Yogurt Bacteria Research Articles

Characterization of Bacteria in Nigerian Yogurt as Promising Alternative to Antibiotics in Gastrointestinal Infections

ABSTRACTGastrointestinal infections are endemic in Nigeria and several factors contribute to their continual survival, including bacterial resistance to commonly used antibiotics. Nigerian yogurts do not include probiotics, and limited information is available about the antimicrobial properties of the fermenters in the yogurt against gastrointestinal pathogens. Therefore, the antimicrobial potentials of bacteria in Nigeria-produced yogurts against intestinal pathogens were investigated in this study. Viable counts of lactic acid bacteria (LAB) in 15 brands of yogurt were enumerated and the bacteria identified by partial sequencing of 16S rRNA gene. Susceptibility of the gastrointestinal pathogens (Salmonella, Shigella and E. coli ) to antibiotics by disc diffusion method, to viable LAB by the agar overlay method, and to the cell-free culture supernatant (CFCS) of the LAB were investigated. Co-culture analysis of LAB and pathogens were also done. Viable counts of 1.5 × 1011 cfu/ml were observed in some yogurt samples. Two genera were identified: Lactobacillus (70.7%) and Acetobacter (29.3%). The Lactobacillus species reduced multidrug-resistant gastrointestinal pathogens by 4 to 5 log while the zones of inhibition ranged between 11 and 23. The Lactobacillus and Acetobacter strains examined displayed good activities against the multidrug-resistant tested pathogens. This is the first report of antimicrobial activities of acetic acid bacteria isolated from yogurt in Nigeria.

EFFECTS OF BAKER’S YEAST ADDITION ON SOME PROPERTIES AND PHYTIC ACID CONTENT OF TARHANA PREPARED WITH DIFFERENT CEREAL AND LEGUME PRODUCTS

Fermentation is an important process for improvement of functional properties of food product. It is also one of the most effective methods for reducing phytic acid content. Tarhana production contains 7 day fermentation by yoghurt bacteria with and without bakers’ yeast. In this study, wheat flour used in tarhana preparation was replaced with different cereal flours (barley, rye and oat), legume flours (chickpea, common bean and lentil) and cereal bran (rye, oat and barley) at 50%, 50% and 25% levels, respectively. All types of flour and bran addition increased the ash and mineral content compared to the control, and the highest ash, calcium, iron, magnesium and zinc content was determined with rye flour addition. After fermentation process, the lowest phytic acid content was found with 50 % barley flour addition. The mean of phytic acid loss after fermentation changed between 90.91% and 94.31% and the lowest phytic acid losses were found with oat and rye bran addition. Tarhana samples produced with yeast had higher mean values for mineral matter, total phenolic content and antioxidant capacity on the other hand gave less appreciation by the panelists. According to general acceptability; the most popular tarhana samples after control was rye flour tarhana sample.

Viability and growth promotion of starter and probiotic bacteria in yogurt supplemented with whey protein hydrolysate during refrigerated storage.

The effect of whey protein hydrolysate (WPH) addition on growth of standard yoghurt cultures and Bifidobacterium adolescentis during co-fermentation and its viability during storage at 4ºC in yoghurts has been evaluated. WPH was obtained with the use of serine protease from Y. lipolytica yeast. Stirred probiotic yoghurts were prepared by using whole milk standardized to 16% of dry matter with the addition of either whey protein concentrate, skim milk powder (SMP), WPH-SMP (ratio 1:1), WPH. The hydrolysate increased the yoghurt culture counts at the initial stage of fermentation and significantly inhibited the decrease in population viability throughout the storage at 4ºC in comparison to the control. The post-fermentation acidification was also retarded by the addition of WPH. The hydrolysate did not increase the Bifidobacterium adolescentis counts at the initial stage. However, the WPH significantly improved its viability. After 21 days of storage, in the yogurts supplemented with WPH, the population of these bacteria oscillated around 3.04 log10 CFU/g, while in samples where SMP or whey protein concentrate was used, the bacteria were no longer detected.

