Application of CO2 micro- and nano-bubbles at lower pressure and room temperature to inactivate microorganisms in cut wakegi (Allium wakegi Araki)
F. Kobayashi, H. Ikeura, M. Tamaki, and Y. Hayata
Book of Abstracts, Southeast Asia Symposium Quality and Safety of Fresh and Fresh Cut Produce Greater Mekong Subregion Conference on Postharvest Quality Management in Chains, August 3-5, 2009, Radisson Hotel, Bangkok, Thailand.
2009
บทคัดย่อ
Cut vegetables have become popular among consumers in the past few decades. Washing with sodium hypochlorite (NaOCl) solution is the most common method used for preventing cut vegetables from spoiling. However, some organic compounds react easily with available chlorine to from toxic chlorinated products. Thus, other disinfection methods to replace NaOCl treatment are being explored. We previously devised an instrument with CO2 micro- and nano-bubbles under pressure less than 2.0 MPa (MNB-CO2) for inactivating microorganisms in food at room temperature. The aim of this study was to investigate the effect of MNB-CO2 on the inactivation of microorganisms in cut wakegi (Allium wakegi Araki), which are difficult to inactivate with NaOCl.
Ten grams of wakegi cut into about 1.0 cm2 pieces was used as a sample. MNB-CO2 treatment was conducted at each condition of pressure (0.1-2.0 MPa), temperature (20-30°C) and solution pH (3.0-6.5) for 10-30 min. Also, for comparison, cut wakegi was immersed in 100 ppm NaOCl solution at 20-30°C for 10-30 min and washed for 5 min to remove residual NaOCl. The numbers of total and coliform bacteria in cut wakegi before and after MNB-CO2 and NaOCl treatments were measured by the colony count method.
Total and coliform bacteria in cut wakegi were effectively inactivated by MNB-CO2. The inactivation effect of MNB-CO2 treatment was almost the as that of NaOCl treatment. The number of total and coliform bacteria significantly decreased with increasing pressure and temperature in the MNB-CO2 treatment, and especially with decreasing the solution pH. These results suggested that MNB-CO2 treatment at pressure less than 2.0 MPa and room temperature was very effective at inactivating microorganisms in cut wakegi as an alternative to NaOCl treatment.