酸乳发酵中优良共生酵母菌的筛选

为了筛选酸乳发酵中与保加利亚乳杆菌优良共生的酵母菌。以保加利亚乳杆菌单菌发酵酸乳为对照,将前期从新疆、西藏和青海等地区传统自制乳制品中分离的27株酵母菌株分别和保加利亚乳杆菌混菌发酵制备酸乳,通过比较凝乳时间、感官特性、质地特性、后酸度、粘度、持水力、乙醛和双乙酰含量等特征,筛选酸乳发酵中与保加利亚乳杆菌优良共生的酵母菌株;基于26S D1/D2区和ITS1序列鉴定菌株。结果显示:27株酵母菌株均没有明显促进凝乳作用,9株菌混菌发酵酸乳在感官评价得分较高(80分以上),其中菌株\     

Simulation modelling of bacterial growth in yoghurt

INDISIM, an individual-based simulator, was used to specifically study the influence of the shape and size of Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in yoghurt processing. To this effect, two different sets of simulations were carried out. In the first set of simulations, it was assumed that the initial acidity of the medium has the same value as the acidity of the cytoplasm of the microorganisms. Hence, the differences in bacterial growth by the two species are only attributable to differences in their geometry. It was found that, in an optimum culture, the growth in biomass of S. salivarius subsp. thermophilus is larger than that of L. delbrueckii subsp. bulgaricus. An important factor for understanding this difference might be the larger mass-to-surface ratio of the former. In the second set of simulations, a simplified model of yoghurt, the parametrisation differs both in the geometry and the metabolism of the two species. The results of these simulations are in very good qualitative agreement with the experimental data of [Lait 69 (1989) 519]. Finally, by inhibiting the uptake of amino acids by S. salivarius subsp. thermophilus, the large relative importance of lactic acid in yoghurt processing was highlighted.     

Evaluation of the inhibitory effect of alginate oligosaccharide on yeast and mould in yoghurt

The use of alginate oligosaccharides (AOS) in fermented dairy products and tested against common spoilage organisms was investigated. In a broth model, yeast growth was measured by optical density, while hyphae propagation of mould was assessed with a live-cell imaging system. Reduction of the growth rate of Candida parapsilosis, Debaryomyces hansenii and Meyerozyma guilliermodii was observed in broth supplemented with 2% (w/v) AOS. Colony forming units (cfu) were enumerated to quantify yeast growth in fresh yoghurt prepared with AOS. Direct observation and pictures were taken to assess mould growth. The time to reach the spoilage limit (10⁶ cfu g⁻¹) with 2% AOS was significantly increased for the yeasts C. parapsilosis and M. guilliermodii, by 11.8% and 22.5% respectively, while no effect of AOS was observed for all mould species. AOS could potentially be used as a food preservative against some yeasts, although a relatively high concentration is required.     

酵母粉浓度对酸奶菌发酵动力参数的影响

详细分析了在乳清基质培养基中添加不同浓度酵母粉(0-15g/L)对酸奶菌株分批发酵动力学参数的影响,包括细菌数增长,乳糖消耗和乳酸生成.结果表明:较高的酵母粉浓度对菌株生长反而有一定抑制作用,适宜的酵母粉浓度为10g/L,该条件下德氏乳杆茵保加利亚亚种KLDS 1.9201乳糖转化率达到77%,乳酸终浓度为50g/L,增殖1Oh后的活茵数为1.96 X 109 CFU/mL;唾液链球菌嗜热亚种KLDS 3.0201的乳糖转化率达到74%,乳酸终产量达到33g/L,发酵培养6h后的活茵数为2.52×109 CFU/mL.     

Influence of brodifacoum and bromadiolone on growth of yoghurt cultures in milk

The influence of brodifacoum and bromadiolone on the growth of yoghurt culture in milk was determined. Milk samples inoculated with a commercial yoghurt culture and serially diluted rodenticides were incubated at 42 °C for 6 h. The yoghurt cultures showed detectable sensitivity (significant change (P < 0.05) in pH in the medium) to brodifacoum at 0.12 mg/mL and to bromadiolone at 0.08 mg/mL. There were significant differences (P < 0.05) in the bacterial count and α‐galactosidase and β‐galactosidase activities in the presence of toxins in milk. The results indicate that brodifacoum and bromadiolone could inhibit the growth of yoghurt culture in milk.     

