螺旋藻益生菌酸乳的研制

探讨了在纯鲜牛乳中添加螺旋藻制剂,经益生乳酸菌发酵,制得一种浅绿色、风味独特的新型营养保健酸奶.通过四因素三水平L9(34)正交试验确定了最佳配方工艺为:合格鲜牛乳,白砂糖7.0%,果胶0.08%(均为质量分数),益生菌L.casei Zhang 4×106g-1,直投式发酵剂CHR HANSEN YC-X11 0.006%,螺旋藻提取液6.0%,发酵温度42℃,发酵时间4 h.     

Proteolytic profiles of yogurt and probiotic bacteria

Nine strains of Streptococcus thermophilus, 6 strains of Lactobacillus delbrueckii ssp. bulgaricus, 14 strains of Lactobacillus acidophilus and 13 strains of Bifidobacterium spp. were screened for proteolytic, amino-, di-, tri- and endopeptidase activity by using the o-pthaldialdehyde-based spectrophotometric assay. Strains showing the highest and lowest proteolytic activity were further studied for their peptidase activities at the extracellular and intracellular levels. The amounts of free amino groups released by S. thermophilus, L. delbrueckii ssp. bulgaricus and L. acidophilus strains were higher than that by Bifidobacterium strains. Aminopeptidase activity was detected for all bacterial strains both at the extracellular and intracellular levels. The specific activity towards the six substrates studied was higher at the intracellular level for all strains. High dipeptidase activity was demonstrated by all bacterial strains for L. delbrueckii ssp. bulgaricus, L. acidophilus, and Bifidobacterium spp. whereas S. thermophilus had greater dipeptidase activity at the extracellular level. All bacterial cultures tested were able to hydrolyse large biologically active peptides, bradykinin, Ala–Ala–Ala–Ala–Ala and the tripeptide substrate Gly–Ala–Tyr at both the extracellular and intracellular levels. However, with the substrates ending with a C-terminal of phenylalanine, the hydrolysis only occurred at the intracellular level.     

Glucose oxidase: A potential option to decrease the oxidative stress in stirred probiotic yogurt

The effect of the addition of glucose oxidase as a technological option todecrease the oxidative stress in a stirred yogurt during 15 days of refrigerated storage was investigated. A significant increase in the viable population of Bifidobacteria longum (6.9–8.7 log CFU g^?1) was observed in all yogurts added with glucose oxidase and glucose. Additionally, the yogurts containing glucose oxidase and glucose presented and caused higher pH, proteolysis rate, and contents of organic acids and aroma compounds, and this effect was comparable to the control sample (without glucose oxidase and glucose). Overall, the combined effect of the glucose oxidase system was important to reduce the oxygen content during storage of the probiotic yogurt. These findings suggest that glucose oxidase is a potential option to decrease the oxidative stress in probiotic yogurts.     

Growth of probiotic bacteria and bifidobacteria in a soy yogurt formulation

Soy beverage and cows' milk yogurts were produced with Steptococcus thermophilus (ATCC 4356) and Lactobacillus delbrueckii subsp. bulgaricus (IM 025). The drop in pH during fermentation was faster in the soy beverage than in cows' milk, but the final pH values were similar. Yogurts were prepared with a yogurt starter in conjunction with either the probiotic bacteria Lactobacillus johnsonii NCC533 (La-1), Lactobacillus rhamnosus ATCC 53103 (GG) or human derived bifidobacteria. The presence of the probiotic bacteria did not affect the growth of the yogurt strains. Approximately 2 log increases in both L. rhamnosus GG and L. johnsonii La-1 were observed when each was added with the yogurt strains in both cows' milk and the soy beverage. Two of the five bifidobacteria strains grew well in the cows' milk and soy beverage during fermentation with the yogurt bacteria. High pressure liquid chromatography (HPLC) analyses showed that the probiotic bacteria and the bifidobacteria were using different sugars to support their growth, depending on whether the bacteria were growing in cows' milk or soy beverage.     

