干酪质地及流变学特性的研究进展

介绍了有关干酪的成分及工艺过程对质地和流变学特性影响的研究。在干酪成分中，蛋白质是影响产品流变学特性的主要因素，酪蛋白空间形成的网状结构构成了干酪流变学的基础。在加工过程中，pH、温度、钙浓度、蛋白水解等所有对干酪成分分子产生变化的因素都可能使干酪的流变学特性和质地发生变化。因此，干酪流变学特性的研究对更好地控制质地，生产出质优价廉的干酪，具有重要的意义。最后，研究状况进行了展望。     

再制干酪贮藏期间的物理及化学变化

再制干酪往往被认为是一种保质期较长的、稳定的干酪食品。事实上，再制干酪即便不被微生物污染，室温下的保质期也只有几个月。贮藏期间，再制干酪的质地和风味都慢慢改变，本文阐述了引起储藏期间再制干酪质地和风味变化的主要原因，对引起这些变化的因素加以分析．并概括了国外关于再制干酪储藏期的研究进展。通过对再制干酪贮藏期质地变化的研究，将有助于干酪生产者更好的预测和控制产品贮藏期间的质量。     

乳中钙、磷的特性及在干酪制造中的作用

乳中的盐类，特别是钙、磷组成的盐类对干酪生产中的凝乳过程和干酪的组织状态以及干酪的缓冲性方面有重要作用。在乳中添加钙离子，可以降低于酪的凝乳时间，增加凝胶硬度。乳的酸化程度和乳清排放时的pH，决定了酪蛋白胶粒中胶体磷酸钙的溶解程度，从而影响了干酪的矿物质含量及干酪的结构和质地，同时使干酪具有较强的缓冲作用。     

蓝纹干酪加工工艺研究

以新鲜牛乳为原料，通过单因素实验和正交实验对蓝纹干酪的加工工艺进行了初步研究，确定了制备蓝纹干酪的工艺流程及参数。新鲜牛乳经添加发酵剂和凝乳酶，凝乳切割，加热，排乳清，入模，盐浴，打孔，经12～14d成熟即得到蓝白相闻的蓝纹干酪。pH值对凝乳质地和霉菌的生长具有显著的影响，添加凝乳酶的最佳pH值为6.1。凝块的加热温度为36℃，保证干酪的硬度，避免干酪打孔后孔隙复合及干酪坍塌。     

我国干酪开发的的产品策略

我国干酪开发的挑战与机遇 伴随着乳品消费多元化的趋势，我国市场上对于干酪的消费需求以每年15％的速度快速增长。但是目前年需求量仅为5000-6000吨左右。2003年我国进口干酪4613吨，如果当年的总需求量按6000吨来计算，则进口量占总需求量的70％以上。我国在“入世”后履行了降低干酪产品关税的承诺，2004年降为12％。随着需求量的增长与关税的下降，进口量还在继续增加，如2005年4月进口了600吨干酪，其中莫兹瑞拉占300吨，8月份只进口了400吨干酪。同时，进口的干酪品种也有所增加，比如2005年上半年进口了300吨澳大利亚产的稀奶油干酪和56吨新鲜干酪，进口国主要有新西兰、澳大利亚、德国、爱尔兰、乌拉圭等，主要进口品种有切达和莫兹瑞拉。     

干酪在中国的发展潜力

本文简要介绍了干酪的营养价值、发展潜力和我国干酪市场的启动，主要从人民消费观念的转变、国家政策的支持和乳制品企业的积极配合等方面，阐述了干酪在中国的发展潜力巨大、商机无限，并对我国干酪的生产提出了建议。     

干酪--21世纪乳制品的主导

对干酪品种营养价值及其在世界乳制品中地位进行了论述，并对干酪发展前景进行了分析。以便让人们认识干酪、了解干酪的营养价值，为干酪商品化提供参考。     

从质构角度优化涂抹再制干酪的工艺参数

研究了影响涂抹再制干酪产品性质的主要因素，通过对产品质构的TPA实验，最终确定了最佳的涂抹再制干酪的工艺参数。结果表明，质量比为1：1的(1个月成熟期的切达干酪：5个月成熟期的切达干酪)混合干酪中加入焦磷酸钠和三聚磷酸钠各0．5％(占原料干酪质量分数)、黄油10％和水70％，在70-75℃水浴中加热，并搅拌7～8min，迅速冷却，所得涂抹型再制干酪的质构与市售的进口再制干酪质构最为接近，且风味良好。     

