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.     

拉伸工艺对Mozzarella干酪品质的影响

选择不同的拉伸温度和拉伸时间,研究拉伸工艺对Mozzarella干酪组成、游离水分和功能特性的影响。结果表明,随着拉伸温度的升高和拉伸时间的延长,干酪的游离水分增加,脂肪和蛋白质质量分数下降,干酪产量下降。拉伸温度为60℃时,干酪的融化性最高,油脂析出性适中,拉伸性较好。延长拉伸时间,导致干酪产量下降,功能特性没有明显提升。本研究确定的最佳拉伸工艺:拉伸温度60℃,拉伸时间10min。     

Mozzarella干酪的研制

以新鲜牛乳为主要原料,通过干酪制造条件的优化研究,确定了制造Mozzarella干酪的工艺流程及主要参数,实验表明,新鲜牛乳经标准化使得酪蛋白与脂肪之比为0．84,然后加入发酵剂和凝乳酶,凝乳形成后,经切割,排乳清,并在热水中拉伸,盐渍即到成品,产品的平均脂肪和水分的含量分别为22．82％和50．74％,达到了Mozzarella干酪的质量要求。     

原料乳热处理条件对Mozzarella干酪品质的影响

采用3×3拉丁方试验设计,3个奶酪槽中原料乳热处理条件分别设为未杀菌,63℃(30min)杀菌,72℃(15s)杀菌。研究干酪加工中原料乳热处理条件对Mozzarella干酪的品质的影响。结果表明,未杀菌乳制干酪的蛋白水解、硬度及弹性与杀菌乳制干酪的蛋白水解、硬度及弹性值具显著差异(p<0.05),未杀菌乳制干酪的蛋白水解显著增加,弹性及硬度显著降低;63℃(30min)及72℃(15s)不同杀菌温度处理的乳制得的干酪之间蛋白水解、硬度及弹性无显著差异;不同热处理乳制干酪之间的融化性和油脂析出性在统计学上无显著差异。     

工艺参数对再制干酪的质构和流变性质的影响

利用质构仪和流变仪对影响再制干酪品质的多个因素进行了研究。结果表明，水分影响再制干酪的质构和流变性质：乳化盐对再制干酪产品的质构没有显著的影响；不同的温度和不同的搅拌时间对样品的质构有着相似的变化；在所有加工条件下．再制干酪的G′始终大于G″，G′和G″没有交叉点，而且复合黏度η^＊随着频率的增加而急剧降低，体系表现出了弱凝胶的特性。     

提高成熟温度加快Mozzarella干酪成熟的研究

制作2批Mozzarella干酪A和B，分别在4℃(A)和7℃(B)下成熟，观察其在成熟期间的变化及测定可溶性N的含量等指标，可知在7℃下成熟的干酪在制作后30d的蛋白水解性、功能特性等和4℃下成熟50d的干酪无显著差异，而和7℃下成熟50d的干酪有显著差异。说明成熟温度显著影响干酪的蛋白水解性。在7℃下贮藏的Mozzarella干酪成熟30d可达到4℃下贮存50d的成熟度，即将成熟温度从4℃提高到7℃，可将成熟期缩短20d左右。     

Effect of freezing and frozen storage on microstructure of Mozzarella and pizza cheeses

Scanning electron microscopy was used to assess the effect of aging before (2, 7, and 14 days at 7 °C) or tempering after (1, 7, and 14 days at 7 °C) freezing, and frozen storage (1 and 4 weeks at −20 °C) on protein matrix of pasta filata Mozzarella and non-pasta filata pizza cheeses using unfrozen samples as controls. Pores and ruptures of reticular structure were observed in frozen-stored pasta filata Mozzarella cheese protein matrix, but cracks and clumps of bacteria were found in frozen-stored non-pasta filata pizza cheese. No obvious differences were discernable between the microstructures of pasta filata Mozzarella cheeses frozen stored 1 and 4 weeks. Formation of the reticular structure in frozen-stored pasta filata Mozzarella cheese progressed during tempering. Microstructure of non-pasta filata pizza cheese frozen stored for 4 weeks contained more extensive cracking and more areas of clumps of bacteria than that was frozen stored for 1 week. Aging of cheese before frozen storage was considered responsible for microstructural cracking; fewer cracks were found in the frozen-stored cheese tempered 1 and 2 weeks, but the clumps of bacteria were still observed.     

