Experimental aflatoxin production in commercial yoghurt

The production of aflatoxins in commercial yoghurt inoculated with Aspergillus parasiticus NRRL 2999 was studied, using different incubation conditions. In all of the experiments, the level of aflatoxins was higher at 28 degrees C than at 15 degrees 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 degrees 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 degrees C was almost 1:1, but generally more aflatoxin G was detected at 15 degrees C. The distribution in mycelium/substrate was approximately 1:1 at both 28 degrees C and 15 degrees C.     

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.     

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.

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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.

     

Distribution and stability of aflatoxin M1 during production and storage of yoghurt.

Yoghurt from cow's milk artificially contaminated with aflatoxin M1 (AFM1) at levels of 0.050 and 0.100 g l(-1) was fermented to reach pHs 4.0 and 4.6. Yoghurt fermented to pH 4.6 was also used for preparing strained yoghurt. Yoghurts were stored at 4 degrees C for up to 4 weeks. Analysis of AFM1 in milk, yoghurt, strained yoghurt and yoghurt whey was carried out using immunoaffinity column extraction and liquid chromatography coupled with fluorometric detection. AFM1 levels in yoghurt samples showed a significant decrease (p < 0.01) compared with those initially added to milk. Growth of culture lactic acid bacteria was not affected in the AFM1 contaminated yoghurts, with the exception of Streptococcus thermophilus that showed a significantly (p < 0.01) lower increase in the yoghurt containing the toxin at high concentration. Following fermentation, AFM1 was significantly lower (p < 0.01) in yoghurts with pH 4.0 than in yoghurts with pH 4.6 at both contamination levels. During refrigerated storage, AFM1 was rather more stable in yoghurts with pH 4.6 than with pH 4.0. The percentage loss of the initial amount of AFM1 in milk was estimated at about 13 and 22% by the end of the fermentation, and 16 and 34% by the end of storage for yoghurts with pHs 4.6 and 4.0, respectively. The percentage distribution ratio of AFM1 in strained yoghurt/yoghurt whey of the initial toxin present in the yoghurt was about 90/10 and 87/13 for the lower and the higher contamination levels, respectively.     

国内6种市售酸奶中的ACE抑制肽研究

选取了不同品牌的6种市售酸奶,通过离心、超滤、凝胶层析分离纯化低分子量(≤1.4 ku)小肽,分析了各酸奶样品中小肽质量浓度及所占比例,并通过ACE抑制实验测定了各小肽收集样的体外抗高血压活性。结果表明,不同市售酸奶的评价指标结果间存在显著性差异(P<0.05),其ACE抑制率依次为样品5(73.0%±2.59%)>样品2(67.3%±3.05%)>样品6(64.2%±3.75%)>样品3(61.9%±2.65%)>样品1(61.7%±2.38%)>样品4(52.4%±3.15%),综合评价样品5为最优。     

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。     

Utilization of soy yoghurt in tarhana production

Tarhana, a traditional fermented food made from a mixture of white wheat flour and yoghurt, is widely consumed in Turkey. Tarhana samples with cow's milk yoghurt, soy milk yoghurt, and a blend of cow's and soy milk yoghurt were produced and evaluated for pH, viscosity, color, and sensory properties. Acid production was slower in soy milk-added samples, and increasing yoghurt amount in tarhana significantly contributed to acidity of the samples (P<0.05). Soy milk-added samples had higher viscosity compared with cow's milk yoghurt-added samples (P<0.05). Soy milk yoghurt bleached the wheat flour and therefore these samples appeared whiter than the cow's milk yoghurt-added samples (P<0.05). Panelists could not detect any beany-off flavor in soy milk yoghurt-added samples and gave similar scores to soy milk yoghurt-added tarhanas for all sensory properties     

发酵增强剂对酸乳生产的影响

<正> 酸乳的生产工艺已流传了好几个世纪,而第一个类似酸乳的产品是通过“自然”发酵而得的,制成品可作短期保存。使用含有特殊的、所谓前生命期(probiotic)菌种的发酵培养物来生产的酸乳制品,由于含有有益健康的微生物,如嗜酸乳杆菌、干酪乳杆菌和双歧杆菌等,故有相当的功能性特点,是当今制造酸乳的新工艺。     

