Characterization of certain bacterial strains for potential use as starter or probiotic cultures in dairy products

The present work was aimed at characterizing 12 strains of lactic acid bacteria (LAB) to obtain improved potential starter or probiotic cultures that could be used for making dairy products from ewe's milk and cow's milk. Eight strains with antimicrobial properties, isolated from ewe's milk and from cheese made from ewe's and/or cow's milk, were studied. They were identified as Enterococcus faecalis (five strains), Lactococcus lactis subsp. cremoris, Leuconostoc mesenteroides, and Lactobacillus paracasei subsp. paracasei (one strain of each species). Additionally, four strains were obtained from the American Type Culture Collection: Lactobacillus casei 393 (isolated from cheese), L. lactis subsp. lactis 11454 (origin nonspecified and a producer of nisin), and two strains isolated from human feces (L. paracasei subsp. paracasei 27092 and Lactobacillus rhamnosus 53103, antibacterial agent producer). All E. faecalis strains showed at least one virulence factor (either hemolysin or gelatinase), which emphasizes the importance of these studies in this species. Both L. lactis strains and most Lactobacillus spp. were good acidifiers in ewe's milk and cow's milk at 30°C. High β-galactosidase activity, as well as aminopeptidase activities that favor the development of desirable flavors in cheese, were detected in all Lactobacillus spp. strains. Furthermore, L. rhamnosus ATCC 53103 showed α-fucosidase activity (thought to help colonization of the intestine) and lack of α-glucosidase activity (a trait considered positive for diabetic and obese humans). This last enzymatic activity was also lacking in L. lactis ATCC 11454. L. mesenteroides was the only strain D(2)-lactic acid producer. The selection of any particular strain for probiotic or dairy cultures should be performed according to the technological and/or functional abilities needed.     

Effect of viable starter culture bacteria in yogurt on lactose utilization in humans

Breath hydrogen production was used as a measure of lactose malabsorption in human test subjects following the consumption of both heated and unheated cultured yogurt. Less hydrogen was produced when the subjects consumed the unheated cultured yogurt than when they consumed the heated product, indicating that lactose hydrolysis was improved in the small intestine of the individuals consuming the unheated cultured yogurt. Lactase activity in yogurt samples was increased in the presence of bile. Yogurt starter bacteria growing in milk normally do not hydrolyze more lactose than needed for their growth. However, the increased lactase activity in the presence of bile indicates that these bacteria could function as a source of lactase to hydrolyze lactose in the small intestine even though the organisms themselves are not expected to grow in that environment.     

低乳糖乳制品的广阔市场前景

本文分析了中国低乳糖奶市场的发展和产品结构,与乳业发达的欧美国家的市场产品和趋势,展望了中国未来低乳糖市场的巨大市场潜力.     

Antimicrobial susceptibility of starter culture bacteria used in Norwegian dairy products

Commercial starter culture bacteria are widely used in the production of dairy products and could represent a potential source for spread of genes encoding resistance to antimicrobial agents. To learn more about the antimicrobial susceptibility of starter culture bacteria used in Norwegian dairy products, a total of 189 isolates of lactic acid bacteria were examined for susceptibility to ampicillin, penicillin G, cephalothin, vancomycin, bacitracin, gentamicin, streptomycin, erythromycin, tetracycline, chloramphenicol, quinupristin/dalfopristin, ciprofloxacin, trimethoprim and sulphadiazine using Etest for MIC determination. Most of the isolates (140) originated from 39 dairy products (yoghurt, sour cream, fermented milk and cheese), while 49 were isolated directly from nine commercial cultures. The bacteria belonged to the genera Lactobacillus, Lactococcus, Leuconostoc and Streptococcus. Only one of the 189 isolates was classified as resistant to an antimicrobial agent included in the study. This isolate, a lactobacillus, was classified as high level resistant to streptomycin. The remaining isolates were not classified as resistant to the antimicrobial agents included other than to those they are known to have a natural reduced susceptibility to. Thus, starter culture bacteria in Norwegian dairy products do not seem to represent a source for spread of genes encoding resistance to antimicrobial agents.     

Angiotensin-converting enzyme inhibition and antioxidant activity of commercial dairy starter cultures

Food Science and Biotechnology - In this study, skim milk fermented with 14 commercial dairy starters were evaluated for their proteolysis ability, angiotensin I-converting enzyme (ACE)-I, and...     

