Bacterial communities and potential spoilage markers of whole blue crab (Callinectes sapidus) stored under commercial simulated conditions

Abstract

Bacterial communities composition using 16S Next Generation Sequencing (NGS) and Volatile Organic Compounds (VOCs) profile of whole blue crabs (Callinectes sapidus) stored at 4 and 10 °C (proper and abuse temperature) simulating real storage conditions were performed. Conventional microbiological and chemical analyses (Total Volatile Base-Nitrogen/TVB-N and Trimethylamine-Nitrogen/TMA-N) were also carried out. The rejection time point was 10 and 6 days for the whole crabs stored at 4 and 10 °C, respectively, as determined by development of unpleasant odors, which coincided with crabs death. Initially, the Aerobic Plate Count (APC) was 4.87 log cfu/g and increased by 3 logs at the rejection time. The 16S NGS analysis of DNA extracted directly from the crab tissue (culture-independent method), showed that the initial microbiota of the blue crab mainly consisted of Candidatus Bacilloplasma, while potential pathogens e.g. Listeria monocytogenes, Pseudomonas aeruginosa and Acinetobacter baumannii, were also found. At the rejection point, bacteria of Rhodobacteraceae family (52%) and Vibrio spp. (40.2%) dominated at 4 and 10 °C, respectively. TVB-N and TMA-N also increased, reaching higher values at higher storage temperature. The relative concentrations of some VOCs such as 1-octen-3-ol, trans-2-octenal, trans,trans-2,4-heptadienal, 2-butanone, 3-butanone, 2-heptanone, ethyl isobutyrate, ethyl acetate, ethyl-2-methylbutyrate, ethyl isovalerate, hexanoic acid ethyl ester and indole, exhibited an increasing trend during crab storage, making them promising spoilage markers. The composition of microbial communities at different storage temperatures was examined by 16S amplicon meta-barcoding analysis. This kind of analysis in conjugation with the volatile profile can be used to explore the microbiological quality and further assist towards the application of the appropriate strategies to extend crab shelf-life and protect consumer's health. © 2019