谷氨酰胺转胺酶在凝固型酸奶加工中的应用研究

主要研究了谷氨酰胺转胺酶在凝固型酸奶加工中的应用,研究结果表明,该酶的最适添加顺序为与发酵剂同时加入到灭菌的乳中;最适添加种类为TG-K;最适添加量为5×10-4g/mL;而且还研究了在贮藏期间,加酶酸奶的质构随时间的变化情况。     

乳清浓缩蛋白在酸奶生产中的应用

以鲜奶，奶粉，乳清蛋白等乳成分为主要原料，研究了乳清浓缩蛋白在酸奶生产中的制做方法，对乳清浓缩蛋白代替部分高档脱脂奶粉生产酸奶产品的保水率，粘度，口感及组织状态进行了比较分析。结果表明，在酸奶生产中，添加一定的浓缩乳清蛋白代替高档脱脂奶粉是可行的，产品较为理想。     

风味型花生酸奶的研制

研究了以鲜乳和花生为原料生产风味型酸奶的最适配方及生产技术条件。结果表明，将花生乳与鲜乳以２∶３的比例混合，再加７％的白砂糖，０．０１％ＣａＣｌ２，０．２％的乳化稳定剂，０．０６％的香精，菌种选用保加利亚乳杆菌和嗜热链球菌以１∶１，３％的接种量，在４３℃条件下发酵４ｈ，可制得优质风味型花生酸奶。     

胶原蛋白酸奶的研制

以新鲜牛乳为原料,添加天然深海鳕鱼皮提取的胶原蛋白,经杀菌、真空浓缩、冷却、添加乳酸菌发酵剂发酵,开发了具有营养和保健功效的胶原蛋白酸奶,其主要成分为:蛋白质4％(其中胶原蛋白≥1％),脂肪3.5％,碳水化合物11％,固形物21.8％(均为质量分数),乳酸菌数9×108 g-1.该生产工艺可行、技术上合理、设备上可操作...     

Differentiation of Streptococcus thermophilus strains in commercial Direct Vat Set yoghurt starter

Based on inhibition of acid production, 100 individual colonies of Streptococcus thermophilus isolated from commercial Direct Vat Set yoghurt starter DVS-M were typed into 2 groups of sensitive and insensitive to phage φ001, which was isolated from the lysis culture of the turbidity test. The ratio between the sensitive and insensitive isolates in DVS-M was calculated at 3:2. Whole-cell protein profile (WCPP) and randomly amplified polymorphic DNA (RAPD) analysis showed that both WCPP and RAPD patterns between sensitive and insensitive isolates were distinct, whereas isolates with the same sensitivity or insensitivity shared common WCPP and RAPD patterns. It suggested that all the sensitive isolates belong to one S. thermophilus strain and all the insensitive isolates belong to another one. This study revealed that DVS-M yoghurt starter consists of 2 S. thermophilus strains with different phage sensitivity.     

Growth and metabolites production by Penicillium brevicompactum in yoghurt

Penicillium brevicompactum, commonly encountered in the indoor air, is known to produce a mycotoxin, mycophenolic acid (MPA). This mould has been isolated from a wide range of foods; considering that we had previously isolated this species from contaminated yoghurt, in this study we have evaluated its growth in yoghurt sweetened with sucrose, fructose and fructose added with fruit pieces. Fungal growth was evaluated monitoring CO(2) production in the headspace during yoghurt storage at 4+/-1, 8+/-1 and 10+/-1 degrees C throughout 21 days. P. brevicompactum grew well in the samples sweetened with fructose at 8 and 10 degrees C. The addition of sucrose influenced the growth negatively, particularly at 4 degrees C. Volatile Organic Compounds (VOC) and MPA production was determined at 8 degrees C in inoculated and uninoculated yoghurt, as well as in liquid malt extract. Differences in VOC profiles and in MPA production were correlated with the age of the fungus and with the growth medium. This study points out for the first time the early qualitative changes in volatile production patterns of a common indoor mould, grown in yoghurt, as well as the production of MPA during storage at refrigeration temperatures.     

