Increasing the moisture content of imitation cheese: effects on texture, rheology and microstructure

Increasing moisture content may be a practical and cost-effective means to control the functional properties of imitation cheese. Imitation cheeses with moisture contents of 46, 50, 52 and 54 g/100 g were manufactured. An increase in the moisture content of the imitation cheese resulted in significantly increased meltability, tan values and decreased hardness (all P<0.05). The relationship between moisture content (x) and meltability (y) was described by the model (r²=0.99). A linear relationship emerged between moisture content (x) and hardness (y), where (r²=0.95) but cohesiveness was unaffected by moisture content. Increasing the moisture content to 52 or 54 g/100 g led to pockets of free water within the cheese and larger but fewer fat globules. The maximum level of moisture that the cheese matrix can retain appears to be 54 g/100 g.     

Proteolysis, lipolysis, volatile compounds, texture, and flavor of Hispánico cheese made using frozen ewe milk curds pressed for different times

Hispánico cheese is manufactured in Spain from a mixture of cow and ewe milk. Production of ewe milk varies throughout the year, with a peak in spring and a valley in summer and autumn. To overcome this seasonal shortage, curd from spring ewe milk may be frozen and used for cheese manufacture some months later. In the present work, ewe milk curds pressed for 15, 60, or 120 min were held at −24°C for 4 mo, thawed, cut to 1-mm pieces, and mixed with fresh cow milk curd for the manufacture of experimental Hispánico cheeses. Control cheese was made from a mixture of pasteurized cow and ewe milk in the same (80:20) proportion. Cheeses, made in duplicate experiments, were analyzed throughout a 60-d ripening period. No significant differences between cheeses were found for lactic acid bacteria counts, dry matter content, hydrophilic peptides, 47 out of 68 vol.tile compounds, texture, and flavor characteristics. On the other hand, differences of minor practical significance between experimental and control cheeses, unrelated to the use of frozen ewe milk curd or the pressing time of ewe milk curd, were found for pH value, aminopeptidase activity, proteolysis, hydrophobic peptides, free amino acids, free fatty acids, and the remaining 21 vol.tile compounds. It may be concluded that the use of frozen ewe milk curd in the manufacture of Hispánico cheese does not alter its main characteristics.     

Effect of exopolysaccharide produced by isogenic strains of Lactococcus lactis on half-fat Cheddar cheese

Fat-reduced cheeses often suffer from undesirable texture, flavor, and cooking properties. Exopolysaccharides (EPS) produced by starter strains have been proposed as a mechanism to increase yield and to improve the texture and cooking properties of reduced-fat cheeses. The objective of this work was to assess the influence of an exopolysaccharide on the yield, texture, cooking properties, and quality of half-fat Cheddar cheese. Two pilot-scale half-fat Cheddar cheeses were manufactured using single starters of an isogenic strain of Lactococcus lactis ssp. cremoris (DPC6532 and DPC6533) that differed in their ability to produce exopolysaccharide. Consequently, any differences detected between the cheeses were attributed to the presence of the exopolysaccharide. The results indicated that cheeses made with the exopolysaccharide-producing starter had an 8.17% increase in actual cheese yield (per 100 kg of milk), a 9.49% increase in moisture content, increase in water activity and water desorption rate at relative humidities ≤90%, significant differences in the cheeses microstructure, and a significant improvement in both textural and cooking properties, without negatively affecting the flavor profiles of the cheeses.     

Composition and aptitude for cheese-making of milk from cows,buffaloes, goats,sheep, dromedary camels,and donkeys

Bovines produce about 83% of the milk and dairy products consumed by humans worldwide, the rest represented by bubaline, caprine, ovine, camelid, and equine species, which are particularly important in areas of extensive pastoralism. Although milk is increasingly used for cheese production, the cheese-making efficiency of milk from the different species is not well known. This study compares the cheese-making ability of milk sampled from lactating females of the 6 dairy species in terms of milk composition, coagulation properties (using lactodynamography), curd-firming modeling, nutrients recovered in the curd, and cheese yield (through laboratory model-cheese production). Equine (donkey) milk had the lowest fat and protein content and did not coagulate after rennet addition. Buffalo and ewe milk yielded more fresh cheese (25.5 and 22.9%, respectively) than cow, goat, and dromedary milk (15.4, 11.9, and 13.8%, respectively). This was due to the greater fat and protein contents of the former species with respect to the latter, but also to the greater recovery of fat in the curd of bubaline (88.2%) than in the curd of camelid milk (55.0%) and consequent differences in the recoveries of milk total solids and energy in the curd; protein recovery, however, was much more similar across species (from 74.7% in dromedaries to 83.7% in bovine milk). Compared with bovine milk, the milk from the other Artiodactyla species coagulated more rapidly, reached curd firmness more quickly (especially ovine milk), had a more pronounced syneresis (especially caprine milk), had a greater potential asymptotical curd firmness (except dromedary and goat milk), and reached earlier maximum curd firmness (especially caprine and ovine milk). The maximum measured curd firmness was greater for bubaline and ovine milk, intermediate for bovine and caprine milk, and lower for camelid milk. The milk of all ruminant species can be used to make cheese, but, to improve efficiency, cheese-making procedures need to be optimized to take into account the large differences in their coagulation, curd-firming, and syneresis properties.     