酸奶生产过程中的关键控制点及影响酸奶品质的因素

针对酸奶生产过程中存在的问题确定关键控制点，着重论述了影响酸奶品质的因素和控制措施。     

聚葡萄糖在酸奶中的应用优势及高纤酸奶市场趋势

聚葡萄糖是一种优良的水溶性膳食纤维,具有良好的理化特性和健康功效。重点阐释了聚葡萄糖在酸奶中的应用优势与酸奶市场现状,并分析了未来酸奶市场的发展趋势及高纤酸奶的巨大市场潜力。     

The effect of diluted yoghurt on the gut microbiology and growth of piglets

At 2 days of age piglets were weaned onto yoghurt or yoghurt diluted to 25% or 50% with base milk. Piglets fed yoghurt grew less well. The diluted yoghurt decreased the coliform count in the stomach and duodenum but had no effect on the numbers of lactobacilli. Tests on a small number of pigs showed that undiluted yoghurt decreased β-glucosidase and β-glucuronidase activity but the effect was lost when the yoghurt was diluted.     

不同混生模式对酸奶发酵剂球杆菌比例的影响

目的:探讨了酸奶菌株的混合发酵特性及最佳的混合模式。方法:在2.5L罐中观察不同发酵温度、pH、接种比例和接种时段对德氏乳杆菌保加利亚亚种KLDS1.9201和唾液链球菌嗜热亚种KLDS3.021混合培养的影响。结果:不同的混生模式均关系到酸奶菌株之间共生的问题。培养条件为42℃和pH6.2,接种比例为KLDS1.9201∶KLDS3.0201=2∶1,或是KLDS3.0201推迟2h接种,将有利于发酵剂菌株混合培养时的球杆菌比例平衡。结论:不同的混生模式是促进酸奶混合菌株协同生长的重要前提。     

Temperature abuse affects the quality of irradiated pork loins

The influence of temperature abuse on the quality of irradiated pork loins was investigated. Pork loins were obtained directly from a local packing plant, sliced and vacuum-packaged. Pork loins were randomly separated into 3 groups, sliced, and assigned to receive 0, 1.5, or 2.5 kGy electron-beam irradiation. Then, each chop was further cut into three equal pieces and assigned to three temperature treatments: Trt I was placed in a refrigerator directly after irradiation; Trt II was left at room temperature for 3 h before refrigeration; and Trt III was exposed at room temperature for 1 h three consecutive days with intermittent storage at 4 °C between exposures. Before irradiation, each loin pieces were vacuum-packaged. Color, 2-thiobarbituric acid reactive substances (TBARS), and volatiles were measured after 0, 14, 28 and 42 days of storage, and water-holding capacity and sensory characteristics of the loins were measured after 0, 14 and 28 days of storage. Temperature abuse had no significant effect on color, oxidation, and volatiles of irradiated pork loins. However, temperature abuse improved water-holding capacity of meat, which could be caused by the accelerated hydrolysis of muscle proteins at higher temperature. Irradiation increased redness, sulfur contents in volatiles and off-odor of pork loin. Off-odor and redness induced by irradiation sustained during storage. Among sulfur compounds, the content of dimethyl disulfide decreased gradually while the level of thiourea remained relatively constant. Irradiation also increased water loss, which might be related to the structural damage in membrane during irradiation. This study shows that temperature abuse has little effect on the quality of irradiated pork.     

酸奶和干酪中有机磷农药的降解动力学研究

采用GC分析,研究乳酸菌发酵荆对酸奶和干酪样品发酵过程中7种有机磷农药残留的降解动力学.结果表明,42℃下7种有机磷农药在牛奶样品中的半衰期是11.0～16.7 h.在两个酸奶样品中他们的半衰期则降至9.6～14.6 h或10.0～15.9 h,所添加的直投式发酵剂显著地促进有机磷农药降解.乳酸菌发酵荆发酵干酪样品120 d后,7种有机磷农药的降解量达到17%～62%.乳酸茵发酵可以提高发酵乳制品的安全性.     