Effects of beta-glucan addition to a probiotic containing yogurt

ABSTRACT:  This study investigated the effects of addition of β-glucan from 2 different cereal sources (oat and barley) on growth and metabolic activity of Bifidobacterium animalis ssp. lactis (Bb-12™) as determined by plating on a selective medium in yogurt during prolonged cold storage. These yogurt batches were compared to unsupplemented and inulin supplemented controls. All batches were also assessed for syneresis. Oat β-glucan addition resulted in improved probiotic viability and stability comparable to that of inulin. It also enhanced lactic and propionic acid production. The barley β-glucan addition suppressed proteolytic activity more than that from oat. These improvements were hindered by greater syneresis caused likely by thermodynamic incompatibility. Small amplitude oscillatory measurements of acidified model mixture of β-glucan/skim milk solids showed formation of casein gel within the β-glucan network. Binary mixtures of β-glucan and skim milk solids had apparent pseudoplastic and non-Newtonian behavior governed mainly by β-glucan contribution. Above critical concentrations, the mixtures underwent phase separation with the lower phase rich in protein. The phase diagram also showed that the addition of β-glucan may be possible at or below 0.24 w/w%.     

传统乳制品中潜在益生植物乳杆菌的体外筛选

对从内蒙古牧区乳制品中分离到的29株植物乳杆菌的耐酸性（pH=3．0）、耐胆汁性（质量浓度3g／L牛胆酸钠）、抗菌活性进行了系统性研究。结果表明，有10株菌具有较好的耐酸耐胆盐特性，结合抗菌特性及黏附性试验结果，菌株WZ47-1，WZ32-2-1和WH13-2有可能成为潜在益生菌菌株。     

Salmonella detection in probiotic products

The presence of large amounts of probiotic bacteria in a sample may interfere with the detection of undesirable microorganisms. To illustrate this, infant formula with various strains of probiotic bacteria and the corresponding probiotic culture powders and premixes were artificially contaminated with low levels of Salmonella. Recovery of Salmonella was generally very poor when the conventional pre-enrichment procedure using buffered peptone water (BPW) was applied. However, this problem was overcome by adding antimicrobial compounds to selectively suppress the growth and/or metabolic activity of the probiotic bacteria and increasing the buffering capacity of the pre-enrichment broth. It is recommended that these analytical constraints are already addressed during the development phase of new probiotic products.     

High throughput non-destructive assessment of quality and safety of packaged food products using phosphorescent oxygen sensors

Intelligent and active packaging technologies have gained attention in recent time due to increased demand by the consumers and manufacturers for sustaining the quality and safety of food products, improved shelf-life as well as real time monitoring of the packaging, storage and handling processes. In this context, phosphorescence based sensors for molecular oxygen (O₂) are important tools for monitoring of packaged products, new product development and optimisation. They allow fast, reversible, real-time and quantitative monitoring of residual O₂ levels in a non-destructive manner, being superior over alternative systems. In this review, we describe the main types of phosphorescent O₂-sensitive materials, fabrication methods and general requirements for sensors for food packaging applications. The main developments and representative examples are provided which illustrate the application of such sensors for monitoring of gaseous and dissolved O₂ in various types of packaged foods and beverages. We also compare commercial O₂ sensing instrumentation and disposable O₂ sensors currently in use.     

Microbial quality and safety of milk and milk products in the 21st century

Milk and milk products have been utilized by humans for many thousands of years. With the advent of metagenomic studies, our knowledge on the microbiota of milk and milk products, especially as affected by the environment, production, and storage parameters, has increased. Milk quality depends on chemical parameters (fat and protein content and absence of inhibitory substances), as well as microbial and somatic cells counts, and affects the price of milk. The effects of hygiene and effective cooling on the spoilage microbiota have shown that proteolytic and lipolytic bacteria such as Pseudomonas or Acinetobacter spp. predominate the spoilage bacterial populations. These bacteria can produce heat‐stable proteases and lipases, which remain active after pasteurization and thus can spoil the milk during prolonged storage. Additionally, milk can become contaminated after pasteurization and therefore there is still a high demand on developing better cleaning and sanitation regimes and equipment, as well as test systems to (quantitatively) detect relevant pathogenic or spoilage microorganisms. Raw milk and raw milk cheese consumption is also increasing worldwide with the growing demand of minimally processed, sustainable, healthy, and local foods. In this context, emerging and re‐emerging pathogens once again represent a major food safety challenge. As a result of global warming, it is conceivable that not only microbiological risks but also chemical risks relating to presence of mycotoxins or plant toxins in milk will increase. Herein, we provide an overview of the major microbial hazards occurring in the 21st century.     

