QUALITY EVALUATION OF VEGETABLES PROCESSED BY MICROWAVE STERILIZATION/PASTEURIZATION
MetadataShow full item record
Microwave (MW) heating overcomes the disadvantages of slow conductive/convective heat transfer inherent in conventional thermal processes, and therefore has the potential to produce safe and high quality vegetable products. This research was conducted to evaluate the quality attributes of pre-packaged diced carrots after MW pasteurization and of diced tomatoes after MW sterilization, in comparison with those subjected to conventional thermal processing. A systematic study of developing MW sterilization or pasteurization processes for tomato and carrot products, and evaluating their influence on product quality is presented in this thesis. A MW-assisted sterilization thermal process (MAST) achieving a target F value of no less than 6 min was developed for processing diced tomatoes packaged in 8-oz pouches, which can deliver a 5D thermal treatment to Bacillus coagulans ATCC 8038 spores. For diced carrots, MW assisted pasteurization processes (MAP) with F90°C= 3 min and F90°C=10 min were developed to achieve at least 6 D reductions of NP C. botulinum type E spores. Thermal resistance of the target bacterium (B. coagulans spores) in tomatoes was characterized, and kinetics of texture degradation of carrots were investigated for developing thermal processes for these products. Tomato/carrot dices with added salts (NaCl/CaCl2) at commonly used commercial levels were processed, and their dielectric properties were determined and used for computer simulation of heating patterns and cold spot locations in sample pouches. The quality related attributes of processed tomatoes (drained weight, soluble solids, color, texture, ascorbic acid, and lycopene content) and carrots (color, texture, pectin methylesterase activity, and carotenoids) were assessed. The results of quality evaluation of the processed products showed that the impact of MW processing on the quality of vegetables depends on the characteristics of the vegetables and the specific quality parameters tested.