Yogurt Bacteria Research Articles

Combined effects of dry matter content, incubation temperature and final pH of fermentation on biochemical and microbiological characteristics of probiotic fermented milk

Combined effects of milk non-fat dry matter content (4, 8 or 12%), incubation temperature (37, 40 or 44°C) and final pH of fermentation (4.2 or 4.5) on biochemical and microbiological characteristics of probiotic fermented milk (Lactobacillus acidophilus LA-5, Bifidobacterium lactis BB-12, and yogurt bacteria) during and immediately after fermentation were investigated. Treatments containing higher dry matter contents had slower pH and redox potential decline rates, faster acidity increase rate, longer incubation time and greater final titrable acidity. Treatments fermented at higher temperatures with lower final pH displayed longer fermentation time and greater final titrable acidity. Treatments with higher dry matter non-fat contents, lower incubation temperatures and higher final pH of fermentation possessed greater viability of probiotic bacteria. The concentration of lactic acid in treatments increased in parallel with the titrable acidity and the concentration of acetic acid were proportional to the viability of bifidobacteria. Key words: Bifidobacteria, fermented milk, Lactobacillus acidophilus, probiotic, viability.

Immune-stimulating effects of lactic acid bacteria in vivo and in vitro

The health-promoting effects of lactic acid bacteria (LAB) are well recognised, making them a popular functional food ingredient. Commercially available probiotic products are often promoted as capable of improving immune defences also in healthy subjects. However, while strain-specific differences exist in the effects of LAB, conventional yoghurt bacteria have proved beneficial as well. For comparing the immunological effects of conventional and probiotic LAB, young healthy women received either a commercially available probiotic fermented milk product or a conventional yoghurt for four weeks. Both treatments showed comparable effects resulting in a stronger immunological reaction to stimuli (natural cytotoxicity against cancer cells, mitogen-induced T-lymphocyte activation and stimulated cytokine production). To study the mechanisms behind these effects, conventional (Lactobacillus delbrueckii) and probiotic (Lactobacillus rhamnosus GG), LAB were compared in vitro at the cellular level. Interestingly, L. rhamnosus GG was more potent in inducing maturation of dendritic cells (DC) that play a substantial role in directing the immune response to stimuli. In turn, L. delbrueckii provoked a higher secretion of proinflammatory cytokines as well as IL-10. These effects were, however, observed only after direct incubation of DC and LAB, not when both were separated by a layer of enterocyte-like Caco-2 cells. LAB also induced cytokine secretion in peripheral blood mononuclear cells in a similar manner and this effect was reduced in a Caco-2 cell model, suggesting a modulating influence of gut epithelial cells. While both conventional and probiotic strains modulate the immune response, specific properties may offer therapeutic options in the treatment of certain diseases.

T2024 Dying in Yoghurt – the Number of Living Bacteria in Probiotic Yoghurt Decreases Under Exposure to Room Temperature

T2024 Dying in Yoghurt – the Number of Living Bacteria in Probiotic Yoghurt Decreases Under Exposure to Room Temperature

Determination of Fatty Acids and Chemical Characteristics of Cokelek Cheese from Cows Milk Using of L. helveticus and/or Yoghurt Bacteria

Cokelek cheese is a very popular dairy product in Turkey. It is produced mainly by boiling of set yoghurt made from cow's milk and then straining in a special cloth bag. In the present work, Cokelek cheeses were manufactured from cows’ milk by fermenting with different starter cultures (yogurt bacteria, Lactobacillus helveticus or mixture of these bacteria), and then denaturing at two different temperatures (85°C or 95°C), to asses the effect on yield, chemical and sensory properties of the products. The yields of Cokelek cheeses coded Y95:C, Y85(inoculated with yogurt culture and heated at 85°C), M95, M85 (inoculated with yogurt culture and L. helveticus (1:1), and heated at 85°C or 95°C), H95 and H85 (inoculated with L. helveticus, and heated at 85°C or 95°C) was found as 19.27 ± 0.21%, 19.78 ± 0.18%, 16.59 ± 0.76%, 18.69 ± 0.39%, 19.71 ± 2.17% and 19.88 ±0.25%, respectively. Statistically, no significant difference (p>0.05) was observed among the TA %, TS %, fat/TS % and salt/TS % level of the samples during storage period. At the 45th day, the saturated fatty acid (SFA)%, total unsaturated fatty acid (TUFA)%, monounsaturated fatty acid (MUFA)% and polyunsaturated fatty acid (PUFA)% varied between 58.89 and 66.71, 27.14 and 31.80, 24.58 and 29.03, and 2.23 and 2.99, respectively. As the log counts of lactococci were determined between 2.50 ± 0.1 and 3.03 ± 0.35, the log counts of lactobacilli were found between 3.60 ± 0.26 and 4.33 ± 0.41 at the 45th day. Total sensory point of the sample made with mixture culture in boiling at 85°C was the highest at the 15th day. The investigation results showed that L.helveticus (single or mixture) might be proposed as a starter culture alternated to yoghurt bacteria in Cokelek cheese made from cow milk.

