Changes of bacterial communities of rainbow trout (Oncorhynchus mykiss) at different processing steps in the production of burgers and their storage life enhancement by an acetate-based preservative

Fresh trout (Oncorhynchus mykiss) is a healthy and nutritious food which can be used for formulating ready-to-cook fish preparations, such as trout burgers. To investigate the impact of processing and the use of an acetate-based preservative on the spoilage microbiota and storage life of burgers, the dynamics of microbial communities were examined by using a combination of culture-dependent/independent techniques, Monte Carlo simulation, and PICRUSt2 analysis. Results of the microbial community analyses showed that most of the taxa of trout were lost during processing into burgers. Along the processing steps, an increase of contamination, with Flavobacterium and Pseudomonas becoming the most relative abundant genera in pulp and burgers, respectively, was observed. The Pseudomonas dynamic pattern was supported by the Monte Carlo simulation, which gave a picture of the bacterial transfer. Verdad® N6, which is a commercially available acetate-rich fermentate, was evaluated as preservative treatment for burgers during their storage life. Pseudomonas dominated the microbial community of stored burgers, irrespective of the treatment. However, their levels were lower in the fermentate-treated samples, which presented Lactobacillus as the second most relative abundant genus. PICRUSt2 analysis showed that Pseudomonas-correlated metabolic pathways of hexitol fermentation were significantly lower at the end of the storage period in burgers supplemented with the fermentate, corroborating Pseudomonas minor contribution to the metabolic activity. In summary, Verdad® N6, through its inhibiting effects on spoilage bacteria is an option for producing burgers with increased storage life.