Changes in salted yoghurt during storage

The study was conducted to determine the gross chemical composition and concentrations of free fatty acids (FFAs) and volatile compounds of salted yoghurt made from indigenous goat's milk. The effects of some chemical properties on sensory attributes of salted yoghurt were also studied. Changes in FFAs (P < 0.01) and volatile compounds were statistically significant (P < 0.05) during storage. The most abundant FFAs were 9‐octadecenoic (C_18:1), hexadecanoic (C₁₆), tetradecanoic (C₁₄) and decanoic (C₁₀) acids, respectively. Ethanol and ethyl acetate were principal volatile compounds through the end of storage period. The storage period affected the intensity of flavour attributes and overall flavour score of salted yoghurt (P < 0.05). According to factor analysis result, chemical compounds including volatiles, FFAs up to C₁₄, tyrosine and titratable acidity, and flavour attributes explained 86.50% and 55.33% of total variance, respectively.     

低聚木糖在保健酸奶中的应用

对低聚木糖保健酸奶的生产工艺和配方进行了实验研究,分别对不同低聚木糖量、接种量、蔗糖量、发酵温度不同条件的选择试验进行了分析研究,经过感官鉴评、理化指标的测定,并通过一系列平行试验和正交试验筛选出了最佳配方为:酸度≤18°T、脂肪≥3.0%、乳固体≥11.5%的原料乳,0.45g/100mL低聚木糖,4%接种量,41℃发酵温度,7%蔗糖。得到了既有生理功能,口感又好的产品,为乳品厂新产品的开发提供了参考依据。     

Experimental aflatoxin production in commercial yoghurt

Summary The production of aflatoxins in commercial yoghurt inoculated withAspergillus parasiticus NRRL 2999 was studied, using different incubation conditions. In all of the experiments, the level of aflatoxins was higher at 28 °C than at 15 °C and higher in a damaged container than in an intact container (related to microaerophilic conditions). No fungal growth or aflatoxin production was seen at 10 °C. Both fungal growth and aflatoxin concentration vary throughout the incubation period instead of progressively increasing. The ratio of aflatoxin B and G (B: G) at 28 °C was almost 1:1, but generally more aflatoxin G was detected at 15 °C. The distribution in mycelium/substrate was approximately 1:1 at both 28 °C and 15 °C.

---

Experimentelle Aflatoxinproduktion im Joghurt des Handels

Zusammenfassung Die Produktion von Aflatoxin mitAspergillus parasiticus beimpften Joghurt des Handels wurde unter verschiedenen Bedingungen studiert. In allen Experimenten war die Aflatoxinmenge bei 28 °C höher als bei 15 °C und bei beschädigten Verpackungen höher als in intakten, entsprechend den mikroklimatischen Bedingungen. Kein Pilzwachstum und keine Aflatoxinproduktion war bei 10 °C zu beobachten. Sowohl das Pilzwachstum als auch die Aflatoxinkonzentration variieren in der Inkubationsperiode, anstatt progressiv zuzunehmen. Die Menge von Aflatoxin B und G (B: G) bei 28 °C war 1:1, aber generell mehr Aflatoxin G wurde bei 15 °C nachgewiesen. Die Verteilung im Mycel und Substrat war ungefähr 1:1, Sowohl bei 28 °C als auch bei 15 °C.

     

HACCP在风味酸牛乳生产中的应用

阐述了HACCP在酸牛乳生产中的应用。通过对酸牛乳生产中的危害分析（HA），介绍了酸牛乳生产中常见的质量缺陷，包括缓慢发酵，污染噬菌体，质构缺陷及气体的产生，并结合酸牛乳的生产工艺进行关键控制点（CCP）的分析。分析结果表明，在以下关键点进行控制会大大减少酸牛乳成品质量缺陷；（1）选择优质无抗原料；（2）正确的热处理；（3）无菌接种条件；（4）发酵过程中温度的探讨；（5）清洁的环境；（6）低温储存。     

Experimental aflatoxin production in home-made yoghurt

Fungal growth and aflatoxin production by an aflatoxigenic strain during the manufacture of yoghurt are described. This completes previous studies which show that yoghurt may be a good substrate for aflatoxin production. Two factors were of special interest: (a) the temperature of the elaboration process (45 degrees C) and (b) the effect of lactic bacteria. Either during the elaboration of yoghurt or during its cooling from 45 degrees C to 4 degrees C, the necessary conditions required to start fungal growth are given; these are adequate enough for the synthesis of small quantities of aflatoxins. However our results do not clearly show that lactic bacteria have an influence on fungal growth and aflatoxin production.     

