雅致放射毛霉添加量对牦牛霉菌奶酪品质的影响

研究毛霉添加量对牦牛霉菌奶酪品质的影响,确定最佳添加量及发酵时间。采用单因素实验设计,固定其他工艺参数,研究雅致放射毛霉的不同添加量(质量比:0.2%、0.3%、0.4%),测定成熟过程中奶酪的性能指标(感官评分、质构指标、营养成分、pH、蛋白质与脂肪分解指标)。结果表明:毛霉添加量为0.3%,奶酪品质及感官指标最佳;随着毛霉添加量增加,水分、蛋白质、脂肪含量、pH均呈下降趋势,灰分呈上升趋势。成熟至第6 d时,牦牛霉菌奶酪感官指标最佳;随成熟时间延长,pH4.6醋酸盐缓冲液可溶性氮含量、12%三氯乙酸可溶性氮含量、硫代巴比妥酸值、酸价不断升高。因此,发酵剂添加量0.3%,发酵6 d时,牦牛霉菌奶酪品质最佳。     

原料乳冷藏时间对牦牛乳硬质干酪理化指标的影响

冷链贮存运输已广泛运用于各大乳制品生产，冷藏时间的长短对原料乳及其制作的干酪理化品质具有重要影响。该研究以冷藏24、48、72 h牦牛乳为原料制作硬质干酪，比较了硬质干酪成熟过程中的理化指标变化规律。结果表明，在0～6个月成熟期中，冷藏24、48、72 h牦牛乳制成的硬质干酪中水分含量、脂肪含量呈现降低趋势，NaCl含量呈现增加趋势。pH值在成熟初期下降，到成熟后期又逐渐升高；pH 4.6可溶性氮、12%三氯乙酸可溶性氮和游离氨基酸总量呈现增加趋势。整个成熟过程中，3组牦牛乳硬质干酪中pH 4.6可溶性氮、12%三氯乙酸可溶性氮以及游离氨基酸总量始终为冷藏72 h组>冷藏48 h组>冷藏24 h组。该研究可为牦牛乳的冷藏及其在干酪加工中的应用提供理论参考。     

相对湿度对牦牛毛霉霉菌奶酪成熟过程中品质的影响

为研究不同相对湿度对牦牛霉菌奶酪成熟过程中品质的影响,并确定其在成熟过程中的最佳相对湿度和成熟时间,本实验以牦牛霉菌奶酪为试验材料,将其分别置于相对湿度为30%、50%、70%条件下成熟,测定其在成熟过程中感官品质、质构、pH、营养成分、蛋白质和脂肪分解指标以及挥发性风味物质的变化。结果表明:相对湿度为50%,成熟6 d时,奶酪的感官评分最高且质构较佳。随着成熟时间的延长,三个实验组的水分、蛋白质和脂肪含量呈下降趋势,灰分逐渐上升;pH呈先下降后保持不变或上升。除成熟第0和8 d外,在同一成熟时间点,相对湿度为30%的水分含量均显著低于其他两组(P<0.05);灰分、蛋白质和脂肪含量变化不明显;相对湿度为50%的pH下降速度最快。pH4.6醋酸盐缓冲液可溶性氮含量、12%三氯乙酸可溶性氮含量、酸价和硫代巴比妥酸值均在奶酪成熟过程中不断升高,且相对湿度为50%时值最高。对牦牛毛霉霉菌奶酪挥发性风味物质检测发现,相对湿度为50%,成熟第6 d时,奶酪的风味物质含量较高。因此,牦牛霉菌奶酪在相对湿度为50%,成熟6 d时,其品质最佳。     

白牦牛乳硬质干酪加工工艺技术研究

以甘肃天祝牧区白牦牛乳为原料制作硬质干酪,优化加工白牦牛乳硬质干酪的工艺参数,并用扫描电镜(SEM)观察成熟期干酪的微观结构。结果表明,白牦牛乳硬质干酪在发酵剂添加量3%,凝乳酶添加量30μl/100ml,凝乳温度40℃,凝乳pH6.1,氯化钙添加量0.03% 时,品质较好,其成熟30d 时蛋白质含量为27.82%,脂肪含量为36.43%,出品率为15.5%;成熟30d 和90d 的白牦牛乳干酪微观结构变化明显。     

瑞士乳杆菌对Gouda干酪品质的影响

将瑞士乳杆菌作为辅助发酵剂添加到Gouda干酪中,以未添加瑞士乳杆菌的干酪作为空白对照,观察Gouda干酪在成熟期间的成分、成熟率、蛋白质降解、组织状态的变化情况。同时通过测定氨基酸含量及品尝试验对干酪进行感官评价。结果显示:在120 d的成熟期内两种干酪的蛋白质、脂肪、水分、盐分和灰分含量均未发现明显的差异,而添加瑞士乳杆菌的干酪成熟第30天的成熟率、SDS-PAGE电泳条带数量以及谷氨酸含量均明显高于对照样。添加0.1%的瑞士乳杆菌不仅加快Gouda干酪的成熟,而且提高了干酪的感官品质。     

