Effect of precooking and polyphosphate treatment on the quality of microwave cooked catfish fillets

In the U.S. market place, there are many examples of precooked poultry products designed to be reheated in a microwave oven and, to a lesser extent, fish products such as tilapia. However, few U.S. catfish products are designed to be microwave cooked or reheated. The first objective of this study was to examine the properties of microwave cooked raw frozen catfish fillets and oven precooked (to 62.8°C) frozen fillets and then reheated by microwave cooking. The second objective was to evaluate changes in properties as a consequence of treatment with a commercial polyphosphate blend (Individually Quick Frozen [IQF]). The sample analysis included weight loss, proximate content, color (CIE L*a*b*), pH, mechanical texture (hardness), and lipid peroxidation (TBARS) measurements. Frozen fillets which contained polyphosphate showed <4% moisture loss after microwave cooking, relative to a 12% moisture loss for fillets without polyphosphate. A large cooking loss of ~40% was observed for precooked fillets after microwave cooking, correlated with a higher percent moisture loss (11% and 13% for fillets with and without polyphosphate, respectively) to comparable samples that were not precooked. For both types of fillets, an increased amount of yellow color was observed for precooked fillets after microwave cooking, relative to comparable fillets that were not precooked. Fillet hardness determined by peak force revealed an overall harder texture (~1.1–1.8 times) for fillets without polyphosphate than fillets with polyphosphate. This study will be used to develop precooked catfish products that can be reheated in a microwave oven.