Effect of natural starter culture activity on ethanol content in fermented dairy products

The influence of kefir grains' activation time on kefir pH changes and ethanol production was investigated. The proposed exponential pH model was used successfully to describe any decrease in pH during 24 h fermentation. Furthermore, the influence was investigated of differently active kefir grains on the correlation between ethanol and yeast population in grains and kefir drink respectively. Results showed that longer-activated grains produce more ethanol and have a larger number of yeasts than grains, which are activated for only a few days. The number of yeasts in a kefir product also increases over the grains' activation time.     

Influence of compounds associated with fermented dairy products on the growth of lactic acid starter and probiotic bacteria

The growth of 24 strains of lactic acid starter bacteria (Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus and Lactococcus lactis) and 24 strains of probiotic bacteria (Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus paracasei, Lactobacillus rhamnosus and bifidobacteria) in liquid media containing different substances was assessed. The substances used were salts (NaCl and KCl); sugars (sucrose and lactose); sweeteners (acesulfame and aspartame); aroma compounds (diacetyl, acetaldehyde and acetoin); natural colorings for fermented milk (red, yellow and orange colorings); flavoring agents (strawberry, vanilla, peach and banana essences); flavoring–coloring agents (strawberry, vanilla and peach); nisin, natamycin and lysozyme. Bacterial growth in the presence of natural fruit juices (green apple, kiwi, pineapple, peach and strawberry) with or without neutralization and cell viability in lactic acid acidified (pH 4 and 5) milk for 4 weeks at 5°C were also studied.Some compounds (KCl, sweeteners, aroma compounds, natamycin, flavoring agents and the peach flavoring–coloring agent) did not influence the growth of the strains in the concentrations commonly used in the dairy industry. The effect of other substances (especially flavoring–coloring agents) on the growth of lactic acid starters and probiotic bacteria was strain-dependent. Natural fruit juices weakly inhibited mainly S. thermophilus strains. Cell viability during cold storage in acidified milk was satisfactory for L. delbrueckii subsp. bulgaricus and L. casei group strains. For L. acidophilus and Bifidobacterium, the decreases in cell counts at pH 5 were negligible. Nevertheless, decreases from 1.6 to 6.2 and from 0.1 to 7.6 log orders, respectively were observed at pH 4.     

Commercial bacterial starter cultures for fermented foods of the future

Starter cultures for fermented foods are today developed mainly by design rather than by screening. The design principles are based on knowledge of bacterial metabolism and physiology as well as on the interaction with the food product. In the genomics era, we will obtain a wealth of data making design on a rational basis even simpler. The design tools available are food grade tools for genetic, metabolic and protein engineering and an increased use of laboratory automation and high throughput screening methods. The large body of new data will influence the future patterns of regulation. It is currently difficult to predict in what direction the future regulatory requirements will influence innovation in the food industry. It can either become a promoting force for the practical use of biotechnology to make better and safer products, or it can be limiting the use of starter cultures to a few strains with official approval. Successful cultures based on modern technology is expected to be launched in the areas of: probiotics, bioprotection, general improvement of yield and performance for the existing culture market and probably the introduction of cultures for fermenting other food products. A scientific basis for dramatic innovations that could transform the culture industry is currently being established.     

Heat-induced changes in dairy products containing sucrose

The aim of the present work was to analyse the influence of the variables reaction temperature, casein–sucrose ratio and pH, on the kinetic parameters of gelation reactions, the gelation time and the functionality of casein micelles in concentrated milk systems containing sucrose.     

Influence of starter cultures on the antioxidant activity of kombucha beverage

This paper investigates the influence of starter cultures, obtained from kombucha isolates, on the antioxidant activity of kombucha beverages. Three starter cultures were used as follows: (1) mixed culture of acetic bacteria and Zygosaccharomyces sp. (SC1); (2) mixed culture of acetic bacteria and Saccharomyces cerevisiae (SC2); as well as (3) native local kombucha. The starter cultures were added to black and green tea sweetened with 7% of sucrose. Fermentation was carried out at 28 °C for 10 days. Antioxidant activity to hydroxyl and DPPH radicals was monitored. Kombucha beverage on black tea has shown the highest antioxidant activity to both types of radicals with starter SC1, while the green tea beverage has shown the highest activity with native kombucha. The main reason for the different antioxidant activities, beside tea composition, was ascribed to differing production of both vitamin C and total organic acids in the investigated systems.     

3种测定乳制品中乳糖含量方法的比较

为确定一种快速、简易、灵敏的测定乳糖的方法,比较了直接滴定法、蒽酮法和碘量法3种方法测定乳制品中乳糖含量的差异.结果表明:平行试验直接滴定法精度最低,但其乳糖回收率的最大相对误差最小;蒽酮法精度高,但其乳糖回收率的最大相对误差最大,而且蒽酮试剂腐蚀性强,操作不安全;碘量法的精度与乳糖回收率的最大相对误差均介于直接滴定与蒽酮比色法之间,综合而言,碘量法的重复操作性强,结果准确,测定乳制品中乳糖含量可优选碘量法.     

