Microbiological spoilage and investigation of volatile profile during storage of sea bream fillets under various conditions
Volatile organic compound (VOC) profile was determined during storage of sea bream (Sparus aurata) fillets under air and Modified Atmosphere Packaging (MAP CO2/O-2/N-2: 60/10/30) at 0,5 and 15 degrees C. Microbiological, TVB-N (Total Volatile Base Nitrogen) and sensory changes were also monitored. Shelf-life of sea bream fillets stored under air was 14,5 and 2 days (d) at 0,5 and 15 degrees C respectively, while under MAP was 18, 8, and 2 d at 0, 5 and 15 degrees C respectively. At the end of shelf life, the total microbial population ranged from 7.5 to 8.5 log cfu/g. Pseudomonas spp. were among the dominant spoilage microorganisms in all cases, however growth of Brochothrix thermosphacta and Lactic Acid Bacteria (LAB) were favoured under MAP compared to air. TVB-N production was favoured at higher temperatures and under air compared to lower temperatures and MAP. TVB-N increased substantially from the middle of storage and its value never reached concentrations higher than 30-35 mg N/100 g, which is the legislation limit, making it a poor chemical spoilage index (CSI). A lot of alcohols, aldehydes, ketones and ethyl esters that were detected in the present study have been reported as bacterial metabolites, others as products of chemical oxidation while others as aroma constituents. VOCs such as 3-methylbutanal, acetic acid, ethanol, ethyl esters of isovaleric and 2-methylbutyric acids, 1-penten-3-ol, 1-octen-3-ol and cis-4-heptenal appeared from the early or middle stages and increased until the end of storage. From those only 3-methylbutanal, acetic add, ethanol and the ethyl esters have been reported as microbial origin, making them potential CSI candidates of sea bream fillets. (C) 2014 Elsevier B.V. All rights reserved.