干酪乳制品下一个消费热点

干酪是最古老的加工食品之一。大约公元前3000年，远古的苏美尔人记载了将近20种软质干酪，这是历史上对于干酪的首次记载。欧洲和埃及也发现了大约公元前3000年的制造干酪的设备遗迹。根据这些证据，我们也只能猜测干酪加工的开始时间，而不是干酪最初出现的时间。较为可信的一种说法是，早在公元前10000年，当绵羊和山羊被驯养的时候，牧羊人就开始利用羊奶变酸凝固、凝乳和乳清之间自然分开的现象，将凝乳中的水排干，然后经成型和干燥，使凝乳成为一种简便而又富有营养的食品。在羊乳干酪出现后的2000-3000年，开始出现牛乳制成的干酪。     

乳清的发酵特性及澄清发酵乳清饮料的研制

工业发达的国家十分重视乳清的再利用。我国乳品工业起步较晚，特别是干酪工业更是如此。近年来，随着改革开放的需要，我国的干酪生产也逐渐多了起来，如北京东直门乳品厂生产的Edam干酪，黑龙江长吉岗生产的cheddar干酪和再制干酪，以及1994年投产的包头骑士乳品集团公司，全部设备和技术从APV丹麦D．－W公司引进，设计能力为日处理鲜乳50吨，年产cheddar和Ifollda干酪共1500吨，重制干酪700吨。因此，随着我国干酪产量的不断增加，乳清的开发利用也日显迫切。利用乳清生产饮料，较其它利用方式具有工艺简单、设备投资少、产品消费量大…     

基于HS-SPME-GC-MS分析茶叶提取物对奶酪挥发性风味的影响

采用顶空固相微萃取法结合气相色谱质谱联用技术(headspace-solid phase microextraction-gas chromatography-mass spectrometry,HS-SPME-GC-MS)对原奶酪、绿茶奶酪和茯砖茶奶酪挥发性风味物质提取测定,分析茶叶提取物对奶酪挥发性风味的影响。结果显示,原奶酪、绿茶奶酪和茯砖茶奶酪分别检出37、36、39种挥发性风味物质。2-壬酮、苯甲醛、苯甲醇和3-辛酮为原奶酪的特征挥发性风味物质,己酸、4-苯基-1-环己烯和芳樟醇为绿茶奶酪的特征风味物质。癸酸乙酯、十二烷酸乙酯、辛酸乙酯和9-癸烯酸乙酯为茯砖茶奶酪的特征风味物质。三种奶酪感官评定分析显示,绿茶与茯砖茶奶酪具有较高的感官评分。综上,茶叶提取物可有效改善奶酪风味,对奶酪品质具有积极地促进作用。     

纳他霉素在软酪及干酪中降解情况研究

本文研究了纳他霉素在软质乳酪和于酪成熟过程中的降解以及在乳酪表面的渗透情况。纳他霉紊在乳酪中的残留量用紫外分光光度法进行测定。实验表明，纳他霉素不影响到乳酪的后熟，只停留在乳酪的表面，并在乳酪的发酵后期逐渐消失，纳他霉素的降解速度取决于乳酪的种类及不同的处理方式。     

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。     

Effect of calcium and water injection on structure-function relationships of cheese