Clinical trial: the effects of a fermented milk containing three probiotic bacteria in patients with irritable bowel syndrome – a randomized, double‐blind, controlled study

The effects of probiotic bacteria in IBS remain controversial. To study the effects of a probiotic product on IBS symptoms. We randomized 74 IBS patients to receive 8 weeks of daily treatment with 400 mL milk fermented with the yoghurt bacteria and containing Lactobacillus paracasei, ssp. paracasei F19, Lactobacillus acidophilus La5 and Bifidobacterium lactis Bb12 (Cultura; active) or acidified milk without these bacteria (control). The primary endpoint was the proportion of subjects reporting adequate relief of their IBS symptoms at least 50% of the weeks. IBS symptom severity, psychological symptoms and quality of life were assessed. The proportion of responders was 38% (14/37 patients) in the active group and 27% (10/37 patients) in the control group (P = 0.3). IBS symptom severity improved significantly in both groups during the treatment period. This change was greater in the active group during the first 2 weeks, but thereafter, no significant group differences were seen. We could not detect a clearly positive effect of fermented milk containing three probiotic bacteria on GI symptoms in IBS patients compared with the control treatment. However, a trend towards a more favourable effect during the first weeks was seen in the active group.

Europe puts health claims to the test

The emergence of so-called functional foods--foods that have been modified to promote better health in one way or another--has done wonders for food company balance sheets over the past 20 years. Probiotic dairy products are a prime example. Starting in the 1990s with Yakult, a bacteria-enriched yogurt drink made by a Japanese company of the same name, sales of such products took off along with that of others, such as French food group Danone's probiotic product, labelled Activia. By launching such products, companies were anticipating consumer trends. As Sue Davies, chief policy adviser at Which? a not-for-profit consumers' organization based in the United Kingdom, puts it: People embraced food products offering health benefits because there's a natural tendency to go for the quick fix rather than cut down on saturated fat, sugar or salt, or eat more fruits and vegetables. Fast forward to today and you can't walk down the aisle of a supermarket in any developed country without seeing ads touting the benefits of additives, such as omega-3s/DHA, lycopene or antioxidants. Even sugar-packed fizzy drinks proclaim their electrolytic value and call themselves sports drinks. But does adding vitamins to sugar water make it any healthier? And what about adding extra bacteria in yogurt? [ILLUSTRATION OMITTED] Back in 2004, monthly journal Drug and Therapeutics Bulletin asked that very question and came to the conclusion that the evidence that probiotics improved intestinal flora was patchy, while the broader claim that such products increased consumers' well-being and helped them fight allergies was unreliable. Drinking lots of Activia didn't make much difference to a healthy person, they found, although it did not have any harmful effects. But that didn't mean, of course, that other products that proclaim healthy properties couldn't have harmful effects. Adding vitamins to a sweet doesn't make the sweet healthier, says Dr Francesco Branca, director of WHO's department of Nutrition and Health Development, adding that if the addition of vitamins encourages people to overindulge in sweets it can be said to be harmful. It is this issue of whether such products mislead people into unhealthy choices that is at the heart of the European Union's regulation No. 1924/2006 on nutrition and health claims, which became applicable in July of 2007 and is only now starting to deliver results. the words of Davies: Prior to 2007 there wasn't enough control in the EU to ensure that health claims actually promoted healthier choices rather than undermining some of the healthy eating advice that was given by independent nutritionists and government authorities. The idea behind the legislation is that claims made in relation to health benefits need to be backed by scientific evidence. The body that decides whether such claims are indeed backed by credible data is the European Food Safety Authority (EFSA), which provides scientific advice to the European Commission. July 2008 the Commission asked EFSA to prepare a scientific opinion on health claims that were permissible in the European Union and provided EFSA with a draft list containing 4185 entries that had been boiled down from the 44 000 claims supplied by the Member States. To date EFSA has asked for clarifications on more than half of the draft list, and in the words of Branca, the authority is drowning in paper. Part of the problem is the indigestible nature of the inputs it is trying to assess. Says Branca: In some cases you only have incomplete information as the potential effects have been obtained under experimental circumstances. But then the dose might vary, the compound might vary, and the circumstances of absorption might vary. It will be difficult to evaluate the complexities of the interactions in real diet situations. Based on the new regulation, EFSA says it approved the first batch of opinions on Article 13 health claims in July and that it will be releasing opinions on 1024 health claims by September this year. …

