Non-fermented Milk Research Articles

The Association of Yogurt Starters with Lactobacillus casei DN 114.001 in Fermented Milk Alters the Composition and Metabolism of Intestinal Microflora in Germ-Free Rats and in Human Flora–Associated Rats

The aim of this study was to compare the effects of milk and of various fermented milks on the composition and metabolic activities of the intestinal microflora. Groups of eight rats were fed for 6 wk a diet containing 30% nonfermented milk (M), yogurt (Y), milk fermented with Lactobacillus casei (LcFM) or milk fermented with the association of L. casei DN 114.001 and yogurt starters (LcYFM). In the first study, the survival of the lactic acid bacteria from the fermented milks was assessed by bacterial enumeration in feces of germ-free rats (GF rats) fed milk or fermented milks. The metabolic activities of the lactic acid bacteria were studied in these rats by the measurement of glycolytic activities and products of bacterial fermentation, i.e., acetate and lactate (isoforms L and D). In a second study, the effects of fermented milks on the composition and metabolism [gas, glycolytic activities, short-chain fatty acids (SCFA), alcohol and ammonia] of human flora were studied using human flora–associated rats (HF rats). In GF rats, the survival of L. casei in the feces did not differ between those fed the LcFM and LcYFM diets. L. bulgaricus was detected in the feces of the rats fed Y, whereas Streptoccus thermophilus was found in the feces of the LcYFM group. In HF rats, fecal concentration of Bifidobacteria was greater in the LcFM group than in the others. β-Glucuronidase (EC 3.2.1.31) activity was lower in rats fed LcFM and Y than in those fed M and LcYFM, whereas β-galactosidase (3.2.1.23), α-glucosidase (EC 3.2.1 20) and β-glucosidase (EC 3.2.1.21) activities were higher in the LcYFM group compared with the others. Methane excretion was higher in rats fed Y than in other groups. Cecal SCFA concentrations did not differ in LcFM, Y and M groups, but total SCFA, acetate, propionate and butyrate were significantly greater in the LcYFM group. These results suggest that milk fermented with the combination of L. casei and yogurt starters leads to specific effects that are different from the simple addition of the effects found with yogurt and milk fermented with L. casei. These specific effects are potentially beneficial to human health.

Survival During Frozen and Subsequent Refrigerated Storage of Lactobacillus acidophilus Cells as Influenced by the Growth Phase

Cells of Lactobacillus acidophilus propagated in peptonized milk nutrient broth maintained at pH 5 were harvested during the late logarithmic (log) phase and at 6h into the stationary phase of growth. Concentrated cultures were prepared from each age of cells, frozen, and stored at –196°C. The concentrated cultures were assayed for numbers of total and bile-tolerant lactobacilli, β-galactosidase activity, and ability to assimilate cholesterol before and after storage at –196°C. Nonfermented acidophilus milk, prepared following 28 d of storage at –196°C from each concentrated culture, was tested before and after 0, 7, 14, 21, and 28 d of storage at 7°C. No decrease in numbers of total or bile-tolerant lactobacilli, β-galactosidase activity, or amount of cholesterol assimilated was observed for any of three strains studied during storage at –196°C. There were no significant differences between the two harvest times during storage at this temperature for any of the three strains. However, when the cells were suspended in milk and stored at 7°C, the numbers of total and bile-tolerant lactobacilli declined over time as did the β-galactosidase activity and the ability to assimilate cholesterol. The cells from L. acidophilus 223, harvested 6h into the stationary phase, exhibited significantly less decrease in total numbers during extended storage at 7°C than did the cells harvested in the late logarithmic phase. There was little or no difference in the decline in numbers of total lactobacilli between the two harvest times for strains 606 and 107. All strains decreased significantly in β-galactosidase activity and the ability to assimilate cholesterol during storage in milk at 7°C with no significant differences between the two harvest times.

