Thermal processing determination time for fermented and acidified indigenes Iranian vegetables

Abstract

Vegetables may be preserved by fermentation, direct acidification, or a combination of these, along with pasteurization, to yield products with an extended shelf life and enhanced safety. Effect of lowering the pH, either by adding acid or lactic fermentation, on thermal process requirements for canned vegetables was investigated. Malic acid was preferred for acidification of canned vegetables. Addition of acid to covering brine was preferable to the blanching in acid solution, as the acidification was uniform, and it reduced the extent of discolouration. Acidification by lactic fermentation, using 2% hot brine to cover the prepared vegetable, reduced the pH to 3.8 in 3 days. Fermentation is initiated by the species of Leuconostoc and Lactobacillus followed by Pediococcus and Streptococcus, Process time, based on a sterilisation value of = 3.5 min, was adequate to render the canned acidified vegetables (pH ≤ 4.0) microbiologically safe. The process time required for mm and mm cans, having initial temperature of 65°C, was 15 min or less in boiling water. Colour of the lactic fermented canned products was superior to canned vegetables acidified with malic acid. Both had texture similar to that of the freshly cooked vegetables. Products acidified by fermentation had minimal sour taste.

Keywords

• acidified vegetables
• canning
• fermented vegetables
• microbial changes
• storage studies
• thermal processing