Semester

Spring

Date of Graduation

2012

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Jacek Jaczynski.

Abstract

The amount of fish by-products is huge and there is a large potential for making more value-added products from this raw material. On the other hand, dark chicken meat has been considered as a major underutilized commodity due to the increasing demand for further processed breast meat products. If proper meat recovery technology is successfully applied, the recovered meat can result in added revenue for a processor as well as reduce environmental pollution associated with disposal of the processing by-products. The overall objective of this study was to recover functional proteins from whole gutted fish and dark chicken meat by using isoelectric solubilization/precipitation (ISP). Product development that incorporates the "voice of consumer" is crucial to understand and satisfy consumers' needs to manage these product development challenges.;Color properties of restructured products made of proteins recovered from chicken processing by-products is poor. The by-products contain bones, skin, fat, etc. that affect color of restructured products. Therefore, in the first study, effect of TiO2 as a whitening agent at 0-1 g/100 g and canola oil at 10 g/100 g on color and texture of heat-set gels were investigated. TiO2 at 1 g/100 g with canola oil resulted in slightly better (P < 0.05) whiteness of drumstick gels than breast gels. TiO 2 did not deteriorate gel texture, which was generally comparable to breast gels. This research indicates that ISP allows recovery of proteins from skin-on bone-in dark chicken-meat processing by-products without removal of bones, skin, and fat prior to processing. Addition of TiO2 to proteins recovered from these by-products allows development of heat-set gels with color and texture comparable to chicken breast gels.;Apart from the appearance, muscle food products can be modified by adding ingredients considered beneficial for health or by eliminating or reducing components that are considered harmful. High salt intake contributes to hypertention, the major risk factor for cardiovascular disease. Salt is commonly added during processing of seafood products to enhance protein gelation and hence texture as well as microbial safety. In the second study, salt or KCl-based salt substitute at 0 (control), 0.17, 0.34, and 0.51 M was added to surim. This study demonstrated that salt substitute and salt result in comparable (P>0.05) physicochemical properties of surimi gels, but gels developed with salt substitute have significantly lower (P<0.05) sodium content. Therefore, salt substitute can be used to replace NaCl in low-sodium surimi seafood products.;The next study compared protein endothermic transitions (thermal denaturation), rheological properties (protein gelation), and fundamental texture properties (shear stress and strain at mechanical fracture) of Alaska pollock surimi gels made with 0 (control), 1, 2, and 3 g/100 g of salt (NaCl) with equal molar concentration of salt substitute. The elastic modulus (G') increased when salt or salt substitute was added to surimi. Surimi gels with salt substitute and salt at equal molar concentrations had similar texture properties (shear stress and strain). Based on this study, salt substitute can be used in the development of low-sodium surimi seafood products without significant change in gelation and texture.;There is an increasing interest in incorporation of o-3 PUFA rich oils in food products with a simultaneous sodium reduction. Since the protein isolate is recovered from fish and used in a formulated food product, it is a logical vehicle for increasing the consumption of o-3 PUFAs and concurrent reduction of dietary sodium. In the next study, the protein isolate was recovered from whole gutted trout (bone-in, skin- and scale-on) using ISP processing. The isolate was used as a main ingredient to develop heat-set gels made with o-3 PUFA rich oils (flaxseed, algae, fish, krill, and blend) and KCl-based salt substitute. The effect of o-3 PUFA rich oils on chemical characterization of fatty acid composition and their oxidation, spoilage index (total volatile basic nitrogen) and fundamental texture properties of trout heat-set gels was investigated. This study indicated that trout gels enriched with PUFA rich oils can be considered healthful food in terms of the risk of cardiovascular diseases.;These studies demonstrated it is feasible to develop functional food made of muscle proteins recovered with isoelectric solubilization/precipitation from low-value dark chicken meat and fish processing by-products. The functional foods developed in these studies were nutritionally enhanced and had comparable instrumental quality attributes to respective products made of chicken breast meat or surimi seafood. Although the results of these studies point towards the potential for a novel, marketable functional food product, sensory tests and storage stability study are recommended.

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