红枣干酪加工工艺研究

红枣干酪是在原料乳中添加枣泥制成的,符合中国人口味的风味干酪。对影响红枣干酪凝乳效果的主要因素进行了研究,试验结果表明:添加4%的枣泥,原料乳浓度越大,凝乳效果越好,用巴氏杀菌或高温短时杀菌,调节酸度到24°T,添加0.04%的CaCl2,凝乳效果较好。     

甜干酪的加工工艺研究

研究凝乳酸度、凝乳温度、氯化钙添加量、凝块切割大小、排乳清温度和糖添加量对甜干酪的产率和凝乳特性的影响.结果表明,甜干酪的最佳加工工艺参数为:凝乳酸度26 °T,凝乳温度42℃,氯化钙添加量为0.018%,凝块切割大小4mm～6mm.排乳清温度44℃～48℃,糖添加量为2%～4%.     

花生乳干酪加工工艺研究

花生乳干酪是以部分花生乳代替牛乳制成的符合中国人口味的风味干酪。本试验对影响混合乳干酪凝乳效果的主要因素进行了研究,结果表明:当花生乳添加量为20%,发酵酸度为24°T,皱胃酶添加量为0．30%, CaCl2添加量为0．06%时凝乳效果较好。     

硬质干酪加工工艺中关键技术参数的研究与优化

以cheddar干酪加工工艺为基础,针对工艺中影响产品质量的工艺参数进行试验分析,找出对产品质量最有影响的关键因素.通过单因素初步试验,进而进行了多因素交叉影响试验,采用LSR法进行多重比较分析.分析结果表明:发酵剂添加量3.0%(质量分数),熟化终止pH值为6.5,保温搅拌温度40℃,保温搅拌时间40 min为适宜的工艺参数,所制得的干酪质量达到统一的标准并且稳定.     

响应面法优化原生马苏里拉干酪加工工艺

以干酪感官评分为指标,研究发酵温度、发酵终点pH值和热烫拉伸时间对原生马苏里拉干酪品质的影响,并采用响应面法优化原生马苏里拉干酪加工工艺.确定原生马苏里拉干酪的最优制作工艺为:发酵温度为33℃,发酵终点pH值为6.1,热烫拉伸时间为10 min,响应面分析模型预测的感官评定分数为94.38.在此条件下生产的原生马苏里拉...     

响应面法优化Camembert干酪加工工艺

在氯化钙添加量、凝乳酶添加量、凝乳温度、排乳时间等单因素实验的基础上,根据Box-Behnken中心组合实验设计原理,采用4因素3水平响应曲面分析法,以凝乳效果为响应值建立二次多项回归模型,并验证模型的有效性。实验结果表明：Camembert干酪最佳制作工艺为氯化钙添加量为0．06％,凝乳酶添加量为0．02％,凝乳温度为32℃,排乳时间为30min。在此条件下,理论凝乳效果得分为89．63,验证值为89．50。     

羊奶牛奶混合干酪加工工艺研究

为改进羊奶牛奶混合干酪加工工艺,本实验以羊奶粉和鲜牛奶为原料,研究了牛奶添加比例、不同凝乳酶、杀菌条件、酸化条件和氯化钙添加量对混合干酪凝乳效果、出品率和感官品质的影响。结果表明,添加35% 的鲜牛奶,选用羔羊皱胃酶为凝乳酶,巴氏杀菌(63℃,30min),酸化pH6.20,氯化钙添加量为0.02% 时混
合干酪的品质较好。     

响应面法优化双蛋白干酪加工工艺

根据Box-Behnken中心组合实验设计原理,采用4因素3水平响应曲面分析法,以凝乳效果为响应值建立二次多项回归模型,并验证模型的有效性。实验结果表明：双蛋白干酪最佳制作工艺为豆乳添加量为20％（V／V）,氯化钙添加量0．04％,凝乳酶添加量为0．02％,凝乳温度为32℃。在此条件下,理论凝乳效果得分为87．67,验证值为88．00。     