A 23S rDNA-targeted polymerase chain reaction-based system for detection of Staphylococcus aureus in meat starter cultures and dairy products.

A polymerase chain reaction-based system for detection of Staphylococcus aureus was developed. The system consisted of the following components: (i) selective enrichment, (ii) DNA isolation, (iii) amplification of DNA with primers targeted against the 23S rRNA gene, and (iv) evaluation of the specificity of the polymerase chain reaction by Southern hybridization and nested polymerase chain reaction. The method achieved a high degree of sensitivity and unambiguity as required for the detection of contaminants in food starter preparations. The method permitted detection of Staphylococcus aureus in preparations of meat starter cultures containing Staphylococcus carnosus either alone or in combination with lactobacilli, pediococci, and/or Kocuria varians. Detection limits were sufficiently low to show within 12 h the presence of 10(0) CFU of S. aureus in starter preparations containing 10(10) CFU of S. carnosus. The system was also applied to dried skim milk and cream. For detection without selective enrichment, a protocol was developed and permitted detection of 120 CFU of S. aureus in 1 ml of cream within 6 h. With nested polymerase chain reaction, the detection limit was decreased by one order of magnitude.     

Influence of alcoholic and malolactic starter cultures on bioactive amines in Merlot wines

The influence of alcoholic and malolactic fermentations on the levels of amines in Merlot wines was investigated. Saccharomyces bayanus, S. cerevisiae, Lactobacillus plantarum, Oenococcus oeni (DSM 7008 and 12923) and spontaneous fermentations were used. Four of the 10 amines investigated were detected: spermidine, serotonin, putrescine and cadaverine. When considering the factors independently, the malolactic bacteria significantly affected the levels of serotonin and total amines, whereas the fermentation yeasts significantly affected the levels of spermidine (two way Kruskal–Wallis, p ? 0.05). Spermidine levels were significantly higher in wines produced with S. cerevisiae. Significantly higher serotonin levels were found in wines made with L. plantarum. Putrescine and cadaverine were not detected in wines produced by spontaneous alcoholic fermentation or by L. plantarum. There were significant differences in alcohol content, total and volatile acidity, sulphite levels and taste quality among wines (Tukey test, p ? 0.05).     

Acceleration of Thai fish sauce fermentation using proteinases and bacterial starter cultures

ABSTRACT:  A means to accelerate fish sauce fermentation without adversely affecting fish sauce quality was investigated. Starter cultures prepared from Virgibacillus sp. SK33, Virgibacillus sp. SK37, and Staphylococcus sp. SK1-1-5 were added separately to anchovy that was hydrolyzed by 0.25% Alcalase at 60 °C for 2 h followed by 0.5% Flavourzyme at 50 °C for 4 h. The mixtures were then adjusted to contain 25% solar salt and incubated at 35 °C for 4 mo. α-Amino contents of all inoculated samples were higher than the control (without the addition of starter culture) during the course of fermentation. After 4-mo fermentation, the samples inoculated with Staphylococcus sp. SK1-1-5 contained the highest α-amino content of 733.37 ± 13.89 mM while that of the control was 682.67 ± 3.33 mM. Amino acid profiles of inoculated samples showed similar patterns to that of commercial product fermented for 12 mo, with glutamic, aspartic, and lysine being predominant amino acids. Virgibacillus sp. SK33 appeared to decrease histamine content of fish sauce by 50% when compared to the control. Volatile compounds analyzed by GC–MS of all inoculated samples fermented for 4 mo exhibited a similar pattern to those of the 12-mo-old commercial product. Samples inoculated with Staphylococcus sp. SK1-1-5 produced higher levels of volatile fatty acids and showed similar sensory characteristics to the commercial fish sauce fermented for 12 mo. Staphylococcus sp. SK1-1-5 is a potential strain that can be applied to produce fish sauce with overall sensory characteristics of traditional fish sauce in shorter time.     

