解淀粉芽孢杆菌GSBa-1凝乳酶在马苏里拉干酪中的应用

对分离自酒曲的1 株解淀粉芽孢杆菌GSBa-1发酵所产凝乳酶进行研究,该酶凝乳活力高而蛋白水解活力低,纯酶凝乳活力可达1.46×106 SU/g;使用该凝乳酶和商品凝乳酶制作马苏里拉干酪,并对干酪理化成分、成熟过程中pH值和微生物指标及干酪成熟前后质构特性、游离脂肪酸、可溶性蛋白、风味和干酪性能等指标进行对比分析。结果显示,理化成分上菌株凝乳酶与商品凝乳酶制作的干酪相接近（P＜0.05）。干酪在成熟过程中,发酵剂存活数先增加后减少,但其差异不大;菌株凝乳酶制作的干酪pH 4.6可溶性蛋白含量较多,干酪的游离氨基酸总量（76 mg/100 g）也高于商品凝乳酶制作的干酪游离氨基酸总量（55.3 mg/100 g）;菌株凝乳酶制作的干酪质构特性优于商品凝乳酶制作的干酪;电镜结果显示,菌株凝乳酶制作的干酪内部网状结构更充实;菌株凝乳酶具有稍强的蛋白水解活力,导致其制作的干酪风味物质种类多于商品凝乳酶制作的干酪,风味物质更加丰富。干酪样品的保形性和拉丝性实验测定结果显示,2 种凝乳酶制作的干酪性能差异不大（P＞0.05）;对2 种凝乳酶制作的干酪进行感官评定,其总评分相接近。以上结果表明,解淀粉芽孢杆菌GSBa-1凝乳酶在一定程度上可代替小牛凝乳酶应用于马苏里拉干酪的生产。     

促成熟牦牛乳半硬质(切达)干酪成熟特性及挥发性风味物质变化研究

为探究牦牛乳半硬质干酪促成熟特性并确定经促成熟处理后的最佳成熟期,该实验选用经促成熟工艺处理的干酪与未处理干酪进行对比研究成熟期间(20、40、60、80 d)干酪质构与理化性质,并探究促成熟干酪在不同成熟期挥发性风味物质的变化。结果表明,在促成熟条件下牦牛乳半硬质干酪40～60 d硬度、黏性、弹性、凝聚性、咀嚼性变化明显(P<0.05)。理化性质方面水分含量逐渐降低,pH值升高,脂肪含量下降,实验组干酪酸价及过氧化值均上升,且高于对照组,表明促成熟效果好。采用固相微萃取-气相色谱-质谱联用技术检测出促成熟牦牛乳半硬质干酪成熟期间产生66种风味物质,其中主要特征风味物质包括酯类(丁酸丁酯)、酸类(丁酸)、酮类(2-丁酮)、醇类(1-丁醇)。促成熟干酪中酸类、酮类、醇类物质的含量显著增加。综上所述,促成熟干酪在成熟40～60 d质构与营养成分均达较高标准,特征风味物质含量上升,显著缩短成熟时间,为牦牛乳半硬质干酪的快速成熟和市场发展提供了理论依据。     

水牛乳和荷斯坦牛乳切达干酪成熟期间质量特性对比

为了了解水牛乳和荷斯坦牛乳切达干酪成熟期间的质量特性,采用了理化测定、质构测定和感官评定相结合的方法对其进行研究.结果表明:在成熟期90 d内,不同成熟温度下,两种干酪的蛋白质质量分数减少约为1％～4％,脂肪质量分数减少约为4％～10％,且成熟温度越高,质量分数下降越大,水牛乳干酪中蛋白和脂肪质量分数均高于荷斯坦牛乳干酪且两种成分的下降量也是水牛乳干酪更高;pH值呈现先下降后上升趋势.在90 d成熟期间,两种干酪的硬度先上升后下降,凝聚性上升,弹性下降.经感官评价,两种干酪在10℃成熟60天时风味最佳,水牛乳切达干酪略受偏爱.可用于水牛乳切达干酪成熟期内质量控制.     

