Optimization for koji-making technology of fermented almond paste by response surface methodology

In order to enrich the almond product market, using cold-pressed defatted almond protein powder as raw material, Aspergillus oryzae and Aspergillus niger as koji-making strains, a fermented almond paste was prepared by mixed strains fermentation method. Using protease activity as response value, the koji-making technology was optimized by single-factor and response surface tests. The results showed that the optimal koji-making technology for fermented almond paste was as follows: mixed fungal powder addition 0.7%, koji-making temperature 30 ℃, and inoculum ratio of A. oryzae and A. niger 3∶1. Under these optimized conditions, the protease activity was 0.62 g amino acid nitrogen per 100 g koji, sensory score was 8.6, the koji had rich flavor, fresh yellow-green color, soft texture, and uniform mycelium distribution, which provided a preliminary enzymatic finished koji guarantee for the development of almond paste products.