Author ORCID Identifier

https://orcid.org/0009-0009-1178-4633

Semester

Spring

Date of Graduation

2025

Document Type

Dissertation (Campus Access)

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Patrick Brett Kenney

Committee Co-Chair

Kimbery M. Barnes

Committee Member

Kimbery M. Barnes

Committee Member

Jianbo Yao

Committee Member

Beth M. Cleveland

Committee Member

Hillar Klandorf

Abstract

Texture is one of the most important attributes for examining and evaluating fish quality. Many factors affect fish texture, including genetics, age, dietary composition, fat and moisture content, collagen characteristics, handling, storage time, and temperature. This research evaluated impact of genetics, diet, and age on lipid accumulation; collagen quality and quantity; body composition changes, in response to growth fillet quality and texture in rainbow trout.

Two studies were conducted. The first study examined genetics influences on collagen characteristics, fillet composition, and cooked fillet texture in 15-month-old trout. Eight families were selected based on the cooked shear force. No significant differences were observed in soluble, insoluble, total hydroxyproline (HYP) content and the percentage of soluble HYP among families (P > 0.05). However, families with greater whole-body weights exhibited higher separable and fat-free separable muscle weights, thicker fillets, and higher cooked yields (P < 0.05). Collagen solubility was not related to texture development for these fish; instead, fat and moisture content, cooked yield, and fillet thickness had a greater impact, due to cooking rate differences and the lubricating effect of fat.

The second study examined effects of age, diet and genetics on lipid deposition, collagen characteristics, and fillet texture in both raw and cooked stages. Two fast- (F1 and F2) and two slow-growing (S1 and S2) families were selected based on growth performance. Fish were fed either fishmeal (FM) or fishmeal-free (FMF) diets. Family S1 reached a whole-body weight comparable to the fast-growing families when averaged across age and diet. While FM-fed fish were larger, they had lower fillet yield than FMF-fed fish, possibly due to differences in visceral fat accumulation. Among age groups, visceral adipocytes of 9-month-old fish had the largest area and diameter (P < 0.05); reduced area and diameter likely reflected recruit of new adipocytes for additional lipid storage in 11-month-old fish. Whole-body crude fat of 11-month-old fish was the highest among the three harvest ages. Collagen characteristics were significantly influenced by age, with 6-month-old fish exhibiting the highest soluble HYP content (P < 0.05), a trend that was further pronounced after cooking when comparing 9 and 11-month-old muscle. Although collagen content did not differ between diets in raw fillets, FM-fed fish had higher soluble and total HYP in cooked fillets (P < 0.05). Fillet texture varied by age, diet, and genetics. Raw fillets from 9-month-old fish had higher shear force than those from 11-month-old fish, but the trend reversed after cooking (P < 0.05). FMF-fed fish had firmer raw fillets (P < 0.05), though this difference disappeared after cooking. Genetics influenced growth, body composition, adipocyte size, and fillet texture (both raw and cooked), but did not affect collagen characteristics.

Overall, genetics, diet and age significantly influenced body composition, fat accumulation, and collagen properties, which in turn affected fillet texture and quality in rainbow trout.

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