混合型大豆干酪成熟中蛋白质降解特性的研究

对混合型大豆干酪成熟过程中蛋白质的降解及感官特性变化进行了研究。检测了混合型大豆干酪成熟过程中pH4．6水溶性氮、12％三氯乙酸氮、5％磷钨酸氮和游离氨基酸含量的变化；在不同成熟时间下对混合型大豆干酪进行了感官评定。结果表明，随着成熟时间的延长，混合型大豆干酪的pH4．6水溶性氮、12％三氯乙酸氮、5％磷钨酸氮的含量增大；游离氨基酸含量变化较为显著；8℃下成熟30d时，混合型大豆干酪的感官特性最好。     

市售天然成熟干酪滋味特征差异性研究

利用气相色谱质谱联用仪、氨基酸分析仪对8种典型天然成熟干酪的主要滋味成分进行分析,通过滋味活力值和感官评定阐明8种干酪间的滋味差异情况。结果表明:除了山羊乳干酪和布里干酪,其他6种干酪中游离氨基酸对滋味均有贡献,特征滋味氨基酸有缬氨酸和赖氨酸,即干酪共同带有苦味和甜味,而蓝纹干酪特征性氨基酸种类最丰富,滋味最强;8种干酪共检测到11种游离脂肪酸,共有的特征滋味脂肪酸为己酸、壬酸、癸酸、月桂酸和肉豆蔻酸。其中酸味程度最强的为艾达姆干酪,帕玛森干酪的醇厚感最强;8种干酪氯化钠含量明显高于阈值,可显著感受到咸味。经感官分析,干酪的滋味中咸味和鲜味比较突出,蓝纹干酪滋味强度最强。     

非成熟Mozzarella干酪的品质研究

通过改进传统Mozzarella干酪的工艺,制备了非成熟Mozzarella干酪,使用质构测定仪、改良的Schreiber实验法、电子显微等方法分别测定了样品的TPA质构、融化性、油脂析出性、拉丝性和微观结构.结果表明,非成熟Mozzarella干酪的功能特性与传统Mozzarella干酪相比有所提高;微观结构显示成熟...     

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。     

提高成熟温度加快Mozzarella干酪成熟的研究

制作2批Mozzarella干酪A和B，分别在4℃(A)和7℃(B)下成熟，观察其在成熟期间的变化及测定可溶性N的含量等指标，可知在7℃下成熟的干酪在制作后30d的蛋白水解性、功能特性等和4℃下成熟50d的干酪无显著差异，而和7℃下成熟50d的干酪有显著差异。说明成熟温度显著影响干酪的蛋白水解性。在7℃下贮藏的Mozzarella干酪成熟30d可达到4℃下贮存50d的成熟度，即将成熟温度从4℃提高到7℃，可将成熟期缩短20d左右。     

干酪成熟过程中的微生物变化

干酪的成熟过程，是在添加酶及各种微生物的协同作用下完成的。干酪中的微生物，不仅有我们人为添加的发酵微生物，而且还含有残活在巴氏杀菌原料乳中的以及在制造和成熟过程中污染的微生物。在这些微生物的共同作用下，参与干酪成熟过程中的物理、化学以及感官性能的变化     

霉菌表面成熟干酪的生化变化

使用自传统食品中筛选出的霉菌制作霉菌表面成熟干酪,研究其在成熟过程中的化学组分、各种含氮成分的变化,以及酪蛋白的降解情况.在一定成熟条件下,干酪的蛋白质和脂肪总含量变化不大,乳糖被降解利用;蛋白质在成熟过程中发生不同程度降解,在成熟12d时蛋白质降解速率增加,产生大量不同大小的肽;pH在成熟过程中增大.     