花生乳牛乳新鲜干酪加工工艺优化

用花生乳代替部分牛乳生产新鲜干酪,对花生乳添加比例、氯化钙添加量、凝乳酶添加量3个因素对凝乳效果的影响分别进行单因素试验,确定各自合适比例后,再采用L9(33)正交试验,确定花生乳牛乳新鲜干酪最佳生产工艺。结果表明花生乳添加量20%、氯化钙添加量0.06%、凝乳酶添加量0.002%时制作出的新鲜花生乳牛乳干酪成品呈乳白色、柔软、有弹性、具有花生风味,产品出品率为16.33%。     

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。     

Identification of the Pseudomonas fluorescens group as being responsible for blue pigment on fresh cheese

New cases of blue cheese discoloration has led to recent research to identify the causal agent and factors that favor blue pigment appearing. Nonetheless, very few reports have described the source of contamination and the measurements to eradicate the microbiological source on cheese farms by determining the relation between blue discoloration on fresh cheese and the Pseudomonas fluorescens group. Thus, 60 samples from a cheese farm (cheese, equipment surfaces, tap water, and raw and pasteurized milk) were analyzed by phenotypical, MALDI-TOF, 16S rRNA sequencing and pulsed-field gel electrophoresis tests to determine the causal agent. The results obtained by pulsed-field gel electrophoresis with restriction enzymes XbaI and SpeI confirmed tap water as the initial contaminated source. The above-mentioned result was essential to avoid Pseudomonas contamination due to the most residual microorganisms being inactivated through a new disinfection program.     

霉菌成熟软质干酪工艺参数优化的研究

对影响霉菌成熟软质干酪加工关键因素进行了研究。结果表明,发酵剂添加量为0.01%效果较好,CaCl2添加量为0.02%为宜,凝块切割大小为15mm3效果较好,装模pH值为5.4效果较好,加盐量为1.5%为宜,霉菌添加量为0.005%可得较好的产品品质。     

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.     

响应面法优化黑豆干酪工艺条件

采用Box-Behnken中心组合响应面试验,研究黑豆干酪的最佳工艺条件,建立氯化钙添加量、凝乳酶添加量以及凝乳温度对凝乳效果影响的二次多项回归模型,并验证模型的有效性.结果表明,黑豆干酪的最佳工艺条件:氯化钙添加量0.06％、凝乳酶添加量0.025％、凝乳温度32℃.此时模型预测凝乳效果评分为88.5,验证实验结果为88.0,与理论预测值基本吻合.     

Mozzarella干酪生产工艺的优化

选择了影响Mozzarella干酪生产的3个关键因素：热缩温度、堆酿pH值和热烫拉伸温度；采用三因素二次通用旋转组合设计，以干酪的实际产率、pH值为4．6可溶性N，质量分数为12％的TCA可溶性N和感官评定值为指标，进行综合评定。优选出Mozzarella干酪的最优工艺参数为：热缩温度38℃，堆酿pH值为5．25，热烫拉伸温度58℃。在这一条件下，生产的干酪产率及综合质量最好。同时探讨了3个因子对以上4个指标的影响，为生产不同用途的Mozzarella干酪提供了一定的理论依据。     

Genome-based analysis of Pseudomonas paracarnis RQ057, a strain responsible for blue discoloration spoilage in processed cheese

A strain of Pseudomonas causing blue discoloration was isolated from processed cheese ‘Requeijão em Barra’ and studied by whole-genome sequencing. The strain RQ057 was identified as Pseudomonas paracarnis using the TYGS web server and also by in silico DNA–DNA hybridisation and ANIb calculation. Pyoverdine biosynthetic clusters, integrative and conjugative elements (ICE), prophage regions and genomic islands (GIs) were predicted. Furthermore, we observed that copies of genes related to the tryptophan biosynthetic pathway (trpCBAFD), which are exclusive to strains causing blue discoloration, are contained in the region identified as ICE and which was also identified in GIs. This genomic region also contains genes for transposase, type IV transport system (T4SS) and pili construction. Thereby, we can assume that this region contains potential conjugative-transposon-like mobile genetic elements and it has plasmid-like conjugative properties.     