Survival of Lactobacillus bulgaricus and Bifidobacterium animalis in yoghurts made from commercial starter cultures during refrigerated storage

All over the world, fermented dairy products have been consumed for nutrition and maintenance of good health for a very long time. This study evaluated the survival of Lactobacillus delbrueckii ssp. bulgaricus and Bifidobacterium animalis ssp. lactis BB-12 in yoghurts after the manufacturing during the shelf-life up to 21 days at 4 °C, which is mostly accepted by the consumers. The titratable acidity and pH showed the same patterns of increase or decline after manufacturing and storage of yoghurts. There was a significant difference (p <0.05) in acidity between yoghurts in glass bottle and plastic cup. The increase in numbers of lactobacilli and bifidobacteria and their survival during storage time were dependent on the species and strain of associative yoghurt bacteria (control-only yoghurt lactic acid bacteria and experimental containing except yoghurt culture also Bifidobacterium animalis ssp. lactis BB-12) and on the packaging material (glass bottle versus plastic cup). It was observed, that counts of bifidobacteria were lower than counts of Lactobacillus delbrueckii ssp. bulgaricus (190 to 434 x 107 at 1d) and slowly increased (p <0.001) at maximum level on day 7 (294.3 - 754 x 107) and then slowly declined to 6.33 x 107 in glass bottle and 2.33 x 107 in plastic cups, respectively. Lactobacillus delbrueckii ssp. bulgaricus multiplied better in glass bottles than in plastic cups, as observed during experimental period in-group with Bifidobacterium animalis ssp. lactis BB-12. At the end of the storage period at 4 ºC, viable counts of lactobacilli were higher (p <0.001) in glass bottles. Al the yoghurts, contained the recommended levels of lactobacilli and bifidobacteria (107 cfu.g-1) at the end of storage period (21 d).

The viability of yogurt bacteria in selected plant beverages

The viability of yogurt bacteria in selected plant beverages

The effects of starter cultures on chemical, biochemical and sensory properties of low‐fat Tulum cheeses during ripening

Three different commercial starter cultures, Choozit™ MA 11 (MA), Choozit™ BT 01 (BT) and Choozit™ Feta A (Feta), were used to remedy textural and aromatic defects and improve the overall quality of low‐fat Tulum cheeses. Chemical and sensory analyses as well as electrophoresis were performed. Supplemental yoghurt bacteria and Lactobacillus helveticus were found to be key contributors in proteolysis with varying protein breakdown capacities. The results suggest that using appropriate culture combinations could result in low‐fat Tulum cheeses with better sensory characteristics and proteolysis rates.

Preparation, structural characterisation and release study of novel hybrid microspheres entrapping nanoselenium, produced by green synthesis.

The main goal of this study was to synthesise and characterise different formulations based on alginate and alginate/chitosan microspheres containing nanoselenium (nano-Se) for controlled delivery applications. Nanosize elemental selenium was produced by using probiotic yogurt bacteria (Lactobacillus casei) in a fermentation procedure. The structural and morphological characterisation of the microspheres was performed by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. FTIR and XRD pattern indicated that was an effective cross-linking of selenium nanoparticles within the polymeric matrix in both cases. The SEM images reveal that selenium nanoparticles are mainly exposed on the surface of alginate, in contrast to porous structure of alginate/chitosan/nano-Se, interconnected in a regular network. This architecture type has a considerable importance in the delivery process, as demonstrated by differential pulse voltammetry. Selenium release from both matrices is pH sensitive. Moreover, chitosan blended with alginate minimise the release of encapsulated selenium, in simulated gastric fluid, and prolong the duration of release in intestinal fluid. The overall effect is the enhancement of total percentage release concomitant with the longer duration of action. The authors' formulation based on alginate/chitosan is a convenient matrix to be used for selenium delivery in duodenum, caecum and colon.

Prevention of DNA damage and anticarcinogenic activity of Activia® in a preclinical model.

