Isoelectric Solubilization/precipitation Research Articles

Application of isoelectric solubilization/precipitation processing to improve gelation properties of protein isolated from pale, soft, exudative (PSE)-like chicken breast meat

Isoelectric solubilization/precipitation (ISP) process has been attempted to improve gelation properties of pale, soft, exudative (PSE)-like chicken breast meat protein. The protein was recovered at pH values of 2.5, 3.0, 3.5, 11.0, 11.5 and 12.0. The results showed that ISP treated PSE-like chicken breast meat with pH 11.0 and pH 3.5 significantly increased (P < 0.05) gel hardness and water retention capacity. Whiteness of cooked sample was obviously enhanced while the extraction carried out at pH 3.5, 11.0, 11.5 and 12.0 (P < 0.05). SDS-PAGE indicated ISP process significantly affected salt extracted protein profile rather than that of total protein. ISP treatment altered the dynamic rheological behavior of PSE-like samples. Since enhanced hardness was induced by ISP, the low elastic (G′) modulus revealed ISP-extracted sample form more rigid gel instead of elastic one. Based on our study, the best gel properties were obtained by solubilizing the PSE-like chicken breast muscle at pH 11. In conclusion, this method may have potential to increase the economic value of PSE-like chicken breast meat by improving the protein gelation properties.

Low molecular weight bioactive peptides derived from the enzymatic hydrolysis of collagen after isoelectric solubilization/precipitation process of turkey by-products

A process based on the isoelectric solubilization/precipitation (ISP) method was developed to recover collagen from low value poultry by-products. The application of the ISP process to turkey heads generated protein isolates and an insoluble biomass that was used to extract collagen. Isolated turkey head collagen was then enzymatically hydrolyzed for different time periods using alcalase, flavorzyme, and trypsin. The enzymatic hydrolysis approaches consisted of digesting collagen with each one of the 3 enzymes alone (alcalase, flavorzyme, or trypsin), or one of the 3 combinations of 2 enzymes (alcalase/flavorzyme, alcalase/trypsin, or flavorzyme/trypsin), or a cocktail of all 3 enzymes together (alcalase/flavorzyme/trypsin). The molecular weight distribution of turkey head collagen hydrolysates was determined using size exclusion chromatography and matrix-assisted laser desorption ionization-time of flight-mass spectrometry. The enzyme cocktail produced collagen hydrolysates with the greatest amount of low molecular weight peptides ranging from 555.26 to 2,093.74 Da. These collagen peptides showed excellent solubility over a wide pH range (2– 8) and were able to bind cholic and deoxycholic acids and significantly (P < 0.05) inhibited plasma amine oxidase in a dose- and time-dependent manner. The ISP process combined with enzyme cocktail hydrolysis represents a potential new way to produce low molecular weight bioactive collagen peptides from low value poultry by-products.

Fish protein isolate: Development of functional foods with nutraceutical ingredients

Fish processing by-products are usually discarded. However, they contain protein and ω-3 fatty acids. Isoelectric solubilization/precipitation (ISP) allows efficient recovery of fish protein isolate (FPI) that can be used in the development of nutraceutical products destined for human consumption. In the United States, market for nutraceutical food products in 2007 was estimated to be worth $27 billion. Forecasts for growth of nutraceutical food products range between 8.5 and 20% per year or about four times that of the food industry in general. With this demand for new products comes a need for product development and supporting literature. Consumers expect nutraceutical food products to have good sensory quality that is similar to the traditional foods in the market. Thus, this contribution focuses on the development of nutraceutical seafood products from ISP-recovered FPI by incorporating such ingredients as ω-3 oil, dietary fiber, and salt substitute.