不同植物油脂对涂抹再制干酪品质的影响

研究以不同种类油脂作为原料油脂制得的涂抹再制干酪产品在品质上的变化。对添加不同原料油脂的涂抹再制干酪硬度、涂抹性、色度和感官方面进行考察并比较。研究发现,添加稻米油、山茶籽油的涂抹再制干酪硬度与对照组硬度接近,与全黄油对照组分别相差10.99%、7.44%。添加稻米油、花生油的涂抹再制干酪涂抹性接近对照组,分别与对照组20.59%、22.57%。其中添加花生油和葵花籽油的涂抹再制干酪ΔE^*值与对照组分别相差0.30%、0.28%,在色泽上较接近对照组样品。添加稻米油样品感官总评分高达88.85。但添加花生油样品坚果味明显,添加菜籽油样品异味与苦味明显,添加起酥油产品可涂抹性差,三者接受度低。综合各项结果,稻米油是替代黄油作为涂抹再制干酪原料油脂较好的选择。     

Preliminary evaluation of endogenous milk fluorophores as tracer molecules for curd syneresis

A front-face fluorescence spectroscopy probe was installed in the wall of a laboratory-scale cheese vat. Excitation and emission filters were chosen for the selective detection of vitamin A, tryptophan, and riboflavin fluorescence. The evolution of the fluorescence of each fluorophore during milk coagulation and syneresis was monitored to determine if they had the potential to act as intrinsic tracers of syneresis and also coagulation. The fluorescence profiles for 2 of the fluorophores during coagulation could be divided into 3 sections relating to enzymatic hydrolysis of κ-casein, aggregation of casein micelles, and crosslinking. A parameter relating to coagulation kinetics was derived from the tryptophan and riboflavin profiles but this was not possible for the vitamin A response. The study also indicated that tryptophan and riboflavin may act as tracer molecules for syneresis, but this was not shown for vitamin A. The evolution of tryptophan and riboflavin fluorescence during syneresis followed a first-order reaction and had strong relationships with curd moisture and whey total solids content (r = 0.86-0.96). Simple 1- and 2-parameter models were developed to predict curd moisture content, curd yield, and whey total solids using parameters derived from the sensor profiles (standard error of prediction = 0.0005-0.394%; R² = 0.963-0.999). The results of this study highlight the potential of tryptophan and riboflavin to act as intrinsic tracer molecules for noninvasive inline monitoring of milk coagulation and curd syneresis. Further work is required to validate these findings under a wider range of processing conditions.     

发酵乳酪乳清中风味物质的分析研究

采用顶空固相微萃技术(HS-SPME)对发酵乳酪乳清中挥发性风味物质进行提取,并利用气相色谱-质谱联用技术(GC-MS)对挥发性风味物质进行分离鉴定。共鉴定出30种化合物,其中酸类物质质量分数最高,占总量的19.85%;其次为酮类,占总量的12.55%。在发酵乳酪乳清中这些挥发性物质中酸类和酮类物质可能为其重要的风味特征物质。     

复合乳化剂防止常温贮藏再制干酪油脂析出的研究

为解决常温贮藏再制干酪加工过程及贮藏期间的油脂析出问题,本研究以油析性为评定指标,从6种乳化剂中筛选出4种效果较好的乳化剂,在确定常温贮藏再制干酪最适亲水亲油平衡值(HLB值)后,根据HLB值将不同乳化剂进行复配,得到了1种最佳组合的复合乳化剂配方.结果表明,最适HLB值为12.2,复合乳化剂最佳配比(均为质量分数):14％单甘脂,30％六聚甘油单硬脂酸酯,56％的蔗糖脂肪酸酯,乳化剂总用量为0.4％.同时将样品置于(22±2)℃条件下,贮藏90 d,定期检测产品油性变化,均小于对照组,且差异显著(P＜0.05),说明添加该复合乳化剂有效.     

Physicochemical differences between Croatian cheese matured in a lamb skin sack (Sir iz misine) and cheese matured in a rind throughout ripening

The aim of this study was to research differences in physicochemical parameters between Croatian cheese in a lamb skin sack (Sir iz misine) and cheese in a rind throughout ripening. Cheese in a sack had significantly (P < 0.05) lower content of total solids, fat, proteins and salt which showed the ‘protective’ effect of skin sack and higher permeability of natural rind. The water‐soluble nitrogen in the total nitrogen (%TN) and 12% trichloroacetic acid‐soluble nitrogen (%TN) at the end of ripening was significantly (P < 0.05) higher in cheese in a sack than in cheese in a rind which indicates intensive proteolysis in cheese in a sack.