Relationship between Sensory and Instrumental Hardness of Commercial Cheeses

ABSTRACT: The effect of deformation (10% to 90%) and deformation rate (0.2 to 10 mm/s) on both maximum compression force and correlation between sensory and instrumental measurements of hardness were investigated for 26 commercial cheeses. Log-linear regression models were used to model the relationship between deformation rate and maximum compression force and fitted well to the relationship, indicating that maximum compression force is a log linear function of deformation rate. Deformation had a large effect on the correlation between sensory and instrumental hardness, while deformation rate had a small effect. The optimal deformation and deformation rate for the maximum correlation were 70% to 90% and 1.0 mm/s, respectively. This implies that an optimal combination of deformation and deformation rate can be used for maximizing the correlation between sensory and instrumental hardness for cheese products.     

涤纶微细纤维筒子纱染色性能的探讨

主要通过比较涤纶微细纤维膨松线与普通涤纶短纤维线性能的差异,进而研究涤纶微细纤维物理结构对染色的影响以及涤纶微细纤维的染色工艺,并介绍了涤纶微细纤维染色中的注意事项和合适的染色工艺。     

乳糖替代凝乳酶制作大豆干酪技术初探

对加酶发酵制作干酪的传统方法进行了改进,用添加乳糖的方法来代替添加酶进行发酵.试验综合考察了影响混合豆乳(豆乳和牛乳)干酪凝乳的几个因素,即豆乳添加量、发酵剂添加量、乳糖添加量和乳酸钙添加量,并确定混合豆乳干酪的最佳凝乳工艺参数.试验结果表明,最佳工艺参数为:80%豆乳 3%发酵剂 3%乳糖 0.1%乳酸钙.     

Partial characterization of dextran-degrading enzyme obtained from blue cheese

Degradation of dextran beads was observed when the water-soluble fraction of a blue cheese extract was applied to the top of a Sephadex G-150 or G-200 column. This phenomenon suggests the presence of a specific enzyme that can hydrolyze dextran. After removal of casein components from the blue cheese fraction, ammonium sulfate treatment and gel filtration chromatography were performed to isolate the enzyme fraction. The enzymatic products were analyzed by thin-layer chromatography and gel filtration chromatography and identified as isomaltooligosaccharides. The isoelectric point of this enzyme fraction was approximately 4.9, as determined by isoelectric focusing using Rotofor, and the molecular weight of the fraction was 65 kDa, as estimated by sodium dodecyl sulfate (SDS)-PAGE. Optimum pH for enzymatic activity was 5.0 to 5.3. A partial N-terminal amino acid sequence of 20 residues was determined to be ATPDEWRSRSIYFMLTDRGA from an enzyme fraction further purified by ion-exchange chromatography and native PAGE. This sequence showed a maximum homology of 80% with alpha-amylase or Taka amylase that originated from various microorganisms.     

Inactivation of Listeria innocua in brined white cheese by a combination of nisin and heat

The objective of this study was to investigate the effect of nisin alone and in combination with heat (63 °C/5 min) on the inactivation of Listeria innocua in white cheese. Nisin was added at different concentrations (500, 1000, and 1500 IU ml⁻¹) to pasteurized milk before curd formation. The curd was soaked for 24 h in 10% solution of brine containing ca 10⁶ CFU ml⁻¹ of a cocktail mixture of three strains of L. innocua. Part of the nisin treated samples were heat treated at 63 °C/5 min. Total mesophilic count (TMC), L. innocua survivors and changes in the pH of white cheese were monitored each 2 d for a period of 12 d of storage at 4 or 10 °C. Nisin at 500 IU ml⁻¹ did not diminish TMC in white cheese compared to the control. The combination of heat and nisin (1000 or 1500 IU ml⁻¹) exhibited a bacteriostatic effect on TMC throughout the storage period at 4 or 10 °C. Nisin at 500 IU ml⁻¹ had a marginal inhibitory activity against L. innocua. However, nisin at 1000 and 1500 IU ml⁻¹l resulted in a more than 2 log₁₀ reduction in L. innocua count and the effect was more prominent at 10 °C. In comparison, the combination of nisin (1000 or1500 IU ml⁻¹) and heat treatment exhibited a synergistic inhibitory activity against L. innocua, where a complete elimination of the organism was accrued after 6 and 8 d of storage at 10 and 4 °C. Therefore, nisin and heat combination could be used as a prudent hurdle to preclude the growth of Listeria in white cheese, especially under the condition of abused refrigeration conditions.     