Isoelectric Solubilization/Precipitation as a Means To Recover Protein Isolate from Striped Bass (Morone saxatilis) and Its Physicochemical Properties in a Nutraceutical Seafood Product

Excessive dietary intake of Na (i.e., NaCl) contributes to hypertension, which is a major risk factor for cardiovascular disease. Normally, NaOH and HCl are used to dissolve and precipitate, respectively, fish muscle proteins in isoelectric solubilization/precipitation (ISP), therefore contributing to increased Na content in the recovered fish protein isolates (FPI). Substitution of NaOH with KOH may decrease the Na content in FPI and, thus, allow development of reduced-Na seafood products. In this study, FPI was recovered with ISP using NaOH or KOH. In order to develop a nutraceutical seafood product, the FPI was extracted with NaCl or KCl-based salt substitute and subjected to cold- or heat-gelation. In addition, standard nutraceutical additives (ω-3 fatty acids-rich oil and dietary fiber) along with titanium dioxide (TiO2) were added to FPI. Color, texture, dynamic rheology, Na and K content, and lipid oxidation of the FPI gels were compared to commercial Alaska pollock surimi gels. FPI gels had greater (p < 0.05) whiteness, good color properties (L*a*b*), and generally better textural properties when compared to surimi gels. Although the ISP-recovered FPI and surimi developed similar final gel elasticity, the proteins in FPI and surimi had different gelation pattern. A reduction (p < 0.05) of Na content and simultaneous increase (p < 0.05) in K content of FPI gels was achieved by the substitution of NaOH with KOH during ISP and NaCl with the KCl-based salt substitute during formulation of the FPI paste. Although cooking and addition of NaCl during formulation of the FPI paste increased (p < 0.05) lipid oxidation in FPI gels, TBARS values were much below rancidity levels. These results indicate that KOH can replace NaOH to recover FPI from whole gutted fish for subsequent development of nutraceutical seafood products tailored for reduction of diet-driven cardiovascular disease.

Functional food products made from fish protein isolate recovered with isoelectric solubilization/precipitation

Isoelectric solubilization/precipitation (ISP) allows efficient recovery of fish protein isolate (FPI) that could be used in functional foods. There is an increasing interest in incorporating ω-3 polyunsaturated fatty acids (PUFAs) oils in food with a simultaneous sodium reduction. FPI was recovered from whole gutted trout using ISP. FPI was used as a main ingredient in heat-set gels made with ω-3 PUFAs oils (flaxseed, algae, fish, krill, and blend) and KCl-based salt substitute. The objectives were to determine (1) protein gelation, (2) color and texture, and (3) sodium and potassium content of the developed functional food (i.e., heat-set gels). Color properties were improved except when krill or algae oil was added. Texture profile analysis showed that ω-3 PUFAs generally did not affect texture of trout protein gels. The addition of ω-3 PUFAs oil improved heat-induced protein gelation as demonstrated by dynamic rheology. Elastic modulus increased when ω-3 PUFAs oil was added except krill oil. Salt substitute resulted in reduced sodium and increased potassium content in the heat-set gels. The functional food products developed from FRI were nutritionally enhanced with ω-3 PUFAs, had reduced sodium and increased potassium; while the color and texture properties were good and gelation properties were improved.

Dynamic rheology and endothermic transitions of proteins recovered from chicken-meat processing by-products using isoelectric solubilization/precipitation and addition of TiO2

