地衣芽孢杆菌凝乳酶对切达干酪成熟过程中蛋白水解的影响

利用地衣芽孢杆菌凝乳酶制作切达干酪和切达干酪类似物,分析干酪成熟过程中各蛋白水解指标的变化规律,以揭示地衣芽孢杆菌凝乳酶对切达干酪成熟过程中蛋白水解的影响。结果表明,CDF组（添加地衣芽孢杆菌D3.11凝乳酶所制切达干酪）、CD3组（添加地衣芽孢杆菌D3.11凝乳酶但未添加发酵剂制成的干酪类似物）和CCF组（添加商品凝乳酶所制切达干酪）干酪蛋白含量、pH 4.6-可溶性氮、12%三氯乙酸-可溶性氮、5%磷钨酸-可溶性氮、总游离氨基酸含量均随着成熟时间延长呈显著增加趋势,并且成熟期间CDF组干酪均显著高于CCF组干酪（P＜0.05）;十二烷基硫酸钠-聚丙烯酰氨凝胶电泳分析表明,CDF组干酪α-酪蛋白水解程度较大;pH 4.6-可溶性肽段分析表明,随着干酪的成熟,总肽含量呈先增加后下降趋势,但疏水性肽与亲水性肽的比值呈持续下降趋势,在成熟第6个月时,CDF组、CD3组和CCF组干酪疏水性肽与亲水性肽比值分别为2.668、2.822、3.788。主成分分析表明,3 组干酪的蛋白水解程度与成熟度呈正相关,与疏水性肽和亲水性肽的比值呈负相关。以上结果表明,利用地衣芽孢杆菌凝乳酶制作的干酪蛋白水解度更高,但其疏水性肽比例较小,研究结果可为地衣芽孢杆菌凝乳酶在干酪生产中的应用提供理论依据。     

Fynbo Cheese NaCl and KCl Changes during Ripening

In a model study we assumed that the cheese is a homogeneous solid with nonuniform initial concentration distributions, cheese surfaces are rendered impermeable after brining, and the generalized Fick's law form is valid for expressing the diffusive fluxes of solutes. NaCl and KCl concentrations at selected positions during distribution in Fynbo cheese kept at 12°C, after salting 10 hr in a brine of 100 g NaCl/L and 100 g KCl/L at the same temperature, were determined experimentally and compared with predicted values with the model at different storage times up to 30 days. Homogeneous distribution of solutes was reached at 20 days ripening, as predicted by the model and verified experimentally.     

豆奶干酪成熟过程中蛋白水解的研究

本文主要研究了豆奶干酪成熟过程中蛋白水解的变化,并与纯牛乳干酪进行比较。结果表明:豆奶干酪中pH4.6 SN 和12%TCA SN随着时间的延长逐渐增高,而且pH4.6 SN的增长速度比12%TCA SN快,这与纯牛乳干酪是一致的,但豆奶干酪的可溶性氮低于同一时期的纯牛乳干酪。     

常温奶酪加工技术及货架期稳定性研究进展

对不同加工技术如热杀菌、真空干燥、超高压、盐溃、气调包装等在延长奶酪货架期中的应用进行综述,探讨了目前常温奶酪加工技术研究中存在的问题和局限,综述了不同加工技术条件对产品货架期内的微生物含量、理化指标、风味的影响,以期为常温奶酪的研究开发提供依据.     

益生菌切达干酪成熟过程中细菌群落的多样性分析

采用选择性培养基和聚合酶链式反应和变性梯度凝胶电泳（polymerase chain reaction-denaturing gradient gelelectrophoresis,PCR-DGGE）技术,研究益生菌切达干酪成熟过程中（6 ℃,180 d）细菌群落构成及益生菌（干酪乳杆菌LC2W）的存活情况。结果表明：SBM和MSE等选择性培养基存在选择专一性不强的缺点,不能客观反映干酪内各种微生物的动态变化;随着切达干酪成熟时间的增加,发酵剂嗜热链球菌和乳酸乳球菌的数量明显下降,而非发酵剂菌群乳杆菌的数量和主要种类呈上升趋势;干酪成熟180 d后,干酪乳杆菌LC2W的存活量仍高于1×108CFU/g。切达干酪能作为干酪乳杆菌LC2W存活的良好载体;PCR-DGGE技术和选择计数法联用更加适合干酪细菌群落结构的分析。     

