Phenolics Profile, Antioxidant Activity and Flavor Volatiles of Pear Juice: Influence of Lactic Acid Fermentation Using Three Lactobacillus Strains in Monoculture and Binary Mixture

The aim of this study was to evaluate the effects of lactic acid fermentation using three Lactobacillus strains (Lactiplantibacillus plantarum 90, Lactobacillus helveticus 76, and Lacticaseibacillus casei 37) in monoculture and binary mixture on phenolics profile, antioxidant activity and flavor volatiles in pear juice. Results showed that the colony counts of binary mixture were higher than monoculture in fermented pear juice. The total content of phenols was increased, while that of flavonoids was decreased significantly during fermentation (p < 0.05). Antioxidant activities in fermented peer juice including DPPH and ABTS radical scavenging abilities and ferric reducing antioxidant power (FRAP) were significantly improved (p < 0.05). Binary mixture of Lactiplantibacillus plantarum 90 and Lacticaseibacillus casei 37 fermentation exhibited strong DPPH radical scavenging ability, due to the increase in vanillic acid and arbutin contents. Furthermore, lactic acid fermentation improved the formation of alcohols, esters, acids and terpenoids, and reduced the contents of aldehydes and ketones. Thirty new compounds including 15 alcohols, seven esters, five acids, and three terpenoids were observed in fermented pear juice. Hierarchical cluster revealed that flavor volatiles in pear juice were improved dramatically by Lactobacillus strains fermentation, and there were dramatic differences between monoculture and binary mixture.

PRODUCTION OF LACTIC ACID WORT-BASED BEVERAGES WITH MINT ESSENTIAL OIL ADDITION

Lactic acid wort-based beverages are functional, non-alcoholic, with low pH value and produced by the fermentation of wort by lactic acid bacteria. They are not well accepted by consumers because of their poor sensory characteristics. Therefore, 0.025 and 0.05 % (v/v) mint (Mentha piperita) essential oil was used as a tool for improvement of lactic acid wort-based beverages organoleptic profile. Wort was produced by 60% Pilsen malt, 20% Vienna malt, and 20% Caramel Munich ІІ malt. It was inoculated with probiotic lactic acid bacteria Lactobacillus casei ssp. rhamnosus LBRC11 at a concentration of 107 cells/ml and fermentation was carried out at constant temperature of 25°C. The dynamics of pH, concentration of viable cells, phenolic compounds and antioxidant activity were monitored and the beverages obtained were evaluated by a tasting panel. The results showed that addition of mint essential oil in concentration of 0.025 and 0.05 % (v/v) inhibited lactic acid fermentation but improved the sensory profile of the beverage obtained only when 0.025% mint essential oil was added. Mint essential oil addition led to an increase in the total phenolic compounds concentration, phenolic acids and flavonoid phenolic compounds, measured by Folin–Ciocalteu and modified Glories method but resulted in a decrease in the antioxidant activity, measured by the DPPH radical scavenging assay, cupric reducing antioxidant power (CUPRAC) and ferric reducing antioxidant power (FRAP). The antioxidant activity measured by the ABTS radical scavenging assay was almost equal for the beverages with and without mint essential oil addition. The results obtained will be used for modeling of lactic acids fermentation with addition of mint essential oil for the production of functional wort-based beverages. Keywords: lactic acid fermentation, wort, mint essential oil, phenolic compounds, antioxidant activity

Optimisation of Lactic Acid Fermentation from Cassava Peel by Lactobacillus casei (ATCC334)

The demand for lactic acid is steadily increasing due to the desire of its bioproduction over chemical synthesis. The associated cost, however, is a significant hurdle. This study reports lactic acid fermentation by Lactobacillus casei ATCC334 from cassava peel. It investigates the effect of unhydrolysed cassava peels, acidic, alkali hydrolysates; fermenting pH; substrate concentration; nitrogen source concentration; duration; and inoculum size. An attempt at a cheaper purification and recovery protocol relative to those currently in use was similarly performed. Acidic hydrolysate yielded 10.53%, unhydrolysed substrate gave 4.80% with alkali hydrolysate yielding 4.75%. The highest LA yield was obtained at pH 6.0, 2.0% v/v inoculum size, 25% w/v substrate concentration, 5% nitrogen source concentration. A post-optimisation combination yielded 18.3% LA suggesting that one-factor-at-a-time may be unsuitable for optimisation studies involving cassava peel and L. casei ATCC334. FTIR spectra of product suggests effective partial purification. Hence, an improvement in the optimization strategy for production is recommended for subsequent study.

