In this study, the Alaska pollock protein isolate(APPI) was hydrolyzed by Neutrase for 20, 40, 80, 120, 160, 200, and 240 min. Hydrolysates with different molecular weights were produced and they were named as H1–H7....In this study, the Alaska pollock protein isolate(APPI) was hydrolyzed by Neutrase for 20, 40, 80, 120, 160, 200, and 240 min. Hydrolysates with different molecular weights were produced and they were named as H1–H7. Furthermore, the effects of hydrolysis on the average molecular weights, functional properties(solubility, oil-holding capacities, foaming activities, and emulsifying properties), and antioxidant activities(1, 1-diphenyl-2-picrylhydrazyl, superoxide, and hydroxyl free radical-scavenging activities) were determined. It was found that when the degree of hydrolysis(DH) increased, the average molecular weights of the hydrolysates decreased significantly. The functional properties of APPI were also significantly improved. The hydrolysates of APPI exhibited better solubility, emulsifying activities, and foaming activities. Hydrolysates with low molecular weights(<1 kDa) had better solubility, oil-holding capacities, and emulsifying activities, while hydrolysates with higher molecular weights(>1 kDa) had better foaming activities. In addition, the hydrolysates exhibited excellent antioxidant properties, while the inhibition values of 1, 1-diphenyl-2-picryl hydroxyl(DPPH), superoxide, and hydroxyl free radical-scavenging activities, were 85.22%, 53.56%, and 75.00% respectively, when the concentration of the hydrolysates was 5.0 mg mL^(-1). The lower the average molecular weight was, the higher was the antioxidant activity. These results indicated that hydrolysis with Neutrase is an effective method for improving the functional and antioxidant properties of APPI. The hydrolysates of APPI displayed great potentials to be used as natural antioxidants in protein-rich aqueous foods such as nutrient supplements and sports beverages.展开更多
Alaska pollock is an important protein source which is extensively used in the food industry. Pollock protein isolates(PPI) with significantly enriched protein contents could be prepared using isoelectric solubilizati...Alaska pollock is an important protein source which is extensively used in the food industry. Pollock protein isolates(PPI) with significantly enriched protein contents could be prepared using isoelectric solubilization/precipitation(ISP) processing; however, the functional properties of this process is limited by the large amount of water-insoluble proteins. In this study, we investigated the influence of high hydrostatic pressure(HHP) treatment on the solubility and structural changes of PPI. PPI obtained using ISP is treated with hydrostatic pressures of 200, 300, 400, and 500 MPa for up to 15 min, and the HHP-treated samples were observed to exhibit significantly improved solubilities. Further biochemical assays reveal that the continuous HHP treatments reduce the contents of free sulfhydryl groups and promote the formation of macromolecules with better water solubilities, which may induce the solubility improvements of the HHP-treated PPI. Our results indicate that HHP can be utilized to effectively prepare highly water-soluble Alaska pollock protein in food processing.展开更多
The composition of muscle tissues of a deep-sea species, the giant grenadier(Albatrossia pectoralis), and a mesopelagic species, the Alaska pollock(Theragra chalcogramma), are compared. Grenadier is proved to have a h...The composition of muscle tissues of a deep-sea species, the giant grenadier(Albatrossia pectoralis), and a mesopelagic species, the Alaska pollock(Theragra chalcogramma), are compared. Grenadier is proved to have a higher moisture content(91.7%) and lower protein(7.4%) and lipid(0.3%) contents. The factors responsible for the softening and moisture separation during processing of grenadier are identified. Contents of some fractions of non-protein nitrogenous components, including trimethylamine oxide(TMAO) and free amino acids, are clarified. The proportion of the main myofibrillar proteins myosin and actin, which is considered as an indicator of efficiency of structure formation in fish muscle tissue during processing, is almost 20% lower in giant grenadier than in pollock. The effects of endogenous protease, Са^2+-ATPase and transglutaminase on the processes of autolysis, denaturation, and possibility of myofibrillar proteins cross-linking were also studied. The proposed technology of getting a nutritionally balanced, gel-like, ready-to-use foodstuff from grenadier fillet includes its enrichment with pollock muscle tissue and supplementing with a binary structure-forming agent containing collagen and chitosan. Nutritional value of the products is assessed by the method of biological assay and by determining the denaturation changes of myofibrillar proteins. The modes of fine mincing and thermal processing, as well as the shelf-life of the finished product are justified. The developed technology of producing a ready-to-eat food from giant grenadier will allow a more efficient use of this underutilized resource.展开更多