瓶装酸奶生产过程中的包装质量控制

瓶装酸奶的瓶子是回收后清洗重复使用的,清洗不当会给消费者健康造成威胁并引起消费者投诉。介绍了瓶子清洗程序、提高洗瓶合格率的措施,及清洗过程中出现异常情况所采取的处理措施。     

速溶酸奶的生产工艺

以全脂奶粉 (或新鲜牛奶 )、白砂糖、活性乳酸菌等为原料 ,通过对速溶酸奶的生产工艺进行了研究 ,提出了适宜的生产工艺和配方。     

绿豆酸乳的研制

以绿豆和鲜牛乳为主要原材料，以保加利亚乳杆菌和嗜热链球菌为混合发酵菌种，利用发酵法生产绿豆酸乳，采用正交试验法，优选出最佳配方及生产技术条件。研究结果表明：将绿豆浆与鲜牛乳以1：2（v/v）的比例混合，再加9%的白砂糖、0.2%的稳定剂，保加利亚乳杆菌和嗜热链球菌以1：1.5混合，且用3%的接种量，在42℃下发酵5h可制得优质绿豆酸乳。     

酸奶中保加利亚乳杆菌的抗药性实验研究

测定了10种常用抗菌药物对市售酸奶中分离的57株保加利亚乳杆菌的MIC。结果表明，泰能、克林霉素、林可霉素、头孢唑啉和红霉素对乳杆菌的抗菌或活性最强，MIC90值为0．25～2．0mg／L，敏感率为96．5％～86．0％其次是阿莫西林、复方新诺明、青霉素，其MIC90值为2．0～4．0mg／L，敏感率为84．3％～78、9％。庆大霉素、氯霉素其MIC90值为4．0～16．0mg／L，敏感率为63．2％～59．7％。酸奶中的保加利亚乳标菌存在抗药性，其抗药性基因是否具转移性有待于进一步研究。     

植物乳杆菌KLDS1.0391在酸奶体系中的细菌素产生特点

植物乳杆菌KLDS1.0391能够合成细菌素,也是益生菌,在食品中既可作为益生菌使用,也可作为辅助发酵剂用于生物防控,该研究主要考察了KLDS1.0391菌株在酸奶体系中细菌素的产生特点。研究结果表明,在发酵的6 h期间,抑菌活性随发酵时间延长而增强,发酵结束时,添加植物乳杆菌KLDS1.0391酸奶组的抑菌活性显著高于仅使用酸奶发酵剂的对照组(P<0.01)。与对照组相比,加入辅助发酵剂的实验组的感官品质未发生明显的变化。植物乳杆菌KLDS1.0391具备开发益生酸奶的潜力。     

Suitability of high-dynamic-pressure-treated milk for the production of yoghurt

The aim of this work was to evaluate, using the response surface methodology, the effects of different levels of high-pressure homogenization (HPH) on the microbiological and rheological characteristics of yoghurts having different contents of fat and milk solids. The HPH treatment of milk resulted a useful tool to obtain yoghurts having a greater variety of textures associated to a high microbiological quality. In fact, all the yoghurt types obtained by using milk treated with different levels of pressure were characterized by cell loads of the starter cultures higher than 8 log₁₀ cfu ml⁻¹ immediately after the fermentation and than 7 log₁₀ cfu ml⁻¹ after 60 days of storage at 4°C. The HPH treatment seems to favor the growth of Streptococcus thermophilus with respect to that of Lactobacillus delbrueckii subsp. bulgaricus, regardless of the level of pressure applied. The use of a Central Composite Design (CCD) and the polynomial models obtained permitted to individuate the levels of the three independent variables (pressure level, milk solids and fat concentration) able to maximize the growth of starters during the fermentation process, to minimize their viability loss during the refrigerated storage as well as to define their effects on the product viscosity.