The Benefits of Lactic Acid Bacteria in Yogurt on the Gastrointestinal Function and Health

The nutritional value of yogurt and Lactic Acid-producing Bacteria (LAB) on the gastrointestinal health and function, have been investigated in this study. Both Lactobacillus bulgaricus and Streptococcus thermophilus (LAB) species, contribute to the formation of yogurt as a result of anaerobic fermentation of lactic acid in the milk. The present study focuses on the effect of yogurt consumption as a basic Mediterranean dietary tradition, improving the health and longevity. Among adults, life expectancy was the highest in the world and the rate of coronary heart disease, cancer and other diet related chronic disease, were among the lowest, in which yogurt is considered the main source of diary products in the Mediterranean diet, incorporated with other healthy foods (fruit, vegetable, brown bread, cereals and olive oil). Numerous studies suggested beneficial therapeutic effect of (LAB) bacteria in the yogurt on the gut health. (LAB) bacteria can protect against enteric infection and inhibit chemically Carcinogens induce tumorization in the gastrointestinal tract. Combination of Probiotics active culture and prebiotics non digestible food ingredient, beneficially affect the host by improving the survival of live microbial dietary supplement through its transit in the gut and by stimulating the activity of colon bacteria, specially Bifidobacteria and Lactobacilli genera. The benefits of yogurt consumption on the gastrointestinal function mediated through the gut micro flora, bowel transit and the enhancement of gastrointestinal immune responses. Certain disease with gastrointestinal tract such as, lactose intolerance, diarrhea, colon Cancer, inflammatory bowel disease and other bacterial infection were inhibited through high consumption of yogurt as based diary food product.

Probiotic stability of yoghurts containing Jerusalem artichoke inulins during refrigerated storage

Experimentally prepared Jerusalem artichoke inulins (JAI) were compared with two commercial chicory root inulins for their prebiotic potentials in media broth model and growth-sustaining ability in non-fat yoghurts. Experimental yoghurts were made with 12% reconstituted skim milk (RSM) supplemented with 4% inulin powders, inoculated with mixed cultures of Lactobacillus casei LC-01, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (1:0.5:0.5 based on supplier’s recommendation) and incubated overnight at 37 °C. Non-supplemented yoghurt was prepared from 16% RSM and used as control. The survival and acidifying activity of lactic and probiotic cultures in all yoghurts were investigated on weekly intervals during the shelf life of 28 days at 4 °C. Incorporation of JAI resulted in improved viability of LC-01, maintaining >7.0 log CFU/g during cold storage but did not affect the viability of yoghurt bacteria in comparison with the control.

Cholesterol-Lowering Effect of Probiotic Yogurt in Comparison with Ordinary Yogurt in Mildly to Moderately Hypercholesterolemic Subjects

Background and Aims: Hypercholesterolemia is the most important risk factor for cardiovascular diseases. In this study, we compared the effect of consuming probiotic yogurt with that of ordinary yogurt on serum cholesterol level in mildly to moderately hypercholesterolemic subjects. Methods: This randomized and crossover trial included 14 healthy subjects with serum total cholesterol 5.17–7.76 mmol/l. They did not consume yogurt for a 2-week prestudy period and added 300 g/day of milk to their diet. After this period, they were randomly allocated to 2 groups to receive either 300 g of ordinary yogurt or probiotic yogurt (fermented with a starter composed of Lactobacillus acidophilus and Bifidobacterium lactis in addition to bacteria in ordinary yogurt) for 6 weeks as a substitution for milk. After a 4-week washout period, the crossover was made and the study lasted for another 6 weeks. Blood lipid tests were done at the beginning and at the end of each period. Results: Consumption of probiotic yogurt in comparison with ordinary yogurt caused a significant decrease in serum total cholesterol (p < 0.05). Comparison of other blood lipid indices did not show any significant differences between these 2 periods. Conclusion: Yogurt containing two probiotic bacteria strains, L. acidophilus and B. lactis, had a cholesterol-lowering effect in hypercholesterolemic subjects.

