Thermal Processing of Acidified Vegetables: Effect on Process Time-Temperature, Color and Texture
Harsimar Singh, Hosahalli S. Ramaswamy
Abstract
The objective of this study was to compare the quality of low-acid vegetables conventionally thermal processed with those subjected to modified thermal processing following acidification to pH < 4.6. For conventional processing, a process lethality (Fo value) equivalent of 5 min at 121.1 °C (commercially sterilization) was used, while those that are acidified were pasteurized, such as acidic foods, to a lethality value of 10 min at 90 °C. Acidification was performed with citric acid by immersion of vegetables in an ultrasonic bath. The quality of raw, blanched, acidified, pasteurized and sterilized products were compared for color and textural characteristics. The acidified thermal processing yielded significantly better retained color and textural properties, almost similar to blanched vegetables, while those subjected to the conventional processing resulted in significant texture loss. The process temperatures were significantly lower, and corresponding process intensities were significantly less severe with the acidified thermal process, providing significant energy saving opportunities. The absorbed acid could easily be leached out by heating/holding the vegetables in tap water, if it was desired, to reduce the acidity level in the processed vegetables. There is significant current interest in acidified thermal processing of low acid- foods with quality retention being the main focus. While it is possible that some meat products may suffer quality loss, for vegetables, in general, the negative influence is significantly low, and the positive potential for quality retention, energy savings and process efficiency are very high.