脱脂及全脂硬质干酪成熟特性的研究

研究脱脂(脂肪含量3.81%)及全脂(脂肪含量50.17%)硬质干酪在不同成熟期的成熟特性,为硬质干酪的工艺改进和货架期的延长提供理论参考。将实验室自制的脱脂和全脂硬质干酪在4℃真空包装下贮藏使其成熟。测定不同成熟时间(0~35 d)干酪的理化性质,经方差分析,研究成熟时间对干酪成熟特性的影响。在真空包装4℃贮藏下,随着成熟时间的延长,脱脂和全脂干酪的水分、灰分和脂肪含量逐渐下降,酸度和蛋白质处于先升高后下降的趋势,而pH4.6-SN和12%TCA-SN则表现为逐渐上升的趋势。脱脂和全脂干酪的8种必需氨基酸含量较丰富在38%。2种干酪的质构特性随成熟时间的增长变化较为显著。在水分、蛋白质含量、氨基酸总量以及质构方面,脱脂干酪优于全脂干酪;而在酸度变化、蛋白质降解方面,全脂干酪优于脱脂干酪。     

甲醇芽孢杆菌凝乳酶对马苏里拉干酪加工特性的影响

为了探究甲醇芽孢杆菌（Bacillus methanolicus）凝乳酶在马苏里拉干酪加工中的应用,分别以使用甲醇芽孢杆菌凝乳酶、混合酶制剂（含质量分数10%甲醇芽孢杆菌凝乳酶和90%商品凝乳酶）制作的马苏里拉干酪作为实验组,以商品凝乳酶干酪作为对照组,测定不同组别干酪成熟期间的蛋白水解特性、质构、风味和微观结构变化,研究甲醇芽孢杆菌凝乳酶对马苏里拉干酪加工特性的影响。结果表明,实验组干酪在成熟过程中pH值（4.6～5.3）、微生物数量（8.80～9.68（lg（CFU/g）））与对照组无显著差异（P＞0.05）;实验组干酪水分质量分数（混合酶干酪为（43.21±1.17）%、甲醇芽孢杆菌凝乳酶干酪为（46.15±0.94）%）均显著高于对照组（（41.08±1.04）%）,得率（混合酶干酪为（9.27±0.17）%、甲醇芽孢杆菌凝乳酶干酪为（9.46±0.16）%）也显著高于对照组（（8.98±0.13）%）（P＜0.05）;且实验组干酪的蛋白水解特性（pH 4.6时可溶性蛋白、酪蛋白水解程度和游离氨基酸质量分数）以及风味物质种类和相对含量等指标也优于对照组干酪。但是实验组中甲醇芽孢杆菌凝乳酶干酪保形性相对欠佳,感官评定得分偏低,混合酶干酪与对照组质构及感官基本得分一致,因此甲醇芽孢杆菌凝乳酶可以作为商品酶的部分代替品应用于干酪的生产中。     

添加不同分子量乳清肽对快速成熟干酪的影响

以干酪成熟期间的p H值、可溶性氮质量分数、游离脂肪酸及质构特性为检测指标,通过研究添加不同分子量的乳清肽对干酪快速成熟影响,确定乳清肽具有促进干酪快速成熟的作用。结果表明:添加乳清肽能够促进干酪成熟期间p H值、可溶性氮及干酪质构特性产生变化,提高成熟速度;分子量为3 000 u以下的乳清肽促进干酪快速成熟效果最佳,在35 d成熟期内,添加分子量3 000 u乳清肽的干酪,p H值由5.62降至5.35,p H4.6 SN由4.8%增至19.32%,质量分数12%TCA SN由3.02%增至11.7%,游离脂肪酸(FAA)由2.5%增至11.97%,硬度和凝聚性呈先下降后增加的趋势,弹性和呈先上升后下降的趋势。     

两种羊奶干酪成熟期间理化和生化特性研究

对硬质、半硬质羊奶干酪成熟90d内理化和生化特性的研究表明:硬质、半硬质羊奶干酪的pH在成熟过程中都呈先减小后增大的趋势,水分含量逐渐降低,盐含量逐渐增大,蛋白质和脂肪含量先增大后减小.在蛋白质降解产物中,pH4.6水溶性氮(WSN-N)、12%三氯乙酸氮(TCA-N)、5%磷钨酸氮(PTA-N),氨基酸态氮(AAN)含量都呈上升趋势.在脂肪降解产物中,ADV值、羰基价和TBA值变大,POV值在干酪成熟过程中上升和下降交替出现.     

