Improving viability of Lactobacillus acidophilus and bifidobacteria in yogurt using two step fermentation and neutralised mix

Fermentation with probiotic bacteria and then with yogurt bacteria increased the initial counts of Lactobacillus acidophilus 2409 and Bifidobacterium longum 1941 in yogurt and their viability during six weeks storage at 4°C was satisfactory. Neutralisation of mix with Ca(OH)2 also increased initial counts of L. acidophilus 2409 and B. longum 1941 with satisfactory viability. Two-step fermentation increased the incubation time by 2 h and neutralisation of mix with Ca(OH)2 by 20 to 60 min.link_to_subscribed_fulltex

A simple method for selective enumeration of lactobacillus acidophilus in yogurt supplemented with L. acidophilus and bifidobacterium spp

Effects of various antibiotics and of addition of various sugars as sole carbon source to minimal nutrient agar base were studied in order to develop a simple and reliable method for selective enumeration of L acidophilus in yogurt containing Streptococcus thermophilus, Lactobacillus delbrueckii ssp. bulgaricus, L. acidophilus, and Bifidobacterium spp. Application of antibiotics was found to be unsuitable for selective enumeration of L acidophilus. Use of salicin as a sole carbon source in the minimal nutrient base medium was found to suppress the growth of all the 4 groups of bacteria studied except that of L. acidophilus. Salicin medium was successfully used for selective enumeration of L acidophilus from pure cultures and from yogurts containing the 4 groups of lactic acid bacteria.link_to_subscribed_fulltex

Antimutagenic properties of probiotic bacteria and of organic acids

Antimutagenic activities of live and killed cells of 6 strains of Lactobacillus acidophilus and 9 strains of bifidobacteria and of organic acids usually produced by these probiotic bacteria were determined using 8 potent chemical mutagens and promutagens. The mutagens and promutagens used were N-methyl, N'-nitro, N-nitrosoguanidine; 2-nitroflourene; 4-nitro-O- phenylenediamine; 4-nitroquinoline-N-oxide; Aflatoxin-B; 2-amino-3-methyl- 3H-imidazoquinoline; 2-amino-1-methyl-6-phenyl-imidazo (4,5-b) pyridine, and 2-amino-3-methyl-9H-pyrido (3,3-6) indole. The mutagenicity of these mutagens and antimutagenic activity of probiotic bacteria against the mutagens were determined according to the Ames TA-100 assay using a mutant Salmonella typhimurium. Efficiency of bacterial cells in binding or inhibiting these mutagens was also investigated. Live cells of probiotic bacteria showed higher antimutagenic activity and their efficiency in inhibiting the mutagens was better than killed bacterial cells. Live bacterial cells bound or inhibited the mutagens permanently, whereas killed bacteria released mutagens upon extraction with dimethyl sulfoxide. Among the organic acids, butyric acid showed highest inhibition of mutagens followed by acetic acid. Lactic and pyruvic acids did not show appreciable levels of inhibition.link_to_subscribed_fulltex

Improving viability of Lactobacillus acidophilus and Bifidobacterium spp. in yogurt

Viability of probiotic bacteria was assessed in yogurt prepared using ruptured or whole cells of yogurt bacteria (Lactobacillus delbrueckii ssp. bulgaricus 2515 and Streptococcus thermophilus 2010), and whole cells of probiotic bacteria (Lactobacillus acidophilus 2409 and one species of Bifidobacterium; B. longum 1941, B. pseudolongum 20099, B. infantis 1912, B. bifidum 1900 or B. bifidum 1901). Yogurt bacterial cells were ruptured to release their intracellular β-galactosidase (β-gal) and reduce their viable counts to improve the viability of probiotic bacteria. Viable counts of probiotic bacteria after fermentation were 2 log cycles higher in yogurt made with ruptured yogurt bacteria and whole cells of probiotic bacteria and their viability after 6 weeks storage remained above the recommended level of 106 cfy g-1, possibly due to the higher level of β-gal released as a result of rupture of yogurt bacterial cells. Yogurt made with ruptured cells of yogurt bacteria contained less hydrogen peroxide during fermentation. Ruptured or whole cells of yogurt bacteria produced similar levels of acetaldehyde. Thus, with the approach outlined in this study, viability of probiotic bacteria could be improved without compromising the flavour of the product.link_to_subscribed_fulltex

Evaluation of media for selective enumeration of Lactobacillus acidophilus and Bifidobacterium species