应用红曲霉发酵剂生产洛伐他汀普洱茶初探

应用红曲霉菌株M13(Monascus purpureus Went)制成三种不同形式的发酵剂,接种于经灭菌处理的普洱晒青毛茶进行发酵实验,对发酵茶样的洛伐他汀含量进行测定。结果表明,初始和三翻都接种固体发酵剂的出堆茶样中积累的洛伐他汀含量最高,达到了0.291mg/g。感官审评结果表明:红曲霉发酵剂发酵的普洱茶具有米曲香的特点。应用红曲菌株制成的发酵剂可以发酵出含有洛伐他汀的普洱茶,这为洛伐他汀普洱茶的研发奠定了基础。      

Design and implementation of a strategy to reduce bacteriophage infection of dairy starter cultures

Bacteriophages can cause a significant economic loss for the dairy industry which uses lactic starter cultures to produce fermented dairy products including cheeses and yoghurt. Over the past 25 years, a number of different approaches have been explored and implemented to reduce the problems of bacteriophage infection in part through the development of bacteriophage resistant lactic acid starter culture strains. A strategy employing antisense RNA designed against essential bacteriophage replication functions has proven to be a unique system for engineering bacteriophage resistant Lactococcus lactis starter cultures. Resistance to a class of bacteriophages has been achieved, for example, by expression of an antisense RNA targeted against a conserved yet cryptic bacteriophage gene. This approach may prove useful for engineering a set of truly isogenic strains to be used in a starter culture rotation plan.     

Influence of starter cultures on the free fatty acids during ripening in Tea sausages

The influence of starter cultures on the free fatty acids content during ripening of Tea sausages, typical dry sausages produced in the south of Croatia, was studied. Three batches of Tea sausages were produced using different starter mixtures (Staphylococcus xylosus S81 and Lactobacillus sakei G20; Staphylococcus xylosus S142 and Lactobacillus sakei G20; Staphylococcus xylosus S206 and Lactobacillus sakei G20), while the control batch was produced without a starter. The amounts of free fatty acids present in the samples at the end of the ripening period were not significantly different, suggesting that the lipolytic enzymes naturally occurring in meat could play a predominant role in the free fatty acids release. Oleic and linoleic acids were present in the highest concentrations, while only small quantities of short-chain fatty acids were detected, with acetic acid being the most representative one.     

发酵剂抗氧化活性对发酵肉制品品质的影响研究进展

发酵肉制品历史悠久、风味独特、贮藏期长,深受消费者喜爱。本文从肉制品发酵过程中蛋白质降解的角度出发,结合近年发酵肉制品相关研究进展,阐述了影响肌肉蛋白质降解的因素,包括微生物蛋白酶和内源酶的作用机制、肉制品发酵核心微生物的蛋白酶水解活性;分析了肉制品发酵过程中经微生物蛋白酶或内源酶作用后肌肉蛋白质结构的变化,包括蛋白质二级、三级结构及功能性质的改变,并综述了蛋白质降解对发酵肉制品质地和风味的改善,以及蛋白质过度降解造成的品质劣变。最后对未来的研究方向进行展望,旨在为肉制品发酵控制的深入研究提供思路。     

弱后酸化发酵剂对长保质期酸奶品质特性影响的研究

研究5种弱后酸化发酵剂在搅拌型酸奶中的应用。结果表明,科.汉森公司的YF-622菌种发酵的酸奶蛋白质水解能力最弱,后酸化程度最小,30℃贮存13 d后酸度仅为89°T,并且其黏度、持水力和感官特性也明显优于其他4种菌种发酵的酸奶,乳酸菌活菌数达到国家标准的最低限制(≥106 cfu/mL)。因此,可将其应用于长保质期酸奶的生产。     

Multi-enzyme biosensors with amperometric detection for determination of lactose in milk and dairy products

 In home-made sensors coimmobilizing enzymes in thin-layer plexi-cells on natural protein membranes, three enzyme cells: β-galactosidase and galactose oxidase (A), β-galactosidase and glucose oxidase (B) and β-galactosidase, galactose oxidase and glucose oxidase (C) were built into a flow-injection-analyzer system. The lactose was decomposed and oxidized by the immobilized enzymes and the hydrogen peroxide generated during the enzymatic reactions was determined by amperometric detection. The parameters for biochemical and electrochemical reactions (concentration of buffer, temperature, flow rate) were optimized in each enzyme cell. The pH optima of the lactose measurement was determined in the three enzyme cells mentioned above. The pH optimum of the cells A, B and C were 6.4, 4.5 and 4.8, respectively. The measuring ranges were 1–5 mM, 2–10 mM and 1–5 mM, while the detection limits were 0.5, 1.0 and 0.5 mM, respectively. More than 600, 1000 and 800 samples could be measured with these cells, respectively. Commercial milk and instant dessert powder products were analysed also. Our results showed that the cells B and C were more suitable for the determination of the lactose content of milk. For samples of dairy products containing added glucose, starch and other carbohydrates, enzyme cell A could be used for the efficient determination of lactose in one step. Received: 24 August 1998 / Revised version: 9 November 1998