Capillary zone electrophoresis for enumeration of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in yogurt

Enumeration of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus is a priority due to their importance in yogurt production. Capillary electrophoresis (CE) of both bacteria could be achieved in 7.2 min with a resolution of 3.2 in the background electrolyte (BGE) containing 4.5 mM Tris(hydroxymethyl) amminomethane (TRIS)–4.5 mM boric acid–0.1 mM ethylenediamine tetraacetate (EDTA) (TBE) buffer (pH 8.4) and 0.05% (v/v) polyethylene oxide (PEO), using a capillary of 47.5 cm (effective length) × 100 μm i.d., injection of 50 mbar × 3 s followed by −5 kV × 120 s, a voltage and temperature of 20 kV and 25 °C, respectively. Appropriate amounts of PEO in the BGE, sample preparation (i.e. vortex) and introduction were key factors for their separation. A short hydrodynamic injection followed by applying reversed polarity voltage could compress the bacteria into narrow zones, which were detected as separated single peaks. Method linearity ( r 2 > 0.99), precision (%RSDs < 9.3%), recovery (% R = 91.7–106.7%) and limit of quantitation (1.0 × 10 6 colony forming unit per mL (CFU/mL)) were satisfactory. Results from the CE analysis of both bacteria in yogurt were not statistically different from those of the plate count method ( P > 0.05). The CE method can be used as an alternative for quantitation of L. delbrueckii subsp. bulgaricus and S. thermophilus in yogurt since it was reliable, simple, cost and labor effective and rapid, allowing the analysis of 3 samples/h (comparing to 2d/sample by plate count method).

Optimization of Growth and Storage Conditions for Lactic Acid Bacteria in Yogurt and Frozen Yogurt

The optimal conditions for growth and storage of the lactic acid bacteria were studied. Both sucrose (up to 3%, w/v) and skim milk (up to 12%, w/v) increased the number of lactic acid bacteria. However, the effect of sucrose plus skim milk was not superior to that of skim milk alone. The cell number was maximal at pH 5.0-5.5 during the growth of bacteria and at pH 4.63 during the storage period of yogurt. The final cell number of yogurt stored for 150 days at −18 ≈ −12°C was 1/3 of the initial cell number.

Textural properties of mango soy fortified probiotic yoghurt: optimisation of inoculum level of yoghurt and probiotic culture

SummaryThe effect of yoghurt bacteria and probiotic culture on the textural characteristics of mango soy fortified probiotic yoghurt (MSFPY) is studied. The TA‐XT2 Texture Analyser was used to measure the textural characteristics of MSFPY prepared from blends containing varying proportions of yoghurt bacteria [Streptococcus thermophilus (ST), Lactobacillus bulgaricus (LB)] and probiotic culture [Bifidobacterium bifidus (BB), Lactobacillus acidophilus(LA)]. MSFPY samples were prepared by using blends of 78.3% toned milk, 14.5% soy milk and 7.2% mango pulp. Texture profile data were used to develop regression models for dependent variables – hardness, cohesiveness, adhesiveness, springiness and gumminess. The optimisation of culture addition was done by comparing the yoghurt with the MSFY as control sample (ST and LB at 2%, 1:1) The mean optimum culture addition rate of –1.43 (0.79%) ST, –1.51 (0.75%) LB, –1.43 (0.79%) BB and –1.10 (0.95%) LA is recommended for yielding an acceptable and good quality of MSFPY.

Postgenomic analysis of streptococcus thermophilus cocultivated in milk with Lactobacillus delbrueckii subsp. bulgaricus: involvement of nitrogen, purine, and iron metabolism.

