Mould starter selection for extended solid-state fermentation of quinoa

Abstract

Solid-state fermentation of plant materials with food grade moulds is considered a method of obtaining bioactive food products and additives. However, the use of quinoa seeds as a substrate in such a process has not been thoroughly studied to date. In this paper, extended fermentation with Rhizopus oligosporus, Aspergillus oryzae and Neurospora intermedia (tempe, koji and oncom moulds, respectively) was performed in order to enhance the antioxidant potential of coloured quinoa (as measured by the total soluble phenols, ABTS˙+ and ˙OH scavenging activities, and the reducing power).The most efficient of the examined strains was Rhizopus, which caused an average improvement in the aforementioned qualities of 220% (black seeds) and 129% (red seeds), as compared to pre-cooked seeds. Four-day fermentation with Rhizopus resulted in a drastically enhanced amount of vanillin in the free phenolic fraction (130-fold in black quinoa seeds). However, the overall level of free and bound phenolics (as measured by the HPLC-DAD-ESI-TOF-MS method) in the material decreased. Both total peptides and individual free amino acid levels were significantly increased, which corresponded with the high antioxidant potential of the material. The fermented quinoa was also significantly enriched with total dietary fibre with dominant insoluble fraction.