Prevalence and stability of lysozyme in cheese

The use of the preservative and potential allergen hen egg white lysozyme in cheese production has to be declared. In the present study, an HPLC method with fluorescence detection (HPLC-FLD) was optimised and validated for the analysis of lysozyme in cheese. Lysozyme was detected in concentrations between 30.8 and 386.2 mg/kg cheese in 30 out of 46 analysed commercial cheese samples. During cheese production and storage for 0–54 weeks a lysozyme satellite peak (LSP) was detected, which totals up to 18% of the lysozyme content. Mass spectrometry and peptide mass fingerprint revealed that LSP possesses the same primary structure as lysozyme. Since disulphide scrambling could not be detected, LSP was assigned to a conformational isomer of lysozyme. As a consequence, LSP was included in the HPLC-FLD analysis of lysozymes in cheese.     

Valuation of milk composition and genotype in cheddar cheese production using an optimization model of cheese and whey production

A mass balance optimization model was developed to determine the value of the κ-casein genotype and milk composition in Cheddar cheese and whey production. Inputs were milk, nonfat dry milk, cream, condensed skim milk, and starter and salt. The products produced were Cheddar cheese, fat-reduced whey, cream, whey cream, casein fines, demineralized whey, 34% dried whey protein, 80% dried whey protein, lactose powder, and cow feed. The costs and prices used were based on market data from March 2004 and affected the results. Inputs were separated into components consisting of whey protein, ash, casein, fat, water, and lactose and were then distributed to products through specific constraints and retention equations. A unique 2-step optimization procedure was developed to ensure that the final composition of fat-reduced whey was correct. The model was evaluated for milk compositions ranging from 1.62 to 3.59% casein, 0.41 to 1.14% whey protein, 1.89 to 5.97% fat, and 4.06 to 5.64% lactose. The κ casein genotype was represented by different retentions of milk components in Cheddar cheese and ranged from 0.715 to 0.7411 kg of casein in cheese/kg of casein in milk and from 0.7795 to 0.9210 kg of fat in cheese/kg of fat in milk. Milk composition had a greater effect on Cheddar cheese production and profit than did genotype. Cheese production was significantly different and ranged from 9,846 kg with a high-casein milk composition to 6,834 kg with a high-fat milk composition per 100,000 kg of milk. Profit (per 100,000 kg of milk) was significantly different, ranging from $70,586 for a high-fat milk composition to $16,490 for a low-fat milk composition. However, cheese production was not significantly different, and profit was significant only for the lowest profit ($40,602) with the κ-casein genotype. Results from this model analysis showed that the optimization model is useful for determining costs and prices for cheese plant inputs and products, and that it can be used to evaluate the economic value of milk components to optimize cheese plant profits.     

Mould contamination in production of semi-hard cheese

Air, equipment, plastic film, brine and milk were sampled from four cheese factories in Norway during the period September 1997 to May 1999 in order to identify the critical points for mould contamination in the production process. Altogether, 672 samples were collected. Penicillium brevicompactum was the most frequently isolated species from three of the factories, while Geotrichum candidum was the most frequently isolated species from the fourth. P. commune, P. palitans, P. solitum and P. roqueforti ss. roqueforti, all common contaminants on cheese, were found in samples of air and equipment, and the former was also isolated from plastic film. The results in the present study showed that the mould levels in the cheese factories varied between the different control points. The mould levels at some of the air control points had high mould counts while the mould levels in milk and brine, on equipment and on plastic film, generally were low. The fungi at the control points with high mould levels consisted of common cheese contaminants as well as species not commonly isolated from cheese. The statistical analysis showed that air was the major source of the important cheese contaminants P. commune and P. palitans during the production process. High quality air with low number of cheese contaminants in production rooms, especially the wrapping room, is important in order to reduce mould contamination.     

The use of halloum cheese for the production of processed cheese

Halloum is a white, semi-hard cheese made in a number of countries around the Mediterranean and in the Middle East from raw milk. In this study, halloum was made from natural raw milk and from milk acidified to pH 4.5 before renneting. Processed cheese was made from the two types of halloum using 4.2% emulsifying salts and 20–25% added water. There was an increase in protein, fat and total solids in the processed cheese made from acidified halloum, but a taste panel gave a higher sensory rating to the processed cheese based upon normal halloum.     

红曲与桔霉素

因红曲中含有桔霉素 ,将使我国的红曲出口受到很大影响。本文介绍了红曲中桔霉素的产生及合成途径 ;桔霉素的分子式、结构、物理和化学性质、毒性、抑菌性和检测方法等内容。     

用乳清粉生产乙醇的研究

通过细胞固定化技术和混合发酵方式,对马克思克鲁维酵母和酿酒酵母混合发酵乳清粉产乙醇进行了研究。对比研究了游离细胞、混合游离细胞、单一固定化细胞、混合固定化细胞混菌和共固定化细胞混菌5种发酵方式发酵乳清粉生产乙醇。实验结果表明:混菌发酵要优于单一菌种发酵,固定化细胞发酵要好于游离细胞发酵。相对其他4种发酵方式,采用混合固定化马克思克鲁维酵母和固定化酿酒酵母混菌发酵方式,2种固定化菌种比例为1∶1时,利用乳清粉发酵可以获得最高的乙醇浓度5.3%vol,发酵周期最短为48h,乳糖利用率为1.64g(/L.h)。固定化细胞可以连续使用8个批次。     

