Potential application of Saccharomyces boulardii as a probiotic in goat's yoghurt: survival and organoleptic effects

Potential application of Saccharomyces boulardii in yoghurts could offer an alternative probiotic product to people suffering from antibiotic‐associated diarrhoea whilst on treatment. Three different yoghurts were made using goat's milk. Yoghurt 1 was the control with only starter culture added to the milk. For Yoghurt 2, S. boulardii was added in parallel with the starter culture, and for Yoghurt 3, the yeast was added after the yoghurt was coagulated by the starter. Duplicate counts for lactic acid bacteria (LAB) and S. boulardii alongside organoleptic assessment were carried out every 3 days following manufacture and storage at 6 °C. Our results demonstrate that S. boulardii can survive in high numbers for the period of 4 weeks tested without significant changes in taste. Very important is the fact that the presence of the yeast stimulated the survival of the LAB, which in both yeast yoghurts were significantly higher than in the control.     

葡萄糖氧化酶及其应用

葡萄糖氧化酶是需氧脱氢酶,易溶于水,不溶于有机溶剂。工业生产多从黑曲霉中提取,该酶主要与过氧化氢酶共同作用催化葡萄糖产生葡萄糖酸,同时消耗氧。葡萄糖氧化酶广泛应用于食品、医药、饲料等行业中,起到了去除葡萄糖、脱氧、杀菌等作用。     

GC–MS-based metabolomics approach reveals metabolic variations between probiotics incorporated cow and goat milk yoghurt

The work is aimed at elucidation of metabolite profile of probiotic yoghurts prepared from cow milk (CPY) and goat milk (GPY) using gas chromatography–mass spectrometry-based untargeted metabolomics approach. A total of 192 metabolites including 49 differentially expressed metabolites (DEMs) were observed, wherein amino-acids, peptides and analogues constituted 41.93% of the metabolite sub-class. Acetic acid, glycine, Thr-Ala, octanoic acid, l -kynurenine and 2-amino adipic acid were among the top 15 DEMs. A significant relationship with seven key metabolic pathways including glycolysis, lysine degradation, purine metabolism, fatty acid biosynthesis, tryptophan metabolism, nicotinate and nicotinamide metabolism and glycine, serine and threonine metabolism has been established based on their impact values.     

面粉中添加葡萄糖氧化酶后巯基变化的研究

为研究葡萄糖氧化酶氧化面粉中的巯基生成二硫键,从而改善面团流变性质的作用机理,采用GB/T14614-93方法测定面粉试验仪的性质;用重铬酸钾氧化法检测不同葡萄糖氧化酶作用条件下巯基的含量,结果表明:面粉中巯基减少量与葡萄糖氧化酶酶活力和浓度相关,但并不是简单的正向变化,还受到外界条件的影响,说明葡萄糖氧化酶氧化面粉中的巯基生成二硫键是一个复杂的过程。     

黑曲霉A9葡萄糖氧化酶的提取纯化

为研究葡萄糖氧化酶的酶学性质、催化机理等问题,利用黑曲霉(Aspergillus niger)A9,经发酵、破碎细胞,得到胞内葡萄糖氧化酶,然后经超滤浓缩、硫酸铵盐析、DEAE-纤维素离子交换层析、Sephadex G-100凝胶过滤分离纯化。试验结果表明:通过控制离子交换层析与分子筛层析的具体操作条件,大部分杂蛋白被除去,所得酶蛋白经PAGE电泳鉴定为单一条带,达到电泳纯。测定其比活力为1779.29U/mg,比初始发酵液提高20.13倍。建立了一套操作简单、快速且费用低廉的黑曲霉A9葡萄糖氧化酶的提纯方案。     

GLUCOSE OXIDASE REACTION FOR ESTIMATION OF GLUCOSE WITHOUT HORSERADISH PEROXIDASE. SOME MICROBIOLOGICAL AND FERMENTATION APPLICATIONS

An enzymic method has been developed for analysis of glucose. Glucose oxidase acts on glucose to produce hydrogen peroxide which acts to directly reduce the green Cu(II) 2–2′-bicinchoninate complex to a violet complex without horseradish peroxidase. A concentration range of 20–200 μM glucose was used but the reaction shows a linear range of 20–800 μM glucose. Interference is controlled by using a blank determination which has not been treated with glucose oxidase. The reaction has been used to estimate glucose levels in Saccharomyces cerevisiae fermentation and α-amylase, invertase and β-galactosidase reactions and coloured corn-steep fermentation media.     

