RESUMO
BACKGROUND: Low molecular-weight phenolic fractions (LMPFs) were extracted from Albion (LMPF-A) and Camarosa (LMPF-C) strawberry cultivars. Their antibacterial activity against Listeria monocytogenes and Salmonella Typhimurium cocktails in vitro and in vivo was investigated using strawberry juice as a food model. This study also sought to determine their antibacterial mechanism. RESULTS: Quercetin was identified as a principal compound in both phenolic fractions. The minimum bactericide concentration (MBC) values were 750 and 850 µg mL-1 (LMPF-C) and 800 and 950 µg mL-1 (LMPF-A) against S.Typhimurium and L. monocytogenes, respectively. The possible antibacterial activity of the phenolic extracts could be related to the release of phosphate and potassium ions, the effect of the disruption of membrane integrity on L. monocytogenes, and the effect of the inhibition of dihydronicotinamide adenine dinucleotide (NADH) oxidase activity on S. Typhimurium. Quercetin and kaempferol were the most active compounds in producing bacterial damage. Strawberry juice supplemented with the phenolic fractions and incubated at 37, 20, and 4 °C reduced bacterial viability; moreover, after treatment with the phenolic fraction at the lowest temperature, no viable cells were detected after 7 days' incubation. Salmonella was more sensitive to the supplements than Listeria in strawberry juice. CONCLUSIONS: This study could form the basis for the development of natural antibacterial agents that could be included in natural juice or used by the pharmaceutical industry. © 2020 Society of Chemical Industry.
Assuntos
Antibacterianos/farmacologia , Fragaria/química , Sucos de Frutas e Vegetais/microbiologia , Listeria monocytogenes/efeitos dos fármacos , Viabilidade Microbiana/efeitos dos fármacos , Extratos Vegetais/farmacologia , Polifenóis/farmacologia , Salmonella typhimurium/efeitos dos fármacos , Antibacterianos/química , Frutas/química , Sucos de Frutas e Vegetais/análise , Listeria monocytogenes/crescimento & desenvolvimento , Extratos Vegetais/química , Polifenóis/química , Salmonella typhimurium/crescimento & desenvolvimentoRESUMO
Amaranth is a rediscovered pseudocereal with high nutritional properties. Lactic acid fermentation can increase the functional and nutritional value of foods. The aims of this study were to isolate and evaluate the functionality of lactic acid bacteria (LAB) from amaranth. LAB strains (n = 29) isolated from amaranth sourdough and grains included Lactobacillus (L.) plantarum (n = 8), L. rhamnosus (n = 6), Enterococcus (E.) mundtii (n = 4), E. hermanniensis (n = 3), E. durans (n = 1), Enterococcus sp. (n = 1), Leuconostoc (Lc.) mesenteroides (n = 3), and Lc. mesenteroides subsp. mesenteroides (n = 3). Only 21% of the strains showed the ability to synthesize capsular exopolysaccharides or display ropiness and only 8 strains showed amylolytic activity. L. plantarum CRL 2106 and E. durans CRL 2122 showed the highest phytase activity, which is of importance for mineral bioavailability. L. plantarum CRL 2106 and CRL 2107 and Lc. mesenteroides subsp. mesenteroides CRL 2131 synthesized the highest concentrations of B2 and B9 vitamin (140-250 ng/mL). This study demonstrates the potential of LAB to improve the nutritional and functional values of pseudocereal-derived foods.