Ripening and spoilage of sugar salted herring with and without nitrate.

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Abstract
Summary: Microbial and chemical changes during ripening with and without nitrate and spoilage of sugar salted (barrel salted) herring were studied using fish from different fishing grounds and different initial quality and fat content. The fish were stored for ripening at 4–6°C for 18 months.The microbial activity in the barrels during ripening was generally low. The flora, which was predominantly aerobic, did not change much during storage and consisted mainly of moderately halophilic gram negative rods (∼ 70%), gram positive cocci (∼ 20%) and yeast (∼ 3%). Some of the microorganisms present were able to reduce trimethylamine‐N‐oxide (TMAO), but none attacked sucrose, which is the sugar added to the curing salt in the barrels. There was no correlation between TMAO reduction and ripening.As both the viable counts and, sometimes, the composition of the microflora could vary considerably in barrels classified as normal, the microorganisms are considered to play a minor role in the ripening process.Two types of microbial spoilage have been identified. The most common type, characterized by development of sour, sour/sweet or putrid off odours and flavours, was caused by growth of a gram negative obligate anaerobic halophilic organism. A second type of spoilage, characterized by development of fruity off odour, was caused by growth of osmotolerant yeast species.