Buffering action of nonacid vegetables

does not appear. First page follows. Juices from all plant tissues exhibit more or less ability to resist changes in pH value on the addition of strong acids or bases(15).3 The substances responsible for this buffering capacity have not been completely defined largely owing to the complexity of the systems involved. The complex nature of the extracted juices increases the difficulties of identifying the specific buffer substances. In those plant juices which have been investigated most extensively, the buffer capacity has been ascribed to organic acids(10), dialyzable acid-salt systems(14), proteins(6), and acid phosphates(9). Probably the buffering is also due to the adsorption reactions of the colloids as well as to dissociation of the weak acids or bases that may be present. The buffering capacity of nonacid vegetables is of particular importance in connection with the use of acidified brines in canning. Cruess, Fong, and Liu(4) found that nonacid vegetables canned with a sufficiently acid brine to bring their pH value below 4.5 may be readily pasteurized in boiling water and need not be processed in steam-heated pressure cookers. These investigators found, however, that the nonacid vegetables exerted a pronounced buffering action when canned in brines acidified with hydrochloric, citric, or acetic acids: a marked rise in pH value of the added brine occurred during heating. The increase was much greater than could be accounted for by diffusion, and they concluded that the rise in pH value was probably caused principally by the action of buffer substances dissolved from the vegetables. Bigelow and Cathcart(2) had also noted that when beans were canned with tomato sauce there was an increase in pH value of the sauce which they stated to be “due to diffusion of acids into the beans.” Aside from the work of the above investigators, no detailed study of the buffer capacity of nonacid vegetables is available.