Streptococcus thermophilus is one of the most widely used lactic acid bacteria in the dairy industry, in particular in yoghurt manufacture, where it is associated with Lactobacillus delbrueckii subsp. bulgaricus. This bacterial association, known as a proto-cooperation, is poorly documented at the molecular and regulatory levels. We thus investigate the kinetics of the transcriptomic and proteomic modifications of S. thermophilus LMG 18311 in response to the presence of L. delbrueckii subsp. bulgaricus ATCC 11842 during growth in milk at two growth stages. Seventy-seven different genes or proteins (4.1% of total coding sequences), implicated mainly in the metabolism of nitrogen (24%), nucleotide base (21%), and iron (20%), varied specifically in coculture. One of the most unpredicted results was a significant decrease of most of the transcripts and enzymes involved in purine biosynthesis. Interestingly, the expression of nearly all genes potentially encoding iron transporters of S. thermophilus decreased, whereas that of iron-chelating dpr as well as that of the fur (perR) regulator genes increased, suggesting a reduction in the intracellular iron concentration, probably in response to H(2)O(2) production by L. bulgaricus. The present study reveals undocumented nutritional exchanges and regulatory relationships between the two yoghurt bacteria, which provide new molecular clues for the understanding of their associative behavior.

MANGO SOY FORTIFIED PROBIOTIC YOGURT: EFFECT OF CULTURE ADDITION AND TEMPERATURE ON TEXTURAL CHARACTERISTICS

ABSTRACT Mango soy fortified probiotic yogurt (MSFPY) samples were prepared by using blends of toned milk (78.3%; 3% milk fat and 8.5% milk solid not fat), soy milk (14.5%) and mango pulp (7.2%) using yogurt bacteria and probiotic bacteria, namely, Bifidobacterium bifidus and Lactobacillus acidophilus. This work was conducted to see the effect of varied levels (0.5, 1, 1.5, 2 and 2.5%) of inoculum of yogurt and probiotic culture and the effect of different temperatures (10, 20 and 30C) on textural profile (hardness, cohesiveness, adhesiveness, springiness and gumminess). As per central composite rotatable design for four variables and five levels, 31 experiments were conducted. Textural profile data obtained at different temperatures of MSFPY were used to calculate temperature coefficients of all the textural properties, which were fitted into the second‐order polynomial model. Hardness temperature coefficients ranged from−0.92 to−1.97% per C, cohesiveness temperature coefficients ranged from−0.42 to 0.53% per C, adhesiveness temperature coefficients ranged from−2.74 to−3.73% per C, springiness temperature coefficients ranged from−1.47 to 5.07% per C and gumminess temperature coefficients ranged from−0.94 to−1.92% per C.PRACTICAL APPLICATIONSYogurt has been attributed nutraceutical, therapeutic and probiotic effects such as digestion enhancement, immune system boosting, anticarcinogenic activity and reduction in serum cholesterol. This study showed the effect of addition of yogurt bacteria and probiotic bacteria in combination andtemperature on textural properties. As health awareness increases among consumers, they also want the texture of the product to remain the same. If the product has to be consumed at either low or room temperature, one may predict the textural parameters of the mango soy fortified probiotic yogurt at different temperatures.

Yogures frescos frente a pasteurizados: estudio comparativo de sus efectos sobre los parámetros microbiológicos, inmunológicos y el bienestar gastrointestinal

To determine whether the beneficial effects of yogurt are dependent on the viability of lactic bacteria and exclusive to fresh yogurt, by comparison with the effects of yogurt that is pasteurized after fermentation. Using a double-blind design in a healthy adult population over 75 days, we compared the effects of fresh and pasteurized yogurt on microbiological (presence of viable bacteria in yogurt and DNA detection in feces) and immunological (nephelometry, hematometry, and flow cytometry) parameters. A questionnaire was used to assess gastrointestinal comfort. Differences in lactose absorption after ingestion of fresh or pasteurized yogurt were determined by breath hydrogen analysis. There were no significant differences in the results obtained for microbiological or immunological parameters, gastrointestinal comfort, or lactose test between the two types of yogurt ingested. Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) was isolated in 0.7% of the fecal samples analyzed. Streptococcus thermophilus was not found in any sample. DNA from lactic bacteria was detected in only 12.5% of the samples analyzed. Transit through the gastrointestinal tract affects survival of L. bulgaricus and S. thermophilus. No differences were found in the immunological parameters, gastrointestinal comfort, or lactose overload after intake of fresh or pasteurized yogurt.