瑞士乳杆菌对契达干酪成熟期间品质的影响

干酪的成熟是形成干酪特有的组织状态、质地和风味的关键工序。将分离自内蒙古传统乳制品中的瑞士乳杆菌SMN2-1作为非发酵性乳酸菌添加到契达干酪的生产中,通过检测其成熟过程中理化指标、气味变化和质构特性等指标,分析了瑞士乳杆菌对契达干酪成熟的影响。结果显示:在90 d的成熟期内,两组干酪的蛋白质、脂肪、水分和盐分含量之间差异不显著(p>0.05),但添加瑞士乳杆菌SMN2-1的干酪成熟第90 d的气味明显改变,内聚性、弹性和咀嚼性等物性指标均高于对照,因此添加瑞士乳杆菌SMN2-1可以有效促进蛋白质分解和干酪的成熟,同时改善干酪的风味和质地。     

成熟温度和时间对半硬质干酪成熟特性影响研究

研究成熟温度和时间对半硬质干酪成熟特性的影响。将干酪分别在4、10、16℃条件下成熟,测定其在90d 内品质变化规律。结果表明,在90d 成熟期内,pH 值先下降后升高,最后趋于稳定;pH4.6 可溶性氮含量和12% 三氯乙酸可溶性氮含量逐渐升高;乳酸菌总数逐渐下降。成熟温度对干酪的感官品质、pH 值、蛋白质的降解和乳酸菌总数影响显著。4℃成熟的干酪,在第90 天时,感官品质达到最好;10℃成熟的干酪,在第45天时,感官品质达到最好;16℃成熟的干酪,感官品质较差。根据感官品质和其他参数的变化规律,确定半硬质干酪的最佳成熟温度为10℃,最佳成熟时间为45d。     

脂质体微胶囊化中性蛋白酶在Cheddar干酪快速成熟中的应用

尝试通过添加不同剂量的脂质体微胶囊化中性蛋白酶来加快Cheddar干酪的成熟;测定了不同成熟期内干酪的pH值、可溶性氮含量以及干酪的质构的变化,经过综合感官分析,确定了最适添加量。结果表明,添加脂质体微胶囊中性蛋白酶加快了干酪的成熟,其中,0.01%的添加量既加快了干酪成熟,又没有导致干酪在风味、质构等品质方面的缺陷。     

Edam牦牛干酪工艺优化及成熟过程中微观结构、挥发性风味物质的变化

为开发牦牛乳干酪新品种，以青藏高原牦牛乳为原料，在单因素试验研究基础上，以发酵剂添加量、预酸化pH、浸洗温度、盐渍浓度为试验因素，通过正交试验优化Edam牦牛硬质干酪的发酵工艺，并采用扫描电子显微镜、固相微萃取-气相色谱-质谱联用技术(solid-phase microextraction-gas chromatography-mass spectrometry, SPME-GC-MS)分析Edam牦牛硬质干酪成熟期内的微观结构和风味物质变化。实验结果表明，Edam牦牛硬质干酪的最佳工艺为发酵剂添加量0.006%(质量分数)、pH 5.6、浸洗温度45℃、盐渍浓度12%(质量分数);扫描电镜结果表明，随着成熟时间的延长，蛋白质网状结构逐渐分解，脂肪球水解，蛋白体系变得疏松，硬度下降；SPME-GC-MS在Edam牦牛硬质干酪不同成熟期(0、20、40、60、80 d)共检测出75种挥发性风味成分，包括酸、醇、酮、酯、醛及其他类化合物，关键风味物质有丁酸、乙酸、戊酸、己酸、1-丁醇、苯乙醇及2-戊酮。     

牦牛乳硬质乳酪成熟特性的研究

对牦牛乳硬质乳酪成熟特性进行研究。检测其成熟过程中感官指标、质构指标、营养成分、微生物指标、蛋白质与脂肪分解指标的变化,确定其成熟时间。结果表明:牦牛乳硬质乳酪在成熟过程中,质构指标呈先上升后下降的趋势,在(45~60)d范围内感官品质最佳;p H、水分、蛋白质及脂肪含量均呈下降趋势,灰分含量上升;蛋白质水解及脂肪分解反应在成熟过程中一直进行,并在(45~60)d阶段反应较快;微生物方面乳酸菌总数先上升后下降,而细菌总数呈下降趋势。综合考虑牦牛乳硬质乳酪成熟时间为60 d时品质最佳,风味最好,各项指标达到最优值。     