红曲与核霉素

因红曲中含有桔霉素,将使我国的红曲出口受到很大影响。本文介绍了红曲中桔霉素的产生及合成途径;桔霉素的分子式、结构、物理和化学性质、毒性、抑菌性和检测方法等内容。     

Innovative improvement of Shanklish cheese production in Lebanon

Shanklish is a traditional Lebanese cheese, native to the Middle East and derived from the coagulation of yoghurt. To improve its processing and productivity, micellar casein (MC) and whey protein (WP) were added to milk at different concentrations (1% and 2%). Five lots of Shanklish with three repetitions were processed as follows: C (control), WP50 (enrichment with 1% WP), WP100 (2% WP), MC50 (1% MC), and MC100 (2% MC). Shanklish-yielding capacity and physicochemical properties of Shanklish were evaluated. Results showed that cheese yield increased with the addition of both MC and WP and especially in WP100. Also, adding WP and MC modified cheese nutritional values by increasing total protein and decreasing fat content, with ash content and water content increasing as well. This fortification played an important role on Shanklish texture, by stabilising the final product in terms of syneresis.     

Simultaneous use of transglutaminase and rennet in white-brined cheese production

The effects of renneting temperature (30 °C or 34 °C) on textural properties, proteolysis and yield of white-brined cheese made by simultaneous use of microbial transglutaminase (mTG) and rennet were investigated. Incorporation of mTG resulted in higher yield values for experimental cheeses than for the control cheeses at both renneting temperatures. The total solids contents of the cheeses treated with mTG were remarkably lower than the control cheeses; but the former cheeses had higher protein-in-dry matter levels. The TPA profiles of the cheeses showed that the incorporation of mTG led to modification in the textural properties. The development of proteolysis in the cheeses treated with mTG was slightly slower than the control cheeses at both coagulation temperatures. To conclude, the specific action of mTG on milk proteins could be successfully exploited to modify the textural properties and to increase the yield of white-brined cheese.     

Causes and control of early gas production in cheddar cheese

Early gas production in cheddar cheese is a sporadic and recurrent problem. In this article the major causal agents of unwanted gas production are discussed and potential gas producing organisms in cheddar cheese are identified. Results of investigations of gas production in commercial plants and control measures are presented. It is concluded that early gas production in cheddar cheese results from a number of interacting factors, including lactose and citrate levels in the curd, the temperature of curd/cheese during pressing and curing, the salt in moisture level and the levels of gas producing, non-starter lactic acid bacteria in the cheese.     

瑞士奶酪生产工艺研究

以新鲜牛乳为主要原料,根据瑞士奶酪的生产工艺,采用L9(34)正交实验的方法,研究了不同切割尺寸、发酵剂添加比例、发酵剂添加量、发酵温度和切割pH对瑞士奶酪色泽、滋气味和组织状态的影响,确定了生产瑞士奶酪的最佳工艺条件为发酵剂添加量0.02%(质量分数),凝块切割尺寸0.6cm,切割pH6.60,发酵剂(唾液链球菌嗜热亚种∶瑞士乳杆菌∶谢氏丙酸杆菌)添加比例2∶2∶1,发酵温度37℃。     

The production of low fat Cheddar-type cheese

A technique has been developed for the production of Cheddar-type cheese of intermediate (25%) and low (16%) fat content. The development of flavour and texture in these cheeses was monitored over a six-month maturation period. At the lower level of fat, the cheese did not develop adequate Cheddar flavour, and the cheese was over-firm. At the intermediate level of fat, a mild Cheddar flavour was produced, and the texture improved.     

豆奶干酪生产工艺参数优化研究

研究了豆奶干酪的加工工艺,筛选出最优工艺参数组合。重点研究了CaCl2添加量、热缩温度、堆酿pH对豆奶干酪感官评定的影响。结果表明,CaCl2添加量对豆奶干酪感官评定值影响最大,其次为热缩温度、堆酿pH。     

直接酸化法生产Mozzarella干酪工艺的研究

采用磷酸、柠檬酸直接对合格标准化杀菌乳进行酸化,按照无腌渍干盐法生产工艺制作Pizza用Mozzarella干酪.研究这两种酸不同酸化pH值对生产工艺的影响.结果表明,采用柠檬酸直接酸化原料乳pH值到6.1,发酵剂添加量1.2%,凝乳酶添加量0.0015%(均为质量分数,下同),蒸煮温度40℃,堆酿100 min.热烫温度58℃可以得到理想的产品,对产品产率的影响不大.采用磷酸直接酸化原料乳pH值到5.6,发酵剂添加量0.8%,凝乳酶添加量0.0005%,蒸煮温度40℃,堆酿120 min,热烫温度65℃可以得到理想的产品,可提高5%的产品得率.采用柠檬酸较采用磷酸直接酸化得到的千酪产品具有较好的奶油香味,较柔软的凝块,但产品的水分质量分数相对稍高.     

