Semester

Summer

Date of Graduation

2011

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

P. Brett Kenney.

Abstract

Trout fillets, subjected to refrigeration (4°C; 3 or 7 d) by frozen storage (-25°C; 0 or 30 d) combinations, were cooked; texture, determined by a novel, variable-blade (VB) attachment, was compared with a widely-used Allo-Kramer shear (AK) attachment to determined its sensitivity in detecting variation in fillet texture. Instrumental texture was related to sensory measurements to determine attachments' accuracy in assessing cooked fillet texture. Weight of raw fillets decreased after 30-d frozen storage. Fillet weight further decreased after cooking. Moisture content decreased while fat content remained constant. The AK attachment detected differences in energy of shear, which decreased after 30-d frozen storage. Shear force increased after cooking and could be detected by VB attachment. The VB attachment, in a perpendicular direction, demonstrated the effect of shear direction; force determined by this configuration correlated with sensory hardness and cook loss.;Fertile and sterile fish were chosen as a model to describe key contributors to fillet texture. Two sets of 60 diploid (2N; fertile) and triploid (3N; sterile) females were harvested at 6 age endpoints (16, 18, 20, 21, 21, and 24 mo). From November 2008 (20 mo) to January 2009 (21 mo), GSI of 2N females increased substantially and their growth were at equal rate to those of 3N females. By November 2008, 2N females had a lower muscle fat content and higher moisture content than 3N females. Shear force negatively correlated with fillet fat content. Regardless of ploidy, raw fillets were softer between November 2008 and January 2009. Alkaline-insoluble hydroxyproline (a-i HYP) content of 2N muscle increased substantially in March 2009 (24 mo), and this response was consistent with increased energy of shear (g*mm). In March 2009, denaturation peaks (Tmax) of actin from 2N females were higher than those observed in 3N females (78.17 v. 77.27°C). Muscles of 2N fish were more elastic than those of 3N fish in a thermal scan ranged from 35-40°C. At temperatures greater than or equal to 45°C, muscle from younger (16 mo) fish was more elastic than older fish (18-24 mo). Lipid accumulation, observed primarily in 3N females, may lubricate and soften muscle fibers, and protect them from losing functionality at spawning when animals are on a high plane of nutrition.;Lastly, the VB was compared to the AK attachment for (1) its sensitivity in discriminating texture variation and (2) its predictability in relating texture parameters to alkaline insoluble HYP content. In the maturation study, the VB detected effect of age endpoint on cooked texture; minimum firmness was observed in January compared with December and March. In the storage regimen study, regimen*cooking state affected fillet texture; AK detected effect of 30-d frozen storage on raw texture; whereas, VB detected this effect after cooking. In both studies, VB texture was not correlated with collagen insolubility; the finding may have been due to limited sample size and range of variation in texture and fillet composition.

Download

Share

COinS