Inhibition of Psychrotrophic Organisms by Propionicin PLG-1, a Bacteriocin Produced by Propionibacterium thoenii

Propionibacterium thoenii strain P127, which produces the bacteriocin propionicin PLG-1, was grown in a skim milk medium and produced bacteriocin in that medium. No bacteriocin activity was detected in skim milk medium in which strain P127-1, a bacteriocin-negative variant of strain P127, had been grown.Five psychrotrophic spoilage or pathogenic organisms (one strain each of Listeria monocytogenes, Pseudomonas fluorescens, Vibrio parahaemolyticus, Yersinia enterocolitica, and one strain of Corynebacterium sp.) were incubated for 24h in laboratory medium, nonfermented skim milk, and skim milk that had been fermented by strain P127 or P127-1. Strains were inhibited only in the skim milk fermented by strain P127, as evidenced by loss in numbers of viable cells after 24h at 10°C and less growth than in other media after 24h at optimal growth temperatures. Growth of selected strains was delayed or slowed during prolonged incubation (21 d) at 10°C. Propionicin PLG-1 shows promise as a preservative for food products.

Bacterial Growth and Volatile Compounds in Yoghurt‐Type Products from Soymilk ContainingBifidobacterium ssp

ABSTRACTThe growth of bacteria normally used to produce yoghurt was compared in soymilk and cow milk. Whether or notBifidobacterium ssp. was present, fermented soymilks [soyoghurt (S), soyoghurt + bifi‐dobacteria (SB)] were less acidic than fermented cow milks [yoghurt (Y), yoghurt + bifidobacteria (YB)]. When bifidobacteria were present (in SB), streptococci were more numerous than lactobacilli. Bifidobacteria in YB stimulated maximal growth of both yoghurt bacteria. In comparison to nonfermented milks, acetaldehyde and diacetyl increased in all cultures. Ethanol increased only in S/SB and acetone was detected only in Y/YB. Quantities of volatile products in Y/'YB were slightly lower than those in Y/S. In all cultures, n‐hexanal was almost totally absent.

Milk consumption, lactose and copper in the aetiology of ischaemic heart disease

Milk is a poor source of copper — a nutrient which is known to be limiting or marginal in many western diets. Lactose (a major nutritional constituent of milk) may interfere with copper utilization in milk and in the overall diet. It is postulated that the strong association between the consumption of milk and dairy products (especially fresh milk and non-fermented milk products) and the incidence of ischaemic heart disease (IHD) indicates a central role for a dietary copper deficiency in the aetiology of this disease.

Effect of a Mixture of Lactobacillus casei and Lactobacillus acidophilus Administered Orally on the Immune System in Mice

The effects of an orally-administered mixture of Lactobacillus casei and Lactobacillus acidophilus on the immune system in Swiss albino mice were studied. Non-fermented milk containing viable cultures of both microorganisms was fed for different consecutive days to the animals, the effect of such feeding on their immune system was evinced by macrophage and lymphocyte activation. An increase both in the in vitro phagocytic activity of peritoneal macrophages and in the carbon clearance activity was observed. As regard the lymphocytic activity, the mixture produced a higher activation than that in the control mice. The enhanced macrophage and lymphocytic activity by administering cultures via the oral route, suggest the advisability of using the mixture of bacteria for a more efficient stimulation of the host immune response.

Growth of Mice Fed Milk Fermented with Lactobacillus acidophilus

The effects of milk fermented by Lactobacillus acidophilus on growth of Swiss albino mice were tested. Mice were fed a stock diet and drinking water containing one of these milk additions: no supplementary milk (control), 10% liquid skim milk, 10% milk containing a viable culture of L. acidophilus, or 10% milk fermented by L. acidophilus. After 4 weeks mice receiving the fermented acidophilus milk had consumed more total feed and gained more weight than had the control mice, but not more than those fed the liquid skim milk or the nonfermented acidophilus milk.

Effect of feeding fermented milk on the incidence of chemically induced colon tumors in rats.

The effect of feeding skim milk fermented by Streptococcus thermophilus or Lactobacillus bulgaricus on the incidence of chemically induced colon tumors was studied in rats. Weanling Fisher-344 rats were fed chow plus skim milk (SM), chow plus SM fermented by S. thermophilus, chow plus SM fermented by L. bulgaricus, or chow plus water until sacrifice at 36 weeks, or before if moribund. Colon tumors were induced by s.c. injections of 1,2-dimethylhydrazine hydrochloride during weeks 3 through 22. The control (chow + water) group received saline injections. The survival rate of the rats fed fermented milks was significantly higher than that of the rats fed nonfermented milk. The latter had a significantly higher incidence of ear-duct tumors than the rats receiving fermented milk. The percentage of rats showing colon tumors was similar among all three experimental groups. The control group did not have any tumors. The rats receiving fermented milk had a significantly higher incidence of small-intestine tumors than those receiving nonfermented milk. The rats on S. thermophilus milk had the lowest percentage of malignant colon tumors of the three experimental groups. Results indicated that the feeding of fermented milks altered the metabolism of 1,2-dimethylhydrazine and shifted the target organ from the ear duct to the small intestine. In addition, the colon tumor distribution for the fermented-milk groups appeared to shift toward the anus.

