretching step, and time of brining varied from one batch to another as required by the experimental design, outlined by a surface response model. Proteolysis was assessed during ripening of samples, which was prolonged for at least 3 mo, by means of electrophoresis, nitrogen fractions, and soluble peptide mapping. The amount of soluble nitrogen at pH 4.6 was not significantly different in cheeses obtained by diverse procedures, but it increased during ripening of all samples. This result was coincident with the breakdown of α_s1- and β-caseins evidenced by electrophoresis, which reached similar extents at late stages of ripening, regardless of the cheese-making process. Multivariate analysis on soluble peptide profiles obtained by liquid chromatography also detected sample grouping according to ripening time, but did not evidence any separation caused by the cheese-making technology. We concluded that the changes in the cheese-making process assayed in this work were insufficient to produce significant differences in proteolysis of the cheeses. Ripening time had more influence on proteolysis of Mozzarella cheeses than any other assayed variable.     

Comprehensive analysis of proteolysis during 8 months of ripening of high-cooked Old Saare cheese

We applied capillary electrophoresis, liquid chromatography coupled with tandem mass-spectrometry (MS/MS), and ultra-performance liquid chromatography to determine the composition of water-insoluble and water-soluble proteinaceous fractions of the cheese and to study in detail the degradation of caseins during 8 mo of ripening of Estonian high-temperature cooked hard cheese Old Saare. The application of high-resolution and high-accuracy MS/MS enabled identification of more than 3,000 small peptides, representing a fairly full casein peptidome containing peptides of 4 to 25 AA in length: 1,049 from β-casein (CN), 944 from α_S1-CN, 813 from α_S2-CN, and 234 from κ-CN. The majority of β-CN- and α_S1-CN-derived peptides originated from the N-terminal parts of the molecule, f6-93 and f1-124, respectively; peptides from α_S2-CN arose predominantly from the C-terminal end f100-162. At the beginning of ripening, we found a relatively high amount of peptides originating from the glycomacropeptide part of κ-CN, whereas peptides from para-κ-CN prevailed during the later stages of ripening of the cheese. The cleavage patterns of β-CN, α_S2-CN, as well as α_S1-CN, showed that primary proteolysis was started mainly by plasmin, although a low proteolytic activity of chymosin was also evident. Based on the analysis of cleavage sites, we observed a significant participation of proteolytic enzymes, including amino- and carboxypeptidases, of both mesophilic and thermophilic starter bacteria in further hydrolysis of oligopeptides during the ripening. Several new phosphopeptides were detected in the result of MS/MS data analysis. The profiles of the estimated concentrations of phosphopeptides revealed that those originating from β-CN and α_S1-CN accumulated during cheese maturation. In contrast, we did not notice any generation of phosphopeptides from the highly phosphorylated part of α_S2-CN, f25-80, presumably due to the inaccessibility of this region to the action of plasmin and chymosin. The analysis of cleavage sites and the combination of principal component and clustering analyses provided a characterization of the complex dynamics of formation and degradation of peptides during cheese maturation. We made an attempt to obtain a comprehensive picture of proteolysis during Old Saare cheese ripening on the basis of the detailed peptidomic data, including also the less abundant peptides determined by MS/MS, and complemented by the data on intact caseins and free AA and reported the results in the paper.     

成熟温度和时间对半硬质干酪成熟特性影响研究

研究成熟温度和时间对半硬质干酪成熟特性的影响。将干酪分别在4、10、16℃条件下成熟,测定其在90d 内品质变化规律。结果表明,在90d 成熟期内,pH 值先下降后升高,最后趋于稳定;pH4.6 可溶性氮含量和12% 三氯乙酸可溶性氮含量逐渐升高;乳酸菌总数逐渐下降。成熟温度对干酪的感官品质、pH 值、蛋白质的降解和乳酸菌总数影响显著。4℃成熟的干酪,在第90 天时,感官品质达到最好;10℃成熟的干酪,在第45天时,感官品质达到最好;16℃成熟的干酪,感官品质较差。根据感官品质和其他参数的变化规律,确定半硬质干酪的最佳成熟温度为10℃,最佳成熟时间为45d。     