Effect of whey pH at drainage on physicochemical, biochemical, microbiological, and sensory properties of Mozzarella cheese made from buffalo milk during refrigerated storage

The objective of this research was to determine the effect of drainage pH on physicochemical, biochemical, microbiological and sensory properties of Mozzarella cheese made from buffalo milk during refrigerated storage. Four vats of cheese were made at 4 different whey drainage pH (6.2, 5.9, 5.6, and 5.2). Lower drainage pH caused higher pH 4.4-soluble N and pH 4.4-soluble N:total N. Interaction of drainage pH at d 1 and 30 of storage on all soluble nitrogen fractions was significant. Degradation of caseins in samples made at a drainage pH of 6.2 was lower than that of other cheese samples. The decreasing whey drainage pH significantly increased counts of thermophilic and mesophilic lactobacilli of the samples during refrigerated storage. No coliforms or Escherichia coli were detected in the cheeses. The average sensory property scores of all cheese samples were very close, and, as expected, storage time had a negative effect on all sensory scores.     

不同发酵剂对Mozzarella干酪品质的影响

采用嗜热链球菌和嗜热乳杆菌作为Mozzarella干酪的发酵剂，研究单一嗜热链球菌发酵剂与嗜热链球菌和嗜热乳杆菌组成的混合发酵剂对Mozzarella干酪品质的影响。结果表明，混合菌作发酵剂制得的干酪品质优于用单一嗜热链球菌作发酵剂的干酪。     

Mozzarella cheese: 40 years of scientific advancement

An overview is presented of selected advances in the science of mozzarella cheese during the past 40 years. This is not intended to be a comprehensive review but rather to focus on several key milestones in the ongoing quest to understand the physicochemical basis for cheese structure and function. In keeping with the theme of this symposium, this paper highlights the pivotal role that Professor P. F. Fox had in shaping my understanding of mozzarella structure–function and the direction of my research during the past decade. The unfolding of mozzarella science has ebbed and flowed, with significant advances being made early on that were not fully recognized until much later.     

Rheology and melt characterization of low-fat and full fat Mozzarella cheese made from microfluidized milk

Microfluidization of cheese milk at different temperatures and pressures altered the meltability and rheological properties of Mozzarella cheese. Pasteurized milks, standardized to 1.0 (low-fat (LF)) or 3.2 (full fat (FF)) g fat/100 g milk, heated to 10, 43, or 54 °C, and then microfluidized at pressures of 34, 103, or 172 MPa, were used to manufacture Mozzarella cheese. Cheeses made from nonmicrofluidized milks served as controls. During the hot water step, only control cheeses and cheeses made with milk microfluidized at 10 °C could be stretched while all others had short curds that did not fuse together. Cheese responses to different stresses (heat, compression, torsion, and oscillatory shear) were measured after 1 and 6 weeks of storage. FF cheeses made with the control milks and milks processed at 10 °C/34 MPa or 10 °C/103 MPa were softer and less rigid, and had the lowest visco-elastic properties and the highest meltabilities of all the cheeses. Microfluidization of the cheese milk did not improve the melt or rheology of LF cheeses. Microfluidization of milk with fat in the liquid state at higher pressures resulted in smaller lipid droplets that altered the component interactions during the formation of the cheese matrix and resulted in LF and FF Mozzarella cheeses with poor melt and altered rheology.     