Colorectal cancer is a global public health issue. Studies have pointed to the protective effect of probiotics on colorectal carcinogenesis. Activia® is a lacto probiotic product that is widely consumed all over the world and its beneficial properties are related, mainly, to the lineage of traditional yoghurt bacteria combined with a specific bacillus, DanRegularis, which gives the product a proven capacity to intestinal regulation in humans. The aim of this study was to evaluate the antigenotoxic, antimutagenic, and anticarcinogenic proprieties of the Activia product, in response to damage caused by 1,2-dimethylhydrazine (DMH) in Swiss mice. Activia does not have shown antigenotoxic activity. However, the percent of DNA damage reduction, evaluated by the antimutagenicity assay, ranged from 69.23 to 96.15% indicating effective chemopreventive action. Activia reduced up to 79.82% the induction of aberrant crypt foci by DMH. Facing the results, it is inferred that Activia facilitates the weight loss, prevents DNA damage and pre-cancerous lesions in the intestinal mucosa.

Survival and detection of coliforms, Enterobacteriaceae, and gram-negative bacteria in Greek yogurt

Despite the widespread use of coliforms as indicator bacteria, increasing evidence suggests that the Enterobacteriaceae (EB) and total gram-negative groups more accurately reflect the hygienic status of high-temperature, short-time pasteurized milk and processing environments. If introduced into milk as postpasteurization contamination, these bacteria may grow to high levels and produce a wide range of sensory-related defects. However, limited information is available on the use and survival of bacterial hygiene indicators in dairy products outside of pasteurized fluid milk and cheese. The goal of this study was to (1) provide information on the survival of a diverse set of bacterial hygiene indicators in the low pH environment of Greek yogurt, (2) compare traditional and alternative detection methods for their ability to detect bacterial hygiene indicators in Greek yogurt, and (3) offer insight into optimal hygiene indicator groups for use in low-pH fermented dairy products. To this end, we screened 64 bacterial isolates, representing 24 dairy-relevant genera, for survival and detection in Greek yogurt using 5 testing methods. Before testing, isolates were inoculated into plain, 0% fat Greek yogurt (pH 4.35 to 4.65), followed by a 12-h hold period at 4 ± 1°C. Yogurts were subsequently tested using Coliform Petrifilm (3M, St. Paul, MN) to detect coliforms; Enterobacteriaceae Petrifilm (3M), violet red bile glucose agar and the D-Count (bioMérieux, Marcy-l'Étoile, France) to detect EB; and crystal violet tetrazolium agar (CVTA) to detect total gram-negative bacteria. Overall, the non-EB gram-negative isolates showed significantly larger log reductions 12 h after inoculation into Greek yogurt (based on bacterial numbers recovered on CVTA) compared with the coliform and noncoliform EB isolates tested. The methods evaluated varied in their ability to detect different microbial hygiene indicators in Greek yogurt. Crystal violet tetrazolium agar detected the highest portion of coliforms, whereas EB Petrifilm detected the highest portion of EB, as well as highest portion of total gram-negative bacteria. Additionally, the D-Count method allowed for faster detection of EB in yogurt by generating results in approximately 13 h rather than the 24 h required when using EB Petrifilm and violet red bile glucose agar. Results from this study indicate that the coliform and EB groups encompass a broad range of dairy-relevant gram-negative bacteria with the ability to survive in Greek yogurt, supporting their use as microbial hygiene indicator groups in low-pH fermented dairy products.

Physicochemical evaluation of sheep milk yogurts containing different levels of inulin