Our objectives were to determine the effect of calcium and water injection on cheese structure and to relate changes in structure to changes in functional properties of cheese. Cheese with fat and moisture content similar to that of low-moisture part-skim Mozzarella was made according to a direct-acid, stirred/pressed-curd procedure. The cheese was then cut into blocks that were high-pressure-injected from one to five times, with either water or a 40% calcium chloride solution. Successive injections were performed 24 h apart. After 42 d of refrigerated storage, cheese microstructure and functionality were analyzed. When injected three or more times, water tended to increase cheese weight. The control, uninjected cheese, had the typical structure of a stirred/pressed-curd cheese: protein matrix interspersed with areas that originally contained fat and/or serum. Injecting water increased the area of cheese matrix occupied by protein, but it did not affect textural properties or melting of cheese. In contrast, when calcium was injected, a decrease in cheese weight was observed that was manifested through syneresis. The moisture content and pH of the cheese decreased as well. Calcium injection also decreased the area of cheese matrix occupied by protein. Cheese hardness increased, and cohesiveness and melting of cheese decreased upon calcium injection. We concluded that adding calcium to cheese alters how the proteins interact, which is manifested as changes in cheese microstructure. Such changes in cheese structure provide an understanding of changes in functional attributes of the cheese.     

长春地区消费者干酪口味调查分析报告

通过对长春地区650余名消费者干酪风味、口感和营养需求等的调查,分析了不同年龄段的消费群体对干酪口味的需求.调查结果表明,大多数消费者没有食用过真正的西式干酪,在干酪的口味方面普遍喜欢风味淡、盐分低、质地柔软的新鲜干酪、软质干酪或再制干酪.本调查的结果为开发适合国人口味的干酪提供了依据.     

Application of salt whey in process cheese food made from Cheddar cheese containing exopolysaccharides

The objective of this work was to use salt whey in making process cheese food (PCF) from young (3-wk-old) Cheddar cheese. To maximize the level of salt whey in process cheese, low salt (0.6%) Cheddar cheese was used. Because salt reduction causes undesirable physiochemical changes during extended cheese ripening, young Cheddar cheese was used in making process cheese. An exopolysaccharide (EPS)-producing strain (JFR) and a non-EPS-producing culture (DVS) were applied in making Cheddar cheese. To obtain similar composition and pH in the EPS-positive and EPS-negative Cheddar cheeses, the cheese making protocol was modified in the latter cheese to increase its moisture content. No differences were seen in the proteolysis between EPS-positive and EPS-negative Cheddar cheeses. Cheddar cheese made with the EPS-producing strain was softer, and less gummy and chewy than that made with the EPS-negative culture. Three-week-old Cheddar cheese was shredded and stored frozen until used for PCF manufacture. Composition of Cheddar cheese was determined and used to formulate the corresponding PCF (EPS-positive PCF and EPS-negative PCF). The utilization of low salt Cheddar cheese allowed up to 13% of salt whey containing 9.1% salt to be used in process cheese making. The preblend was mixed in the rapid visco analyzer at 1,000 rpm and heated at 95°C for 3 min; then, the process cheese was transferred into copper cylinders, sealed, and kept at 4°C. Process cheese foods contained 43.28% moisture, 23.7% fat, 18.9% protein, and 2% salt. No difference in composition was seen between the EPS-positive and EPS-negative PCF. The texture profile analysis showed that EPS-positive PCF was softer, and less gummy and chewy than EPS-negative PCF. The end apparent viscosity and meltability were higher in EPS-positive PCF than in EPS-negative PCF, whereas emulsification time was shorter in the former cheese. Sensory evaluation indicated that salt whey at the level used in this study did not affect cheese flavor. In conclusion, process cheese, containing almost 13% salt whey, with improved textural and melting properties could be made from young EPS-positive Cheddar cheese.     

Effect of pH on the chemical composition and structure-function relationships of cheddar cheese

