Date of Award

2001

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

First Advisor

Witoon Prinyawiwatkul

Abstract

Between 45--55% of viscera, head, skin, intestine and slurries are generally generated as byproducts or waste from catfish filleting process. Our preliminary study showed that the crude fat content of the whole catfish viscera was 30--35% (wet basis) and the total o-3 fatty acids of oils recovered from the whole and/or portioned viscera ranged from 4.3--20.9 mg/g (dry basis). Catfish viscera may serve as an excellent source of health-promoting oil. Yield of purified (deodorized) catfish visceral oil was 65.7% and contained considerable amounts of DHA (1.21 mg/g of oil) and omega-3 fatty acid (4.6 mg/g of oil). A rapid microwave-assisted method for fatty acid analysis was developed. The microwave heating power (%) and time (sec) required for maximal fatty acid recovery were determined. Heating at 100% power for 80 sec yielded the highest recovery of DHA (C22:6 o-3) and arachidonic acid (C20:4 o-3). The adsorption of free fatty acid of crude catfish oil was performed with chitosan, activated carbon and/or activated earth as adsorbents. Batch adsorbent experiments were carried out to assess equilibrium parameters. Chitosan was the most effective adsorbent to adsorb free fatty acids. The fixed-bed adsorption study showed that the highest percent of bed length was used when chitosan was used as an adsorbent. Melting points, specific heat capacity, enthalpy, and heat resistance were studied using DSC (Differential Scanning Calorimeter) and TGA (Thermogravimetric analysis). Melting points, enthalpy, and specific heat capacity varied greatly among the catfish oils from different processing stages due to differences in impurities. Catfish visceral oils from different processing steps showed different rates of weight loss with increased temperature. Suitability of Newtonian, Herschel-Bulkley, Bingham plastic, and Casson models to characterize the flow behavior of catfish oils form different processing steps was investigated. The Casson equation sufficiently described the flow behavior of catfish oils. The research findings from this study will benefit the whole catfish industries and will set a good model for fish oil recovery from other fish species as well.

ISBN

9780493563312

Pages

202

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