我国进口干酪制品中硝酸盐、亚硝酸盐含量调查及暴露风险评估研究

目的 了解我国进口干酪制品中硝酸盐、亚硝酸盐含量水平,并评估我国成人干酪消费人群健康风险。方法 基于我国市售的进口干酪制品中硝酸盐、亚硝酸盐含量和2012年我国居民干酪消费量数据,通过概率评估方法,对我国成人干酪消费人群的膳食硝酸盐、亚硝酸盐暴露量进行估计,并分别与联合国粮农组织/世界卫生组织食品添加剂联合专家委员会（JECFA）制定的硝酸盐每日允许摄入量（ADI）和欧洲食品安全局（EFSA）制定的亚硝酸盐ADI比较后进行风险表征。结果 162份进口干酪样品中,硝酸盐的检出率为89.5%,平均含量为11.23 mg/kg;亚硝酸盐仅2份检出,含量为0.4和0.6 mg/kg。不同种类进口干酪制品中硝酸盐的平均含量从高到低依次为软质、半硬质、其他、硬质。我国成人通过进口干酪硝酸盐的平均暴露量为5.13 μg/kg BW/d,占ADI的0.14%,高暴露人群（P95）为20.06 μg/kg BW/d,占ADI的0.55%。结论 我国进口干酪制品中硝酸盐的检出率较高,且不同种类进口干酪制品其含量存在差异,而亚硝酸盐检出率很低。我国成人通过进口干酪暴露硝酸盐的健康风险较低。     

Sensory analysis and species-specific PCR detect bovine milk adulteration of frescal (fresh) goat cheese

The Brazilian market for dairy products made from goat milk is increasing despite the seasonality of production and naturally small milk production per animal, factors that result in high-priced products and encourage fraud. In Brazil, no official analytical method exists for detecting adulteration of goat dairy products with cow milk. The aim of this study was to design a strategy to investigate the adulteration of frescal (fresh) goat cheeses available in the Rio de Janeiro retail market, combining analysis of cheese composition and the perception of adulteration by consumers. Commercial goat cheeses were tested by using a duplex PCR assay previously designed to authenticate cheeses, by targeting the mitochondrial 12S ribosomal RNA genes of both species simultaneously. The PCR test was able to detect 0.5% (vol/vol) cow milk added during goat cheese formulation. The analysis of 20 locally produced goat cheeses (20 lots of 4 brands) showed that all were adulterated with cow milk, even though the labels did not indicate the addition of cow milk. To estimate the ability of consumers to perceive the fraudulent addition of cow milk, a triangle test was performed, in which cheeses formulated with several different proportions of goat and cow milk were offered to 102 regular consumers of cheese. Detection threshold analysis indicated that almost half of the consumers were able to perceive adulteration at 10% (vol/vol) cow milk. Effective actions must be implemented to regulate the market for goat dairy products in Brazil, considering the rights and choices of consumers with respect to their particular requirements for diet and health, preference, and cost.     

超高压处理对干酪质构的影响

研究超高压(Ultra High Hydrostatic Pressure,HHP;200,600 MPa/10min)处理对5种市售干酪的硬度、黏着性、弹性、内聚性、咀嚼性和回复性6个功能特性的影响。结果显示,5种干酪在200 MPa处理时,其黏着性、弹性、内聚性、回复性差异不显著(P0.05),即较低压力处理对干酪的质构影响不大;超高压处理后,干酪的硬度和耐咀性分别降低31%,39%,且压力越大降低越显著(P0.05);高压处理后蓝纹、稀奶油干酪的内聚性分别增加了21%,15%;帕马森、切达干酪经超高压处理其各个性质基本无显著变化,而马索里拉、蓝纹、稀奶油干酪的各个功能性均有显著差异,说明超高压处理对干酪质构的影响与水分含量有关,即水分含量越高的干酪其质构受超高压处理变化越显著。     

植物蛋白干酪的研制

介绍了植物蛋白干酪的研制方法。以大豆蛋白为原料,经过乳酸菌的发酵及制作等工艺生产出植物蛋白干酪,这种植物蛋白干酪营养丰富,风味独特,保存期较长,可直接食用,还可作为生产保健食品的优选原料。