Influence of extracts of different Feijoa (Acca sellowiana) leaf genotypes on the lactic fermentation performed by a mixed culture

Abstract

The objective of this research was to evaluate the influence of the addition of aqueous extracts of Feijoa leaf genotypes (Acca Selowiana) (Access 2316, Alcântara, Helena, Mattos and Nonante) on the lactic fermentation performed by Streptococcus thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus, in MRS broth and milk. The total content of phenolic compounds (TPC), the antioxidant activity (AA) and the antimicrobial activity were determined. For the samples fermented in MRS broth, with and without the presence of extracts, the parameters analyzed were the kinetics of cell growth, TPC, AA, pH, and bacterial microscopy. For the samples fermented in whole milk, the parameters analyzed were pH, titratable acidity, moisture, ash, protein, total solids, and sensory profile. There was inhibition of the mixed culture’s growth in the dilution of 80% of the extracts (TPC 75.82 - 110.90 mg EAG g-1), the other experiments having been performed with TPC below 70 mg EAG g-1. The kinetics of growth was 16 hours. For the fermented samples, there were changes to the TPC and antioxidant activity, except for the one fermented with the Access 2316 extract, for which activity remained the same. The microscopy showed predominance of Streptococcus thermophilus. In the fermented milks, pH decreased, and acidity increased, and the sensory profile was modified by the addition of the extracts. The addition of Feijoa leaf extracts in fermentation enriches the fermented product with phenolic compounds and antioxidant activity and can be a viable alternative for the provision of bioactive compounds.