Mozzarella干酪生产工艺的优化

选择了影响Mozzarella干酪生产的3个关键因素：热缩温度、堆酿pH值和热烫拉伸温度；采用三因素二次通用旋转组合设计，以干酪的实际产率、pH值为4．6可溶性N，质量分数为12％的TCA可溶性N和感官评定值为指标，进行综合评定。优选出Mozzarella干酪的最优工艺参数为：热缩温度38℃，堆酿pH值为5．25，热烫拉伸温度58℃。在这一条件下，生产的干酪产率及综合质量最好。同时探讨了3个因子对以上4个指标的影响，为生产不同用途的Mozzarella干酪提供了一定的理论依据。     

乳化盐对再制马苏里拉乳酪品质的影响

乳化盐是再制乳酪的关键原料。通过测定烘焙功能性和流变性,研究乳化盐对再制马苏里拉乳酪品质的影响,结果表明,乳化盐对再制马苏里拉乳酪烘焙功能性有显著影响,随着型号为"JOHA PZ14"的复合磷酸盐添加比例的提高,再制马苏里拉乳酪融化性和油脂析出性增加,拉伸性先增加后降低,褐变性降低。选择型号为"JOHA PZ7":"JOHA PZ14"乳化盐=4:1时,再制马苏里拉乳酪烘焙功能性最接近天然马苏里拉乳酪。     

Microbiological safety and quality of Mozzarella cheese assessed by the microbiological survey method

Dairy products are characterized by reduced shelf life because they are an excellent growth medium for a wide range of microorganisms. For this reason, it is important to monitor the microbiological quality of dairy products and, in particular, the total viable count and concentration of Escherichia coli, as they are indicators of the hygienic state of these products. In addition, in dairy products such as Mozzarella cheese, it is important to monitor the concentration of lactic acid bacteria (LAB), as they are the major components of starter cultures used in cheese production, contributing to the taste and texture of fermented products and inhibiting food spoilage bacteria by producing growth-inhibiting substances. For these reasons, to ensure the quality and safety of their products, cheese makers should monitor frequently, during fresh cheese production, the concentration of LAB and spoilage bacteria. However, usually, small- to medium-size dairy factories do not have an internal microbiological laboratory and external laboratories of analysis are often too expensive and require several days for the results. Compared with traditional methods, the microbiological survey (MBS) method developed by Roma Tre University (Rome, Italy) allows faster and less-expensive microbiological analyses to be conducted wherever they are necessary, without the need for a microbiological laboratory or any instrumentation other than MBS vials and a thermostat. In this paper, we report the primary validation of the MBS method to monitor LAB concentration in Mozzarella cheese and the analysis, using the MBS method, of total viable count, E. coli, and LAB concentrations in the production line of Mozzarella cheese as well as during the shelf life of the product stored at 20°C. The results obtained indicate that the MBS method may be successfully used by small- to medium-size dairy factories that do not have an internal microbiological laboratory. Using the MBS method, these dairy factories can monitor autonomously the microbiological safety and quality of their products, saving both time and money.     

Understanding the role of calcium in functionality of part skim Mozzarella cheese

The impact of calcium on softening, melting, and flow characteristics of part skim Mozzarella cheese was evaluated. Four cheeses containing different calcium levels (viz. 0.65, 0.48, 0.42, and 0.35%) were manufactured by direct acidification using glucono-delta-lactone on four different occasions. Preacidification of milk was done to alter the calcium content of the cheeses. Cheeses were made with uniform composition. Lowering of calcium to 25, 35, and 45% levels increased the melt by 1.4, 2.1, and 2.6 times, respectively, 1 d after manufacture. Low calcium cheeses softened and melted at lower time and temperatures. These cheeses flowed faster and to a greater extent. Higher proteolysis at a faster rate was observed in low calcium cheeses. Refrigerated storage up to 30 d also increased melt area, flow rate, extent of flow, and soluble protein and lowered softening and melting times in all the cheeses. The effect of calcium reduction was more noticeable as compared to the effect of storage on functionality of Mozzarella cheese. Improved softening, melting, and flow properties of low calcium part skim Mozzarella cheese is a clear advantage to cheese manufacturers and end users as they may not have to wait 15 to 20 d for proteolysis of cheese to obtain desired melt properties.     

