Nagendra P. Shah

Viability of Yoghurt and Probiotic Bacteria in Yoghurts Made from Commercial Starter Cultures

Viability of yoghurt and probiotic bacteria was assessed during manufacture and 35 d storage in yoghurt made from four commercial starter cultures. The titratable acidity, pH and dissolved oxygen content showed similar patterns of increase or decrease during manufacture and storage of yoghurt, whereas concentration of hydrogen peroxide increased in the product prepared with cultures that contained L. delbrueckii ssp. bulgaricus. The increase in numbers of probiotic organisms during manufacture and the viability of these organisms during storage were dependent on the species and strain of associative yoghurt organisms. The viability of L. acidophilus was affected by the presence of L. delbrueckii ssp. bulgaricus, whereas bifidobacteria exhibited better stability in the yoghurt prepared from cultures that contained L. delbrueckii ssp. bulgaricus. The viability of both probiotic organisms was improved when the dissolved oxygen concentration was low in the product. The storage temperature of yoghurt affected the viability of bifidobacteria, but not L. acidophilus. The variations in titratable acidity, pH, dissolved oxygen and hydrogen peroxide were almost identical at storage temperatures of 4 and 10 °C. In one of the commercial cultures, 3 log cycles inhibition of bifidobacteria was observed from initial counts of >106 mL−1.

Effects of milk-derived bioactives: an overview.

Milk contains various components with physiological functionality. Peptides derived from caseins and whey proteins including opioid peptides, antihypertensive peptides, casein phosphopeptides, alpha- and beta-lactorphins and albutensin have been shown to possess various bioactive properties. This review considers an overview of the bioactive components in milk proteins and whey and their physiological function.

Survival of Lactobacillus acidophilus and Bifidobacterium bifidum in Commercial Yoghurt During Refrigerated Storage

Abstract 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 10 7 –10 8 g −1 viable cells of L. acidophilus , whereas the other two products contained ⩽ 10 5 of this organism initially. Similarly, the initial count of B. bifidum was 10 6 –10 7 g −1 in two of five products, while the viable numbers of this organism were ⩽ 10 3 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.

Effectiveness of ascorbic acid as an oxygen scavenger in improving viability of probiotic bacteria in yoghurts made with commercial starter cultures

The viability of yoghurt and probiotic bacteria was assessed during manufacture and 35 days storage of yoghurt supplemented with four levels of ascorbic acid using four commercial starter cultures. There were no marked differences in titratable acidity and pH of the yoghurt, whereas oxygen content and redox potential varied in yoghurts with various levels of ascorbic acid. Hydrogen peroxide content was initially higher in the products prepared with starter cultures that contained Lactobacillus delbrueckii ssp. bulgaricus. During storage of yoghurt, increase in oxygen content and redox potential and percentage retention of ascorbic acid were identical for all four starter cultures, but different at various levels of ascorbic acid. The oxygen content and redox potential gradually increased during storage in plastic cups and remained lower with higher levels of ascorbic acid. Loss of ascorbic acid occurred during manufacture and storage, with an average retention of only 15–20% after about 35 days storage of yoghurt at 4 °C. The viable counts of Streptococcus thermophilus were lower, whereas those of L. delbrueckii ssp. bulgaricus were higher, with increasing concentration of ascorbic acid. The counts of Lactobacillus acidophilus during storage decreased less rapidly with increasing concentration of acsorbic acid for all four starter cultures, whereas the counts of bifidobacteria remained unchanged.

Effect of cysteine on the viability of yoghurt and probiotic bacteria in yoghurts made with commercial starter cultures

Viability of yoghurt bacteria (Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus) and probiotic bacteria (Lactobacillus acidophilus and bifidobacteria) was assessed during manufacture and 35d storage in yoghurts made with four commercial starter cultures supplemented with 0, 50, 250 and 500mg L−1 cysteine. Incubation time to reach a pH of 4.5 was greatly affected by the addition of cysteine. During refrigerated storage, the relative drop in pH was higher in yoghurts containing 250 and 500mg L−1 cysteine, but similar in yoghurts prepared with 0 and 50mg L−1 cysteine. The redox potential remained negative for 25–30d in yoghurt supplemented with 500mg L−1 cysteine, but remained positive throughout storage in yoghurt made without cysteine. The redox potential gradually increased to positive values in all yoghurt samples; however, the rate of increase was affected by the level of cysteine and the type of starter culture. Supplementation with 50mg L−1 of cysteine promoted the growth of yoghurt bacteria in yoghurts made with all the four commercial starter cultures. The growth of S. thermophilus was adversely affected with cysteine above 50mg L−1 and electron micrographs showed cellular damage at 500 mg L−1 cysteine. Counts of L. acidophilus during manufacture and storage were higher in yoghurt containing 250 mg L−1 cysteine. Addition of cysteine adversely affected the viability of bifidobacteria in yoghurts made with starter cultures that contained both yoghurt bacteria, whereas the viability was improved in yoghurts made with starter cultures that contained S. thermophilus as yoghurt bacteria.

