Exploring the use of Aspergillus oryzae for the development of innovative fish-based sausages

Introduction: Consumer interest in fermented foods and sustainable protein sources has increased considerably in recent years, driving the development of novel food products. Although fermented meat sausages are widely consumed, fermented fish-based alternatives remain scarce. This study explored the use of Aspergillus oryzae during the production of an innovative Portuguese-style fish-based sausage and evaluated its microbiological, physicochemical, and nutritional characteristics.

Methods: Fish-based sausages were produced using yellowfin tuna (Thunnus albacares) and surface-inoculated with A. oryzae. After fermentation and dehydration until approximately 40% weight loss, physicochemical parameters (pH and water activity), proximate composition, and microbiological analyses were determined according to standardized methods at different processing stages.

Results: Nutritionally, the product was characterized by a high protein content (30.5 g/100 g) and a fat content below 0.5 g/100 g, meeting the criteria for the “high protein” and “fat-free” nutrition claims defined by European legislation (Regulation (EC) No. 1924/2006). Physicochemical analysis showed a pH of 6.24 and an a_w of 0.926, indicating the need for refrigerated storage. Mesophilic aerobic counts increased by 2.4 log CFU/g after fermentation and remained stable thereafter. Mould counts increased by 4.3 log CFU/g in the final product, which may be associated with the inoculation of the product. Lactic acid bacteria increased by 3.8 log CFU/g, while yeast counts decreased throughout processing. Enterobacteriaceae levels remained stable from the beginning, and Listeria monocytogenes, Clostridium spp., and Bacillus cereus remained below the detection limit (<50 CFU/g).

Conclusions: The results demonstrate the feasibility of using A. oryzae during the production of an innovative fish-based sausage. The developed product exhibited a satisfactory microbiological profile and a favorable nutritional composition, meeting the criteria for the European “high protein” and “fat-free” nutrition claims, thereby supporting its potential as an innovative and sustainable alternative to conventional fermented sausages.