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Modified atmosphere packaging pre-storage treatment for thermal control of E. coli ATCC 25922 in almond kernels assisted by radio frequency energy

Cheng, Teng, Wang, Shaojin
Journal of food engineering 2019 v.246 pp. 253-260
Escherichia coli, air, almonds, color, energy, fatty acids, heat tolerance, heating systems, modified atmosphere packaging, pasteurization, peroxide value, radio waves, seeds, sustainable technology
The purposes of this study were to validate modified atmosphere packaging (MAP) pre-storage for reducing surviving populations and thermal resistance of E. coli ATCC 25922 in almond kernels. A 6 kW, 27.12 MHz radio frequency (RF) assisted hot air heating system was used to conduct thermal treatments of 1.5 kg MAP pre-storage samples. Surviving populations of E. coli ATCC 25922 in almond kernels with 8.0% wet basis were determined weekly for 12-week pre-storage and samples were removed at five different time intervals during thermal treatments to achieve at least 4-log reduction. The results showed that reduction levels of E. coli for MAP and regular atmosphere packaging (RAP) were 1.47 ± 0.08 and 0.61 ± 0.05 log CFU/g after 12-week pre-storage. The 4-log reduction time of E. coli in MAP was 18 ± 1 min holding after RF assisted heating to 75 ± 2 °C, reducing 40% pasteurization time as compared with RAP pre-storage. Fatty acid and peroxide values remained within acceptable range (FA < 0.6% and PV < 1.0 meq/kg), and color values of treated samples were not significantly (p > 0.05) different from those of untreated ones. MAP pre-storage assisted thermal treatments induced by RF energy may hold potential as an effective and environmentally friendly method to control E. coli ATCC 25922 in almond kernels.