发酵乳制品中益生菌的包囊技术

由 于 益 生 菌 能 够 促 进 人 体 健 康 , 得 它 们 在 发 酵 乳 制 品 中 使 的 应 用 日 益 增 多 ,然 而 ,益 生 菌 在 这 些 乳 制 品 中 的 活 性 较 低 。 一 些 研 究 表 明 ,通 过 包 囊 的 方 式 可 以 保 护 菌 体 ,提 高 它 们 的 生 存 能 力 。 挤 压 法 和 乳 化 法 是 适 用 于 发 酵 乳 制 品 中 益 生 菌 包 囊 的 两 种 技 术 。 本 文 综 述 了 发 酵 乳 制 品 中 益 生 菌 的 包 囊 技 术 、包 囊 中 存 在 的 问 题 及 解 决 方 法 ,以 及 用 亲 水 性 胶 体 包 囊 细 胞 在 益 生 菌 生 产 中 的 应 用 。     

酸奶中多肽物质的初探

国外已有报道发酵乳品中也存在由乳酸菌的发酵作用而产生的多肽类物质。本文主要对酸奶中的水溶性肽类做初步的研究:6种市售酸奶各50mL,8000r/min离心20min,上清液于1000Da透析,再用聚乙二醇6000浓缩,最后Tricine-SDS-PAGE电泳。结果表明,不同菌种产生不同的多肽,且发酵条件不同产生的肽类物质也不同。     

蓝靛果花青素对乳酸菌生长及酸奶后酸化的影响

以热浸渍法、冷浸渍法、常温浸渍法为基础,通过部分添加不同浓度的二氧化硫和果胶酶,探究不同浸渍工艺对葡萄醪中单宁、总酚含量、pH值、色度、色调等指标的影响。结果表明,冷浸渍法（浸渍温度4 ℃、二氧化硫添加量50 mg/L、浸渍时间13 h）浸提时,葡萄醪中单宁含量6.884 mg/L,总酚含量122.332 mg/L,pH值3.85,色调最低,色度最高;常温浸渍法（浸渍温度20 ℃、二氧化硫添加量50 mg/L、浸渍时间13 h）浸提时,葡萄醪中单宁含量7.612 mg/L,总酚含量134.756 mg/L,pH值3.85,色调最低,色度最高;热浸渍法（浸提温度80 ℃,浸渍时间100 min）浸提时,葡萄醪中单宁含量23.451 mg/L,总酚含量264.688 mg/L,pH值3.43,色调最低,色度最高。     

Experimental aflatoxin production in home-made yoghurt

Summary Fungal growth and aflatoxin production by an aflatoxigenic strain during the manufacture of yoghurt are described. This completes previous studies which show that yoghurt may be a good substrate for aflatoxin production. Two factors were of special interest: (a) the temperature of the elaboration process (45 °C) and (b) the effect of lactic bacteria. Either during the elaboration of yoghurt or during its cooling from 45 °C to 4 °C, the necessary conditions required to start fungal growth are given; these are adequate enough for the synthesis of small quantities of aflatoxins. However our results do not clearly show that lactic bacteria have an influence on fungal growth and aflatoxin production.

---

Experimentelle Aflatoxinproduktion im hausgemachten Joghurt

Zusammenfassung Es werden das Pilzwachstum und die Aflatoxinproduktion durch aflatoxigene Stämme während der Herstellung von Joghurt beschrieben. Dies ergänzt frühere Studien, die zeigten, daß Joghurt ein gutes Substrat für die Aflatoxinproduktion ist. Zwei Faktoren waren von speziellem Interesse: a) die Temperatur bei der Herstellung (45 °C) und b) der Einfluß der Milchsäurebakterien. Entweder während der Herstellung des Joghurts oder während der Kühlung von 45 °C auf 4 °C sind die erforderlichen Bedingungen für das Pilzwachstum gegeben. Diese sind ausreichend für die Synthese kleiner Mengen von Aflatoxin. Jedoch zeigen unsere Ergebnisse nicht klar, ob die Milchsäurebakterien einen Einfluß auf das Pilzwachstum und die Aflatoxinproduktion haben.