借助电子鼻对中式传统奶酪货架期进行预测

使用传统的分析方法和商用电子鼻对市售2种中式传统奶酪的货架期进行了预测。通过pH值、酸度和持水力的变化速率判断产品的质量变化;同时,使用电子鼻对相同贮藏期的样品的顶空气味指纹进行检测。结果表明:采用电子鼻系统中的LDA(线性判别法)能更准确判别出不同储藏时间的奶酪,并且和经典的分析方法预测的货架期基本是一致的。     

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）。     

营养素货架期内的衰减

对婴幼儿配方乳粉营养素衰减进行研究,分析加速试验周期内蛋白质、脂肪、碳水化合物、维生素、矿物质及可选择性成分营养素衰减情况。结果显示,经过180 d货架期加速试验研究,营养有不同程度衰减,其中维生素B1、叶酸、维生素D、锰、碘、二十碳四烯酸、二十二碳六烯酸、1,3-二油酸2-棕榈酸甘油三酯衰减率较高。     

解淀粉芽孢杆菌GSBa-1凝乳酶对羊奶干酪成熟特性的影响

为探究解淀粉芽孢杆菌GSBa-1凝乳酶制备的羊奶干酪(干酪B)成熟特性的变化,以采用商业凝乳酶和同批次羊奶制作的干酪(干酪A)为对照组,比较两组干酪在60d成熟期主要组分、质构特性、微生物指标及风味物质的变化。结果表明,两组干酪得率相差不大。成熟期间干酪的水分、蛋白质及脂肪含量呈先上升后下降趋势,干酪B始终高于干酪A;干酪游离氨基酸总量在成熟期间呈先下降后上升趋势,且干酪B中苯丙氨酸、天冬氨酸、异亮氨酸、甲硫氨酸、丝氨酸含量高于干酪A。成熟前期干酪B质构特性优于干酪A。干酪A成熟后乳酸乳球菌数量增加了(5.22±0.02)%,干酪B无显著变化(P>0.05)。成熟期内,两组干酪中挥发性风味物质种类和含量均增加,但干酪B中的壬酸、辛醇、2-庚酮、2-壬酮、二甲基砜使羊奶干酪风味独特、浓郁。因此,GSBa-1凝乳酶具备替代商业凝乳酶用于羊奶干酪生产的潜力,可对干酪风味的形成和品质的提升起到一定促进作用。     

Effects of Flavor and Texture on the Sensory Perception of Gouda‐Type Cheese Varieties during Ripening Using Multivariate Analysis

The impact of flavor composition, texture, and other factors on desirability of different commercial sources of Gouda‐type cheese using multivariate analyses on the basis of sensory and instrumental analyses were investigated. Volatile aroma compounds were measured using headspace solid‐phase microextraction gas chromatography/mass spectrometry (GC/MS) and steam distillation extraction (SDE)‐GC/MS, and fatty acid composition, low‐molecular‐weight compounds, including amino acids, and organic acids, as well pH, texture, and color were measured to determine their relationship with sensory perception. Orthogonal partial least squares‐discriminant analysis (OPLS‐DA) was performed to discriminate between 2 different ripening periods in 7 sample sets, revealing that ethanol, ethyl acetate, hexanoic acid, and octanoic acid increased with increasing sensory attribute scores for sweetness, fruity, and sulfurous. A partial least squares (PLS) regression model was constructed to predict the desirability of cheese using these parameters. We showed that texture and buttery flavors are important factors affecting the desirability of Gouda‐type cheeses for Japanese consumers using these multivariate analyses.     

