Eficácia de óleos essenciais de Mentha spp. no controle de leveduras deteriorantes em sucos de frutas

Abstract

Fruit juices, widely consumed due to their attractive taste chacarteristics, refreshing aspect and nutrient richness, are susceptible to microbial spoilage, mainly by yeast.Several conservation technologies are applied in order to extend the shelf life of fruit juices, however, there is a growing consumer demand for less use of synthetic preservatives inn these products. The objective of this study was to evaluate the efficacy of essential oils of Mentha piperita L.(MPEO), M.spicata L. (MSEO) and M. x villosa Huds. (MVEO) to inactivate spoilage yeasts (Candida albicans, C. tropicalis, Pichia anomala and Saccharomyces cerevisiae) in Sabouraud dextrose broth (SDB) and in cashew, guava, mango and pineapple juice for 72 h refrigerated storage. The effects of incorporating of an effective dose of MSEO (1.875 uL/mL) to inhibit yeasts tested on physicochemical and sensory characteristics of fruit juices were evaluated. The effects of MPEO on membrane integrity, membrane potential, enzyme activity and efflux pump activity of S. cerevisiae in cashew and guava juice through the use of propidium iodide (PI), oxonol trimetin (DIBAC4 (3)), fluorescein diacetate (FDA) and ethidium bromide (EB) were evaluated using flow cytometry. The MPEO and MSEO displayed a minimum inhibitory concentration (MIC) of 1.875 uL/mL against the yeast strains tested, while, the MVEO displayed a MIC of 3.75 uL/mL. A> 5 log reductions in the counts of C. albicans, P. anomala and S. cerevisiae were observed in cashew and guava juices containing 7.5 and 3.75 uL/mL of the MPEO; however, these concentrations were not effective to cause the same reduction in yeast counts in mango and pineapp juices over storage time evaluated. The incorporation of 3.75 uL/mL of MSEO or 15 uL/mL of MVEO caused a ≥ 5 log reductions in the counts of C. albicans, P. anomala and S. cerevisiae in SDB; 1.875 uL/mL of MSEO or 15 uL/mL of MVEO caused ≥ 5 log reductions in the counts of P. anomala and S. cerevisiae in cashew and guava juices. In pineapple juice, 3.75 uL/mL of MSEO caused ≥ 5 log reductions in the counts of P. anomala and S. ceverisae; 15 uL/mL of MVEO caused ≥ 5 log reductions in S. cerevisae counts in mango juice. The incorporation of 1.875 uL/mL of MSEO did not affect the physicochemical parameters (soluble solids, pH and titratable acidity) of the tested juice as well as did not induce negative impacts to cause its possible sensorial rejection. Particularly, fruit juices with MSEO were reported as having characteristic juice color, pleasant taste and refreshing taste; howerer, they also obtained high scores for non-characteristic fruit aroma and mint odor and taste. The incorporation of 1.875 uL/mL of MPEO into cashew and guava juices strongly compromised membrane permeability, membrane potential, enzymatic activity and efflux pump activity in S. cevevisiae cells, revealing a action mechanism involving different functions in the target cell. The results obtained in this study show, in general, the potential of essential oils extracted from Mentha species, particularly MPEO and MSEO, as antimicrobials for use in the formulation strategies of contaminant yeast control of fruit juice.