Weak acids’ microbial and sensorial effect on marinated herring

Abstract: Marinated herring is a food product usually with a sauce containing acetic acid. In this project the weak acids malic acid, citric acid, and lactic acid were evaluated for use in the sauce for marinated herring instead of using acetic acid. The microbial and sensorial effects of the acids were evaluated. From the sensorial test, the marinated herring in a sauce with lactic acid was chosen as the favourite of the majority in the sensory panel since it was milder than the rest. The type with sauce containing malic acid was the least favoured due to high sourness and unbalanced flavours. It was concluded from the sensorial test that there were only small differences between the versions. The texture of the herrings was believed by the panel to differ between the acids but texture analysis showed no significant difference. Accelerated test and microbial tests with the pickled herring jars to evaluate the shelf life indicated that there was no big difference in the presence of microorganisms depending on the acid. In the project accelerated tests using MRS growth medium inoculated with Lactobacillus plantarum (L. plantarum) CCUG 30503 T were performed. The MRS was modified with sodium chloride and weak acids to resemble the environment in a pickled herring jar. The results indicated that L. plantarum can grow well in the presence of acetic acid, malic acid, citric acid, and lactic acid. Malic acid and citric acid had least effect on the bacteria while the acetic acid had the highest effect resulting in a lower growth. In the samples with lactic acid the level of L. plantarum was stable on a higher concentration than in the rest of the samples when the highest concentration had been reached.