A process of preparing a hydrolysate of an edible solid substrate is provided. The edible solid substrate may be of animal or plant origin including edible animal meat, fish meat, shellfish meat or an edible plant or a combination thereof. The process includes preparing a fermented koji from a protein containing material and a carbohydrate, mixing the fermented koji with a selected edible solid substrate to form a mixture and hydrolysing the mixture in an environment with less than 2% salt content, preferably in a substantially salt-free condition. In another embodiment, the fermented koji may be prepared from an edible solid substrate itself. The hydrolysate may be further subjected to a moromi fermentation stage to obtain a food composition. Alternatively, a culture of a lactic acid bacteria may be inoculated to the mixture prior to the hydrolysis, which therefore eliminates the moromi fermentation and accelerated the process.