The Interactions among Isolates of Lactiplantibacillus plantarum and Dairy Yeast Contaminants: Towards Biocontrol Applications

Yeast diversity in the cheese manufacturing process and in the cheeses themselves includes indispensable species for the production of specific cheeses and undesired species that cause cheese defects and spoilage. The control of yeast contaminants is problematic due to limitations in sanitation methods and chemicals used in the food industry. The utilisation of lactic acid bacteria and their antifungal products is intensively studied. Lactiplantibacillus plantarum is one of the most frequently studied species producing a wide spectrum of bioactive by-products. In the present study, twenty strains of L. plantarum from four sources were tested against 25 species of yeast isolated from cheeses, brines, and dairy environments. The functional traits of L. plantarum strains, such as the presence of class 2a bacteriocin and chitinase genes and in vitro production of organic acids, were evaluated. The extracellular production of bioactive peptides and proteins was tested using proteomic methods. Antifungal activity against yeast was screened using in vitro tests. Testing of antifungal activity on artificial media and reconstituted milk showed significant variability within the strains of L. plantarum and its group of origin. Strains from sourdoughs (CCDM 3018, K19-3) and raw cheese (L12, L24, L32) strongly inhibited the highest number of yeast strains on medium with reconstituted milk. These strains showed a consistent spectrum of genes belonging to class 2a bacteriocins, the gene of chitinase and its extracellular product 9 LACO Chitin-binding protein. Strain CCDM 3018 with the spectrum of class 2a bacteriocin gene, chitinase and significant production of lactic acid in all media performed significant antifungal effects in artificial and reconstituted milk-based media.

Innovative application of postbiotics, parabiotics and encapsulated Lactobacillus plantarum RM1 and Lactobacillus paracasei KC39 for detoxification of aflatoxin M1 in milk powder

This study aimed to evaluate aflatoxin M1 (AFM1) level in milk powder and infant milk formulae, in addition to applying innovative methods for AFM1 & AFB1 detoxification. Fifty random samples of milk powder and infant formulae (25 of each) were collected from the Egyptian markets for assessing AFM1 level using ELISA technique. Bioactive components comprising cell free supernatants (postbiotic), acid-dead cells (parabiotic) and the encapsulated-cells of Lactobacillus plantarum RM1 and Lactobacillus paracasei KC39 were evaluated for their antifungal activity against toxigenic mold strains and their impact on AFB1 and AFM1 reduction in reconstituted milk powder. AFM1 concentration in unpacked milk powder was higher than that of packed samples and infant formulae, although these differences were not significant (P > 0.05). About 96.0, 29.4 and 25.0% of the tested infant formulae, unpacked, and packed milk powder were unacceptable in terms of the AFM1 limit defined by Egyptian and European standards, while all samples were in accordance with the USA/FDA standard. All tested mycotoxigenic strains were sensitive to the different treatments of the probiotics with the highest sensitivity regarding Fusarium strain with L. paracasei KC39 compared to other genera. The degradation ratios of AFM1 using the bioactives of the L. paracasei KC39 were higher than that of L. plantarum RM1 bioactives. Additionally, KC39 parabiotic manifested the best AFB1 reduction (60.56%). In conclusion, the positive and highly significant relationship (P < 0.05) between these effective biocompounds mirrors their major detoxification role which gives a safe solution for AFs contamination issues in milk and milk products.

Lubrication and Sensory Properties of Emulsion Systems and Effects of Droplet Size Distribution

The functional and sensory properties of food emulsion are thought to be complicated and influenced by many factors, such as the emulsifier, oil/fat mass fraction, and size of oil/fat droplets. In addition, the perceived texture of food emulsion during oral processing is mainly dominated by its rheological and tribological responses. This study investigated the effect of droplet size distribution as well as the content of oil droplets on the lubrication and sensory properties of o/w emulsion systems. Friction curves for reconstituted milk samples (composition: skimmed milk and milk cream) and Casein sodium salt (hereinafter referred to as CSS) stabilized model emulsions (olive oil as oil phase) were obtained using a soft texture analyzer tribometer with a three ball-on-disc setup combined with a soft surfaces (PDMS) tribology system. Sensory discrimination was conducted by 22 participants using an intensity scoring method. Stribeck curve analyses showed that, for reconstituted milk samples with similar rheological properties, increasing the volume fraction of oil/fat droplets in the size range of 1–10 µm will significantly enhance lubrication, while for CSS-stabilized emulsions, the size effect of oil/fat droplets reduced to around 1 µm. Surprisingly, once the size of oil/fat droplets of both systems reached nano size (d90 = 0.3 µm), increasing the oil/fat content gave no further enhancement, and the friction coefficient showed no significant difference (p > 0.05). Results from sensory analysis show that consumers are capable of discriminating emulsions, which vary in oil/fat droplet size and in oil/fat content (p < 0.01). However, it appeared that the discrimination capability of the panelist was significantly reduced for emulsions containing nano-sized droplets.

