Assessment of the Effects of Back Sloping on Some Starter Culture Strains and the Organoleptic Qualities of their Yoghurt Products

Fermented milk is an essential commodity in Africa and beyond. Many techniques have been developed over time for the manufacture of different forms of yoghurt products. One of these Traditional methods includes back slopping). The advantages of this method include faster fermentation rates due to reduction in lag time, and subsequent production of relevant metabolites as well as allowing for a more reliable product formation on a consistent basis. The aim of this study was to better understand, the effects of back sloping on the microbial community as well as on the organoleptic characteristics of the yoghurts produced using the method. The model from this work could be used to study the dynamics of the microbial community associated with back-slopping practices and the understanding of possible associated defects in order to allow better control over the application of the method on commercial levels. We characterized the yoghurt produced from both microbial compositional study using culture-dependent morphological examinations on MRS, M17, Nutrient Agar and Potato dextrose Agar, as well as from organoleptic point of view. The results show that back sloping up to three-fold (batch) gave increasing acceptance but decreased afterwards. Acidification activity which determines proteolysis of casein for coagulation to take place also increased up to three folds. Residual lactose, syneresis and moisture content also decreased favourably by three fold order. Therefore, back sloping could be recommended on commercial level especially in the developing countries where facilities for consistent supply of pouched starter culture are limited because, aside the above mentioned advantages, this process also favours the growth of bacteria which release antimicrobial substances thereby ensuring the growth of the same species while reducing the growth of other organisms thereby preserving the products’ quality.

Carbonate and Oxalate Crystallization by Interaction of Calcite Marble with Bacillus subtilis and Bacillus subtilis–Aspergillus niger Association

Rock surfaces in natural systems are inhabited by multispecies communities of microorganisms. The biochemical activity of microorganisms and the patterns of microbial crystallization in these communities are mostly unexplored. Patterns of calcium carbonate and calcium oxalate crystallization induced by bacteria Bacillus subtilis and by B. subtilis together with Aspergillus niger on marble surface in vitro in liquid medium and in humidity chamber—were studied. Phase identification was supported by XRD, SEM, EDXS; metabolite composition was determined by GC–MS. It was found that the activity of B. subtilis–A. niger associations significantly differ from the activity of B. subtilis monocultures in the same trophic conditions. The phase composition and the morphology of the forming crystals are determined by the composition of the metabolites excreted by the microorganisms—particularly by the ratio of the concentrations of extracellular polymeric substances (EPS) and oxalic acid in the medium. The acidification activity of micromycetes may suppress the formation of bacterial EPS and prevent the formation of calcite. The present results can be used in the development of biotechnologies using microbial communities.

Genotypic and phenotypic characterization of food-associated Lactobacillus plantarum isolates for potential probiotic activities

ABSTRACT Lactic acid bacterium, Lactobacillus plantarum, has been applied, for centuries, for food and drink fermentations. Given the benefits associated with fermented products, Lb. plantarum strains have captured considerable industrial and scientific interest, so that they are included as fundamental components of functional foods. Indeed, some strains are marketed as probiotics. In the present study, food- and gut-associated Lb. plantarum isolates were genetically characterized by multilocus sequence typing (MLST) and phenotypically characterized for properties that could influence their probiotic potential. MLST and phylogenetic analysis stratified 22 Lb. plantarum isolates into six lineages. The isolates were further phenotypically characterized by an in vitro assay to assess their potential gut community influence via a limited number of assays including acidification activity, strain displacement activity and their intrinsic range of antibiotic resistance. Given growing recognition of the benefits of fermented foods, and the prevalence of Lb. plantarum in these applications, this study highlights analysis of a subset of preliminary important strain-specific features. These features are of interest to all stakeholders, to inform isolate comparison and selection for current functional food associations, and that can serve as a basis for future strain and food-microbe fermentation product development.

Effect of the Degree of Polymerization of Fructans on Ex Vivo Fermented Human Gut Microbiome

Prebiotic supplements are used to promote gastrointestinal health by stimulating beneficial bacteria. The aim of this study was to compare the potential prebiotic effects of fructans with increasing degrees of polymerization, namely fructooligosaccharides (FOS) and inulins with a low and high polymerization degree (LPDI and HPDI, respectively), using an ex vivo fermentation system to simulate the colonic environment. The system was inoculated with pooled feces from three healthy donors with the same baseline enterotype. Changes in microbiota composition were measured by 16S metagenomic sequencing after 2, 7, and 14 days of fermentation, and acid production was measured throughout the experiment. Alpha-diversity decreased upon inoculation of the ex vivo fermentation under all treatments. Composition changed significantly across both treatments and time (ANOSIM p < 0.005 for both factors). HPDI and LPDI seemed to be similar to each other regarding composition and acidification activity, but different from the control and FOS. FOS differed from the control in terms of composition but not acidification. HDPI restored alpha-diversity on day 14 as compared to the control (Bonferroni p < 0.05). In conclusion, the prebiotic activity of fructans appears to depend on the degree of polymerization, with LPDI and especially HPDI having a greater effect than FOS.

Influence of flaxseed components on fermented dairy product properties

The addition of flaxseed meal and flaxseed oil on the growth and viability of Lactobacillus acidophilus CCDM 151 and yoghurt culture CCDM 21 during cold storage in fermented milk was tested. It was found that the oil addition in the amount of 0.6% w/w in milk did not influence the growth and acid production of Lactobacillus acidophilus CCDM 151, while the acidification activity of yoghurt culture was slightly lower compared to pure milk and connected with lower growth of Streptococcus thermophilus. On the contrary the addition of meal in amount of 7.6% w/w into milk stimulated the growth and acid production of Lactobacillus acidophilus CCDM 151. The viability of both tested cultures during one month storage of fermented milks at 5 ± 1°C was not influenced by the oil supplementation but the addition of meal decreased their viability significantly. The unusual volatile compounds acetone and butane-2-on were detected by SPME-GC in yoghurt with meal. Unlike oil, the addition of flaxseed meal increased the yoghurt firmness and influenced negatively yoghurt taste and flavour.

The Nutrition of Buffalo Milk: A Comparison with Cow Milk

Milk is the essential source of nutrition for young mammals before they are able to digest other types of food. To explore the complex nutritive value of buffalo milk, the general composition, buffer capacity, the properties of buffalo yogurt were analyzed, meanwhile, cow milk as a control group was also studied. The results show that the nutritional value of buffalo milk is higher than that of cow milk, exhibiting the high protein, fat, lactose, total solids and nonfat solids contents, and the high buffer capacity. Yogurt with the probiotics characterized by acidification activity, syneresis and water-holding capacity, has the functional of lactobacillus resisting lactose intolerance and reducing constipation. Buffalo yogurt shows the higher stability and nutritional value.