Doctoral Dissertations

Date of Award

12-1987

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Food Science and Technology

Major Professor

Sharon Melton

Committee Members

J. Larry Wilson, John R Mount, Frances A. Draughon

Abstract

Two fish diets, trout chow pellets (A) and alfalfa pellets (P), were evaluated as to their effects on growth, lipid level and compo-sition, fatty acid (FA) composition of polar and neutral lipids, and sensory characteristics of grass carp (Ctenopharyngodon idella). During the 6 month feeding experiment, fish fed A gained 661 g/fish compared to 358 g for fish fed P. In addition, total lipid con-tent in fish fed A increased from 1.84 to 3.72% in 4 months time, but remained approximately the same in fish fed P (P< 1.0%) across feed-ing times. Three phospholipid classes: sphingomyelin (6 to 13%), lecithin (55 to 63%), and cephalin (25 to 35%) were affected by feed-ing time (P<0.05). Nineteen FA were found in the phospholipids: 14:0, 16:01, 16:0, 16:1, 18:0, 18:1, 18:11, 18:2ω6, 18:3ω6, 18:3ω3, 20:1, 20:2, 20:3, 20:4ω6, 20:5ω3, 20:5ω6, 22:5uω3, 22:6ω3, and 24:1. Significant differences between diets were found in the percentages of 14 acids, and feeding time also significantly affected the levels of these acids. All of the previous FA except 16:01 plus 9 additional 16:11, 17:0, 17:1, 20:0, 22:1, 23:0, 24:0, 24:4 and an unknown, were found in the neutral lipids. Significant differences between diets were found in the percentages of 18 acids in the neutral lipids, and feeding time significantly affected the levels of 19 of the acids. Compared with fish fed P, fish fed A had higher levels of monounsatur-ated FA (MONO) and lower levels of omega-6 polyunsaturated FA (PUFA) in both neutral and polar lipids; there were higher levels of saturated FA (SAT) and omega-S PUFA in the phospholipids but lower levels of SAT and omega-3 PUFA in the neutral lipids. Compared to P, A had lower percentages of SAT (40.9 vs. 51.1), omega-6 PUFA (12.1 vs. 18.2), and omega-3 PUFA (15.8 vs. 24.7) and a higher percentage of MONO (31.0 vs. 5.3). There was no significant difference between the flavor of grass carp fed P (3.6) and that of catfish (3.7), but the panel (n = 93) scored the flavor of grass carp fed A (3.4) lower than that of catfish (P<0.06). They also found no significant differences in texture among the three fish samples. Compared with catfish acceptability (3.6), grass carp fed P tended to have lower acceptability (3.4), but grass carp fed A a significantly lower acceptability (3.3). The main reason given for scoring the acceptability of grass carp lower than that of catfish was the presence of small bones in the fillets. This indicates that either grass carp must be bigger at market-size than those in this study (1585 g) or the bones must somehow be removed.

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