自然发酵黄豆酱的微生物安全性的分析

对从11份农家和7份市场上销售的自然发酵黄豆酱样品进行了微生物的安全性检验和部分理化指标的测定，检验的项目包括细菌落总数、芽孢杆菌总数、大肠杆菌、沙门氏菌、志贺氏菌、腊样芽孢杆菌、金黄色葡萄球菌和肉毒梭菌。实验结果表明，所分析样品中菌落总数超过10^4个/g的样品有89％，腊样芽孢杆菌的检出率为30％，但含量不高，豆酱中的细菌总数除了与生产环境有关外，与产品的水分活度的相关性很大。     

不同季节原料乳中主要微生物和理化指标分析

研究了冬季、春季和夏季原料乳的主要理化指标和微生物指标。3个季节内,蛋白质、乳脂、乳糖和干物质的变化范围分别是3.38%～3.52%,3.98%～4.26%,4.80%～4.85%和12.78%～13.19%。理化指标检测结果表明冬季牛乳的营养成分高于春夏两季,并且3个季节的乳成分均高于生鲜牛乳的收购标准;此外,对原料乳中主要的微生物:总菌数、乳酸菌、大肠菌群、沙门氏菌、蜡样芽孢杆菌、单增李斯特菌和嗜冷菌的菌数进行了检测。结果中未检测到沙门氏菌、蜡样芽孢杆菌和单增李斯特菌,其他微生物质量分数均在可接受范围内,但是大肠菌群的出现说明需要建立相关的卫生质量标准。     

酱油理化检验项目的探讨

商业部部颁标准(SB70—74—78)规定酱油的理化检测项目为七项,即比重、无盐固形物、食盐、总酸、氨基酸态氮、还原糖、总氮。对照日本等酱油理化检测项目,我们着重对浙江省十种酱油进行了酒精、总糖、pH值、缓冲能、N性蛋白质的测定,并探讨了酱油理化检测应增减的项目。     

新疆疆岳驴乳理化和微生物指标分析

对50头新疆疆岳驴乳的化学成分以及微生物指标进行分析.结果表明,驴乳各项理化指标分别为:总干物质9.50%、蛋白质1.52%、脂肪1.18%、乳糖6.39%、灰分0.38%.与牛乳相比较,驴乳各项指标更接近母乳.微生物检测结果为(lg CFU/ml):细菌总数4.17、芽孢菌2.40、乳酸菌3.30、金黄色葡萄球菌2.83、肠科菌1.18.     

促酱醪发酵芽孢杆菌的筛选及应用

用酪素平板法从高盐稀态酱醪中筛选出56 株蛋白酶活性较好的菌株,牛津杯法复筛后制曲测定酶活性,得到淀粉酶活性最高的菌株CS1.11、蛋白酶活性最高的菌株CS1.13及纤维素酶活性最高的菌株CS1.17;16S rRNA序列测定结合形态学分析,CS1.11、CS1.13、CS1.17分别鉴定为贝莱斯芽孢杆菌（Bacillus velezensis）、甲基营养型芽孢杆菌（B. methylotrophicus）、枯草芽孢杆菌（B. subtilis）;分别将3 株实验菌与对照菌枯草芽孢杆菌CS1.03单独进行制曲后盐卤发酵,发现CS1.13发酵酱油氨态氮质量浓度最高,为5.12 g/L,CS1.11发酵酱油还原糖质量浓度最高,为27.20 g/L,与其酶活性结果一致,4 株菌对酱油总酸含量影响不大;顶空固相微萃取气相色谱-质谱联用内标法定性及定量分析发酵酱油发现,3 株实验菌与对照菌均具有产生吡嗪类物质及其前体乙偶姻和2,3-丁二醇的优势,且3 株实验菌优于对照菌;吡嗪类物质能赋予酱油良好的风味及健康因子,是芽孢杆菌酱油发酵的特征风味物质。筛选自高盐稀态酱醪的芽孢杆菌CS1.11、CS1.13、CS1.17有促酱醪发酵、丰富酱油风味、增进健康因子的潜力,具备良好的应用前景。     

