Acid Equilibrium Development in Mushrooms, Pearl Onions and Cherry Peppers

Mushrooms, pearl onions, and cherry peppers were packed with either citric acid or acetic acid to determine the time required for the pH inside the particulates to decrease to 4.8 or less. The blanched products were packed into home canning jars, covered with acidified brine, and pasteurized in steam at 100°C. After storage at 25°C, pH measurements were taken on samples of drained brine, individual particulates, and a puree of all particulates. With acetic acid, equilibrium pH was achieved in approximately 1, 15, and 30 d for mushrooms, onions, and peppers, respectively. Longer times would be required to achieve equilibrium pH for each product with citric acid. The time required for the pH inside the particulates to decrease to 4.8 or less was a function of acid type, initial acid concentration, and the product being acidified. With sufficient acidulant to achieve an equilibrium pH of 4.6 or less, the time required for particulates of mushrooms, onions, or peppers to decrease to pH 4.8 or less was 7 d or less in all instances. Since studies (inoculated packs) of similar products have shown that a minimum of about 10 d is required for Clostridium botulinum growth at a pH of 5.0, the rate of acidification for these products was sufficient to prevent growth of C. botulinum .