Quality and shelf life of sliced root of Platycodon grandiflorum treated by ozon-microbubble-heat shock

Abstract

The quality and shelf life of sliced root of Platycodon grandiflorum (Doraji) treated by ozon-microbubble-heat shock (OMH) were investigated by combining modified-atmosphere packaging [MAP, (50% O2+15% CO2+35% N2)]. The study was based on microbiological (total viable bacteria, fungi, Enterobacteriaceae and coliforms numbers), physicochemical and sensory changes. OMH treatment was effective in reducing microbial populations of the sliced Doraji, especially Enterobacteriaceae and coliforms reduced by 2 log CFU/g. However OMH-MAP treatment remained the aerobe and fungi numbers. Regarding the color, OMH-MAP delayed the change of Hunter b* and the sliced Doraji by OMH-MAP treatment exhibited lower decrease of flavor and overall acceptability compared to those by polypropylene packaging after tap water treatment (Control). The OMH and 50%O2+15%CO2 MAP treatment gave better sensory quality and extended shelf-life for sliced Doraji (~3 days longer shelf-life than Control). Flavor was significantly related to overall acceptability at both Control and OMH-MAP, whereas total coliforms prevalence was associated with overall acceptability at only OMH-MAP. Therefore microbubble-heat shock treatment may improve microbial safety and sliced Doraji by OMH treatment can stored under 50%O2+15%CO2 treatment for up to 7 days. Thus, OMH and MAP treatment may be used in maintaining the storage quality and marketability of sliced Doraji.