The present study aimed to evaluate the physicochemical parameters of sheep milk yogurt smoothies (SMY) containing inulin at different levels (0, 2, 4, and 6%). Titratable acidity and pH, yogurt bacteria counts, fatty acids profile, and healthy lipid indices were evaluated during 28 d of refrigerated storage. As expected for yogurts, Streptococcus thermophilus counts decreased 1 to 3 log cycles and Lactobacillus delbrueckii ssp. bulgaricus counts decreased 1 to 2 cycles from d 1 to 28. The protective effect of inulin on bacteria survival and viability in the food matrix was not verified in the prebiotic SMY during storage, regardless of inulin level. Although lower post-acidification was observed in prebiotic SMY due to inulin addition, no changes were verified in short-chain fatty acids (SCFA) or polyunsaturated fatty acids (PUFA). In contrast, an increase in medium- and long-chain fatty acids (MCFA and LCFA) and monounsaturated fatty acids (MUFA) was observed during storage in all SMY. The most significant levels of fatty acids in SMY were oleic acid, followed by palmitic and myristic acids. A high positive correlation between conjugated linoleic acid (CLA) and oleic acid (r=0.978) was observed. The cis-9,trans-11 CLA isomer represented approximately 78% of total PUFA and 2% of total fatty acids, whereas α-linoleic acid comprised about 22% PUFA and 1% of total fatty acids in SMY. The fatty acid changes during storage were associated with the metabolic activity of the starter bacteria, especially for oleic acid and cis-9,trans-11 CLA isomer. Thus, the SMY represented a great source of these compounds. We observed that inulin levels did not affect fatty acids. A nonsignificant decrease in atherogenic index was observed during storage in all SMY, and a positive correlation (r=0.973) was found between atherogenic index and thrombogenic index of SMY. High correlations were observed between lauric and myristic acids and saturated fatty acids (r=0.907 and r=0.894, respectively), providing evidence of their atherogenic and thrombogenic potential. A negative correlation was observed between stearic acid and atherogenic index (r=−0.612) and between oleic acid and atherogenic index. Sheep milk yogurt could be characterized as a food with low atherogenic and thrombogenic risk because of its healthy lipid composition. Therefore, addition of inulin to SMY could be a good option to improve functionality of this food matrix for dairy companies wishing to enter the functional food market.

Segmentation of microscopic images of bacteria in Bulgarian yoghurt by template matching

Segmentation of microscopic images of bacteria in Bulgarian yoghurt by template matching

Comparison of the effect of green, white and black tea on Streptococcus thermophilus and Lactobacillus spp. in yogurt during refrigerated storage

This study investigated the effects of green, white and black tea (Camellia sinensis) on lactic acid production and the viability of Streptococcus thermophilus and Lactobacillus spp. in yogurt during 3weeks of refrigerated storage. Three types of tea water extracts were added into a milk-starter culture mixture and incubated at 42°C until the pH was reduced to 4.5. All yogurts were then refrigerated (4°C) for up to 21days and samples were analyzed for pH, titratable acid and viable counts of yogurt bacteria. Higher pH values (p<0.05) were shown in tea yogurts than plain yogurt (PY). Green tea yogurt (GTY) showed the highest pH followed by black tea yogurt (BTY) and white tea yogurt (WTY), respectively for the overall storage period. However, higher acid production was observed in all tea yogurts (0.78–0.99% lactic acid equivalent; LAE) than plain yogurt (0.70–0.91% LAE). Inclusion of three types of tea extracts did not affect significantly (p>0.05) the viability of Lactobacillus spp. and S. thermophilus compared to PY during storage. All the three types of tea yogurt maintained a high level of S. thermophilus and Lactobacilllus spp. counts through refrigerated storage and this can ensure health benefits to be delivered to consumers on daily consumption.

Evaluation the Sensory and Probiotics Properties of the Yogurt Supplemented with Carrot Juice

This study aimed to develop a new type of yogurt through addition of carrot juice. Yogurt is a fermented milk product obtained from fermentation of Lactobacillus bulgaricus and Streptococcus thermophilus strains. The effect of carrot juice at different levels (0%, 8%, 16%, 24%) on sensory properties and the viability of probiotic bacteria in yogurts during storage (21 days) at refrigerated temperature (4°C) was evaluated. The yogurt supplementation with 24 % carrot juice significantly improves the stability of the lactic acid bacteria, that contained the recommended levels of 10 7 cfu/g) probiotic bacteria at the end of 21-days shelf life. The yogurt with 24% carrot juice was the most appreciated (7.07 points), followed by the classic yogurt (6 points), yogurt with 8% (5.28 points) and yogurt with16% carrot juice (5.5 points).