不同凝乳酶对切达干酪成熟的影响研究

本文比较了米黑毛霉凝乳酶、小牛皱胃酶和木瓜蛋白酶制备的切达干酪成熟期间的感官品质和理化性质。结果表明,小牛皱胃酶和米黑毛霉凝乳酶制作的干酪在成熟期60d和90d时,感官评价值达到最大,在90d成熟期内,木瓜蛋白酶干酪的感官评分值始终低于小牛皱胃酶和米黑毛霉凝乳酶;在干酪成熟期间,三种干酪在水分含量、pH、总氮、pH 4.6-SN以及12%TCA-SN含量的变化趋势一致;在成熟期0-90d内,三种干酪蛋白降解程度是小牛皱胃酶干酪米黑毛霉凝乳酶木瓜蛋白酶;在成熟期0-30d时,小牛皱胃酶和米黑毛霉凝乳酶对总氮影响差异不显著(P0.05),成熟期0-30d和60-90d时,这两种酶对干酪pH 4.6-SN以及12%TCA-SN影响差异不显著(P0.05)。     

红曲霉对类Camembert干酪成熟期质构和风味的影响

本实验以牛乳为原料,以Camembert干酪的加工工艺为基础,分别通过添加和不添加(对照)辅助发酵剂红曲霉制作两种不同的类Camembert干酪。在40 d成熟期内对两种干酪的质构和风味参数进行测定,探究红曲霉对干酪成熟期水分质量分数、蛋白水解度、质构和风味变化的影响。结果表明,随着成熟期的延长,两种干酪水分质量分数下降,蛋白水解度逐渐增加,两种干酪质构参数的变化趋势相似,其硬度和弹性在0~8 d不断增加,8 d后随成熟期延长呈下降的趋势;胶性和咀嚼性是二次特性,二者均与硬度呈正相关;黏着性不断提高而回复性不断降低。加入红曲霉后,干酪水分质量分数增大,蛋白水解程度加剧;干酪的黏着性提高,而硬度、弹性、胶性、咀嚼性和回复性降低,说明加入红曲霉后干酪口感更柔软、质地更加均匀。随成熟期延长,两种干酪中酸、酮、醇、酯类物质总含量变化趋势相似,有机酸和醇类含量在成熟期前16 d不断增加,之后开始降低,酮类物质逐渐积累,酯类物质含量在前24 d不断增加,之后含量逐渐稳定。加入红曲霉使干酪不同有机酸的含量和比例发生改变,使得以其为前体物质合成的醇、酮、酯类含量和比例也发生变化,其中带来花香和蜂蜜香气的2-十一酮、2-十三酮、苯乙醇、丁二醇以及具有水果香气的己酸乙酯、辛酸乙酯、癸酸乙酯含量在红曲干酪中显著高于白霉干酪(P0.05),而产生奶香味的壬酮、辛酮、癸酮等和具有蘑菇味的1-辛烯-3醇含量低于白霉干酪。     

凝乳酶对牦牛乳硬质干酪成熟期间蛋白降解的影响

以新鲜牦牛乳为原料,采用小牛皱胃酶、木瓜蛋白酶和微生物凝乳酶制作硬质干酪,探讨凝乳酶种类对牦牛乳硬质干酪成熟期间蛋白质降解的影响。结果表明:三种凝乳酶牦牛乳硬质干酪成熟过程中,不同凝乳酶牦牛乳硬质干酪在成熟期间蛋白质降解能力存在较大差异,总氮(TN)、p H4.6水溶性氮(p H4.6-SN/TN)、12%的三氯乙酸氮(12%TCA-N/TN)、5%磷钨酸氮(5%PTA-N/TN)含量、游离氨基酸均随成熟时间延长不同程度的增加,蛋白氮和酪蛋白氮逐渐降低,多肽氮呈先升高后下降趋势,且微生物凝乳酶降解牦牛乳硬质干酪蛋白能力显著(p0.05)高于木瓜蛋白酶和小牛皱胃酶。     