Flavour profiles and survival of starter cultures of yoghurt produced from high-pressure homogenized milk

Volatile carbonyl compounds, organic acids and yoghurt bacteria counts were investigated in yoghurts made from ultra-high pressure homogenized milk. Yoghurts were manufactured from milk treated using ultra-high pressure homogenization at 200 or 300 MPa and at 30 °C or 40 °C, and compared with those produced from heat-treated milk with 3% added skim milk powder. To study the evolution of these parameters, samples were analysed after days 1, 14 and 28 of storage. Yoghurts from milk heat-treated or treated at 300 MPa had very similar profiles of organic acids and volatile compounds, as well as similar bacterial counts of both starter cultures. In comparison, yoghurts from milk treated at 200 MPa at either 30 °C or 40 °C gave different profiles, together with a sharp decrease in counts of lactobacilli. During storage, only slight differences in flavour compounds and yoghurt bacteria counts were detected, except in those samples from milk treated at 200 MPa.

Growth and activity of Bulgarian yogurt starter culture in iron-fortified milk

Bulgarian yogurts were manufactured and fortified with 8, 15 and 27 mg of iron kg(-1) of yogurt. The growth and acidifying activity of the starter culture bacteria Streptococcus thermophilus 13a and Lactobacillus delbrueckii subsp. bulgaricus 2-11 were monitored during milk fermentation and over 15 days of yogurt storage at 4 degrees C. Fortifying milk with iron did not affect significantly the growth of the starter culture during manufacture and storage of yogurt. Counts of yogurt bacteria at the end of fermentation of iron-fortified milks were between 2.1 x 10(10) and 4.6 x 10(10) CFU ml(-1), which were not significantly different from numbers in unfortified yogurts. In all batches of yogurt, the viable cell counts of S. thermophilus 13a were approximately three times higher than those of L. delbrueckii subsp. bulgaricus 2-11. Greater decrease in viable cell count over 15 days of storage was observed for S. thermophilus 13a compared to L. delbrueckii subsp. bulgaricus 2-11. Intensive accumulation of lactic acid was observed during incubation of milk and all batches reached pH 4.5 +/- 0.1 after 3.0 h. At the end of fermentation process, lactic acid concentrations in iron-fortified yogurts were between 6.9 +/- 0.4 and 7.3 +/- 0.5 g l(-1). The acidifying activity of starter culture bacteria in the control and iron-fortified milks was similar. There was no increase in oxidized, metallic and bitter off-flavors in iron-fortified yogurts compared to the control. Iron-fortified yogurts did not differ significantly in their sensorial, chemical and microbiological characteristics with unfortified yogurt, suggesting that yogurt is a suitable vehicle for iron fortification and that the ferrous lactate is an appropriate iron source for yogurt fortification.

Effect of green and black teas ( Camellia sinensis L.) on the characteristic microflora of yogurt during fermentation and refrigerated storage

The effect of tea on the fermentation and survival of yogurt microorganisms was studied. Green and black teas were added to milk at the beginning of fermentation. Acidity of yogurt products and survival of their microflora were studied during 42 days at 4 °C. Results showed that the presence of tea did not significantly ( P < 0.05) influence the yogurt characteristic microorganisms. HPLC studies demonstrated that yogurt bacteria did not affect tea catechins when they were incubated together for 48 h. Indeed, all five products reached about 10 9 CFU/ml after 6 h of fermentation. Viability during 6 weeks storage at 4 °C varied very little (8.35 < log CFU/ml < 8.65). Similarly, green and black teas had no effect on lactic acid levels of the final products (after 6 weeks of storage, acidity remained above 80 °D). According to these findings, addition of teas or tea catechins to yogurt can be recommended to take advantage of their beneficial properties on human health attributed to their antioxidant and antimicrobial activities.