The objectives of this study were to determine the effect of pH on chemical, structural, and functional properties of Cheddar cheese, and to relate changes in structure to changes in cheese functionality. Cheddar cheese was obtained from a cheese-production facility and stored at 4 degrees C. Ten days after manufacture, the cheese was cut into blocks that were vacuum-packaged and stored for 4 d at 4 degrees C. Cheese blocks were then high-pressure injected one, three, or five times with a 20% (wt/wt) glucono-delta-lactone solution. Successive injections were performed 24 h apart. Cheese blocks were then analyzed after 40 d of storage at 4 degrees C. Acidulant injection decreased cheese pH from 5.3 in the uninjected cheese to 4.7 after five injections. Decreased pH increased the content of soluble calcium and slightly decreased the total calcium content of cheese. At the highest level, injection of acidulant promoted syneresis. Thus, after five injections, the moisture content of cheese decreased from 34 to 31%, which resulted in decreased cheese weight. Lowered cheese pH, 4.7 compared with 5.3, also resulted in contraction of the protein matrix. Acidulant injection decreased cheese hardness and cohesiveness, and the cheese became more crumbly. The initial rate of cheese flow increased when pH decreased from 5.3 to 5.0, but it decreased when cheese pH was further lowered to 4.7. The final extent of cheese flow also decreased at pH 4.7. In conclusion, lowering the pH of Cheddar cheese alters protein interactions, which then affects cheese functionality. At pH greater than 5.0, calcium solubilization decreases protein-to-protein interactions. In contrast, at pH lower than 5.0, the acid precipitation of proteins overcomes the opposing effect caused by increased calcium solubilization and decreased calcium content of cheese, and protein-to-protein interactions increase.     

益生菌干酪成熟过程中微生态变化的研究进展

随着人们健康意识及对益生菌产品需求的增强,有关益生菌干酪的研究和加工也不断增多。益生菌干酪在成熟过程中,由于受到益生菌的作用,干酪会发生一系列复杂的微生态理化反应,从而影响到产品的风味、质构、安全性和功能性等特性。本文重点综述了益生菌干酪在成熟过程中微生态变化的研究进展,包括益生菌在干酪基质中的存活、益生菌干酪在益生菌作用下发生的理化特性变化以及组学方法在益生菌干酪中的应用等,以期为提升干酪加工技术水平、推动益生菌干酪产品的研制以及促进我国干酪产业的发展提供参考。     

Effect of zinc fortification on Cheddar cheese quality

Zinc-fortified Cheddar cheese containing 228 mg of zinc/kg of cheese was manufactured from milk that had 16 mg/kg food-grade zinc sulfate added. Cheeses were aged for 2 mo. Culture activity during cheese making and ripening, and compositional, chemical, texture, and sensory characteristics were compared with control cheese with no zinc sulfate added to the cheese milk. Compositional analysis included fat, protein, ash, moisture, zinc, and calcium determinations. The thiobarbituric acid (TBA) assay was conducted to determine lipid oxidation during aging. Texture was analyzed by a texture analyzer. An untrained consumer panel of 60 subjects evaluated the cheeses for hardness, off-flavors, appearance, and overall preference using a 9-point hedonic scale. Almost 100% of the zinc added to cheese milk was recovered in the zinc-fortified cheese. Zinc-fortified Cheddar cheese had 5 times more zinc compared with control cheese. Zinc-fortified cheese had higher protein and slightly higher fat and ash contents, whereas moisture was similar for both cheeses. Zinc fortification did not affect culture activity during cheese making or during the 2-mo aging period. The TBA value of control cheese was higher than that of zinc-fortified cheese at the end of ripening. Although zinc-fortified cheese was harder as determined by the texture analyzer, the untrained consumer panel did not detect differences in the sensory attributes and overall quality of the cheeses. Fortification of 16 mg/kg zinc sulfate in cheese milk is a suitable approach to fortifying Cheddar cheese without changing the quality of Cheddar cheese.     

Short communication: Production of cottage cheese fortified with vitamin D

The availability of alternative food products fortified with vitamin D could help decrease the percentage of the population with vitamin D deficiency. The objective of this study was to fortify cheese with vitamin D. Cottage cheese was selected because its manufacture allows for the addition of vitamin D after the draining step without any loss of the vitamin in whey. Cream containing vitamin D (145 IU/g of cream) was mixed with the fresh cheese curds, resulting in a final concentration of 51 IU/g of cheese. Unfortified cottage cheese was used as a control. As expected, the cottage cheese was fortified without any loss of vitamin D in the cheese whey. The vitamin D added to cream was not affected by homogenization or pasteurization treatments. In cottage cheese, the vitamin D concentration remained stable during 3 weeks of storage at 4°C. Compared with the control cheese, the cheese fortified with vitamin D showed no effects of fortification on cheese characteristics or sensory properties. Cottage cheese could be a new source of vitamin D or an alternative to fortified drinking milk.