Physicochemical and microstructural properties and probiotic survivability of symbiotic almond yogurt alternative using polymerized whey protein as a gelation agent.

A plain symbiotic almond yogurt-like product was formulated and developed using a plant-based starter YF-L02 (Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus supplemented with Lactobacillus acidophilus, Lactobacillus paracasei, and Bifidobacterium animalis) and inulin; 0.6% polymerized whey protein (PWP), 0.3% pectin, and 0.05% xanthan gum were optimized for the formula of the almond yogurt alternative. Two groups with/without calcium citrate and vitamin D2 were prepared and analyzed for chemical composition, changes in pH, viscosity, and probiotic survivability during storage at 4 °C for 10 weeks. The results showed that (1) over 10 weeks storage, the differences in the pH, viscosity, and probiotic survivability between the control and the fortified samples were not significant (P > 0.05); (2) the pH of both yogurt samples decreased 0.2 units while their viscosity slightly increased during storage; (3) the populations of L. paracasei and B. animalis remained above 106 cfu/g during the storage, whereas the population of L. acidophilus decreased dramatically during the first 4 weeks, especially the control group; (4) the microstructure was examined by scanning electron microscopy, revealing a compact and denser gel structure formed by 0.6% PWP with the presence of 0.3% pectin and 0.05% xanthan gum. In conclusion, PWP might be a proper gelation agent for the formulation of symbiotic almond yogurt alternative. PRACTICAL APPLICATION: In this study, polymerized whey protein was used as a gelation agent to formulate symbiotic almond yogurt alternatives with comparable physical texture and probiotic survivability to dairy yogurt during storage. This technology may be used for the development of plant-based fermented foods.

Bergamot essential oil nanoemulsions: antimicrobial and cytotoxic activity.

Bergamot essential oil (BEO) is well-known for its food preservation activity, as well as anticancer efficacy. However, the poor BEO water solubility and deriving low bioaccessibility have limited its wider applications. The incorporation in nanoemulsions of BEO and its refined fractions was investigated to enhance its dispersibility in water to promote its antimicrobial activity, tested against Escherichia coli, Lactobacillus delbrueckii, and Saccharomyces cerevisiae, and its cytotoxicity already at low concentrations. Different nanoemulsion formulations were tested based on food-grade ingredients, which were characterized in terms of hydrodynamic diameter and polydispersity index, and physical stability. The antimicrobial activity against all the tested micro-organisms was observed to be higher for BEO in its initial composition, than the light fraction, richer in d-limonene, ß-pinene, and γ-terpinene, or the heavy fraction, richer in linalyl acetate and linalool. Remarkably, the use of BEO nanoemulsions notably enhanced the antimicrobial activity for all the tested oils. BEO exhibited also a measurable cytotoxic activity against Caco-2 cells, which was also enhanced by the use of the different nanoemulsions tested, in comparison with free oil, which discourages the direct use of BEO nanoemulsions as a food preservative. Conversely, BEO nanoemulsions might find use in therapeutic applications as anticarcinogenic agents.

Bioactive properties of probiotic set-yogurt supplemented with Siraitia grosvenorii fruit extract.

Siraitia grosvenorii fruit (SGF) has been used as a natural sweetener and traditional medicine in China for more than two centuries. This study evaluated the effect of SGF extract supplementation (0.5%, 1%, and 2%) on the chemical, microbial and sensory properties of probiotic yogurt. The antioxidant, angiotensin-converting-enzyme inhibitory (ACE-I) and antibacterial bioactivities were determined. SGF extract supplementation improved some of the chemical and physicochemical characteristics. Probiotic yogurt with the fruit extract had significantly more Lactobacillus casei and Lactobacillus bulgaricus, whereas there was no significant effect on the number of Streptococcus thermophiles. The bioactivities were significantly increased by SGF extract supplementation. Probiotic yogurt with 2% SGF extract showed the highest antioxidant, ACE-I, and antibacterial activities, whereas the one with 1% SGF extract conferred the highest sensory attributes score. Overall, SGF extract offers a promising option as a dietary supplement to produce novel dairy products that have high nutritional and bioactivity values.

Role of Probiotic Mixture with and Without Green Tea Extract in Prevention of Hepatorenal Syndrome in Rat Model.

BACKGROUND AND OBJECTIVE: Hepatorenal syndrome (HRS) is a major public health problem in which both liver and kidney dysfunctions are encountered. The present research aimed to investigate the beneficial use of micro-encapsulated probiotic alone (Bifidobacterium bifidum, Lactobacillus delbrueckii and Streptococcus thermophilus mixture) or with green tea alcohol extract in HRS model in rats. MATERIALS AND METHODS: Flavonoids content and in vitro antioxidant activity of the extract were assessed. The animal experiment consisted of 4 groups; control healthy, control with HRS and two test groups with HRS and treated with either the encapsulated probiotic mixture alone or with green tea extract. After 3 weeks; urinary creatinine was determined in 24 h rat urine samples. Colonic microbiota was assessed in faeces. Plasma malondialdehyde, nitrite, C-reactive protein, creatinine, uric acid, urea and the activity of transaminases, catalase (CAT) and angiotensin-1 converting enzyme (ACE-1) were determined with calculation of creatinine clearance. RESULTS: Results showed significant increase in all biochemical parameters of HRS control except for ACE-1, CAT and creatinine clearance that experienced significant reduction along with dysbiosis compared to healthy control. Test groups showed improvement in all biochemical parameters with superiority to probiotic-green tea extract combination. Both treatments produced significant increase in fecal B. bifidum, S. thermophilus and L. bulgaricus and reduction of Staphylococci and Coliform. The effect of probiotic-green tea extract combination was more pronounced concerning the last three. Flavonoids and antioxidant activity of the extract were 1.325±0.01 mg quercetin/g and 98±1.66%, respectively. CONCLUSION: Administration of micro-encapsulated probiotic with or without alcohol green tea extract exerted significant prevention of HRS in rat with superiority to probiotic-green tea extract combination.

