Spoilage Investigation of Chill Stored Meagre (Argyrosomus regius) Using Modern Microbiological and Analytical Techniques

Abstract

Spoilage status of whole and filleted chill-stored meagre caught in January and July was evaluated using sensory, microbiological, 16S metabarcoding and Volatile Organic Compounds (VOCs) analysis. Based on the sensory analysis, shelf-life was 15 and 12 days for the whole fish taken in January and July, respectively, while 7 days for fish fillets of both months. For the whole fish, Total Viable Counts (TVC) at the beginning of storage was 2.90 and 4.73 log cfu/g for fish caught in January and July respectively, while it was found about 3 log cfu/g in fish fillets of both months. The 16S metabarcoding analysis showed different profiles between the two seasons throughout the storage. Pseudomonas (47%) and Psychrobacter (42.5%) dominated in whole meagre of January, while Pseudomonas (66.6%) and Shewanella (10.5%) dominated in fish of July, at the end of shelf-life. Regarding the fillets, Pseudomonas clearly dominated at the end of shelf-life for both months. The volatile profile of meagre was predominated by alcohols and carbonyl compounds. After univariate and multivariate testing, we observed one group of compounds (trimethylamine, 3-methylbutanoic acid, 3-methyl-1-butanol) positively correlating with time of storage and another group with a declining trend (such as heptanal and octanal). Furthermore, the volatile profile seemed to be affected by the fish culturing season. Our findings provide insights into the spoilage mechanism and give information that helps stakeholders to supply meagre products of a high-quality level in national and international commerce.

Volatile Organic Compounds and 16S Metabarcoding in Ice-Stored Red Seabream Pagrus major

“…Red seabream presented similar shelf-life (12 days for both batches based on sensory evaluation) to other ice-stored fish from the Hellenic aquaculture. Shelf-life has been determined from 12 to 16 days for ice-stored gilt-head seabream [ 23 , 24 ] and European seabass [ 25 , 26 ] and from 12 to 15 days for meagre, mainly depending on season of harvesting [ 18 ]. Because shelf-life depends on the initial TVC level, microbial composition, microbial activity, microbial interaction, the type of produced VOCs, etc., under the applied storage conditions [ 9 , 10 ], this study showed that the initial TVC level is a crucial parameter that could be improved in fresh red seabream.…”

“…Aliquots (2 g) of each powdered sample were accurately weighed (±0.01 g) in a porcelain mortar containing 2 g (NH 4 ) 2 SO 4 , homogenized for 20 s and transferred into a 20 mL headspace glass vial. Subsequently, headspace SPME combined with GC-MS analysis was carried out as described by Syropoulou et al [ 18 ].…”

“…The 16S rRNA metabarcoding analysis was applied using the primers 27F (AGRGTTTG ATCMTGGCTCAG) and 519Rmodbio (GWATTACCGCGGCKGCTG), as described by Syropoulou et al [18]. The PCR conditions were as follows: 95 • C for 5 min, followed by 30 cycles of 95 • C for 30 s, 53 • C for 40 s and 72 • C for 1 min, following by a final elongation at 72 • C for 10 min.…”

“…Bioinformatic analysis, including sequences quality filtering, taxonomy classification, rarefaction, and alpha and beta diversity estimation, was applied using the MR DNA ribosomal and functional gene analysis pipeline (www.mrdnalab.com, MR DNA, Shallowater, TX, USA, accessed on 25 December 2021), according to Syropoulou et al [18].…”

“…Headspace SPME sampling combined with GC-MS analysis was used for the monitoring of volatile profile during fish storage on ice. In total, 104 compounds were identified (Table S2), including mostly aldehydes (18), ketones (11), alcohols (18), acids (10) and hydrocarbons (21 aliphatic and 9 aromatic). A lower number of esters ( 5), terpenoids ( 6) and miscellaneous compounds (6) were also detected.…”