干酪成熟初期产生生物胺影响因素的研究

研究了成熟3个星期的干酪产生生物胺的4种影响因素（发酵剂，NaCl，山梨酸钾，水分质量分数），通过氨基酸专用高效液相色谱仪对样品进行了测定。结果表明，发酵剂RA024，NaCl质量分数高，山梨酸钾质量分数在0．2％，水分质量分数低可以抑制生物胺的产生。     

Modeling of pH and acidity for industrial cheese production

A three-layer feedforward neural network was successfully used to model and predict the pH of cheese curd at various stages during the cheese-making process. An extended database, containing more than 1800 vats over 3 yr of production of Cheddar cheese with eight different starters, from a large cheese plant was used for model development and parameter estimation. Neural network models were developed with inputs selected among 33 quantitative and qualitative process variables for final pH of cheese, pH at cutting, and acidity at whey drawing-off and at pressing. In all cases, very high correlation coefficients, ranging from 0.853 to 0.926, were obtained with the validation data. A sensitivity analysis of neural network models allowed the relative importance of each input process variable to be identified. The sensitivity analysis in conjunction with a priori knowledge permitted a significant reduction in the size of the model input vector. A neural network model using only nine input process variables was able to predict the final pH of cheese with the same accuracy as for the complete model with 33 original input variables. This significant decrease in the size of neural networks is important for applications of process control in cheese manufacturing.     

开菲尔直投式发酵剂在益生菌干酪生产中的应用研究

该研究主要将开菲尔粒制备成直投式发酵剂应用于干酪的生产。 以FD-DVS R-704商业干酪发酵剂制作的干酪为对照,对其 理化指标、挥发性香气成分、质构特性和感官指标进行测定与评价。 结果表明,与对照干酪相比,开菲尔干酪的水分含量、pH4.6-可溶 性氮（SN）及12%三氯乙酸（TCA）-SN的含量极显著增高（P＜0.01）,pH值极显著低（P＜0.01）,而粗脂肪比例和总游离氨基酸（TFAA） 含量无显著差异（P＞0.05）,不饱和脂肪酸（UFA）含量显著增高（P＜0.05）;醇类和酯类物质的种类增多;硬度和咀嚼性极显著降低（P＜0.01）,胶黏性极显著增大（P＜0.01）,内聚性和弹性无明显差异（P＞0.05）;开菲尔粒益生菌干酪呈乳白色,表面有光泽,不仅具 有干酪特有的滋味和气味,且具有开菲尔发酵乳的特有风味,带有适宜的酒香味。     

Staphylococcus aureus and Listeria monocytogenes in Norwegian raw milk cheese production

The aim of this study was to survey the presence of Staphylococcus aureus and Listeria monocytogenes during the cheese making process in small-scale raw milk cheese production in Norway.The prevalence of S. aureus in bovine and caprine raw milk samples was 47.3% and 98.8%, respectively. An increase in contamination during the first 2-3 h resulted in a 73.6% prevalence of contamination in the bovine curd, and 23 out of 38 S. aureus-negative bovine milk samples gave rise to S. aureus-positive curds. The highest contamination levels of S. aureus were reached in both caprine and bovine cheese after 5-6 h (after the first pressing). There was no contamination of L. monocytogenes in caprine cheeses and only one (1.4%) contaminated bovine cheese.This work has increased our knowledge about S. aureus and L. monocytogenes contamination during the process of raw milk cheese production and gives an account of the hygiene status during the manufacture of Norwegian raw milk cheeses.     

Storage stability of lutein during ripening of cheddar cheese

Lutein (3,3'-dihydroxy-alpha-carotene) has been identified as a dietary factor that can delay the onset of age-related macular degeneration (AMD). However, available food sources of lutein contain only modest amounts of the carotenoid. Food fortification with lutein extract has been identified as a low-budget approach to prevent the onset or progression of AMD. The objectives of this study were to 1) incorporate various amounts of lutein into Cheddar cheese; 2) examine the color, pH, microbiological, and sensory characteristics of the Cheddar cheese during storage; and 3) analyze the stability of lutein during the cheese maturation process. Lutein extracted from corn was added to Cheddar cheese in quantities of 1, 3, and 6 mg per serving size. Measurements of the lutein stability were carried out by HPLC using a YMC C30 carotenoid column. Microbiological analyses of cheese samples included aerobic plate count, coliform, and yeast/mold counts. The color attributes a* and b* were significantly different between the treatment and control groups; however, no significant difference was observed in L* value and pH. Significant differences among 1, 3, and 6 mg lutein-enriched cheeses were observed in the aerobic plate count and yeast/mold compared with the control. Cheese samples contained no detectable levels of coliforms (< 10 cfu/g). The HPLC data showed quantitative recovery of lutein during the storage period, and no lutein degradation products were identified. These results indicate that lutein, a functional additive with purported ability to prevent or reduce the onset of AMD, can be incorporated into cheese adding value to this product.