Effect of artisanal kid rennet paste on lipolysis in semi-hard goat cheese

This study examined the use of hygienised kid rennet pastes in model cheese systems and also in goat milk semi-hard cheeses to promote lipolysis. The results obtained indicated that the use of rennet paste caused greater lipolysis and increased, mostly, the short-chain free fatty acid (FFA) content. The model systems made with whole goat’s milk using rennet paste and commercial rennet mixture exhibited a higher FFA content than did the rennet paste-free controls (31,600 vs. 25,600 μmol/kg cheese). For the pilot cheeses made with bovine rennet and rennet paste mixture, the increase in FFA level after 45 days of ripening compared with the cheeses prepared only with commercial rennet was as much as 6600 (μmol/kg cheese) and the increase in the butyric acid content was also 1650 (μmol/kg cheese). Moreover, after 15 days of ripening, industrially prepared cheeses made with rennet paste exhibited greater levels of FFA than did the cheeses made with commercial rennet (11,500 μmol/kg at 45 days of ripening). Their flavour was stronger and the organoleptic characteristics were better accepted, which implies less ripening time for commercial cheese manufacture.     

Influence of vegetable and animal rennet on proteolysis during ripening in ewes’ milk cheese

The renewed interest in using enzymes from thistles of the genus Cynara in the making of traditional ewes’ milk cheese prompted us to investigate the effect of vegetable and animal rennet on proteolysis during ripening of Los Pedroches cheese. Casein hydrolysis was found to be much more extensive and faster in cheese made by using vegetable rennet (the amount of soluble nitrogen at 60, 80 and 100 days of ripening was more than 28% greater than that in cheese produced using animal rennet). The levels of insoluble Tyr and Trp were higher in cheese produced with vegetable rennet. PAGE, using gels containing 7 M urea, revealed decreased contents in residual α_s-CN and β-CN, as well as markedly increased levels of the more mobile components in cheese produced from vegetable rennet at the end of ripening. On the other hand, the degree of proteolysis in terms of NPN or its main components (peptides, amino acids and ammonia) was similar in cheese produced using animal or vegetable rennet.     

Evaluation of biogenic amines and microbial counts throughout the ripening of goat cheeses from pasteurized and raw milk

The effect of the hygienic quality of milk on changes in microbial counts and biogenic amine content was evaluated during ripening of goat cheeses manufactured from pasteurized and raw milks at 1, 14, 30, 60 and 90 d. The original milk, rennet, curd and whey were also included in the study. The pH, salt content and extent of proteolysis in the cheese were also evaluated. Spermidine and spermine were the main amines in raw milk, while they were minor amines in cheeses. Other amines increased markedly during ripening, tyramine being the main amine in cheese made from raw milk and cadaverine and putrescine in those produced from pasteurized milk. Enterobacteriaceae counts decreased during ripening whereas those of lactic acid bacteria increased, especially lactobacilli and enterococci. Cheese made from raw milk showed higher microbial counts during ripening than those made from pasteurized milk, especially for Enterobacteriaceae and enterococci, counts being 2 or 3 log units higher. Raw milk cheese showed remarkably higher biogenic amines compared with pasteurized milk cheeses. Therefore, pasteurization of milk causes a decrease in final biogenic amine content of cheese as a result of the reduction of its microbial counts.     

Lipolysis and proteolysis profiles of fresh artisanal goat cheese made with raw milk with 3 different fat contents

