Market life of diced red onion subjected to modified atmosphere packaging and antimicrobial dips
Fresh-cut red sweet onions (Allium cepa L.) have a short shelf life and are subject to loss of acceptable flavour, excessive microbial growth, and discoloration. Atmosphere modification and antimicrobial compounds have the potential to extend shelf-life. Therefore, this study evaluated the effects of modified atmosphere packaging (MAP) and treatments with potassium sorbate (KS) and chlorine dioxide (ClO2) on the quality of diced red onions. Red onions were sanitized, diced, and dipped for 1 min in 1.0% KS, 15 ppm ClO2, or water and spun for 10 s at 3,000 rpm to remove excess liquid. Diced red onions that received no dip treatment served as the control. Onions were then placed into sealed or vented, ridged polylactic acid (PLA) containers. Venting consisted of a single 0.07 mm hole. Packages were stored at 4.5°C and assessed after 0, 7, 12, 14, 18, and 21 days. The O2 concentration in sealed PLA containers decreased to ±1% and the CO2 concentration increased to ±35% after 18 days. The atmosphere composition in the vented containers changed slightly during storage reaching 18% O2 and 4% CO2 after 21 days. Respiration rates increased during storage, but remained the lowest in diced onions treated with 1.0% KS. The electrolyte leakage also increased during storage, but was lowestt in onions treated with ClO2 and water, reaching 30 and 37%, respectively after 21 days, while rates in the KS treated onions and controls reached 55 and 52%, respectively. Onion pH tended to decrease during storage, which was lowest in vented packages. Aerobic and anaerobic microbial plate counts exceeded 106 CFU g-1 after 12 days in all treatments. The aerobic and anaerobic counts were less in sealed packages, but were not significantly affected by antimicrobial dips. Potassium sorbate changed the onion colour from a purple-red to a pink hue. Onions treated with ClO2 appeared dry after 7 days. After 14 days of storage, off-odours developed in association with anaerobic atmospheres and/or microbial growth. The marketable quality of diced red onions was maintained for 12 days in sealed PLA packages.
Forney, C.F., Fan, L., Doucette, C., Jordan, M.A. and Grant, R. (2018). Market life of diced red onion subjected to modified atmosphere packaging and antimicrobial dips. Acta Hortic. 1209, 201-208
Allium cepa, polylactic acid, potassium sorbate, chlorine dioxide, sulfur volatiles, microbial growth