Seven different media were evaluated to determine their suitability for selective enumeration of Lactobacillus acidophilus and Bifidobacterium spp using six strains of Streptococcus salivarius ssp thermophilus, five strains of Lactobacillus delbrueckii ssp bulgaricus, six strains of Lactobacillus acidophilus and nine strains of Bifidobacterium spp. The media which were evaluated were NNLP agar, Bile agar, MRS-galactose agar, MRS-maltose agar, MRS-dextrose agar, MRS-L-arabinose agar and RCA agar. NNLP agar was found to be suitable for selective enumeration of B. bifidum, B. longum, B. pseudolongum and B. thermophilum as this medium suppressed the growth of S. salivarius thermophilus, L. delbrueckii ssp bulgaricus and of L. acidophilus. Bile agar can be used for selective enumeration of L. acidophilus from a product containing L. acidophilus and B. bifidum, B. adolescentis, B. breve or B. longum 20097. Other strains of bifidobacteria grew in Bile agar. MRS-maltose agar can be used for selective enumeration of L. acidophilus from yogurt organisms in a product which does not contain Bifidobacterium spp. MRS-L arabinose agar suppressed the growth of S. salivarius ssp thermophilus, L. delbrueckii ssp bulgaricus, L. acidophilus and bifidobacteria except that of B. longum and B. pseudolongum. Thus, this medium can be used for selective enumeration of B. longum and B. pseudolongum only. In a separate experiment, MRS-L-arabinose agar and NNLP agar were used to selectively enumerate B. longum 1941 from yogurt prepared with S. salivarius ssp thermophilus, L. delbrueckii ssp bulgaricus, L. acidophilus and B. longum 1941 as starter cultures. B. longum colonies were easily differentiated from that ofL. acidophilus, which formed tiny colonies, while S. salivarius ssp thermophilus and L. delbrueckii ssp bulgaricus did not form any colonies.link_to_subscribed_fulltex

Survival of bifidobacteria during refrigerated storage in the presence of acid and hydrogen peroxide

26 Bifidobacteria (survival during refrigerated storage) Survival of 9 strains of bifidobacteria (Bifidobacterium bifidum 1900 and 1901, B. longum 1941 and 20097, B. infantis 1912, B. adolescentis 1920, B. breve 1930, B. pseudolongum 20099 and B. thermophilum 20210) during 6 weeks storage at 4°C in the presence of acid and acid and hydrogen peroxide was studied. Cultures grown in sterile nonfat dry milk for 18 h at 37°C were adjusted to pH 4.3, 4.1, 3.9 and 3.7 with 4N lactic acid, and hydrogen peroxide was added to another set of cultures adjusted to pH 3.7 to 4.3 to achieve a final concentration of 10O μg/ml. After the pH and hydrogen peroxide adjustments, the cultures were stored at 4°C for 6 weeks, and samples were taken at 6 d intervals to determine the viable counts of bifidobacteria. The survival of B. bifidum 1900 and 1901, B. adolescentis 1920, B. breve 1930, B. longum 20097 and B. thermophilum 20210 was adversely affected in presence of acid, and the viability of these strains was even more affected in presence of acid and hydrogen peroxide, indicating a synergistic inhibition of bifidobacteria by acid and hydrogen peroxide. However, B. infantis 1912, B. longum 1941 and B. pseudolongum 20099 survived well in presence of acid and acid and hydrogen peroxide, suggesting that these strains can be used as dietary adjuncts in fermented dairy foods.link_to_subscribed_fulltex

Growth, viability and activity of Bifidobacterium spp. in skim milk containing prebiotics

Growth, activity and mean doubling time (Td) of five Bifidobacterium species in the presence of four types of prebiotics, and concentrations of acetic and lactic acids were determinted during fermentation and after 4 weeks of refrigerated storage. The Td was lowest for B. animalis with raftilose and inulin. Retention of viability of bifidobacteria was greatest with hi-amylose corn starch (hi-maize). The average pH of skim milk at the end of 4 wks storage averaged 4.34 (for B. animalis with raftilose) to 4.07 (for B. longum with inulin). The highest levels of acetic acid and lactic acid were produced by B. pseudolongum with lactulose and B. infantis with lactulose, respectively.link_to_subscribed_fulltex

Survival of Lactobacillus acidophilus and Bifidobacterium bifidum in commercial yoghurt during refrigerated storage

Samples of five brands of commercial yoghurt were obtained directly from the processors and enumeration of viable Lactobacillus acidophilus and Bifidobacterium bifidum and determination of pH was carried out at three-day intervals over a five-week period. Three of the five products contained 107-108 g-1 viable cells of L. acidophilus, whereas the other two products contained ≤ 105 of this organism initially. Similarly, the initial count of B. bifidum was 106-107 g-1 in two of five products, while the viable numbers of this organism were ≤ 103 in the other three products. All the products showed a constant decline in the viable count of L. acidophilus and B. bifidum during storage. Initial pH values ranged from 4.07 to 4.36 and these declined after five weeks of storage to pH 3.8-4.26. © 1995.link_to_subscribed_fulltex