Mozzarella干酪成熟过程中菌相变化规律的研究

为了研究Mozzarella干酪成熟过程中发酵剂菌种对干酪成熟的影响,本试验制作了模拟干酪,并以此为试验模型,分析了全脂Mozzarella干酪成熟过程中菌群的变化规律。结果表明:发酵剂乳酸菌是Mozzarella干酪成熟过程中的主要菌群,而且球菌在干酪成熟过程中占绝对优势;NSLAB对Mozzarella干酪成熟的作用不大。由于采用了真空包装,Mozzarella干酪中的杂菌数始终保持在很低的水平〔大肠菌群≤60MPN/100g,酵母霉菌≤45lg(cfu/g)〕,并且对干酪的成熟无影响。在Mozzarella干酪成熟过程中,乳糖含量逐渐下降,随着乳酸菌的自溶,使LDH增加,对干酪后期的成熟产生积极影响。     

一种毛霉表面成熟干酪的蛋白质水解作用评价

从毛豆腐中分离出一株毛霉,并应用于表面成熟干酪,以研究干酪成熟过程中所发生的蛋白质水解作用。在90d 的成熟过程中,干酪的pH 值增加;蛋白质水解作用的评价指标,如干酪外层的水溶性氮- 总氮比、pH4.6水溶性氮- 总氮比、12g/100mL 三氯乙酸可溶性氮- 总氮比,在成熟90d 后分别增加至(23.68 ± 1.07)%、(19.38 ± 1.32)%和(8.61 ± 0.85)%,并且高于干酪的内部相应指标。SDS-PAGE 和毛细管电泳分析干酪的pH4.6 不溶性组分,结果表明酪蛋白在干酪成熟过程中被降解。对干酪成熟过程中分离出的水溶性组分进行RP-HPLC 分析,结果显示成熟过程中蛋白质被水解以及形成一些新肽分子。     

成熟温度和时间对Cheddar干酪成熟特性的影响研究

通过对不同成熟参数下Cheddar干酪蛋白分解、质构、pH及感官评价的分析,探讨了成熟参数对Cheddar干酪的影响,并得出研究条件下的最优成熟温度和时间,分析了Cheddar干酪在成熟过程中的游离氨基酸变化情况。     

Fate of Aflatoxin M1 during Manufacture and Storage of Feta Cheese

ABSTRACT:  The effect of feta cheese manufacture on aflatoxin M₁ (AFM₁) content was studied using an enzyme immunoassay technique. Feta cheese was made from milk spiked with 1 and 2 μg AFM₁ per kilogram milk. Pasteurization at 63 °C for 30 min caused <10% destruction of AFM₁. During cheese making, the remaining AFM₁ in milk was partitioned between curd and whey with two-thirds retained in the curd and one-third going into the whey. Cheeses were then stored for 2 mo in 8%, 10%, and 12% brine solutions at 6 and 18 °C. There was a 22% to 27% reduction of AFM₁ during the first 10 d of storage, with slightly more loss as salt concentration increased and when the cheese was stored at 18 °C. Further storage caused only slight decrease in AFM₁ and after 30 d of brining there was no difference in AFM₁ content of the cheese based upon salt concentration of the brine. At 18 °C, no further losses of AFM₁ occurred after 30 d, and at 6 °C, there was continued slight decrease in AFM₁ levels until 50 d. After 60 d of brining, there was a total loss of 25% and 29% of the AFM₁ originally present for cheese brined at 6 and 18 °C, respectively. Thus, the combination of pasteurization, conversion of milk into feta cheese, and at least 50 d storage of cheese in brine caused a total loss of about 50% of the AFM₁ originally present in the raw milk.     

Dynamic Headspace Analyses of Volatile Compounds of Cheddar and Swiss Cheese during Ripening

The volatile compounds of Cheddar and Swiss cheeses during ripening for 9 wks at 11°and 21°C, respectively, were analyzed by a dynamic headspace analyzer/gas chromatograph every week. The compounds were identified by a combination of retention times and mass spectra. The volatile compounds of Cheddar increased 5.6 and Swiss cheese 15 times as ripening increased from 0 to 9 wks. The amount of volatile compounds of Swiss cheese was 2.6 times greater than that of Cheddar cheese during ripening. The volatile compounds were ketones, alcohols, aldehydes, esters, acids, sulfur compounds, benzenes, and hydrocarbons. Ketones and alcohols accounted for 92% of volatiles from Cheddar cheese and 88% of those from Swiss cheese.