[cn_name]
[cn_description]
关键词：暂无
[en_acquisition_editor]
2023, 44(1):228-235.
DOI: 10.19663/j.issn2095-9869.20210901002
Abstract:
Antarctic krill (Euphausia superba), an important group of marine zooplankton in the Southern Ocean, is the only fishery resource with extremely rich reserves and a low degree of development in the world. Antarctic krill is considered to be the greatest potential source of high-quality marine protein resources due to its abundant biomass and high protein content. Peptides prepared from Antarctic krill exhibit multiple physiological activities, including osteoporosis relief, glucose metabolism regulation, blood pressure amelioration, antioxidation, fatigue alleviation, and anti-aging activity. The production and development of Antarctic krill peptides has recently become an industry focus; however, existing research has been limited to the optimization of enzymatic hydrolysis processes, mainly involving the screening of suitable enzymes and the optimization of enzymatic hydrolysis conditions. Due to the high mineral content of Antarctic krill and the introduction of buffer salt in the process of enzymatic hydrolysis, current Antarctic krill peptides products have a high salt content, which leads to poor sensory experience and health risks. Hence, a process for desalination of Antarctic krill peptides is needed. Desalination methods for bioactive substances include dialysis, ultrafiltration, nanofiltration, electrodialysis, and macroporous resin adsorption. In the field of membrane separation, nanofiltration technology has been widely used in the purification, concentration, and desalination of food components owing to its advantages: low operation cost, no introduction of exogenous substances, no destruction of materials, and low rejection rate of monovalent ions. In order to improve product quality and ensure market expansion, the process of desalination of Antarctic krill peptides using nanofiltration technology was studied and optimized in this study. Defatted Antarctic krill powder was enzymatically hydrolyzed by alkaline protease to obtain Antarctic krill peptides for further use. The main factors affecting the desalination effect of Antarctic krill peptides (peptides concentration, nanofiltration pressure, and cycle times) were optimized by single-factor and orthogonal tests, using the desalination rate and protein loss rate as evaluation indexes. The experimental optimization ranges included peptides concentration of 1%~5%, nanofiltration pressure of 0.6~1.4 MPa and cycle times of 1~5. The salt contents of the samples before and after desalination were quantified using the silver nitrate titration method; the protein contents of the experimental samples were quantified using the Lowry colorimetric method. The quality indexes of the Antarctic krill peptides after treatment (including the basic nutritional composition: moisture content, protein content, ash content, salt content; amino acid composition; and molecular weight distribution) were systematically evaluated by the corresponding national standard methods. All experiments were performed in triplicate, and data were expressed as mean ± standard deviation. Excel 2016, IBM SPSS 20.0, and Origin 2018 were used for data analysis and chart drawing. Single-factor tests revealed that peptides concentration of 3%, nanofiltration pressure of 1.0 MPa and a cycle time of 2 could be selected as the design basis for the L9 (33) orthogonal test. The range value of the orthogonal test indicated that the degree of influence of the three factors on the desalination effect was as follows: peptides concentration > cycle times > nanofiltration pressure. The optimum conditions for desalting Antarctic krill peptides obtained by k value analysis were as follows: peptides concentration of 3.0%, nanofiltration pressure of 1.2 MPa and a cycle time of 3. Under the optimal condition, the desalination rate of the Antarctic krill peptides reached up to (86.35±2.11)%, and the protein loss rate was controlled at (9.10±0.35)%, demonstrating the feasibility of the process. The salt content of the Antarctic krill peptides after desalination was reduced to (1.14±0.12)% and the protein content was (92.73±2.29)%. The molecular weights of the Antarctic krill peptides after desalination were mainly distributed between 189 Da and 6500 Da, of which the proportion of peptides with molecular weight less than 3000 Da was (88.91±2.19)%, conforming to the molecular weight distribution range of bioactive peptides. The amount of essential amino acids in the Antarctic krill peptides after desalination accounted for (40.06±0.10)% of the total amino acids, and the ratio of essential amino acids to nonessential amino acids was (66.82±0.28)%. The amino acid compositions of the Antarctic krill peptides after desalination were ideal and met the standard stipulated by the FAO/WHO. The established nanofiltration desalination process presented good treatment effects, and the obtained peptides were of good quality and high nutritional value. The production of Antarctic krill protein-related products may be the next key development for the processing industry, since the sole high-value products of Antarctic krill at present are Antarctic krill oil and its derivatives. The established nanofiltration desalination process has practical application value and would provide technical support for the development of high-quality Antarctic krill peptides. This research provides scientific support for the efficient utilization of Antarctic krill resources.