成品酱油微生物污染变质的风险预警

为对微生物污染引起的成品酱油变质进行风险预警,对比研究了成品变质酱油和未变质酱油中还原糖、总酸、氨态氮以及双乙酰4种理化指标。结果表明:耐盐芽胞杆菌污染引起的成品酱油变质,其理化指标产生较大变化,其中还原糖含量大幅下降,总酸、氨态氮以及双乙酰含量明显升高,经测定还原糖含量降幅60%,总酸含量升幅32%,氨态氮含量升幅6.0%、双乙酰含量升幅20.4%时,成品酱油已出现变质现象,可以判断为变质。     

21份酱油样品的菌相分析

对21份酱油样品进行菌相分析,均为革兰氏阳性需氧芽孢杆菌,其中包括蜡样芽孢杆菌。讨论了灭菌方法。     

南美白对虾即食虾仁常温贮藏品质变化与货架期研究

为确定南美白对虾即食虾仁常温贮藏货架期及残留菌种类,采用感官、理化、微生物和电子鼻等分析其品质变化及货架期,并使用16SrRNA测序法鉴定残留菌。结果表明,初始感官品质良好,物理和化学指标均符合标准;常温贮藏中水分含量、水分活度、pH、盐分和色泽(红度和黄度)前4个月无显著性差异,之后水分含量和水分活度降低,盐分和pH升高,红度和黄度存在波动;咀嚼性、硬度和弹性前3个月无显著差异,之后先升后降,而贮藏期间内聚性有波动性。常温贮藏9个月内TVBN和TBA均符合限量要求,菌落总数低于103 CFU/g,个别胀袋虾中残留菌为地衣芽孢杆菌与枯草芽孢杆菌。综合感官、化学和微生物等评定指标,结合电子鼻对即食南美白对虾虾仁品质进行区分,确定其货架期为9个月。     

商用酱油曲精中微生物分布研究

对总好氧菌、总芽孢菌、乳酸菌、肠道菌群及霉菌在商用酱油曲精及种曲中的分布状态进行了研究。结果表明,不同品牌的曲精中微生物分布状态差异显著,其中霉菌的菌落总数均大于109cfu/g,种曲中霉菌的数量只有107cfu/g。而总好氧菌、肠道菌群、乳酸菌及总芽孢菌菌落数均差异显著,分别为102cfu/g~109cfu/g、103cfu/g~109cfu/g、103cfu/g~108cfu/g、104cfu/g~108cfu/g。曲精及种曲中水分及蛋白酶活也存在显著差异。     

酿造酱油微生物标准的分析研究

对酿造酱油中特征微生物进行分离鉴定,并对贮藏和酿造过程中各项微生物卫生指标进行动态分析,结果表明,酱油中细菌主要由耐热的芽孢杆菌和耐盐菌构成.在贮藏过程中,酱油的细菌菌落总数总体呈下降趋势,霉菌和酵母菌落数呈现一个缓慢的上升过程.在酱油酿造过程中,细菌和酵母菌落数随着发酵进程而逐渐降低,霉菌为先扬后抑的变化过程.整个发酵过程不适合大肠菌群生长.     

Secondary effluent disinfection: PAA long term efficiency

The paper summarizes the results of a bench-scale study to evaluate the long-term disinfection efficiency of peracetic acid (PAA). Bacterial counts were repeated 5, 24, and 29 h after the end of the disinfection test, to simulate real re-growth conditions (no residual quenching) and, for the 5 h interval, the potential re-growth (quenching of residual PAA). Fecal coliforms, Escherichia coli, and total heterotrophic bacteria (THB) were enumerated by traditional plate count technique; THB were also enumerated by cytometry. After disinfection, the residual PAA concentration became negligible in about 5 to 11 h, depending on the tested doses. Microbial counts showed that no appreciable re-growth took place after 29 h for coliform group bacteria. For THB, the previously cited enumeration techniques gave different results in re-growth tests, especially for the lowest PAA doses. Indeed plate count technique evaluates the ability to form colonies, while cytometry enumerates intact membrane cells. No regrowth took place, even when no residual disinfectant was present, suggesting that bacteria are unable, even at the lowest doses, to repair damage caused by the PAA disinfecting action. PAA was found to be an efficient disinfecting agent, not only as a bacteriostatic, but also as a bactericide.     