Improving the Viability of Probiotic Bacteria in Yoghurt by Homogenization

In this study, the effect of homogenization pressures (100, 150 and 200 bar) at 50, 60 and 70C and stages (1 and 2) on viability of probiotic bacteria was investigated. The milk used for producing yoghurt samples was homogenized at 100, 150 and 200 bar at 50, 60 and 70C, then heated at 85C for 30 min. After cooling milk to fermentation temperature (42C), it was inoculated with mixture starter culture ABY-1 and incubated. During fermentation, pH dropped until it reached 4.5. After fermentation, yoghurt samples were held in refrigerator. Viability of Lactobacillus acidophilus and Bifidobacterium lactis was determined during a 21-day cold storage (4C). The results of this study showed that with increasing pressure, temperature and stages of homogenization, viability of probiotic bacteria increased during storage (P < 0.05). Practical Applications The viability of probiotic bacteria in probiotic products is so important; and nowadays, it is also considered by consumers. Probiotic yoghurt is one of the most widely used probiotic dairy products around the world, and therefore finding an efficient and practical way to produce it with the highest viability of the probiotic bacteria seems necessary. Homogenization is one of the most important steps in yoghurt production, and temperature, time and stages of homogenization are three main factors in this unit operation. In this study, by changing the homogenization conditions, positive results were found to produce yoghurt with the desirable viability of probiotic bacteria, so that by simultaneously increasing the homogenization temperature, time and stages, the probiotic viability improved during fridge storage.

Viable Counts of Lactic Acid Bacteria in Philippine Commercial Yogurts

Viable Counts of Lactic Acid Bacteria in Philippine Commercial Yogurts

EFFECTS OF ARTICHOKE (CYNARA SCOLYMUS L.) EXTRACT ADDITION ON MICROBIOLOGICAL AND PHYSICO-CHEMICAL PROPERTIES OF PROBIOTIC YOGURT

In this study, the effects of addition of artichoke (Cynara scolymus L.) leaf extract into yogurt (0 or 0.5%) on biochemical parameters (pH, titrable acidity) and the viability of probiotic bacteria (Lactobacillus acidophilus LA-5, Bifidobacterium lactis BB-12) during fermentation and over 28 days of refrigerated storage (4°C) were investigated. Moreover, the amounts of syneresis, total phenolic content, antioxidant activity and sensory attributes of yogurts at the end of fermentation were assessed. Yogurts contained the two yogurt bacteria (Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus: ABY) or only S. thermophilus (ABT) as adjunct culture to probiotics. Yogurts containing Cynara scolymus L. (ABT-C and ABY-C) had faster acidity increase, shorter incubation time and greater final titrable acidity than control yogurts (ABT and ABY). Also, yogurts containing Cynara scolymus L. had lower syneresis, higher total phenolic content and greater antioxidant activity. ABT-C yogurt had the ever greatest viability of probiotics. In case of samples sensory evaluation, generally, the highest total score was related to ABT yogurt whereas lowest total score belonged to ABT-C yogurt.

Influence of Pollen, Chia Seeds and Cranberries Addition on the Physical and Probiotics Characteristics of Yogurt

Yoghurt is a fermented milk product obtained from fermentation of Lactobacillus bulgaricus and Streptococcus thermophilus strains. The effect of bee pollen, chia seeds and cranberries on the viability of probiotic bacteria in yogurts during storage (21 days) at refrigerated temperature (4°C) was evaluated. The yogurt supplementation with 1,4 % chia seeds and 7,6% cranberries significantly improves the stability of the lactic acid bacteria, that contained the recommended levels of (10 6 -10 7 cfu/g) probiotic bacteria at the end of 21-day shelf life.

Green tea yogurt: major phenolic compounds and microbial growth

The purpose of this study was to evaluate fermentation of milk in the presence of green tea (Camellia sinensis) with respect to changes in antioxidant activity, phenolic compounds and the growth of lactic acid bacteria. Pasteurized full fat cow's milk and starter culture were incubated at 41°C in the presence of two different types of green tea extracts. The yogurts formed were refrigerated (4°C) for further analysis. The total phenolic content was highest (p < 0.05) in air-dried green tea-yogurt (MGT) followed by steam-treated green tea (JGT) and plain yogurts. Four major compounds in MGTY and JGTY were detected. The highest concentration of major phenolic compounds in both samples was related to quercetin-rhamnosylgalactoside and quercetin-3-O-galactosyl-rhamnosyl-glucoside for MGTY and JGTY respectively during first 7day of storage. Diphenyl picrylhydrazyl and ferric reducing antioxidant power methods showed highest antioxidant capacity in MGTY, JGTY and PY. Streptococcus thermophillus and Lactobacillus spp. were highest in MGTY followed by JGTY and PY. This paper evaluates the implementation of green tea yogurt as a new product with functional properties and valuable component to promote the growth of beneficial yogurt bacteria and prevention of oxidative stress by enhancing the antioxidant activity of yogurt.

