Pressurized Hot Water Hydrolysis of Shrimp Shell and Chicken Feet for Value-added Compounds Production
Creators: Matouri, Mashaer
Publisher: name: University of Alberta Library
Year: 2023

<p>The interest in the valorization of animal by-products such as shrimp shell and chicken feet has been growing as a sustainable approach to produce valuable biopolymers such as chitosan and collagen, that is also in line with the sustainability concept. These biopolymers could find applications in the food industry to develop sustainable products or functional food ingredients. Acid and enzymatic treatments have been conventionally utilized to produce chitosan and collagen from animal by-products with some limitations as they are not eco-friendly, time consuming, and costly processes. Therefore, the main objective of this thesis research was to obtain chitosan-rich residue and collagen/collagen fragments from animal by-products using subcritical water assisted by ultrasound and pressurized hot water technology, respectively. In the first study, shrimp shell was deproteinized using subcritical water assisted by ultrasound. Then, the deproteinized shrimp shell was demineralized, bleached, and deacetylated to obtain chitosan-rich residue. The nitrogen and free amino acids contents of the hydrolysates, and the degree of deproteination, yield, degree of deacetylation, color, functional groups, crystallinity, and surface morphology of chitosan-rich residue were determined. Subcritical water assisted by ultrasound (1200 W) at 180oC/50 bar/60 min resulted in the highest nitrogen content of 99.01 mg/g shrimp shell. However, the highest degree of deproteination (80.93%) and the highest free amino acid content (70.92 mg/g shrimp shell) were obtained by subcritical water assisted by ultrasound (1200 W) at 260°C/50 bar/60 min. At this condition, chitosan-rich residue with a yield of 10.56%, whiteness index of 60.42, degree of deacetylation of 64.27% with similar functional groups to the alkali treated sample and the commercial sample were obtained. It had a lower relative crystallinity (32.66%) compared to the alkali treated sample (50.64%) and the commercial chitosan (50.52%), indicating its better solubility. In the second study, pretreated chicken feet were processed with pressurized hot water at 40-180°C and 50 bar for 10-60 min. The content of collagen/collagen fragments, degree of hydrolysis, amino acid profile, and molecular weight distribution were determined. The best condition to obtain collagen/collagen fragments of 152.04 mg/g chicken feet was 140°C/50 bar/10 min. At all conditions investigated, hydroxyproline, lysine and glycine were the main free amino acids in the hydrolysates. Increasing the temperature and time increased the degree of hydrolysis where a maximum of 11.64% was obtained at 180°C/50 bar/60 min. The results of molecular weight distribution indicated that collagen was the main component at temperatures of 40-140°C while at higher temperatures of 160°C and 180°C collagen was hydrolyzed to gelatin and collagen fragments, respectively. These results indicated that pressurized hot water technology is promising to valorize animal by-products towards production of valuable-added compounds.</p>