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A face-centered factorial design was used to study the influence of temperature, cellulase, and pectinase concentration on the production of cells during simultaneous saccharification and fermentation of organic and conventional apple substrate pulp. The effects of the variables fermentation temperature (25-35 °C), pectinase concentration (5-25 μL/100 g), and cellulase concentration (4-8 μL/100 g) were analyzed by multiple regression and polynomial models of second order, providing the ideal conditions for yeast cultivation. Cellular production of apple substrates was expressed in log CFU/mL. The optimum condition for temperature was 27.5 °C, and 20 and 5 μL/100 g for pectinase and 8 and 7 μL/100 g for cellulase concentrations for organic and conventional apple pulp, respectively. The observed viability values were in agreement with the predicted values of 8.352 log CFU/mL (organic) and 8.317 log CFU/mL (conventional) apple pulps, thus proving the effectiveness of the models.

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PurposeThe objective of this study was to evaluate the influence of Saccharomyces boulardii on the kinetics of fermentation for organic and conventional apple pulp and to verify the effect of the antioxidant quercetin on the response to cellular oxidative stress.Design/methodology/approachThe kinetic parameters, the content of phenolic compounds, the quantity of quercetin and the antioxidant activity were determined during the fermentation process. The effect of quercetin on cellular oxidative stress was also investigated.FindingsThe content of phenolic compounds, the antioxidant activity and the quercetin concentration were higher in the organic fermented apple pulp (ORG) than in the conventional fermented apple pulp (CON). However, both apple pulps were considered ideal substrates for the growth of S. boulardii, suggesting that they are potentially probiotic. After fermentation, the quercetin concentration in the ORG treatment and YPDQ treatment (YPD broth with 0.1 mg quercetin rhamnoside/mL) increased viability by 9%, while in the CON treatment generated there was an increase of 6% in viability, compared to the YPD control treatment (YPD broth).Originality/valueThe high concentration of quercetin in the organic apple pulp supports the proposal that quercetin reduces the oxidative stress mediated by reactive oxygen species through its antioxidant action on S. boulardii that have similarities to mammalian eukaryotic cells. These findings suggest that fermented organic apple pulp could be consumed as a potential non-dairy probiotic product.

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