Microbiological characterization and functionality of set-type yogurt fermented with potential prebiotic substrates Cudrania tricuspidata and Morus alba L. leaf extracts.

The objective of this study was to investigate the effect of 2 plant leaf extracts on fermentation mechanisms and health-promoting activities and their potential as a nutraceutical prebiotics ingredient for application in dairy products. The individual active phenolic compounds in the plant extract-supplemented milk and yogurts were also identified. Compared with control fermentation, the plant extracts significantly increased the growth and acidification rate of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. In particular, plant extract components, including monosaccharides, formic acid, and hydroxycinnamic acid, such as neo-chlorogenic, chlorogenic, and caffeic acid, together play a stimulatory role and cause this beneficial effect on the growth of yogurt culture bacteria through fermentation. In addition, supplementation with the plant extracts enhanced antioxidant activities with increased total phenolic contents, especially the highest antioxidant activity was observed in yogurt supplemented with Cudrania tricuspidata leaf extract.

Growth and exopolysaccharide yield of Lactobacillus delbrueckii ssp. bulgaricus DSM 20081 in batch and continuous bioreactor experiments at constant pH.

Some Lactobacillus delbrueckii ssp. bulgaricus strains are able to synthesize exopolysaccharides (EPS) and are therefore highly important for the dairy industry as starter cultures. The aim of this study was to investigate the nutritional requirements for growth and EPS production of Lactobacillus delbrueckii ssp. bulgaricus DSM 20081. A medium was developed from a semi-defined medium (SDM) in which glucose was replaced by lactose and different combinations of supplements (nucleobases, vitamins, salts, sodium formate and orotic acid) were added. Constant pH batch fermentation with the modified medium resulted in an EPS yield of approximately 210 mg glucose equivalents per liter medium. This was a 10-fold increase over flask cultivation of this strain in SDM. Although not affecting cell growth, the mixture of salts enhanced the EPS synthesis. Whereas EPS production was approximately 12 mg/g dry biomass without salt supplementation, a significantly higher yield (approximately 20 mg/g dry biomass) was observed after adding the salt mixture. In continuous fermentation, a maximal EPS concentration was obtained at a dilution rate of 0.31/h (80 mg EPS/L), which corresponded to a specific EPS production of 49 mg/g dry biomass.

Isolation and characterization of three novel peptides from casein hydrolysates that stimulate the growth of mixed cultures of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.

In this study, sodium caseinate hydrolysates produced by papain with strong growth-stimulating activity for Streptococcus thermophilus (St) and Lactobacillus delbrueckii subsp. bulgaricus (Lb) were obtained. A series of separation methods including ultrafiltration, macroporous adsorption resin chromatography, gel filtration chromatography, and reverse-phase high-performance liquid chromatography (RP-HPLC) were applied to isolate and purify the peptide(s), which were mainly responsible for the activity. Finally, three novel growth-stimulating peptides, H-2-A, F2-c, and F2-b, corresponding to amino acid residues 29-35 and 103-108 of bovine α(S2)-casein and 181-186 of bovine α(S1)-casein, respectively, were obtained. With supplementation of H-2-A, F2-b, or F2-c at a protein concentration of 0.3%, the biomass yield of these two lactic acid bacteria (LAB) was enhanced by 193.3, 166.7, or 151.7%, respectively. In addition, there were significant (p < 0.05) increases in viable counts of St and lactic acid production of LAB in the presence of the purified peptides.

Influence of artificial sweeteners on the kinetic and metabolic behavior of Lactobacillus delbrueckii subsp. bulgaricus.

The addition of artificial sweeteners to a LAPT (yeast extract, peptone, and tryptone) medium without supplemented sugar increased the growth rate and final biomass of Lactobacillus delbrueckii subsp. bulgaricus YOP 12 isolated from commercial yogurt. Saccharin and cyclamate were consumed during microorganism growth, while the uptake of aspartame began once the medium was glucose depleted. The pH of the media increased as a consequence of the ammonia released into the media supplemented with the sweeteners. The L. delbrueckii subsp. bulgaricus strain was able to grow in the presence of saccharin, cyclamate, or aspartame, and at low sweetener concentrations, the microorganism could utilize cyclamate and aspartame as an energy and carbon source.

Effect of acacia (Robinia pseudo-acacia L.) honey on the characteristic microflora of yogurt during refrigerated storage.

The primary purpose of this research was to monitor the influence of acacia honey addition to yogurt milk on survival of the microbial flora of yogurt during refrigerated storage for 6 wk. Results showed that the presence of honey at 1.0% to 5.0% (w/v) did not significantly influence (P>0.05) the viability of characteristic microorganisms (i.e., Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) in yogurt during storage at 4 degrees C. Similarly, honey had no effect on pH and lactic acid levels of the final products. Despite these findings, enrichment of yogurt with honey is recommended because honey is a natural sweetener that possesses a wide range of beneficial nutritional properties. In addition, at a rate of approximately 3.0% (w/v), it highly improves the sensory quality of the finished product without having a detrimental effect on characteristic lactic acid bacteria.