Selective enumeration of Lactobacillus casei from yogurts and fermented milk drinks

A selective medium (LC agar) was developed for enumeration of Lactobacillus casei populations from commercial yogurts and fermented milk drinks that may contain strains of yogurt bacteria (Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus), probiotic bacteria (Lactobacillus acidophilus and bifidobacteria) and L. casei. Appropriate dilutions were pour-plated in specially formulated LC agar acidified to pH 5.1 and the plates incubated at 27°C for 72 to 96 h under anaerobic conditions. Growth of S. thermophilus was prevented by adjusting pH to 5.1. L. delbrueckii ssp. bulgaricus did not ferment ribose as the carbon source, as a result the organisms did not form colonies. L. acidophilus formed colonies on MRS-ribose agar; however, this organism did not grow in the specially formulated LC agar containing ribose. Similarly, Bifidobacterium spp. did not form colonies in LC agar. L. casei formed colonies on LC agar.

Improving viability of Lactobacillus acidophilus and Bifidobacterium spp. in yogurt

Abstract 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 10 6 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.

Effects of a synbiotic containing Lactobacillus acidophilus ATCC 4962 on plasma lipid profiles and morphology of erythrocytes in hypercholesterolaemic pigs on high- and low-fat diets

The aim of this study was to evaluate the effect of a synbiotic containing Lactobacillus acidophilus ATCC 4962, fructooligosaccharide, inulin and mannitol on plasma lipid profiles and erythrocyte membrane properties in hypercholesterolaemic pigs on high- and low-fat diets. Twenty-four white male Landrace pigs were randomly allocated to four treatment groups for 8 weeks (n 6). Treatment factors were the supplementation of synbiotic (with and without) and dietary fat (5 and 15 %). The supplementation of synbiotic reduced plasma total cholesterol (P = 0.001), TAG (P = 0.002) and LDL-cholesterol (P = 0.045) for both dietary fats. A higher concentration of esterified-cholesterol in HDL of pigs supplemented with synbiotic than the control regardless of dietary fat (P = 0.036) indicated that cholesterol was reduced in the form of cholesteryl esters. Reduced concentration of cholesteryl esters (P < 0.001) and increased concentration of TAG (P = 0.042) in LDL of pigs on synbiotic suggested that LDL-cholesterol was reduced via the hydrolysis of smaller and denser LDL particles. The erythrocytes of pigs without any synbiotic showed more prevalence of spur cells than those given the synbiotic, as supported by the higher cholesterol: phospholipid ratio in erythrocytes (P = 0.001). Also, membrane fluidity and rigidity were improved as supported by the decreased fluorescence anisotropies in the Hb-free erythrocyte membrane of pigs given synbiotic (P < 0.001). The administration of the synbiotic reduced plasma TAG, total cholesterol and LDL-cholesterol in hypercholesterolaemic pigs, possibly in the form of cholesteryl esters, via the interrelated pathways of lipid transporters (VLDL, LDL and HDL). The synbiotic also reduced deformation of erythrocytes via improved membrane fluidity and permeability.

Bioavailability of isoflavone phytoestrogens in postmenopausal women consuming soya milk fermented with probiotic bifidobacteria

We investigated the effects of consuming an isoflavone aglycone-enriched soya milk containing viable bifidobacteria on urinary isoflavone excretion and percentage recovery. Sixteen postmenopausal women were randomly divided into two groups to consume either fermented or non-fermented soya milk. Each group participated in a double-blind, crossover study with three 14 d supplementation periods, separated by a 14 d washout. Subjects ingested three daily dosages of isoflavone via the soya milk and collected four 24 h pooled urine specimens per supplementation period. Soya milks were prepared with soya protein isolate and soya germ, followed by fermentation with bifidobacteria. Isoflavone levels were quantified using HPLC. Non-fermented soya milks at 20, 40 and 80 mg isoflavone/200 ml contained 10 %, 9 % and 7 % aglycone, respectively, with their fermented counterparts containing 69 %, 57 % and 36 % aglycone (P<0.001). A trend to a greater percentage urinary recovery of daidzein and glycitein was observed among women consuming fermented soya milk at a dosage of 40 mg isoflavone (P=0.13). A distinct linear dose response for the fermented soya milk group (R2=0.9993) compared with the non-fermented group (R2=0.8865) suggested less interindividual variation in isoflavone absorption. However, total urinary isoflavone excretion was similar for both groups (P>0.05), with urinary isoflavone recovery at approximately 31 %. Increasing the isoflavone dosage correlated positively with its urinary excretion, but urinary percentage recovery of isoflavone was inversely related to dosage level. Hence, a modest dosage ranging from 20 to 30 mg/d may provide the most bioavailable source of isoflavone, regardless of whether it is via an aglycone-rich fermented soya milk or a glucoside-rich soya milk.

Effect of Partial Substitution of NaCl with KCl on Halloumi Cheese during Storage: Chemical Composition, Lactic Bacterial Count, and Organic Acids Production

The effect of partial substitution of NaCl with KCl on chemical composition, lactic bacterial count, and organic acids profile of Halloumi cheese was investigated. Halloumi cheeses were made and kept in 4 different brine solutions at 18% including NaCl only (HA), 3NaCl : 1KCl (HB), 1NaCl : 1KCl (HC), and 1NaCl : 3KCl (HD) and then stored at 4 degrees C for 56 d. No significant effect was observed between control and experimental cheeses in terms of moisture, fat, protein, lactic bacterial count, and pH values at the same storage period. There was a significant difference in ash, sodium, and potassium contents among experimental cheeses at the same storage period. Ash, sodium, and potassium contents increased significantly during storage at same salt treatment. There was no significant difference in lactic and citric acid contents among experimental cheeses and that of the control. In contrary, there was a significant difference in acetic acid among experimental cheeses. A strong positive correlation was observed between ash, Na, and K contents. An inverse correlation between organic acids and both Na and K contents was also observed.