Lipolysis in cheddar cheese made from raw, thermized, and pasteurized milks

The evolution of free fatty acids (FFA) was monitored over 168 d of ripening in Cheddar cheeses manufactured from good quality raw milk (RM), thermized milk (TM; 65°C × 15 s), and pasteurized milk (PM; 72°C × 15 s). Heat treatment of the milk reduced the level and diversity of raw milk microflora and extensively or wholly inactivated lipoprotein lipase (LPL) activity. Indigenous milk enzymes or proteases from RM microflora influenced secondary proteolysis in TM and RM cheeses. Differences in FFA in the RM, TM, and PM influenced the levels of FFA in the subsequent cheeses at 1 d, despite significant losses of FFA to the whey during manufacture. Starter esterases appear to be the main contributors of lipolysis in all cheeses, with LPL contributing during production and ripening in RM and, to a lesser extent, in TM cheeses. Indigenous milk microflora and nonstarter lactic acid bacteria appear to have a minor contribution to lipolysis particularly in PM cheeses. Lipolytic activity of starter esterases, LPL, and indigenous raw milk microflora appeared to be limited by substrate accessibility or environmental conditions over ripening.     

无糖葛根酸奶的工艺研究

对具有营养保健功能的无糖葛根酸奶的加工工艺进行了初步探讨。结果表明:以鲜葛根为原料,用0.05%VC+0.1%柠檬酸作为护色剂,可制得色泽洁白,质量良好的葛根汁;采用葛根汁:鲜牛奶=3:7的原料配比,阿斯巴甜0.05%,明胶0.15%,将保加利亚乳杆菌和嗜热链球菌以1:1混合作为发酵剂进行发酵,接种量3%,发酵温度42℃,发酵时间5h等工艺条件,可得到品质风味优良的无糖葛根酸奶。     

Proteolytic and lipolytic changes during the ripening of a Spanish craft goat cheese (Armada variety)

The proteolytic and lipolytic changes during the ripening process were investigated in four batches of Armada goat's milk cheese (an artisanal variety produced in the North of Spain), by determining the classical nitrogen fractions, caseins and their degradation products, free amino acids, as well as the acidity of the fat, thiobarbituric acid (TBA) number and free fatty acids. Values obtained for the nitrogen fractions and for caseins and their degradation products show that this cheese undergoes very little protein degradation. A low free amino acids content was observed throughout the ripening process with a predominance of Pro followed by Leu+Ile, Glu acid, Phe, His+Lys and Val. The lipid degrada-tion was very intense from the second month of ripening, only comparable to that reported for cheeses ripened by moulds. The average free fatty acids content increased 20-fold during ripening, reaching final values of 44·5 g kg⁻¹. All the free fatty acids increased considerably during ripening, resulting in a predominance of saturated and unsaturated long-chain acids, followed by medium-chain acids, C₁₀ principally. Short-chain fatty acid content by the end of ripening was higher than that presented in other cheese varieties with a similar high degree of lipolysis. © 1997 SCI.     

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.     

新型酸乳酪的研制

以鲜乳和乳清蛋白浓缩物为主要原料再配合其他辅料制成了一种新型发酵乳制品-酸乳酪（蛋白质量分数4．5％）。通过对样品硬度、拉伸力、脱水收缩作用敏感性、黏度、持水力等参数的测定和感官评价，确定了合理的产品配方，并对产品质量作了评价与分析。结果表明，当乳清蛋白浓缩物为3．7％，白砂糖7．0％，明胶0.3％，果胶0．05％（均为质量分数，下同），选用Str．Lactis and Str．cremoris作为发酵剂，在30℃条件下发酵13h即可得到优质的酸乳酪，该产品具有营养丰富，稳定性好和感官品质佳等特点。     

酶法促熟干酪的研究进展

干酪促熟常用的方法有酶法；修饰发酵剂细胞；提高成熟温度；悬浮液系统法等．其中的酶法促熟干酪研究较为系统。论述了酶法促熟干酪中常用的酶类及其作用，并对其应用前景作以展望。