Chicken-meat processing generates large quantities of by-products (backs, necks, etc.). Dark chicken-meat processing by-products present the lowest value and greatest challenge. Therefore, recovery of functional proteins from this source for inclusion in food products resembling those from light chicken-meat presents the greatest value addition and opportunity. Novel isoelectric solubilization/precipitation (ISP) was applied to model, dark chicken-meat processing by-products (skin-on bone-in chicken drumsticks) to recover muscle proteins. Thermal denaturation (endothermic transitions), gelation (elasticity, G′), and fundamental texture properties (shear stress and strain at mechanical fracture) of the ISP-recovered proteins were determined with differential scanning calorimetry (DSC), dynamic rheometer, and torsion test, respectively; and compared to boneless skinless chicken breast. Endothermic transition of myosin was not detected only when TiO2 was not added, while the ISP-recovered proteins with TiO2 showed small myosin peak and large actin peak. However, the level of TiO2 addition did not affect thermal transition/denaturation of the ISP-recovered proteins. The ISP-recovered proteins had a greater transition for actin compared to chicken breast, suggesting that ISP predisposes this protein to thermal denaturation. Similar to endothermic transitions, elasticity (G′) generally increased when TiO2 was added to the ISP-recovered proteins. Gels made of chicken breast had the highest (P < 0.05) shear stress (i.e., gel strength), but gels made of the ISP-recovered chicken proteins had greater (P < 0.05) shear strain (i.e., gel cohesiveness). Addition of TiO2 to the ISP-recovered proteins resulted in increased (P < 0.05) gel strength. Based on the present study, addition of TiO2 is suggested for the development of restructured food products based on proteins recovered from dark chicken-meat processing by-products using ISP. Although the results of this study point towards a novel food product, further studies are recommended.

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 TiO 2 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. TiO 2 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 TiO 2 was lower ( P < 0.05) than breast gels. TiO 2 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 TiO 2 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.

Improvement of pellet quality with proteins recovered from whole fish using isoelectric solubilization-precipitation

Muscle proteins are known to form thermally induced gel networks and may bind particles such as feed constituents. Dietary incorporation of functional proteins may improve pellet quality. Muscle proteins were recovered from rainbow trout by using isoelectric solubilization-precipitation. The objectives of this study were 1) to determine the proximate composition and amino acid content, AMEn, TMEn, and true amino acid digestibility of trout protein isolate and paste (TPP), and 2) to determine the effects of TPP on feed manufacturing, pellet quality, and true amino acid digestibility of broiler diets formulated to include TPP. Four treatments, consisting of 1) a control, 2) 5% TPP (HTPP), 3) 2.5% TPP (LTPP), and 4) 3.9% added moisture (MOIS), were manufactured at the West Virginia University pilot feed mill using a Latin square design. Five percent TPP had the highest pellet quality, followed by LTPP, MOIS, and the control. The improvement in pellet quality could be attributed to gelation of the recovered proteins. Addition of TPP reduced pellet mill production rate. Relative electrical energy usage decreased with MOIS but increased with HTPP relative to the control and LTPP treatments. Negative effects of increased viscosity likely associated with TPP were absent with LTPP. Digestibility of Asp, Glu, Pro, Ile, and Leu were lower for HTPP than the control. However, Ala digestibility was decreased in LTPP compared with the control. Therefore, fish muscle proteins incorporated at less than 5% of the diet may be beneficial to the broiler industry as a pellet binder and nutritive feed additive.

Compositional Characteristics of Materials Recovered from Whole Gutted Silver Carp (Hypophthalmichthys molitrix) Using Isoelectric Solubilization/Precipitation

Isoelectric solubilization/precipitation (ISP) at acidic and basic pH was applied to whole carp, yielding proteins, lipids, and insolubles. The objective was to characterize composition of recovered materials. Crude protein was concentrated to 89-90% in proteins recovered at acidic pH and to 94-95% at basic pH. Basic pH yielded proteins with more (P < 0.05) essential amino acids (EAAs). EAA content in recovered proteins met FAO/WHO/UNO requirements. ISP did not affect fatty acid (FA) composition. Lipids recovered at acidic pH contained 88-89% of total fat and at basic pH, 94-97%. Total fat in recovered proteins was low, with EPA and DHA at the highest (P < 0.05) percentage for pH 11.5. ISP, particularly basic pH, effectively removed impurities such as bones and scales from whole carp. This is indicated by 3.8-5.8% of ash in recovered proteins compared to 11.2% for whole carp and 5.4% for boneless/skinless carp fillets. Basic pH yielded less (P < 0.05) Ca, P, and Mg in recovered proteins. These minerals were more (P < 0.05) concentrated in insolubles recovered with basic pH. This study indicates that materials recovered from whole carp using ISP have high nutritional value and may be useful in the development of human food and animal feeds.