成熟温度和时间对Cheddar干酪成熟特性的影响研究

通过对不同成熟参数下Cheddar干酪蛋白分解、质构、pH及感官评价的分析,探讨了成熟参数对Cheddar干酪的影响,并得出研究条件下的最优成熟温度和时间,分析了Cheddar干酪在成熟过程中的游离氨基酸变化情况。     

溶菌酶处理发酵剂加速干酪成熟的研究

以pH、蛋白质降解、脂肪酸含量变化及干酪的感官特征为指标,研究了溶菌酶处理发酵剂对干酪成熟的影响。结果表明:实验组干酪的pH在整个成熟期处于对照组1(添加2%发酵剂)干酪和对照组2(添加2.5%发酵剂)的pH之间,表明通过溶菌酶处理发酵剂可明显抑制干酪成熟期间的产酸量;添加溶菌酶处理发酵剂可加速干酪中蛋白质分解和乳脂肪的降解;感官评价结果表明,添加溶菌酶处理发酵剂可提高干酪风味,在相同的成熟时间实验组干酪的质地也较对照组好。      

不同加工方法对快速成熟切达干酪流变和微观结构的影响

通过添加成熟干酪、成熟干酪与微胶囊酶共用和微胶囊复合酶单作用三种促熟方法制备切达干酪样2、样3和样4,非促熟对照为样1,利用流变仪、扫描电镜分析促熟技术对干酪质地的影响。结果表明,随扫描频率增加,四种样品的复数粘度(η*)极显著降低,其G′值和G″值极显著增加(P0.01);相同扫描频率时,四种样品的复数粘度值:样1样3样2样4。所有样品的G′值和G″值都随着温度的升高而显著降低,tanδ值先增加后减小,说明动态扫描时温度变化对快速成熟干酪G′值和G″影响极显著(P0.01)。样1、样2、样3和样4的转变温度分别为37.5℃、32.5℃、35℃和32.5℃。SEM测到样品的结构中\"机械孔洞\"数量和大小明显不同,对照样1和样3中机械孔洞数量多且较大,样2次之,样4几乎没有机械孔洞,说明样4的促熟后的质地相对最好。     

蓝纹干酪成熟期间氨基酸的变化研究

采用HITACHIL—8800型氨基酸自动分析仪测定分析了自制蓝纹干酪成熟过程中的氨基酸组分与含量变化。成熟30～60d期间,所有氨基酸含量都呈现上升趋势,成熟90d时,门冬氨酸、谷氨酸、缬氨酸、蛋氨酸、亮氨酸、苯丙氨酸、精氨酸、脯氨酸几种氨基酸由于转化成其他物质含量有所降低。门冬氨酸降低0.07%,谷氨酸降低0.32%,缬氨酸降低0.09%,蛋氨酸降低0.14%,亮氨酸降低0.22%,苯丙氨酸降低0.02%,精氨酸降低0.07%,脯氨酸降低0.32%。成熟90d时,含量较高的是谷氨酸,亮氨酸,脯氨酸,赖氨酸、酪氨酸。     

