Semester

Summer

Date of Graduation

2001

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

Rainbow trout, Oncorhynchus mykiss, fillets were brined in 8.7 or 17.4% (w/v) sodium chloride solution, respectively, for 30, 60, 90, or 120 min at 3°C. Increased brine concentration decreased brined pH, myosin solubility, brined and cooked moisture content, and water activity, and increased fillet weight loss after brining, cook yield, actin solubility, water-phase salt content, and shear force. Brining time linearly increased myofibrillar protein solubility, fillet weight loss after brining, water-phase salt content, and cooked ash content and linearly decreased water activity and brined and cooked moisture content. An 8.7% (w/v) brine and 90-min brining time resulted in maximum texture development while achieving the water-phase salt content (≥3.5%) required by the Food and Drug Administration.;For ante-mortem handling stress, Arctic charr, Salvelinus alpinus, hatched at 6.5 and 9.5°C and categorized as large, medium, and small when 6-m old, were assigned to four handling stress treatments: (1) processing with no stress; (2) processing immediately after stress; (3) processing 24 h after stress, and (4) processing 48 h after stress. Stress reduced gut weight and muscle a*, increased L* for the 9.5°C group, decreased L* for the 6.5°C group, and increased fillet weight loss after brining. Fish hatched at 9.5°C appeared to be more sensitive to handling stress; fillets from the stressed, 9.5°C group absorbed more brine, increasing salt and ash content of smoked products. Resting for 48 h after stress increased gut weight and enhanced L*.;Poorer texture quality was observed in smoked products produced from frozen fillets. Stabilization of rainbow trout fillets by water, 1% (w/v) sodium lactate, or 8% (w/v) sucrose/sorbitol (1:1 w/w), alone or in combination with 0.5% (w/v) sodium tripolyphosphate/tetrasodium pyrophosphate (1:1 w/w) and/or 0.05% (w/v) magnesium chloride was investigated. Cryoprotectants minimized the negative effects of 90-d frozen storage at -20°C on total and myofibrillar protein solubility, protein surface hydrophobicity, total, free and disulfide sulfhydryl content, and myosin susceptibility to thermal denaturation. Sucrose/sorbitol provided more effective cryoprotection than sodium lactate in preservation of protein structure and improvement of texture quality in smoked fillets. Phosphate enhanced cryoprotective effect. Magnesium chloride tended to accelerate protein denaturation during frozen storage.

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