Preservative Property of Cut Vegetables Subjected to Steam Heating

Abstract

To study the preservative property of various shredded vegetables treated by steam heating, cabbage, cucumber, and welsh onion were heated with steam in the temperature range of 55-60°C for 5-10min. The treated vegetables were stored at 5, 10, and 15°C for 5 days for the measurement of total bacterial and coliform counts. Almost the same study was also performed on carrot, pumpkin, cauliflower, and potato produced in a vegetable processing plant. The heating conditions were 5 min at 60°C for both cabbage and carrot, 30 min at 80°C for pumpkin and 30 min at 85°C for potato. The results obtained were as follows : (1) Both the bacterial and coliform counts of the cabbage and cucumber heated for 5 min at 60°C were less than 300 CFU/g after storage for 5 days at 15°C. (2) The coliform count of the welsh onion treated for 5 min at 60°C was not greater than 300 CFU/g after storage for 5 days at 10°C, even though the bacterial count showed a small increment. (3) The coliform counts of the vegetables produced in the vegetable processing plant were less than 300CFU/g after storage for 5 days at 10°C and for 48hr at 25°C, in spite of the fact that the bacterial counts of the vegetables preserved at 10°C and 25°C were 3. 5 log CFU/g-4.3 log CFU/g and 4. 5 log CFU/g-7.8 log CFU/g, respectively. Thus, we propose that steam heating is a very useful means of prolonging the shell-life of shredded vegetables because bacterial and coliforms are completely killed if the conditions of the treatment are adequate.