Microbial Sour Doughs Influence Acidification Properties and Breadmaking Potential of Wheat Dough

Breads from sour doughs were started with Lactobacillis plantarum (L-73, or B-39) or Lactobacillus brevis (L-62)-, and incorporated at 10, 17.5, or 25%. Lactic and acetic acid production depended on bacterial starter and yeast. Started doughs had longer mixing time, stability, more softening with time; lower resistance to extension; shorter fermentation, less stability, and greater oven rise. Breads had greater volume, lower density, softer crumb and higher slice height. Interactive effects between inoculum and microbial composition of starter were reflected in sensory scores. Adequate sour dough inoculum was lower for heterofermentative strains (10%, L-62) than for homofermentative strains (17.5%, B-39; 25%, L-73), due to deleterious effects on rheological properties.     

Response of dairy cows in early lactation to sodium hydroxide-treated soybean meal

To determine effects of protein and rumen degradability in rations for early lactation cows, four diets (44:56 roughage:concentrate) were formulated to contain 15 or 17.5% CP and supplemental protein from untreated or NaOH-treated soybean meal. Diets were allocated to 34 multiparous Holstein cows from d 22 to 91 of lactation. Treatment means adjusted by covariance using data from d 10 to 21 for average daily milk (kg), milk fat (%), milk protein (%), and SCM (kg) were: 15% untreated 32.9, 3.54, 3.16, and 31.3; 15% NaOH-treated 31.1, 3.59, 3.08, and 29.6; 17.5% untreated 32.2, 3.70, 3.30, and 31.2; and 17.5% NaOH-treated 32.6, 3.58, 3.17, and 30.8. Increasing dietary protein percent raised milk protein percent but not protein yield or yield of other milk components, milk yield, SCM yield, or DM intake. Protein source had no effect on production or feed intake. Decreasing dietary protein percentage and use of NaOH-treated soybean meal reduced rumen ammonia. Degradation of protein in feeds was determined in four rumen fistulated lactating cows. Sodium hydroxide treatment of soybean meal reduced protein degradation in situ.     

青稞麸皮提取物抑制α-葡萄糖苷酶活性研究及成分分析

研究青稞麸皮的正己烷、乙酸乙酯和甲醇提取物对α-葡萄糖苷酶的抑制活性。结果表明,3种不同极性的提取物均显示抑制效果,其中正己烷提取物和乙酸乙酯提取物的抑制活性强于市售α-葡萄糖苷酶抑制剂——阿卡波糖。进一步采用气相色谱-质谱联用法对正己烷提取物中脂肪酸、不皂化物、甾醇进行定性定量分析。正己烷提取物中的脂肪酸主要为亚油酸、油酸、棕榈酸、α-亚麻酸,占总脂肪酸的96.5%,这几种脂肪酸被证实对α-葡萄糖苷酶具有混合型抑制的活性。从不皂化物中分离得65个质谱峰,鉴定出甾醇类、三萜类、高分子脂肪醇等生物活性成分。同时对已鉴定的几种主要游离甾醇进行含量分析,结果显示β-谷甾醇和菜油甾醇为主要甾醇,两者共占总游离甾醇的83%,提取物中的甾醇、三萜类对α-葡萄糖苷酶抑制活性可能有一定贡献。由此可见,青稞麸皮是筛选α-葡萄糖苷酶抑制剂的优质天然资源。     

Physical Characteristics of a Composite Film of Soy Protein Isolate and Propyleneglycol Alginate

Different levels (5, 10, 15, 17.5 or 20% w/w of solid) of propyleneglycol alginate (PGA) were incorporated into soy protein isolate (SPI) films to form biodegradable composite films with modified physical properties. Color of the SPI films was affected (P<0.05) by the incorporation of PGA. Tensile strength increased (P<0.05) with addition of PGA up to 17.5%, while the percentage elongation at break decreased with incorporation of PGA of higher levels. Water vapor permeability and water solubility also decreased by adding PGA up to 10%, but further addition of PGA increased values for these properties. Results suggest that the site of reaction with PGA on the protein chain may become saturated with PGA at the 10% level.     

