Microbiota, volatile compounds and odor during production and storage of rehydrated, packaged, ready-to-cook stockfish of Atlantic cod (Gadus morhua L.)

Summary

Improved quality control and sufficient time of shelf life are essential for the industrialized production of rehydrated stockfish products. The traditional stockfish is sold as dry and needs 7–9 days of rehydration before cooking. Developing high-quality, ready-to-cook products creates an opportunity for the industry to meet the demands of modern households. The aim of the presented study is to identify the quality of vacuum packaged, rehydrated stockfish with different fish raw materials and handling during intermediate storage and rehydration, as well as compare it to other packaging methods of the rehydrated stockfish. Microbial composition and quantity and volatile organic compounds (VOCs) of rehydrated stockfish of Atlantic cod (Gadus morhua) were determined, prepared from two different raw materials, and stored for two months at two different conditions (10 °C or −40 °C) after the outdoor drying and rehydrated either with or without the skin for 7 and 9 days at 2 °C. Furthermore, the role of different packaging methods was tested. Microbial analyses, analysis of VOCs, and sensory descriptive analysis of the odor of the rehydrated and packaged samples were performed. The results indicate a shift in the microbial composition from a predominance of Photobacterium, Acinetobacter, and Pseudomonas in the raw material to a predominance of Psychrobacter, Pseudomonas, and Carnobacterium in the rehydrated stockfish stored using different packaging methods. The total viable count increased during the entire process. Among the VOCs, 3-methyl-1-butanol increased from the dried to the soaked product while the trimethyl amine (TMA) was quite stable. The content of yeast was reduced during rehydration. Odor description by the attributes fermented/sour, sulfurous and ammonia were most pronounced, with additional comments on chlorine and cloying by the assessors to describe quality changes during storage. Both odor and VOCs seem to be promising tools to evaluate quality changes and should be further studied. All in all, small differences in quality were found for rehydrated stockfish, based on fish raw materials, intermediate storage, and rehydration methods, and compared to other packaging methods.