Selection of Alternative Indicators for Monitoring the Washing Effect of Salted Cabbages

Introduction: The washing process is an important step to reduce the level of microorganisms in fresh fruits and vegetables. The real-time effectiveness of washing is hard to be evaluated since it is impossible to measure the microorganism levels on vegetables during continuous washing step.

Purpose: The purpose of this study was to select alternative indicators equivalent to assure the level of microorganisms in salted vegetables in washing processes.

Methods: Throughout the four washing steps, salted cabbages and washed waters were collected, and turbidity and salinity in washed water were measured at predetermined time intervals. The monitoring was repeated for nine months. The level of total aerobic counts and coliforms in cabbages and waters were analyzed. The correlation between the number of total aerobic counts and turbidity or salinity were evaluated.

Results: The level of total aerobic counts in cabbages and waters, turbidity and salinity were decreased with washing steps, while increased with processing time. The range of turbidity was 0-50 NTU while 0-5% of salinity. About 0.8 log CFU/g of total aerobic counts in cabbages, and 0.8-1.2 log CFU/g, 0.8-1.4 log NTU of turbidity and 2% of salinity in washed water were increased with processing time, which means that enough water should be supplied continuously to maintain the level of microorganisms during washing steps. The log CFU/g of total aerobic counts was well correlated with the log scale of turbidity (R² = 0.942) and salinity (R² = 0.804), and the 10 NTU of turbidity and 1% of salinity indicated about 5.0 log CFU/g of total aerobic counts in washed water.

Significance: These results suggest that the real-time monitoring of turbidity system combined with control of water supply would be applied to maintain the washing effect of fresh vegetables.