The objective of this study was to describe the proteolysis and lipolysis profiles in goat cheese made in the Canary Islands (Spain) using raw milk with 3 different fat contents (0.5, 1.5, and 5%) and ripened for 1, 7, 14, and 28 d. β-Casein was the most abundant protein in all cheeses and at all ripening times. Quantitative analysis showed a general decrease in caseins as ripening progressed, and degradation rates were higher for α_S1-casein than for β-casein and α_S2-casein. Furthermore, the degradation rate during the experimental time decreased with lower fat contents. The α_S2-casein and α_S1-casein levels that remained in full-fat and reduced-fat cheeses were less than those in low-fat cheese. In contrast, β-casein also showed degradation along with ripening, but differences in degradation among the 3 cheese types were not significant at 28 d. The degradation products increased with the ripening time in all cheeses, but they were higher in full-fat cheese than in reduced-fat and low-fat cheeses. The free fatty acid concentration per 100 g of cheese was higher in full-fat cheese than in reduced- and low-fat cheese; however, when the results were expressed as milligrams of free fatty acids per gram of fat in cheese, then lipolysis occurred more rapidly in low-fat cheese than in reduced- and full-fat cheeses. These results may explain the atypical texture and off-flavors found in low-fat goat cheeses, likely the main causes of non-acceptance.     

Probiotic cheese production using Lactobacillus casei cells immobilized on fruit pieces

Lactobacillus casei cells were immobilized on fruit (apple and pear) pieces and the immobilized biocatalysts were used separately as adjuncts in probiotic cheese making. In parallel, cheese with free L. casei cells and cheese only from renneted milk were prepared. The produced cheeses were ripened at 4 to 6°C and the effect of salting and ripening time on lactose, lactic acid, ethanol concentration, pH, and lactic acid bacteria viable counts were investigated. Fat, protein, and moisture contents were in the range of usual levels of commercial cheeses. Reactivation in whey of L. casei cells immobilized on fruit pieces after 7 mo of ripening showed a higher rate of pH decrease and lower final pH value compared with reactivation of samples withdrawn from the remaining mass of the cheese without fruit pieces, from cheese with free L. casei, and rennet cheese. Preliminary sensory evaluation revealed the fruity taste of the cheeses containing immobilized L. casei cells on fruit pieces. Commercial Feta cheese was characterized by a more sour taste, whereas no significant differences concerning cheese flavor were reported by the panel between cheese containing free L. casei and rennet cheese. Salted cheeses scored similar values to commercial Feta cheese, whereas unsalted cheese scores were significantly lower, but still acceptable to the sensory panelists.     

Influence of lamb rennet paste on the lipolytic and sensory profile of Murcia al Vino cheese

The influence of lamb rennet paste (71.1% chymosin, 177 international milk-clotting units/mL, 4.57U/g of lipase activity) during the ripening of Murcia al Vino goat cheese was studied. The aim of this study was to improve the knowledge of the effect of lamb rennet paste on the lipolytic patterns in this type of cheese by reference to the evolution of total and free fatty acids. A sensory analysis was carried out to compare cheeses made with commercial and paste rennet. The rennet paste showed higher lipolytic activity, enhancing the production of short-chain free fatty acids. In addition, the cheese produced with lamb rennet paste had a slightly more bitter and piquant taste, making it an attractive commercial alternative that can be used to develop new varieties of goat cheese.     

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。     

Evolution of lipolysis during the ripening of traditional Feta cheese

Lipolysis was studied during ripening of traditional Feta cheese produced in two small dairies, A and B. The cheeses were made from a thermized mixture of ewes’/goats’ milk by using yoghurt as starter and artisanal rennet from lambs’ and kids’ abomasa (cheese A) or mixed artisanal rennet with calf rennet (cheese B).The acid degree value and the free fatty acids (FFA) contents in both cheeses increased sharply up to 18 d (pre-ripening period at 15 °C) and continued to increase throughout ripening. In both mature cheeses, acetic acid was found at high levels (13–18% of the total FFAs). However, except for this, all FFA contents differed significantly (P < 0.05) between the two cheeses throughout ripening. The levels of individual and total C2:0–C8:0, C10:0–C14:0 and C16:0–C18:2 fatty acids were significantly higher (P < 0.05) in cheese A than in cheese B. Presumably the difference, especially in the C2:0–C8:0 content, was due mainly to the type of the rennet used. Butyric acid was the dominant FFA in cheese A (20% of the total FFAs at 120 d), while the most abundant FFAs in cheese B were capric (18%) and lauric acid (18%). In general, the lipolysis degree of the two cheeses was higher than those reported for the industrially-made Feta cheese.In organoleptic evaluation, cheese A had a piquant taste that was attributed to its high content of butyric acid and showed a significantly (P < 0.05) higher total score than cheese B.