A combination of acid lactase from Aspergillus oryzae and yogurt bacteria improves lactose digestion in lactose maldigesters synergistically: A randomized, controlled, double-blind cross-over trial

Lactose digestion can be improved in subjects with impaired or completely absent intestinal lactase activity by administration of lactase preparations and particularly of acid lactase, which is active in the stomach, or by yogurt containing live lactic acid bacteria. It is the question, if lactose digestion can be further enhanced by combining these two approaches. We investigated in a randomised, placebo-controlled, double-blind, 5-arm crossover study on 24 lactose malabsorbers with variable degrees of lactase deficiency if different lactase preparations and freeze-dried yogurt culture affect gastrointestinal lactose digestion after consuming moderate amounts of lactose (12.5 g) by assessing hydrogen exhalation over 6 h. Furthermore, symptoms of lactose intolerance (excess gas production, abdominal pain, diarrhoea or nausea) were assessed using validated questionnaires. All preparations increased lactose digestion and reduced peak hydrogen exhalation by -27% (yogurt), -29/-33% (3300/9000 FCC(1) ((1) One FCC hydrolyses about 5 or 1.7-2.5 mg lactose in aquous solution or in (artificial) chyme, respectively, according to the FCC-III method of the Committee on Codex Specifications, Food and Nutrition Board, National Research Council. Food Chemicals Codex, 3rd edition. Washington, DC, National Academy Press, 1981 It cannot precisely be defined how much lactose can be hydrolysed in vivo by the consumption of a certain number of FCC units.) units acid lactase from Aspergillus oryzae) or -46%, respectively (3300 FCC units lactase plus yogurt culture combined), as compared with placebo (p < 0.001, Friedman test). The combination preparation had not only the strongest effect, but also showed the lowest variance in H(2)-exhalation values (less malabsorbers with no reduction of H(2)-exhalation) Apart from this, both the higher dose lactase and the combination preparation significantly reduced the symptoms most closely associated with H(2)-exhalation, namely flatulences and abdominal pain, respectively. The combined administration of freeze-dried yogurt cultures and acid lactase increases lactose digestion more than either freeze-dried yogurt cultures or acid lactase alone, and more lactose malabsorbers benefited from this effect.

Viability of Lactic Acid Bacteria, Antioxidant Activity and In Vitro Inhibition of Angiotensin-I-Converting Enzyme of Lycium barbarum Yogurt

Lycium barbarum water extract was co-incubated with milk and starter culture during fermentation followed by refrigerated storage. The changes in viable cell counts (VCC) of yogurt bacteria, post-acidification, proteolytic activity, total phenolic content (TPC), antioxidant activity, angiotensin-I converting enzyme (ACE-I) inhibition activity and sensory evaluation were investigated during refrigerated storage (4 °C) up to 21 days. The VCC of Lactobacillusspp. was higher (p < 0.05) in L. barbarum yogurt than plain yogurt on 0 and 3 days of storage. The VCC of Streptococcus thermophilus in L. barbarum yogurt was higher (p < 0.05) than plain yogurt on the first 6 days of storage. Changes in pH were not different between plain and L. barbarum yogurts during 21 days of storage. However, titratable acidity (TA) was higher in fresh (0 day) L. barbarum yogurt (1.05 %; p < 0.05) than in plain yogurt (0.87 %). Proteolytic activity was higher in L. barbarum yogurt (32.0 ± 2.0 μg/g; p < 0.05) than plain yogurt (25.4 ± 1.1 μg/g) only on day 7 of storage, whereas free amino acids showed the highest value on 0 day (0.16 ± 0.1 and 0.20 ± 0.1 mM leucine equivalent for plain and L. barbarum yogurts, respectively). The presence of L. barbarum increased (p < 0.05) TPC and antioxidant activity in yogurt compared to the absence. However, L. barbarum yogurt did not affect ACE-I inhibitory activity during storage period. The addition of L. barbarum increased sweetness, overall aroma and preference scores of yogurt. In conclusion, L. barbarum can enhance yogurt functional properties with antioxidant activity.