High hydrostatic pressure processing on microstructure of probiotic low-fat yogurt

The effect of milk processing on the microstructure of probiotic low-fat yogurt was studied. Skim milk fortified with skim milk powder was subjected to three treatments prior to innoculation: thermal treatment at 85 °C for 30 min, high hydrostatic pressure at 676 MPa for 5 min, and combined treatments of high hydrostatic pressure (HHP) and heat. The processed milk was then fermented by using two different starter cultures containing Streptococcus thermophilus, Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus acidophilus, and Bifidobacterium longum. The microstructure of heat-treated milk yogurt had fewer interconnected chains of irregularly shaped casein micelles, forming a network that enclosed the void spaces. On the other hand, microstructure of HHP yogurt had more interconnected clusters of densely aggregated protein of reduced particle size, with an appearance more spherical in shape, exhibiting a smoother more regular surface and presenting more uniform size distribution. The combined HHP and heat milk treatments led to compact yogurt gels with increasingly larger casein micelle clusters interspaced by void spaces, and exhibited a high degree of cross-linking. The rounded micelles tended to fuse and form small irregular aggregates in association with clumps of dense amorphous material, which resulted in improved gel texture and viscosity.     

Microbial growth in vacuum packaged frankfurters produced in Spain

The effects of storage temperature and time on the microflora of vacuum packed frankfurters were analysed. Total aerobic counts, lactic acid bacteria, Brochothrix thermosphacta and yeast and moulds, were determined as functions of time. Statistically significant differences were observed (P ≤0·001) amongst the counts obtained at 2 and 7°C. At the end of the controlled storage period (42 days) the sausages kept at 7°C showed signs of spoilage. The appearance of superficial slime occurred after 28 days in samples with lactic acid bacteria at counts higher than 10⁸ cfu g⁻¹. The swelling of the pack showed after 42 days in those samples which had a level higher than 5 × 10⁸ cfu g⁻¹. On the contrary, the samples kept at 2°C did not show the aforesaid spoilage signs during the period of controlled storage. Basing our conclusions on the results obtained, a period of shelf life of 28 days was established at 7°C, whilst at 2°C a minimum shelf life of 42 days was obtained.     

益生菌制品的研究进展

益生菌是一种通过改善肠道微生物平衡从而对宿主施加有益影响的微生物添加物,它们对机体有多种其它正常生理菌群无法比拟的生理作用.目前,国内外的益生菌制品种类繁多并形成了产业规模,尤其是日本和欧盟,在中国的发展也是日新月异.针对上述情况,对益生菌制剂的发展概况、工业化生产及应用等问题进行了综述,以期为我国进一步发展益生菌制品提供理论依据.     

益生菌制剂及其发酵性乳制品

益生菌具有特殊的营养和生理功能作用,由于酸奶是益生菌的良好载体,因此益生酸奶的出现成为市场的新宠.本文综述了益生菌的概念和益生菌菌株的选择标准,益生菌作为新型酸奶发酵剂的使用情况,以及益生酸奶的生产与消费情况.     

益生菌制剂及其发酵性乳制品

综述了益生菌的概念和益生菌菌株的选择标准、国外益生菌产品的发展状况、益生菌作为新型酸奶发酵剂的使用情况，以及益生酸奶的生产与消费情况。     

Effect of calcium on the physical properties of stirred probiotic yogurt

The effect of calcium on the viscosity, firmness, and smoothness, as determined by extent of nodulation, of stirred probiotic yogurt produced by bacterial fermentation was investigated. Standardized milk for yogurt manufacture was prepared, and calcium was added or removed from the system. Calcium was added as Ca²⁺ in the form of CaCl₂ (up to 13.6 mM) or nonionic calcium as Gadocal-K (calcium potassium citrate; up to 49.8 mM). Calcium was removed by chelating with sodium citrate (up to 16 mM) or by cation exchange with Amberlite IR-120 plus (sodium form) resin (up to 10 g/L). Calcium chloride and sodium citrate were added either before or after heat treatment of milk, and nonionic calcium was added before heat treatment. Calcium removal by ion exchange was performed before heat treatment. Neither Ca²⁺ addition nor removal by chelation with citrate resulted in stirred yogurt with viscosity, firmness, and smoothness superior to those of the control yogurt, whereas addition of 49.8 mM nonionic calcium and removal of calcium (5.6 mM or ∼10% of total calcium) by cation exchange improved the firmness and viscosity without affecting yogurt smoothness. The study identified Gadocal-K as a possible source of calcium fortification of stirred yogurt without loss of texture.     

