Microbial decontamination of onion powder using microwave-powered cold plasma treatments

• Published in: Food microbiology 2017-04, Vol.62, p.112-123
• Main Authors: Kim, Jung Eun, Oh, Yeong Ji, Won, Mee Yeon, Lee, Kwang-Sik, Min, Sea C.
• Format: Article
• Language: English
• Subjects: Allium cepa; antioxidant activity; Aspergillus; Aspergillus - chemistry; Aspergillus - growth & development; Aspergillus - radiation effects; Bacillus cereus; Bacillus cereus - growth & development; Bacillus cereus - radiation effects; cold; Cold plasma; Colony Count, Microbial; color; decontamination; Decontamination - methods; Escherichia coli; Escherichia coli O157; Escherichia coli O157 - growth & development; Escherichia coli O157 - radiation effects; Food Microbiology; Food Preservation; Food Safety - methods; Foodborne pathogens; Helium; Hot Temperature; Microwave; Microwaves; Onion powder; onions; Onions - chemistry; Onions - microbiology; Plasma Gases; Powders - analysis; Powders - chemistry; quercetin; Quercetin - analysis; sensory properties; spores; Spores, Bacterial - radiation effects; temperature; vacuum drying; volatile compounds
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2016.10.006

The effects of microwave-integrated cold plasma (CP) treatments against spores of Bacillus cereus and Aspergillus brasiliensis and Escherichia coli O157:H7 on onion powder were investigated. The growth of B. cereus, A. brasiliensis, and E. coli O157:H7 in the treated onion powder was assessed during storage at 4 and 25 °C, along with the physicochemical and sensory properties of the powder. Onion powder inoculated with B. cereus was treated with CP using helium as a plasma-forming gas, with simultaneous exposure to low microwave density at 170 mW m−2 or high microwave density at 250 mW m−2. High microwave density-CP treatment (HMCPT) was more effective than low microwave density-CP treatment (LMCPT) in inhibiting B. cereus spores, but induced the changes in the volatile profile of powder. Increase in treatment time in HMCPT yielded greater inhibition of B. cereus spores. Vacuum drying led to greater inhibition of spores of B. cereus and A. brasiliensis than hot-air drying. HMCPT at 400 W for 40 min, determined as the optimum conditions for B. cereus spore inhibition, initially reduced the numbers of B. cereus, A. brasiliensis, and E. coli O157:H7 by 2.1 log spores/cm2, 1.6 log spores/cm2, and 1.9 CFU/cm2, respectively. The reduced number of B. cereus spores remained constant, while the number of A. brasiliensis spores in the treated powder increased gradually during storage at 4 and 25 °C and was not different from the number of spores in untreated samples by the end of storage at 4 °C. The E. coli counts in the treated powder fell below the level of detection after day 21 at both temperatures. HMCPT did not affect the color, antioxidant activity, or quercetin concentration of the powder during storage at both temperatures. The microwave-integrated CPTs showed potential for nonthermal decontamination of onion powder. •Cold plasma treatment at high microwave power density (HMCPT) was investigated.•HMCPT improved the microbiological safety and storage stability of onion powder.•HMCPT inactivated microorganisms effectively on vacuum-dried onion powder.•HMCPT facilitates nonthermal decontamination of onion powder.•HMCPT did not affect antioxidant activity or quercetin content in onion powder.