Solid-state fermentation for single-cell protein enrichment of guava and cashew by-products and inclusion on cereal bars

Abstract Food byproducts derived from industrial processing present high potential to be reused as ingredients for human nutrition. However, even though food byproducts are often reprocessed and studied, few studies report the inclusion of such byproducts on new food products and assess the new product acceptability. Therefore, on our work guava peels and cashew bagasse were subjected to solid-state fermentation for protein enrichment through single-cell protein and then included on cereal bars for human nutrition. The solid-state fermentation of fruit byproducts was carried out at 30 °C, with 70% equilibrium humidity, 0.9 water activity, and initial Saccharomyces cerevisiae yeast concentration of 3% for the cashew bagasse and 5% for the guava peels. The protein-enriched byproducts were included on three different formulations of cereal bars, and physicochemical, instrumental texture, and sensorial analysis was performed. Multivariate analysis was used to investigate the results. Solid-state fermentation resulted in increased 11 times the protein content of both byproducts. Instrumental texture revealed that high dietary fiber content increases hardness and cohesiveness. All cereal bars presented average scores of 7/10 for sensorial attributes and average 4/5 for purchase intention. During the storage period the cereal bars presented increases in the textural parameters when compared to the control bars. However, all samples revealed compositional stability during the 28-day test period. The overall results suggest that the addition of protein-enriched byproducts is an alternative to add nutritional and economic value to cereal bars.