Proteolytic Profiles and Angiotensin‐I Converting Enzyme and α‐Glucosidase Inhibitory Activities of Selected Lactic Acid Bacteria

This study was conducted to examine the growth, proteolytic profiles as well as angiotensin-I converting enzyme (ACE) and alpha-glucosidase (alpha-glu) inhibitory potentials of selected strains of lactic acid bacteria (LAB). Two strains each of yogurt bacteria (Streptococcus thermophilus-1275 and 285, and Lactobacillus delbrueckii ssp. bulgaricus-1092 and 1368), and probiotics (L. acidophilus-4461 and 33200, and L. casei-2607 and 15286, and 1 strain of Bifidobacterium longum 5022), were cultivated in reconstituted skim milk (RSM) at 37 degrees C and their proteolytic profiles and ACE as well as alpha-glu inhibitory activities were determined. Among all the strains of lactic acid bacteria studied, yogurt bacteria grew very well, with the exception of L. delbrueckii ssp. bulgaricus 1368 which showed a slower growth during the initial 3 h of incubation. The growth pattern corresponded well with the decrease in pH for the organisms. All the organisms showed an increase in proteolysis with time. The variations in proteolytic capabilities translated into corresponding variations in ACE inhibitory potential of these organisms. Bifidobacterium longum 5022 showed the highest ACE inhibitory potential followed by L. delbrueckii ssp. bulgaricus 1368, L. casei 15286, S. thermophilus 1275, and L. acidophilus 4461. Organisms with high intracellular enzymatic activities grew well. Also, aminopeptidases of strains of L. acidophilus 4461 and S. thermophilus 1275 that could better utilize proline containing substrates showed enhanced ACE inhibitory potential. Lactic acid bacteria possessed the ability to inhibit alpha-glu activity, which endowed them an antidiabetic property as well.

Influence of Probiotic and Conventional Yoghurt on the Status of Vitamins B1, B2 and B6 in Young Healthy Women

Background: In vitro studies indicate that yoghurt bacteria are able to generate several water-soluble vitamins and therefore yoghurt could be a good source of these micronutrients. However, whether lactobacilli or other viable bacteria release the synthesized vitamins or utilize vitamins from their surroundings is a matter of debate. This study was carried out to investigate whether probiotic and traditional yoghurt bacteria are able to influence the status of different B vitamins (B₁, B₂, B₆) in young healthy women. Methods: In this investigation, female volunteers consumed 100 g/day of probiotic (n = 17) or conventional yoghurt (n = 16) for 2 weeks (T1–T2) and 200 g/day for another 2 weeks (T2–T3). A wash-out phase lasting 2 weeks followed. Plasma and urine concentrations of thiamine (vitamin B₁), riboflavin (B₂) and pyridoxine (B₆) were analyzed using HPLC. The functional parameters, i.e. the erythrocyte transketolase (α-ETK) expressed as TPP (thiamine pyrophosphate) effect, erythrocyte glutathione reductase (α-EGR) and glutamic oxaloacetic transaminase (α-EGOT) were determined photometrically. Results: The plasma levels of vitamin B₁ increased significantly in both the probiotic (p < 0.001) and the control group (p < 0.01) when consuming 200 g yoghurt/day (T2–T3) and decreased to the baseline levels after the wash-out phase (T3–T4). Urinary excretion of thiamine and the TPP effect did not significantly change in either the probiotic or the control group during the period of daily yoghurt consumption (T1–T3). The plasma concentration of flavin adenine dinucleotide (FAD) decreased significantly (p < 0.001) after consuming 100 g yoghurt/day (T1–T2) while plasma concentrations of flavin mononucleotide (FMN) (probiotic: p < 0.01, control: p < 0.001) and free riboflavin increased significantly (probiotic: p < 0.01, control: p < 0.001). Afterwards, the levels of these parameters remained unchanged to the end of the study in both tested groups. The urinary excretion of riboflavin and α-EGR remained unaffected throughout the study in both the probiotic and the control group. The average status of vitamin B₆, evaluated by its plasma level, urinary excretion and α-EGOT was unaffected by daily intake of 100 g (T1–T2) and 200 g yoghurt (T2–T3), respectively, for 4 weeks (T1–T3). Conclusion: The results of the present study indicate that daily consumption of 200 g of both, probiotic and conventional yoghurt for 2 weeks can contribute to the total intake of vitamin B₁ and B₂ reflected by increased levels of plasma thiamine and free riboflavin in healthy women. The diminished plasma FAD and increased FMN concentrations, observed during the period of daily yoghurt consumption in both groups, may be the result of enhanced immune function and an oxidant/antioxidant imbalance, caused by the daily intake of lactic acid bacteria. Since the long term status parameters of all three investigated vitamins (B₁, B₂, B₆) remained unaffected during the investigation the changes in plasma concentrations seem more likely the result of regular yoghurt consumption as a fermented dairy product, rather than of the specific intake of probiotic bacteria.