Influences of Temperature on Lactobacilli of Nonfermented Acidophilus Milks

Growth temperature ranges, generation times, and thermal resistance data were determined for four lactobacilli isolated from cultures used in manufacturing nonfermented acidopbilus milks. One isolate was Lactobacillus acidophilus, judged by physiological characteristics and a guanine plus cytosine content of 36.8 mole %. Another resembled Lactobacillus acidophilus in physiological characteristics but had high guanine plus cytosine content (52.6mol %). Two others apparently were Lactobacillus lactis.

Effect of Fermentation on Lactose, Glucose, and Galactose Content in Milk and Suitability of Fermented Milk Products for Lactose Intolerant Individuals

The lactose, glucose, and galactose content in various fermented milk products was studied by enzymatic methods. Lactose was decreased in all fermented products. After 11 days storage of yogurt the lactose content decreased to about 2.3 g/100g compared to 4.8 g/100g in nonfermented milk. During the same period, galactose content increased from traces in milk to 1.3 g/100g in yogurt. Results were similar with acidophilus and bifidus milk. Buttermilk, kefir, and ropy milk showed 26, 30, and 20% decreases in lactose content.Eight lactose intolerant individuals showed symptoms of abdominal distress and diarrhea following consumption of 500ml of low fat milk whereas ingestion of the same quantity of yogurt or acidophilus milk did not result in any symptoms. Fermented milk products should be considered in formulating diets for lactose-intolerant subjects.

Inhibition of Candida albicans by Lactobacillus acidophilus

Candida albicans grew at pH 4.6 or above in nutrient broth containing 5% glucose but was retarded at pH 7.7 by filtrates of Lactobacillus acidophilus grown in casitone broth. Vaginal implantation of nonfermented acidophilus milk, yogurt, or low-fat milk for preventing recurrence of monilia vaginitis subsequent to treatment with Nystatin was studied with 30 women. Reinfections within 3 mo according to product received were: no milk product, 3; yogurt, 1; nonfermented acidophilus milk, 1; and low-fat milk, 0.

Enumeration of Lactobacillus acidophilus with the Agar Plate Count

Higher plate counts on MRS agar were obtained under anaerobic conditions for three of four strains of Lactobacillus acidophilus and commercially prepared nonfermented acidophilus milks (products A and B) made with two of the strains. Average values for aerobic counts of products A and B were 87 and 60%, respectively, of those for corresponding anaerobic counts. Incubation of plates poured with MRS agar for 72 ± 3 h at 37 C was sufficient for maximal counts. Two strains and the nonfermented acidophilus milks gave highest counts on Standard Methods Agar (SMA). Greatest numbers of bile-resistant colonies were indicated by MRS agar (with 0.2% oxgall). The average of plate counts for products A and B determined on MRS agar with oxgall was 65% of that for corresponding plate counts determined on MRS without oxgall. Buffered distilled water, 0.9% NaCl, and 1% peptone each served satisfactorily as diluent. Overlaying MRS agar in poured plates with additional medium was not advantageous. Plate counts of samples that had been frozen and stored at −26 C or in dry ice were as high as those of duplicate samples that had been stored at 1.7 C.

Influence of Consuming Nonfermented Milk Containing Lactobacillus acidophilus on Fecal Flora of Healthy Males

A milk beverage was prepared by adding a commercially available concentrated culture of Lactobacillus acidophilus to pasteurized low-fat milk. The culture did not alter the flavor of the milk. Consumption of the milk by healthy adult men increased facultative lactobacilli in their feces. No significant effects were observed on numbers of coliforms or anaerobic lactobacilli including bifidobacteria. After consumption of the milk was stopped, the numbers of facultative lactobacilli in the feces decreased. However, in some cases the test subjects retained considerably higher numbers than they had prior to consuming the milk containing Lactobacillus acidophilus. This was particularly true for those whose feces contained small numbers of the facultative lactobacilli before the feeding periods.