The rôle of acidity in vegetable canning

Abstract does not appear. First page follows.

Present industrial methods of sterilizing canned vegetables of low acidity result in considerable injury to texture, flavor, and color because of the high temperatures and long periods of heating necessary to destroy heat resistant organisms. Because of the lack of proper facilities, it is not feasible in many homes, to apply the temperatures necessary to sterilize vegetables, and heating for one to three hours, at the temperature of boiling water, a method formerly recommended for home use, has been proved unsafe because it does not always destroy the spores of B. botulinus.

It is a well recognized fact that vegetables of high acidity, such as rhubarb and tomatoes, are easily sterilized. It is also well known that the addition of dilute organic acids to the brines used in canning makes it possible to preserve vegetables of low acidity by heating at 100° C.

However, previous investigations showed considerable variation in the effect of added acid on the sterilization of various vegetables. Not all vegetables behaved alike. Preliminary observations also showed that at least some of the variations observed could be traced to marked changes in pH value of the acidified brines during heating. Therefore, one part of the present investigation was to determine the magnitude of these changes in pH value.

A second part was to determine more accurately than had been done previously the effect of acidified brines on the sterilization of vegetables of low acidity artificially contaminated with large numbers of heat resistant microörganisms.