再制干酪的研究

以天然干酪为主要原料，通过对再制干酪加工条件以及乳化剂种类和添加量的优化研究，确定了制造块状再制干酪的工艺流程及主要参数。实验表明，块状再制干酪以车达和高达干酪为原材料，按照不同配比使平均成熟期为5～6个月；乳化剂确定使用焦磷酸钠及多聚磷酸钠的混合盐，添加量为2．5％；产品目标水分为46％，目标pH=5．8～6．0；融化条件为：85～87℃．6．5～7min。产品风味柔和、组织状态细腻，符合消费者的饮食习惯；平均理化指标均符合再制干酪质量标准。     

Standardization of milk using cold ultrafiltration retentates for the manufacture of Swiss cheese: effect of altering coagulation conditions on yield and cheese quality

Fortification of cheesemilk with membrane retentates is often practiced by cheesemakers to increase yield. However, the higher casein (CN) content can alter coagulation characteristics, which may affect cheese yield and quality. The objective of this study was to evaluate the effect of using ultrafiltration (UF) retentates that were processed at low temperatures on the properties of Swiss cheese. Because of the faster clotting observed with fortified milks, we also investigated the effects of altering the coagulation conditions by reducing the renneting temperature (from 32.2 to 28.3°C) and allowing a longer renneting time before cutting (i.e., giving an extra 5 min). Milks with elevated total solids (TS; ∼13.4%) were made by blending whole milk retentates (26.5% TS, 7.7% CN, 11.5% fat) obtained by cold (<7°C) UF with part skim milk (11.4% TS, 2.5% CN, 2.6% fat) to obtain milk with CN:fat ratio of approximately 0.87. Control cheeses were made from part-skim milk (11.5% TS, 2.5% CN, 2.8% fat). Three types of UF fortified cheeses were manufactured by altering the renneting temperature and renneting time: high renneting temperature = 32.2°C (UFHT), low renneting temperature = 28.3°C (UFLT), and a low renneting temperature (28.3°C) plus longer cutting time (+5 min compared to UFLT; UFLTL). Cutting times, as selected by a Wisconsin licensed cheesemaker, were approximately 21, 31, 35, and 32 min for UFHT, UFLT, UFLTL, and control milks, respectively. Storage moduli of gels at cutting were lower for the UFHT and UFLT samples compared with UFLTL or control. Yield stress values of gels from the UF-fortified milks were higher than those of control milks, and decreasing the renneting temperature reduced the yield stress values. Increasing the cutting time for the gels made from the UF-fortified milks resulted in an increase in yield stress values. Yield strain values were significantly lower in gels made from control or UFLTL milks compared with gels made from UFHT or UFLT milks. Cheese composition did not differ except for fat content, which was lower in the control compared with the UF-fortified cheeses. No residual lactose or galactose remained in the cheeses after 2 mo of ripening. Fat recoveries were similar in control, UFHT, and UFLTL but lower in UFLT cheeses. Significantly higher N recoveries were obtained in the UF-fortified cheeses compared with control cheese. Because of higher fat and CN contents, cheese yield was significantly higher in UF-fortified cheeses (∼11.0 to 11.2%) compared with control cheese (∼8.5%). A significant reduction was observed in volume of whey produced from cheese made from UF-fortified milk and in these wheys, the protein was a higher proportion of the solids. During ripening, the pH values and 12% trichloroacetic acid-soluble N levels were similar for all cheeses. No differences were observed in the sensory properties of the cheeses. The use of UF retentates improved cheese yield with no significant effect on ripening or sensory quality. The faster coagulation and gel firming can be decreased by altering the renneting conditions.