QUALITY CHANGES OF SEAFOOD IN MICROWAVE ASSISTED PASTEURIZATION

Jungang Wang

The potential of using 915-MHz single-mode pilot-scale microwave assisted pasteurization system (MAPS) for seafood products processing was investigated in this dissertation in three studies: 1) developing a new chemical marker method based on caramelization reaction; 2) studying thermal kinetic degradation of shrimp quality; 3) evaluating textural properties of Pacific whiting (PW) surimi in MAPS. Specifically, a new chemical marker - model food system with high-sensitivity and low-cost properties was developed to determine the heating pattern in MAPS. The caramelization reaction was first used to produce the chemical marker as the time-temperature indicator, and the brown color produced by D-Ribose in an alkali medium (NaOH) linearly increased with the increasing time and temperature. After processing in MAPS, the heating pattern of the new chemical marker - model food could be clearly recognized, and the cold and hot spots were precisely located for future process development. Shrimp and surimi were selected for quality studies related to MAPS processing of seafoods. A kinetic study was conducted to evaluate quality changes of shrimp during thermal processing to select appropriate process conditions using MAPS. Whole shrimp samples (Liptopenaeus setiferus) were heat treated in sealed aluminum cells between 1-80 min at 60 to 100 °C. With increased heating time and temperature, cook loss, area shrinkage, and hardness of shrimp increased and followed a fractional first-order kinetic model, while the overall color change increased and followed a zero-kinetic model. High positive correlations were found among cook loss, area shrinkage, and hardness. Influence of process temperature and time on quality (textural properties) of PW surimi were first investigated with isotherm tests. Better textures were achieved with higher heating rates. A gellan gel model food with dielectric properties similar to surimi was developed and used to determine the location of cold spot in MAPS. A MAPS process was then developed to achieve thermal pasteurization (> 6 log reduction of Clostridium botulinum type E) in cold spot. Textures of PW surimi were significantly improved in MAPS. The research results demonstrate that MAPS is effective in achieving higher quality for heat-sensitive seafood products while ensuring food safety.

QUALITY CHANGES OF SEAFOOD IN MICROWAVE ASSISTED PASTEURIZATION

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