复合天然防腐保鲜液对Mozzarella干酪贮藏期的影响

采用无盐渍新工艺法制作部分脱脂Mozzarella干酪,使用复合天然防腐保鲜液(0.69%茶多酚+0.013%Nisin和溶菌酶(1∶1)+0.0043%那他霉素)对成熟干酪样品进行浸泡处理,并在4℃冷藏,通过每间隔7d测定干酪不同贮藏时间的水分含量、pH、滴定酸度、可溶性氮含量(SN)、SDS-凝胶电泳、未融化干酪质构特性、融化干酪功能特性、微生物指标和感官评定等一系列指标的变化,评定复合天然防腐保鲜液对Mozzarella干酪贮藏效果的影响。实验结果表明:浸泡处理组4℃冷藏49d时的贮藏效果与对照组28d时相当,复合天然防腐保鲜液的使用可有效延长Mozzarella干酪的贮藏期。     

Improving the yield of Mozzarella cheese by phospholipase treatment of milk

Part-skim Mozzarella cheese was manufactured from milk hydrolyzed with fungal phospholipase A₁ prior to renneting. The phospholipase treatment reduced fat losses in whey and cooking water and increased cheese yield as a result of improved fat and moisture retention in the cheese curd. The amount of phospholipids in the whey was reduced because of improved retention of lysophospholipids in the cheese curd. Water binding in the fresh curds and young cheeses up to 3 wk of storage was investigated by a ¹H nuclear magnetic resonance spin-spin relaxation technique. In the fresh curds, 2 dominant water fractions were present, characterized by average spin-spin relaxation times (T₂) of 14 and 86 to 89 ms, respectively. These 2 fractions of low- and high-molecular-mobility water were similar in all cheeses and presumed to represent water associated with the casein matrix and water present in the pores. A few hours after manufacture, cheeses made with phospholipase showed decreased T₂ of the high-mobility fraction, indicating improved water-holding capacity. It is suggested that lysophospholipids released from the fat globule membranes act as surface-active agents in the cheese curd, helping emulsification of water and fat during processing and reducing syneresis. During 3 wk of storage after manufacture, the mobility of both water fractions increased in all cheeses, but was highest in the cheeses made with phospholipase. The increase in mobility during the first weeks of storage has earlier been ascribed to structural changes in the protein matrix, which in principle could be accelerated because of the higher moisture content. However, the microstructure of phospholipase-treated cheese was investigated by confocal laser scanning microscopy and found to be very similar to the control cheese during processing and up to 28 d of storage. In addition, flowability, stretchability, and browning were acceptable and similar in all the manufactured cheeses. Thus, phospholipase hydrolysis of cheese milk improved the cheese yield without changing the cheese microstructure, and resulted in cheese with functional properties that were identical to traditional Mozzarella cheese.     

高水分Mozzarella干酪关键工艺条件的研究

以新鲜的牛乳为原料,采用创新的生产工艺,通过一系列的试验,确定了高水分Mozzarella干酪的关键工艺条件,为Mozzarella干酪的工业化生产提供了理论和技术支持。     

成熟温度对Mozzarella干酪蛋白水解和质构的影响

研究了温度为4,7,10℃时对干酪成熟过程中蛋白水解和质地的影响。结果表明,随着干酪成熟温度的升高,成熟期间干酪中可溶性氮与总氮的比值增加较快,干酪的硬度下降速度也较快。说明在较高的成熟温度下,干酪在较短的时间内能够达到成熟的状态。     

Innovative active packaging systems to prolong the shelf life of Mozzarella cheese

In this work the effectiveness of different antimicrobial packaging systems on the microbial quality decay kinetics during storage of Mozzarella cheese was evaluated. Lemon extract, at 3 different concentrations, was used as active agent, in combination with brine and with a gel solution made of sodium alginate. Shelf life tests were run at 15°C to simulate thermal abuse. The cell load of spoilage and dairy functional microorganisms were monitored at regular time intervals during storage. By fitting the experimental data through a modified version of the Gompertz equation, the shelf life of dairy products packaged in the different systems was calculated. Results show an increase in the shelf life of all active packaged Mozzarella cheeses, confirming that the investigated substance may exert an inhibitory effect on the microorganisms responsible for spoilage phenomena without affecting the functional microbiota of the product.