Effectiveness of micronutrient dietary intake and micronutrients fortifed milk to improve serum zinc concentrations of primary school children

Micronutrient dietary intake of primary school children was evaluated at baseline survey. Then the randomized community intervention trial with pre- and post-intervention evaluation aims to evaluate effectiveness of micronutrient dietary intake and micronutrients fortified milk to improve serum zinc concentrations of primary school children. The two common types of milk on the market are fresh milk and reconstituted milk which were used as food vehicles to fortify 21 different vitamins and minerals and given to 2 groups of school children at a dose of 2 boxes of 180 ml/day, 7 day/ week for 6 months. Each group drank one kind of milk. Control group did not drink milk during the intervention. After the end of the intervention, serum zinc concentration in the two intervention groups improved significantly compared to the baseline (p <0.01). The serum zinc concentrations were increased by 0.65±3.13 μmol/L and 0.75±3.49 μmol/L in the group of drinking micronutrient fortified fresh milk and the group of drinking micronutrients fortified reconstituted milk, respectively Zinc concentration after 6 months and difference of zinc concentration between baseline and 6 months after intervention in intervened groups were improved significantly compared to those of the control group (p<0.05).

κ-casein polymorphism effect on technological properties of dried milk

Introduction. Numerous molecular genetic studies have revealed a correlation between the polymorphism of milk protein genes and the technological properties of milk raw materials. DNA analysis, in particular, initiated research into the influence of allelic variants of κ-casein (CSN3) on thermal stability and cheese suitability of milk. This gives relevance to our study that compares the results of genotypic identification of lactating cows by the κ-casein gene, using raw and processed milk samples. Study objects and methods. Our study used raw and reconstituted milk samples from first-calf cows of the black motley breed with the AA and BB genotypes of the κ-casein gene. The samples were analyzed by standardized and generally accepted chemical engineering methods, as well as by capillary electrophoresis and PCR-RFLP analysis. Results and discussion. We compared the results of tests on thermal stability and cheese suitability of raw and reconstituted milk samples from cows with the AA and BB genotypes of the κ-casein gene. We tried out an integrated approach to monitoring milk raw materials based on the most relevant technological criteria and correlating the data with the associated CSN3 gene identification parameters. The PCR-RFLP analysis revealed reproducible results for both raw and dried milk samples in relation to the genotypical identification by the A- and B- allelic variants of the CSN3 gene. The tests showed higher thermal stability in the reconstituted milk from the BB genotype cow and better cheese suitability in the AA genotype sample. Conclusion. We developed a system for evaluating milk raw materials based on the most important technological parameters in combination with their genotypic characteristics. Our research procedure can unify the accumulation of experimental data and contribute to the formation of bioinformatics algorithms. This approach can be used in mathematical modeling of criteria to evaluate the compliance of the technological properties of milk with the recommended indicators.

Effect of High Temperature, Short Time (HTST) Pasteurization on Milk Quality Intended for Consumption

Background: In the dairy industry, hygienic quality and safety of milk and dairy products are very important for human health.Methods: The samples taken at the inlet and outlet of the HTST pasteurization process were subjected to physicochemical, bacteriological and sensory analysis.Result: showed that pasteurization has not only been beneficial, as in the case of the hygienic quality of raw milk, where the number of the Total Mesophilic Aerobic Flora dropped by 94% after heat treatment, to reach an average of 5.62 × 104 CFU ml-1 of the thermo-resistant bacteria. Heat treatment resulted in a decrease of protein and lactose values for both types of milk. In fact, this loss is more marked in raw milk than in reconstituted milk (4% against 1.8%, respectively, p less than 0.05). Wetting was more marked after pasteurization for raw milk (0.102°C) compared to reconstituted milk (0.014°C). Sensory profiles were modified in both milk types, with a significant decrease in color, viscosity and flavor descriptors and a significant increase in the intensity of smell and taste (p less than 0.05).