Effect of isoelectric solubilization/precipitation and titanium dioxide on whitening and texture of proteins recovered from dark chicken-meat processing by-products

Processing of chicken generates by-products containing muscle proteins attached to bones and skin that, if recovered, could be a functional ingredient in restructured food products. However, color 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, color properties need to be improved. The objectives of this study were to determine effects of isoelectric solubilization/precipitation (ISP) and TiO2 on instrumental color and texture properties of heat-set gels made of proteins recovered from dark chicken-meat processing by-products as compared to gels made of chicken breast meat. Skin-on bone-in chicken drumsticks were used as a model dark chicken-meat processing by-products. TiO2 at 0 -1 g/100 g and canola oil at 10 g/100 g were added to the ISP-recovered proteins followed by cooking. Due to higher (P < 0.05) yellowness (b*) and lower (P < 0.05) lightness (L*), the whiteness of drumstick gels without TiO2 was lower (P < 0.05) than breast gels. TiO2 at 1 g/100 g with canola oil resulted in slightly better (P < 0.05) whiteness of drumstick gels than breast gels. TiO2 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. Although this study shows the potential for a novel, marketable food product, sensory tests are recommended. (C) 2010 Elsevier Ltd. All rights reserved.