Characterization of spoilage markers in modified atmosphere packaged iceberg lettuce

• Published in: International journal of food microbiology Vol. 279; pp. 1 - 13
• Main Authors: Ioannidis, Angelos-Gerasimos, Kerckhof, Frederiek-Maarten, Riahi Drif, Yasmine, Vanderroost, Mike, Boon, Nico, Ragaert, Peter, De Meulenaer, Bruno, Devlieghere, Frank
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20-08-2018; Elsevier BV
• Subjects: Acetic acid; Anaerobic conditions; Anaerobiosis - physiology; Bacteria; Browning; Butanediol; Butanol; Colony Count, Microbial; Dimethyl sulfide; Ethanol; Ethyl acetate; Food Microbiology - methods; Food Packaging - methods; Food Preservation - methods; Fresh-cut iceberg lettuce; Gene sequencing; Hazard assessment; Hexanal; Isopentyl alcohol; Lactic acid; Lactic acid bacteria; Lactococcus - classification; Lactococcus - genetics; Lactococcus - isolation & purification; Lactuca - microbiology; Lettuce; Leuconostoc - classification; Leuconostoc - genetics; Leuconostoc - isolation & purification; Mass spectrometry; Mass spectroscopy; Metagenomics; Microorganisms; Modified atmosphere packaging; Odorants - analysis; Odors; Organic compounds; Oxygen; Packaging; Product quality; Pseudomonas; Pseudomonas - classification; Pseudomonas - genetics; Pseudomonas - isolation & purification; rRNA; Selected ion flow tube mass spectrometry; Shelf life; Spoilage; VOCs; Volatile organic compounds; Volatile Organic Compounds - analysis; Volatile organic compounds; Metagenomics; Fresh-cut iceberg lettuce; Modified atmosphere packaging; Spoilage; Selected ion flow tube mass spectrometry
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2018.04.034

Fresh cut iceberg lettuce spoilage was studied considering the microbial and biochemical activity, the formation of volatile organic compounds (VOC) and consumer acceptability. Lettuce was packaged under three different packaging conditions and stored at 4 °C for 10 days: anaerobic packaging (ANAER), equilibrium modified atmosphere packaging with 3% O2 (EMAP) and perforated packages (AIR).
Results indicated a clear distinction between packaging conditions. EMAP and AIR resulted in a short shelf life (≤5.6 days) which was limited due to browning, leading to consumer rejection as assessed via the Weibull hazard analysis method, while no off-odors were detected. Culture- independent 16 s rRNA gene amplicon sequencing revealed Pseudomonas spp. as the dominating species. In contrast, under ANAER conditions, lactic acid bacteria dominated with genera of Leuconostoc spp. and Lactococcus spp. proliferating, while also oligotypes of Pseudomonas spp. were found. Spoilage under ANAER occurred after 6.6 days and it was related to strong fermentative-like off-odors that were present by the end of storage. As revealed by selective ion flow tube mass spectrometry (SIFT-MS), these odors were associated with several VOCs such as: ethanol, 3-methyl-1-butanol, 2,3-butanediol, (Z)-3-hexen-1-ol, hexanal, acetic acid, ethyl acetate and dimethyl sulfide. Panelists rejected the iceberg lettuce due to the formation of off-odors while the overall appearance remained good throughout the study. Hence a sensor based technology incorporated in the packaging, detecting VOCs and in particular ethanol as dominant compound, could serve as a spoilage indicator for ANAER packed lettuce, which proved to have the longest shelf life.
•Spoilage under anaerobic conditions was dominated by Leuconostoc spp. and Lactococcus spp.•Different species of Pseudomonas proliferated under oxygen containing packaging and anaerobic conditions.•An overall production of >100,000 μg/m3 of total alcohols was observed at the end of shelf life.•3% O2 EMAP iceberg lettuce had a limited shelf life due to discoloration.