Influence of Packaging on Loss of Aroma and Quality of Diced Red Onions.
Fresh-cut onions (Allium cepa L.) have a short self life and are subject to loss of acceptable flavour, excessive microbial growth, and discoloration. Proper packaging can reduce quality loss. Therefore, this study evaluated a package made of the biodegradable polymer polylactide (PLA) for its effectiveness to maintain the aroma and quality of diced red onions. Whole red onions were peeled, sanitized, diced, and placed into ridged PLA containers or polyethylene (PE) bags. The PLA containers were sealed with intact or vented (one 0.07 mm hole) PLA lids and PE bags were sealed with a heat sealer. Onion packages were stored at 4.5°C and assessed after 0, 7, 12, 14, 18, and 21 days for volatile content, package atmosphere composition, respiratory gas exchange rate, electrolyte leakage, pH, microbial quality, and sensory quality. After 7 days, the total headspace volatile content of onions stored in sealed PLA containers decreased by only 15% compared to 98 and 85% in the vented PLA and sealed PE packages, respectively. The retention of volatiles was associated with a greater fresh onion odour. However, after 14 days of storage, off odours developed in association with anaerobic atmospheres and/or microbial growth. During the 21 days of storage, onion respiratory gas exchange rates increased 5- to 6-fold and electrolyte leakage doubled. Aerobic and anaerobic microbial plate counts exceeded 106 CFU/g after 12 days. Marketable quality of diced red onions was maintained for 12 days in the sealed PLA and PE packages.
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