Chemometric analysis of proteolysis during ripening of Ragusano cheese

Chemometric modeling of peptide and free amino acid data was used to study proteolysis in Protected Denomination of Origin Ragusano cheese. Twelve cheeses ripened 3 to 7 mo were selected from local farmers and were analyzed in 4 layers: rind, external, middle, and internal. Proteolysis was significantly affected by cheese layer and age. Significant increases in nitrogen soluble in pH 4.6 acetate buffer and 12% trichloroacetic acid were found from rind to core and throughout ripening. Patterns of proteolysis by urea-PAGE showed that rind-to-core and age-related gradients of moisture and salt contents influenced coagulant and plasmin activities, as reflected in varying rates of hydrolysis of the caseins. Analysis of significant intercorrelations among chemical parameters revealed that moisture, more than salt content, had the largest single influence on rates of proteolysis. Lower levels of 70% ethanol-insoluble peptides coupled to higher levels of 70% ethanol-soluble peptides were found by reversed phase-HPLC in the innermost cheese layers and as the cheeses aged. Non-significant increases of individual free amino acids were found with cheese age and layer. Total free amino acids ranged from 14.3 mg/g (6.2% of total protein) at 3 mo to 22.0 mg/g (8.4% of total protein) after 7 mo. Glutamic acid had the largest concentration in all samples at each time and, jointly with lysine and leucine, accounted for 48% of total free amino acids. Principal components analysis and hierarchical cluster analysis of the data from reversed phase-HPLC chromatograms and free amino acids analysis showed that the peptide profiles were more useful in differentiating Ragusano cheese by age and farm origin than the amino acid data. Combining free amino acid and peptide data resulted in the best partial least squares regression model (R(2) = 0.976; Q(2) = 0.952) predicting cheese age, even though the peptide data alone led to a similarly precise prediction (R(2) = 0.961; Q(2) = 0.923). The most important predictors of age were soluble and insoluble peptides with medium hydrophobicity. The combined peptide data set also resulted in a 100% correct classification by partial least squares discriminant analysis of cheeses according to age and farm origin. Hydrophobic peptides were again discriminatory for distinguishing among sample classes in both cases.     

切达干酪加速成熟方法及其研究现状

概述了对切达干酪的加速成熟的现状与研究方法,通过提高温度、添加促熟酶、修饰发酵剂细胞、高压处理等方法缩短切达干酪的成熟时间,提高经济效益。     

溶菌酶处理发酵剂加速干酪成熟的研究

以pH、蛋白质降解、脂肪酸含量变化及干酪的感官特征为指标,研究了溶菌酶处理发酵剂对干酪成熟的影响。结果表明:实验组干酪的pH在整个成熟期处于对照组1(添加2%发酵剂)干酪和对照组2(添加2.5%发酵剂)的pH之间,表明通过溶菌酶处理发酵剂可明显抑制干酪成熟期间的产酸量;添加溶菌酶处理发酵剂可加速干酪中蛋白质分解和乳脂肪的降解;感官评价结果表明,添加溶菌酶处理发酵剂可提高干酪风味,在相同的成熟时间实验组干酪的质地也较对照组好。     

The effect of three different ripening/storage conditions on the distribution of selected parameters in individual parts of Dutch‐type cheese

The aim of the study was (i) to detect changes of dry matter, NaCl and twenty‐two free amino acids contents, pH and levels of selected microorganisms in four layers of cheese (from edge to core) during ripening and storage period and (ii) to describe the changes of the above‐mentioned parameters caused by early relocation of cheese from optimum ripening conditions to refrigeration temperatures. The number of mesophilic aerobic and facultative anaerobic bacteria and lactic acid bacteria differed significantly (P < 0.05) during the experiment dependent on the analysed layer and ripening/storage conditions. The free amino acid content differed significantly in individual analysed layers of cheese and also according to individual ripening/storage conditions. The highest content of free amino acids was found in samples stored at optimal ripening temperatures. Cheese hardness was also analysed and the lowest one was detected in samples ripened under optimal temperatures for the whole period. Early release of cheeses into storage rooms with lower temperature significantly affected properties of these products.     

Quantification of short-chain free fatty acids in "Terrincho" ewe cheese: intravarietal comparison

Headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry was employed for the quantification of volatile free fatty acids (FFA) in "Terrincho" ewe cheese. Solid-phase microextraction quantitative analysis was feasible under equilibrium situations as long as the conditions of agitation and the adsorption time were held constant. An excellent linear relationship between the amount of the adsorbed analyte and its initial concentration in the sample matrix was obtained when an adequate amount of sample was chosen. Thus, quantification was possible if biases due to competition or linear range excesses were controlled. Solid-phase microextraction sampling was carried out at 65 degrees C, and a fiber coated with an 85-micro/m polyacrylate film was chosen. After equilibration at 65 degrees C for 40 min, the fiber was exposed to the headspace above the sample for 20 min and then inserted into the gas chromatograph. The evolution of the volatile FFA during Terrincho ewe cheese ripening was analyzed for a 60-d period. An overall increase in FFA contents was verified up to 30 d of ripening. Between 30 and 45 d most FFA did not suffer significant changes. All FFA increased significantly by the 60-d ripening period. The excessive lipolysis observed at 60 d of ripening may result in the presence of off-flavors. Principal component analysis performed for intravarietal comparison of volatile FFA composition of 19 Terrincho cheeses, analyzed at 30 ripening days, enabled discrimination between cheeses produced at five different dairy plants.     