Effect of somatic cell count on Prato cheese composition

The objective of this research was to evaluate the effect of 2 levels of somatic cell counts (SCC) in raw milk on Prato cheese composition, protein and fat recovery, cheese yield, and ripening. A 2 × 6 factorial design with 3 replications was performed in this study: 2 levels of SCC and 6 levels of storage time. Initially, 2 groups of dairy cows were selected to obtain low (<200,000 cells/ mL) and high (>600,000 cells/mL) SCC in milks that were used to manufacture 2 vats of cheese: 1) low SCC and 2) high SCC. Milk, whey, and cheese compositions were evaluated; clotting time was measured; and cheese yield, protein recovery, and fat recovery were calculated. The cheeses were evaluated after 5, 12, 19, 26, 33, and 40 d of ripening according to pH, moisture, pH 4.6 soluble nitrogen, 12% trichloroacetic acid soluble nitrogen as a percentage of total nitrogen, and firmness. High-SCC milk presented significantly higher total protein and nonprotein nitrogen and lower true protein and casein concentrations than did low-SCC milk, indicating an increased whey protein content and a higher level of proteolysis. Although the pH of the milk was not affected by the somatic cell level, the cheese obtained from high-SCC milk presented significantly higher pH values during manufacture and a higher clotting time. No significant differences in cheese yield and protein recovery were observed for these levels of milk somatic cells. The cheese from high-SCC milk was higher in moisture and had a higher level of proteolysis during ripening, which could compromise the typical sensory quality of the product.     

乳酸菌胞外多糖对低脂Mozzarella奶酪质构、微观结构等品质的影响

目的 研究乳酸菌胞外多糖对低脂Mozzarella奶酪质构等品质特性的影响。方法 在脱除50%乳脂肪的原料中加入0.5%乳酸菌胞外多糖制作低脂Mozzarella奶酪, 同时以全脂Mozzarella奶酪和低脂Mozzarella奶酪为对照, 对Mozzarella奶酪成熟过程中的硬度、弹性、胶黏性、咀嚼性、融化性、油脂析出性、微观结构及感官评分等指标进行分析。结果 0.5%乳酸菌胞外多糖提高了低脂Mozzarella奶酪的水分含量、出品率, 改善了低脂Mozzarella奶酪致密的结构, 形成了类似全脂Mozzarella奶酪疏松、光滑的组织结构, 降低了低脂Mozzarella奶酪的硬度、胶黏性和咀嚼性, 提高了弹性、融化化性和油脂析出, 成熟90 d加入多糖低脂Mozzarella奶酪的滋味和气味、组织状态、色泽接近全脂Mozzarella奶酪。结论 乳酸菌胞外多糖可以提高低脂Mozzarella奶酪的水分含量和出品率, 改善低脂Mozzarella奶酪的组织结构和质构特性。     

Edam牦牛干酪成熟过程中品质变化及蛋白质降解

为研究Edam牦牛半硬质干酪成熟机理，分别测定成熟0、20、40、60、80 d Edam牦牛干酪的感官、理化、物性、蛋白质和脂肪分解指标，采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳和傅里叶变换红外光谱等方法研究酪蛋白降解情况，通过Pearson相关性分析成熟时间与各指标间的相关性。结果表明：随着成熟时间延长，感官评分先下降后上升；水分含量、pH值下降；亮度值（L*）下降，红度值（a*）和黄度值（b*）值上升；硬度、弹性、胶黏性均上升，凝聚性逐渐下降；储能模量和损耗模量升高，损耗角正切值始终小于1；成熟时间与总氮含量、pH 4.6和12%三氯乙酸条件下干酪中可溶性氮含量等呈极显著正相关（P<0.01）；脂肪含量先升高后降低，游离脂肪酸含量和硫代巴比妥酸值逐渐增加。酪蛋白（casein,CN）降解研究结果表明：αs1-CN、αs2-CN、β-CN及κ-CN均随成熟时间延长而不断降解，成熟80 d时大分子蛋白降解明显；成熟过程中β-折叠、α-螺旋逐渐向无规卷曲转化；成熟时间与羰基含量、表面疏水性呈极显著正相关（P<0.01），与总巯基含量呈显著负相关（P<0.05）。     

Improvement of low fat mozzarella cheese properties using denatured whey protein

Mozzarella cheese was made from buffalo milk (6% fat) or from partially skimmed buffalo milk (2 and 4% fat) with 0.5 and 1% denatured whey protein. Adding whey protein to buffalo milk decreased rennet coagulation time and curd tension whereas increased curd synaeresis. Addition of whey protein to cheese milk increased the acidity, total solids, ash, salt, salt in moisture, also some nitrogen fractions. The meltability and oiling‐off values increased but the calcium values of mozzarella cheese decreased. The sensory properties of low fat mozzarella cheese were improved by addition of whey protein to the cheese milk.     