Spectrophotometric determination of glucose in foods by flow injection analysis with an immobilized glucose oxidase reactor

 A stopped-flow injection analysis system for the determination of glucose is described, based on the iodometric measurement of hydrogen peroxide generated in a glucose oxidase reactor. The detection of the iodine–starch complex was carried out spectrophotometrically. The calibration curve was linear up to 2 mmol l^-1 glucose, with a correlation coefficient, r, of 0.9996. The relative standard deviation was 1.6% (n=5) for 1.0 mmol l^-1 glucose. A sample frequency of 25 samples h^-1 was achieved. This method was applied to the determination of glucose in fruit products and the results obtained using this method were in good agreement with those of a routine enzymatic method. A high dilution of the sample avoided interference from ascorbic acid. The enzyme reactor was stable for 1 month after 200 measurements with no loss of activity. Received: 22 March 1996     

Enhanced survival of spray-dried microencapsulated Lactobacillus rhamnosus GG in the presence of glucose

The survival of spray dried Lactobacillus rhamnosus GG (LGG) preparations encapsulated in whey protein isolate (WPI)-maltodextrin, WPI-maltodextrin-glucose, WPI-inulin, and WPI-inulin-glucose mixtures during storage at 25 °C (11%, 57% and 70% relative humidity, RH) was examined. The glass transition temperature of each encapsulant formulation was also assessed. RH was most important for maintaining viability over time; the inclusion of glucose improved viability, irrespective of when all formulations were in a glassy or rubbery state. When LGG microcapsule powders were stored at the same RH, the addition of glucose in the encapsulant formulation had a greater influence on survival of LGG during storage than the maintenance of a glassy state. Both the maintenance of a glassy state during storage and the incorporation of glucose in the encapsulant formulation were required for optimal survival of probiotic microcapsule powders prepared from fresh cultures.

Practical significance

The incorporation of glucose into the encapsulant formulation prior to spray drying of protein-carbohydrate based LGG formulations improves the survival of LGG during long term storage.     

功能性牦牛酸奶制备、贮藏期内品质及降嘌呤活性研究

为研发一款降嘌呤的功能性牦牛酸奶,以副干酪乳杆菌259和商业发酵剂为发酵菌株,通过单因素实验优化牦牛酸奶菌株接种量,观察牦牛酸奶后熟期及贮藏期品质变化,利用气相色谱-质谱联用技术（GC-MS）解析后熟期和贮藏贮藏期的风味物质变化,高效液相色谱法（HPLC）测定牦牛酸奶的降嘌呤活性。结果表明：牦牛酸奶后熟24 h时,副干酪乳杆菌259接种量5%时感官评分最优,活菌数3.1×10⁸ CFU/mL,酸度为96°T,对黄嘌呤氧化酶（xanthine oxidase,XOD）的抑制率为51.51%。5%接种量副干酪乳杆菌259的牦牛酸奶在贮藏期28 d内活菌数高于10⁷ CFU/m L,酸度低于105.4°T,随贮藏时间增加,pH及持水力逐渐降低,感官品质、硬度、内聚力、黏度、稠度以及对XOD抑制活性先上升后下降;牦牛酸奶后熟期主要风味物质是醇类、酯类、酮类、芳香杂环类以及含硫化合物,贮藏期比后熟期增加了酸类物质;醇类化合物的相对含量和数量最多,赋予酸奶水果香气、花香和甜味;贮藏期牦牛酸奶对肌苷和鸟苷的降解率先上升后下降,最高可达84.6%和86.5%。由此可见,副干酪乳杆菌259发酵的牦牛酸奶品质较好,可抑制黄嘌呤氧化酶活性,有效降解肌苷鸟苷,在预防和辅助治疗高尿酸血症上有较好的应用潜力。     

长货架期酸奶饮料加工工艺的探讨

探讨了酸奶饮料生产的最佳工艺条件和为得到高质量的产品在生产中注意的问题。