Use of an exopolysaccharide-producing strain of Streptococcus thermophilus in the manufacture of Mexican Panela cheese

An exopolysaccharide (EPS) producing strain of Streptococcus thermophilus was evaluated for the production of Panela cheese using two total solids milk (TSM) concentrations (12.5 and 17.5 g/100 mL). This ropy strain increased cheese yield; nevertheless, with 12.5 TSM the increment was higher than with 17.5 TSM. Analysis of cheese composition showed that with 12.5 TSM, the ropy strain increased moisture, but did not change the fat or non fat solids on dry weight basis (dwb), suggesting that the increment of the yield is only due to water retention. In 17.5 TSM cheeses the ropy strain caused an increase in the moisture and fat (dwb), suggesting that besides water retention, fat also contributed to the yield. The difference in yield increment could be explained by cheese composition: higher fat content creates a more hydrophobic environment, which would expel more water than the cheese with lower fat content. Electron microscopy showed EPS attached to the protein matrix of the cheeses. In 17.5 TSM cheeses EPS was observed around the milk fat globules (MFG), confirming that higher TSM causes EPS to bind the MFG besides binding the protein matrix, retaining fat within the cheese. Sensory evaluation demonstrated that ropy cheeses were softer and creamier.     

The effect of temperature and humidity on the developmental period and mortality of Typhaea stercorea (L.) (Coleoptera: Mycetophagidae)

The development of Typhaea stercorea (L.) on kibbled wheat was investigated at temperatures from 15 to 30°C in combination with humidities from 70 to 90% r.h. Eggs hatched at 17.5–30°C but not at 15°C. Incubation periods ranged from 2.5 days at 30°C to 9.5 days at 17.5°C. Larval periods ranged from 9.7 days at 30°C, 90% r.h. to 83.6 days at 17.5°C, 80% r.h. and were more than doubled for each 10% decrease in humidity. At 70% r.h. all larvae died outside the temperature range 22.5–27.5°C. Mortality increased with decreasing humidity in the range tested. Pupal periods ranged from 2.9 days at 30°C, 80% r.h. to 13.8 days at 17.5°C, 90% r.h. At 70% r.h. the lowest temperature for pupal development was 25°C whereas at 90% r.h. it was 17.5°C. The results suggest that this species is essentially a mould feeder and confirm that it requires relatively high humidity to develop.     

THE INFLUENCE OF FAT, ACID, AND SALT ON THE PERCEPTION OF SELECTED TASTE AND TEXTURE ATTRIBUTES OF CHEESE ANALOGS: A SCALAR STUDY

Twelve cheese analogs varying in amounts of fat (10 17.5, and 25%), sodium chloride (0.5 and 2.0%), and citric acid (0.1 and 1.2%) were prepared to determine the influence of the three constituents on taste and texture perception, as well as on the rheological behavior of the analogs. Sourness, saltiness, springiness, firmness, cohesiveness, and adhesiveness were rated by trained judges on a graphic scale. The Instron Universal Testing Machine was used for the rheological studies. Increasing the salt content in the cheese analogs resulted in an increased saltiness and sourness intensity and a decreased pH. Increasing the acid or salt content caused a significant decrease in cohesiveness and springiness and an increase in firmness. A higher fat content resulted in a softer, less springy, more cohesive and adhesive cheese analog.     

Factors controlling the growth of Clostridium botulinum types A and B in pasteurized, cured meats III. The effect of potassium sorbate

The growth of Clostridium botulinum types A and B spores, at 10¹ or 10³ per container, was studied in a pork slurry system containing nitrite (40 μg/g), sodium chloride (2.5, 3.5, 4.5% w/v) sodium isoascorbate (550 μg/g) at varying pH levels, with or without potassium sorbate (0.26% w/v), without heating and after two heat treatments (80°C for 7 min, and 80°C for 7 min + 70°C for 1 hr) followed by storage at 15, 17.5, 20 or 35°C for up to 6 months. At a given spore inoculum, potassium sorbate significantly decreased toxin production, as did increasing NaCl, decreasing pH or decreasing storage temperature. Heat treatment did not significantly affect spoilage or toxin production overall, but interacted significantly with some factors. The effect of sorbate was greater at 3.5% NaCl than at 2.5%, at pH values below 6.0, and at low storage temperature.