Shelf life and quality of probiotic yogurt produced with Lactobacillus acidophilus and Gobdin

This study evaluated the effect of dry white mulberry and walnut paste (Gobdin, a traditional Turkish food) in probiotic yogurt on the survival of Lactobacillus acidophilus and yogurt properties. Six different yogurts were produced with 0%, 5% and 10% Gobdin using Lactobacillus bulgaricus + Streptococcus thermophilus and with 0%, 5% and 10% Gobdin using L. bulgaricus + S. thermophilus + L. acidophilus. The physical, chemical, microbiological and sensorial properties of the yogurts were evaluated based on storage at 4 ± 1 °C. Probiotic shelf life and the most suitable combinations were determined. The highest L. acidophilus count (8.65 log cfu g^?1) was found in the 5% Gobdin‐supplemented yogurt on the 7th day of storage, while the lowest count (8.11 log cfu g^?1) was found in the probiotic control yogurt on the 21st day. Although the L. acidophilus counts in the probiotic yogurts declined during storage, all values found throughout the 21‐day storage period were >8 log cfu g^?1. This is above the level necessary to provide the desired therapeutic effect in probiotic products (10⁶–10⁷ cfu g^?1). The highest overall acceptability score was obtained on the first day from the yogurt with 5% Gobdin. However, all yogurt samples had general acceptability scores between 7 and 8 points from a 9‐point maximum. Thus, this study determined that a new functional yogurt can be produced using L. acidophilus with 5% Gobdin.     

Survival analysis methodology to predict the shelf-life of probiotic flavored yogurt

The feasibility of survival analysis methodology was used to determine the shelf-life of probiotic strawberry flavored yogurt supplemented with Bifidobacteirum animalis DN 173010 W was investigated. The quality parameters of probiotic yogurts were related to storage conditions which they are submitted. The consumers were shown sensitive to changes towards sensory characteristics introduced into the products. Using the survival analysis and considering 25% and 50% probability of consumer rejection, the shelf-life of the probiotic yogurt was estimated at 38 and 53 days, respectively. The findings of this research highlighted the feasibility this technique to determine the shelf-life of foods, in particular, functional foods, as probiotic yogurts.     

The potential of probiotic fermented milk products in reducing risk of antibiotic-associated diarrhoea and Clostridium difficile disease

Currently, the burden of infective antibiotic-associated diarrhoea (AAD) and Clostridium difficile -associated disease (CDAD) is placing considerable strain on health services. The potential of probiotics has been investigated, particularly whether they may help reduce the vulnerability of the elderly to these diseases. Probiotic mechanisms of activity include helping to maintain the normal intestinal microbiota and supporting its ability to resist colonisation by pathogens as well as immune modulation. Despite conflicting results from meta-analyses, there is now increasing evidence that certain Lactobacillus probiotic strains may reduce the risk of AAD and CDAD. Several recent studies report positive results with probiotic-fermented dairy products.     

灵芝多糖益生菌酸奶抗衰老的研究

对D-半乳糖致衰老小鼠分别灌胃添加不同含量灵芝多糖的益生菌酸奶,测定各组处理小鼠脏器指数,血清及不同组织中超氧化物歧化酶(SOD)、丙二醛(MDA)、谷胱甘肽过氧化物酶(GSH-PX)、过氧化氢酶(CAT)活性指标,研究添加灵芝多糖的益生菌酸奶对D-半乳糖致衰老小鼠抗衰老作用的效果。结果表明:添加灵芝多糖的益生菌酸奶可显著提高衰老模型小鼠血清及不同组织中SOD、CAT、GSH-PX活性、降低MDA含量(P0.05),且以高剂量组[1 200 mg/(kg·d)]效果最优。与衰老模型组相比,高剂量组[1 200 mg/(kg·d)]小鼠血清、肝脏、脑组织中SOD活力依次提高20.34%、8.39%、48.95%;小鼠血清、肝脏中GSH-PX活力依次提高38.45%、39.67%;小鼠血清、肝脏、脑组织中MDA含量分别降低38.37%、43.97%、38.39%;小鼠脑组织、肝脏、肾脏中CAT活力依次提高60.02%、55.29%、37.73%。与酸奶组相比,高剂量组小鼠SOD活力依次提高18.36%、1.58%、25.13%;GSH-PX活力依次提高38.45%、30.26%;MDA含量分别降低10.47%、30.96%、18.91%;CAT活力依次提高41.31%、32.07%、26.64%。结论:灵芝多糖添加入植物乳杆菌益生发酵酸奶可发挥灵芝多糖和益生菌酸奶在抗衰老功能方面的协同作用发挥更强抗衰老效果。