INFLUENCE of GLUCONIC ACID ON THERMAL PROCESSING REQUIREMENTS FOR CANNED WHOLE PEELED TOMATOES

Methods of detecting the activities of endogenous tomato pectin esterase and polygalacturonase were developed and used to measure heat resistance parameters for enzymes in tomato homogenates. Addition of 0.44% gluconic acid reduced heat resistance of pectin esterase which is responsible for gel formation in canned whole peeled tomatoes. However, heat inactivation of tomato polygalacturonase, which is responsible for general degradation of texture/consistency in tomato products, was not significantly affected by addition of up to 1.65% by wt gluconic acid. Pectic enzymes in canned whole peeled tomatoes packed in juice in 303 × 406 cans were inactivated in 35 min at 98.9 and 101.7°C, 26 min at 110.0°C or 25 min at 118.3°C.