Effect of forage type,season, and ripening time on selected quality properties of sheep milk cheese

The aim of this research was to study changes in the microbial populations, free AA profile, biogenic amine content, and sensory characteristics of ripened cheeses (100 and 180 d) produced in different seasons (summer, autumn, winter, and spring) from pasteurized sheep milk from 8 commercial flocks fed hay or silage diets. Twenty-one individual AA and 6 biogenic amines were determined by ultra-high performance liquid chromatography. Type of conserved forage for sheep feeding did not affect the variables studied, which is of great interest because hay and silage are low-cost ingredients for sheep feeding. Proteolysis led total free AA concentrations ranging between 35,179.26 and 138,063.71 mg/kg of cheese at 180 d of ripening. γ-Aminobutyric acid, which has been associated with beneficial effects on human health, was the second most abundant AA in all cheese samples, accounting for 15% of total free AA. Spring cheeses showed 2-fold higher concentrations of γ-aminobutyric acid than summer and autumn cheeses at the end of ripening. Overall, spring, winter, and autumn cheeses had lower average concentration of biogenic amines (431.99 mg/kg of cheese) than summer cheeses (825.70 mg/kg of cheese) as well as better sensory characteristics. Therefore, this study could provide the dairy industry with useful information for producing cheeses with valuable nutritional and sensory quality for consumers.     

The effect of elevated temperature on ripening of Dutch type cheese

The aim of this study was to explore the effect of elevated temperature (16 °C) on ripening of Dutch-type cheese. Three slices of each cheese block were further divided into three layers. The processes in the control samples of cheese ripening at 10 °C were also monitored. The contents of free amino acids in accelerated cheese were two times higher than were those in control samples. The highest contents of free amino acids were observed in the cores of all slices of cheeses ripening at both temperatures. The contents of tyramine, in layers of the studied slices, reached almost 500 mg kg⁻¹ during 56 days of the experiment. The contents of biogenic amines in the edges grew even higher. Accelerated cheese showed faster equalisation of hardness than did control samples. The increase of temperature by 6 °C can reduce the ripening time in cellars by approximately one half.     

Influence of starter culture ratios and warm room treatment on free fatty acid and amino acid in Swiss cheese

Quantification of water-soluble volatile free fatty acids (FFA) and free amino acids (FAA) was performed as a ripening index and an indirect measure of flavor development in Swiss-type cheeses. The objective of this research was to assess the effect of warm room treatment (WRT) and usage ratio of starter cultures, Streptococcus thermophilus and Lactobacillus helveticus vs. propionibacteria, on the concentration of FFA and FAA in pilot plant-scale Swiss cheese. A capillary gas chromatograph equipped with a flame ionization detector was used for the analysis of FFA in Swiss cheese. Free amino acids were analyzed by the Cd-ninhydrin method. Starter culture ratios did not affect development of FAA during the cheese ripening. However, duration of WRT had an effect on the concentration of FAA in the Swiss cheese. Free amino acids increased considerably during WRT. A continuous increase in FAA was shown during 70-d ripening time after WRT. The concentrations of C2:0 and C3:0 fatty acids were affected by starter culture ratios after 2-wk WRT, but these differences had mostly disappeared after 3-wk WRT. Similar concentrations of FFA and FAA reported in previous studies were developed in Swiss cheese with a 3-wk WRT and a 0.33:1 ratio of Streptococcus thermophilus and Lactobacillus helveticus to propionibacteria.