基金supported by grants from the China Postdoctoral Science Foundation to Dr.Chuyi Liu(No.2016M592251)
文摘In this study, the Alaska pollock protein isolate(APPI) was hydrolyzed by Neutrase for 20, 40, 80, 120, 160, 200, and 240 min. Hydrolysates with different molecular weights were produced and they were named as H1–H7. Furthermore, the effects of hydrolysis on the average molecular weights, functional properties(solubility, oil-holding capacities, foaming activities, and emulsifying properties), and antioxidant activities(1, 1-diphenyl-2-picrylhydrazyl, superoxide, and hydroxyl free radical-scavenging activities) were determined. It was found that when the degree of hydrolysis(DH) increased, the average molecular weights of the hydrolysates decreased significantly. The functional properties of APPI were also significantly improved. The hydrolysates of APPI exhibited better solubility, emulsifying activities, and foaming activities. Hydrolysates with low molecular weights(<1 kDa) had better solubility, oil-holding capacities, and emulsifying activities, while hydrolysates with higher molecular weights(>1 kDa) had better foaming activities. In addition, the hydrolysates exhibited excellent antioxidant properties, while the inhibition values of 1, 1-diphenyl-2-picryl hydroxyl(DPPH), superoxide, and hydroxyl free radical-scavenging activities, were 85.22%, 53.56%, and 75.00% respectively, when the concentration of the hydrolysates was 5.0 mg mL^(-1). The lower the average molecular weight was, the higher was the antioxidant activity. These results indicated that hydrolysis with Neutrase is an effective method for improving the functional and antioxidant properties of APPI. The hydrolysates of APPI displayed great potentials to be used as natural antioxidants in protein-rich aqueous foods such as nutrient supplements and sports beverages.
基金supported by grant from China Postdoctoral Science Foundation to Dr. Chuyi Liu (No. 2016 M592251)
文摘Alaska pollock is an important protein source which is extensively used in the food industry. Pollock protein isolates(PPI) with significantly enriched protein contents could be prepared using isoelectric solubilization/precipitation(ISP) processing; however, the functional properties of this process is limited by the large amount of water-insoluble proteins. In this study, we investigated the influence of high hydrostatic pressure(HHP) treatment on the solubility and structural changes of PPI. PPI obtained using ISP is treated with hydrostatic pressures of 200, 300, 400, and 500 MPa for up to 15 min, and the HHP-treated samples were observed to exhibit significantly improved solubilities. Further biochemical assays reveal that the continuous HHP treatments reduce the contents of free sulfhydryl groups and promote the formation of macromolecules with better water solubilities, which may induce the solubility improvements of the HHP-treated PPI. Our results indicate that HHP can be utilized to effectively prepare highly water-soluble Alaska pollock protein in food processing.
文摘The composition of muscle tissues of a deep-sea species, the giant grenadier(Albatrossia pectoralis), and a mesopelagic species, the Alaska pollock(Theragra chalcogramma), are compared. Grenadier is proved to have a higher moisture content(91.7%) and lower protein(7.4%) and lipid(0.3%) contents. The factors responsible for the softening and moisture separation during processing of grenadier are identified. Contents of some fractions of non-protein nitrogenous components, including trimethylamine oxide(TMAO) and free amino acids, are clarified. The proportion of the main myofibrillar proteins myosin and actin, which is considered as an indicator of efficiency of structure formation in fish muscle tissue during processing, is almost 20% lower in giant grenadier than in pollock. The effects of endogenous protease, Са^2+-ATPase and transglutaminase on the processes of autolysis, denaturation, and possibility of myofibrillar proteins cross-linking were also studied. The proposed technology of getting a nutritionally balanced, gel-like, ready-to-use foodstuff from grenadier fillet includes its enrichment with pollock muscle tissue and supplementing with a binary structure-forming agent containing collagen and chitosan. Nutritional value of the products is assessed by the method of biological assay and by determining the denaturation changes of myofibrillar proteins. The modes of fine mincing and thermal processing, as well as the shelf-life of the finished product are justified. The developed technology of producing a ready-to-eat food from giant grenadier will allow a more efficient use of this underutilized resource.