Variation of bitter components of the asparagus juices during lactic acid bacteria fermentation

To investigate the bitterness status of asparagus juices during lactic acid fermentation, Limosilactobacillus fermentum Xd, Lacticaseibacillus paracasei Yd, Lactiplantibacillus plantarum 5-7-3 and their various combinations were used for single and mixed fermentation of asparagus juices. The fermentation characteristics and variation of the main bitter substances were studied. For the single and co-fermented samples, the viable counts, pH value and acidity were ranged from 8.33 lg CFU/mL to 8.65 lg CFU/mL, 3.58 to 3.86 and 6.29 g/kg to 6.52 g/kg, respectively. By sensory evaluation, the bitterness of every fermented sample was continuously reduced by at least 77% during fermentation and the corresponding content of total saponins, flavonoids and nine bitter amino acids showed varying degrees of declination. These results suggested that it was feasible to develop novel low-bitter asparagus juices fermented by the lactic acid bacteria used in this study.

Valorization of Fermented Shrimp Waste with Supercritical CO2 Conditions: Extraction of Astaxanthin and Effect of Simulated Gastrointestinal Digestion on Its Antioxidant Capacity

Lactic acid fermentation increases the bioactive properties of shrimp waste. Astaxanthin is the principal carotenoid present in shrimp waste, which can be found esterified in the liquid fraction (liquor) after its lactic acid fermentation. Supercritical CO2 technology has been proposed as a green alternative to obtain astaxanthin from fermented shrimp waste. This study aimed to optimize astaxanthin extraction by supercritical CO2 technology from fermented liquor of shrimp waste and study bioaccessibility using simulated gastrointestinal digestion (GD) of the optimized extract. A Box–Behnken design with three variables (pressure, temperature, and flow rate) was used to optimize the supercritical CO2 extraction. The optimized CO2 extract was obtained at 300 bar, 60 °C, and 6 mL/min, and the estimated characteristics showed a predictive extraction yield of 11.17%, antioxidant capacity of 1.965 mmol of Trolox equivalent (TE)/g, and astaxanthin concentration of 0.6353 µg/g. The experiment with optimal conditions performed to validate the predicted values showed an extraction yield of 12.62%, an antioxidant capacity of 1.784 mmol TE/g, and an astaxanthin concentration of 0.52 µg/g. The astaxanthin concentration decreased, and the antioxidant capacity of the optimized extract increased during gastrointestinal digestion. In conclusion, our optimized supercritical CO2 process is suitable for obtaining astaxanthin from shrimp by-products after lactic acid fermentation.

Evaluation of Probiotic Properties of Pediococcus acidilactici M76 Producing Functional Exopolysaccharides and Its Lactic Acid Fermentation of Black Raspberry Extract

This study aimed to determine the probiotic potential of Pediococcus acidilactici M76 (PA-M76) for lactic acid fermentation of black raspberry extract (BRE). PA-M76 showed outstanding probiotic properties with high tolerance in acidic GIT environments, broad antimicrobial activity, and high adhesion capability in the intestinal tract of Caenorhabditis elegans. PA-M76 treatment resulted in significant increases of pro-inflammatory cytokine mRNA expression in macrophages, indicating that PA-M76 elicits an effective immune response. When PA-M76 was used for lactic acid fermentation of BRE, an EPS yield of 1.62 g/L was obtained under optimal conditions. Lactic acid fermentation of BRE by PA-M76 did not significantly affect the total anthocyanin and flavonoid content, except for a significant increase in total polyphenol content compared to non-fermented BRE (NfBRE). However, fBRE exhibited increased DPPH radical scavenging activity, linoleic acid peroxidation inhibition rate, and ABTS scavenging activity of fBRE compared to NfBRE. Among the 28 compounds identified in the GC-MS analysis, esters were present as the major groups. The total concentration of volatile compounds was higher in fBRE than that in NfBRE. However, the undesirable flavor of terpenes decreased. PA-M76 might be useful for preparing functionally enhanced fermented beverages with a higher antioxidant activity of EPS and enhanced flavors.