添加豆浆对牦牛酸奶品质的影响

将不同添加量（0、20%、40%、60%）豆浆添加到牦牛乳中制备豆浆-牦牛酸奶,探讨不同添加量豆浆对牦牛酸奶理化指标、贮藏期内酸度、质构特性（硬度、稠度、黏聚性与黏性指数）、持水力、乳酸菌数和感官特性的影响。结果表明,在贮藏期内（1～14 d）,随着豆浆添加量在0～60%范围内增加,牦牛酸奶酸度、持水力、质构特性、乳酸菌数均有所下降。添加20%豆浆制备的牦牛酸奶蛋白质、脂肪及非脂乳固体含量分别为3.28 g/100 g、4.58 g/100 g、8.76 g/100 g,乳酸菌数＞107 CFU/mL,感官评分为87.9分,其酸度、持水力、质构、乳酸菌数等与未添加豆浆的对照相比均无显著差异（P＞0.05）。因此,在牦牛乳中添加20%的豆浆制备豆浆-牦牛酸奶是可行的,可进一步推广应用。     

Physicochemical,textural and sensory properties of white soft cheese made from buffalo and cow milk mixtures

The physicochemical, textural and sensory properties of white soft cheeses made from three different buffalo and cow milk mixtures (100:0, 70:30 and 30:70) during 3‐month storage were studied. The increase in buffalo milk concentration resulted in increasing total cheese yield, dry matter (DM) and fat retention and fat in DM content. However, it caused reductions in moisture content, salt intake, hardness, chewiness, elasticity, sensory hardness and sensory cohesiveness of the samples. The percentage of water‐soluble nitrogen to total nitrogen increased during storage resulting in decreased fracturability, hardness (textural and sensory), cohesiveness (textural and sensory), springiness, chewiness and elasticity. The panellists evaluated the white soft cheese made with buffalo milk as the most acceptable.     

Multiparametric analysis of cheese using single spectrum of laser-induced breakdown spectroscopy

The potential of using laser-induced breakdown spectroscopy (LIBS) for prediction of chemical quality/control parameters in a cheese matrix was investigated. Traditional methods are usually time-consuming and require complex pre-treatments, the use of toxic chemicals and laboratories and personnel equipped with these analytical skills. In this study, 11 different chemical analyses commonly performed on cheese samples were conducted using traditional methods on 82 full-fat, white pickled and ripened cheese samples. Additionally, these parameters of interest were correlated with multi-elemental spectra of LIBS using partial least squares regression. The results obtained for moisture, dry matter, salt, total ash, total protein, pH, fat, acidity, water soluble nitrogen, trichloroacetic acid soluble nitrogen, and phosphotungstic acid soluble nitrogen (R_cal² = 0.964, 0.959, 0.970, 0.973, 0.952, 0.971, 0.733, 0.762, 0.714, 0.633, and 0.707, respectively) indicated that LIBS could be used as an alternative or complementary method in quality control of cheese.     

Influence of microfiltration and adjunct culture on quality of Domiati cheese

The effects of microfiltration and pasteurization processes on proteolysis, lipolysis, and flavor development in Domiati cheese during 2 mo of pickling were studied. Cultures of starter lactic acid bacteria isolated from Egyptian dairy products were evaluated in experimental Domiati cheese for flavor development capabilities. In the first trial, raw skim milk was microfiltered and then the protein:fat ratio was standardized using pasteurized cream. Pasteurized milk with same protein:fat ratio was also used in the second trial. The chemical composition of cheeses seemed to be affected by milk treatment—microfiltration or pasteurization—rather than by the culture types. The moisture content was higher and the pH was lower in pasteurized milk cheeses than in microfiltered milk cheeses at d 1 of manufacture. Chemical composition of experimental cheeses was within the legal limits for Domiati cheese in Egypt. Proteolysis and lipolysis during cheese pickling were lower in microfiltered milk cheeses compared with pasteurized milk cheeses. Highly significant variations in free amino acids, free fatty acids, and sensory evaluation were found among the cultures used in Domiati cheesemaking. The cheese made using adjunct culture containing Lactobacillus delbrueckii ssp. lactis, Lactobacillus paracasei ssp. paracasei, Lactobacillus casei, Lactobacillus plantarum, and Enterococcus faecium received high scores in flavor acceptability. Cheeses made from microfiltered milk received a higher score in body and texture compared with cheeses made from pasteurized milk.