Antarctic krill (Euphausia superba), an important group of marine zooplankton in the Southern Ocean, is the only fishery resource with extremely rich reserves and a low degree of development in the world. Antarctic krill is considered to be the greatest potential source of high-quality marine protein resources due to its abundant biomass and high protein content. Peptides prepared from Antarctic krill exhibit multiple physiological activities, including osteoporosis relief, glucose metabolism regulation, blood pressure amelioration, antioxidation, fatigue alleviation, and anti-aging activity. The production and development of Antarctic krill peptides has recently become an industry focus; however, existing research has been limited to the optimization of enzymatic hydrolysis processes, mainly involving the screening of suitable enzymes and the optimization of enzymatic hydrolysis conditions. Due to the high mineral content of Antarctic krill and the introduction of buffer salt in the process of enzymatic hydrolysis, current Antarctic krill peptides products have a high salt content, which leads to poor sensory experience and health risks. Hence, a process for desalination of Antarctic krill peptides is needed. Desalination methods for bioactive substances include dialysis, ultrafiltration, nanofiltration, electrodialysis, and macroporous resin adsorption. In the field of membrane separation, nanofiltration technology has been widely used in the purification, concentration, and desalination of food components owing to its advantages: low operation cost, no introduction of exogenous substances, no destruction of materials, and low rejection rate of monovalent ions. In order to improve product quality and ensure market expansion, the process of desalination of Antarctic krill peptides using nanofiltration technology was studied and optimized in this study. Defatted Antarctic krill powder was enzymatically hydrolyzed by alkaline protease to obtain Antarctic krill peptides for further use. The main factors affecting the desalination effect of Antarctic krill peptides (peptides concentration, nanofiltration pressure, and cycle times) were optimized by single-factor and orthogonal tests, using the desalination rate and protein loss rate as evaluation indexes. The experimental optimization ranges included peptides concentration of 1%~5%, nanofiltration pressure of 0.6~1.4 MPa and cycle times of 1~5. The salt contents of the samples before and after desalination were quantified using the silver nitrate titration method; the protein contents of the experimental samples were quantified using the Lowry colorimetric method. The quality indexes of the Antarctic krill peptides after treatment (including the basic nutritional composition: moisture content, protein content, ash content, salt content; amino acid composition; and molecular weight distribution) were systematically evaluated by the corresponding national standard methods. All experiments were performed in triplicate, and data were expressed as mean ± standard deviation. Excel 2016, IBM SPSS 20.0, and Origin 2018 were used for data analysis and chart drawing. Single-factor tests revealed that peptides concentration of 3%, nanofiltration pressure of 1.0 MPa and a cycle time of 2 could be selected as the design basis for the L9 (33) orthogonal test. The range value of the orthogonal test indicated that the degree of influence of the three factors on the desalination effect was as follows: peptides concentration > cycle times > nanofiltration pressure. The optimum conditions for desalting Antarctic krill peptides obtained by k value analysis were as follows: peptides concentration of 3.0%, nanofiltration pressure of 1.2 MPa and a cycle time of 3. Under the optimal condition, the desalination rate of the Antarctic krill peptides reached up to (86.35±2.11)%, and the protein loss rate was controlled at (9.10±0.35)%, demonstrating the feasibility of the process. The salt content of the Antarctic krill peptides after desalination was reduced to (1.14±0.12)% and the protein content was (92.73±2.29)%. The molecular weights of the Antarctic krill peptides after desalination were mainly distributed between 189 Da and 6500 Da, of which the proportion of peptides with molecular weight less than 3000 Da was (88.91±2.19)%, conforming to the molecular weight distribution range of bioactive peptides. The amount of essential amino acids in the Antarctic krill peptides after desalination accounted for (40.06±0.10)% of the total amino acids, and the ratio of essential amino acids to nonessential amino acids was (66.82±0.28)%. The amino acid compositions of the Antarctic krill peptides after desalination were ideal and met the standard stipulated by the FAO/WHO. The established nanofiltration desalination process presented good treatment effects, and the obtained peptides were of good quality and high nutritional value. The production of Antarctic krill protein-related products may be the next key development for the processing industry, since the sole high-value products of Antarctic krill at present are Antarctic krill oil and its derivatives. The established nanofiltration desalination process has practical application value and would provide technical support for the development of high-quality Antarctic krill peptides. This research provides scientific support for the efficient utilization of Antarctic krill resources.
2022, 43(2):215-227.
DOI: 10.19663/j.issn2095-9869.20210108004
Abstract:
This study aimed to compare the edible yield and flavor characteristics of Chinese mitten crabs (Eriocheir sinensis) from four regions in Jiangsu Province, China, to provide a theoretical basis and guidance for understanding consumer preference. For this, representative authentic Chinese mitten crabs from Yangcheng Lake, Gucheng Lake, Tai Lake, and Xinghua were used. The edible yield, flavor profiles, free amino acids, flavor nucleotides, and free fatty acids were measured, and the degree of flavor was evaluated using the taste activity value and equivalent umami concentration (EUC). The results showed that Tai Lake crabs had the highest edible yield [(33.08±0.31)% in male crabs, (37.65±1.09)% in females]. Yangcheng Lake and Gucheng Lake crabs had similar flavor profiles, as did Tai Lake and Xinghua crabs; however, Yangcheng Lake and Gucheng Lake crabs were sweeter, whereas Tai Lake and Xinghua crabs had a better umami flavor, although their bitterness and astringency were also high. Yangcheng Lake crabs had the highest sweet amino acid content in whole edible parts, male crab meat, female crab meat, and crab yolk: (676.65±1.30) mg/100 g, (899.00±2.88) mg/100 g, (950.34±4.78) mg/100 g, and (309.86± 0.73) mg/100 g, respectively. Whole edible parts and male crab meat from Tai Lake crabs had the highest umami amino acid content [(98.06±4.07) mg/100 g and (123.76±6.72) mg/100 g, respectively] and the highest EUC values [(11.62±0.66) g MSG/100 g and (15.29±2.58) g MSG/100 g, respectively]. Finally, total free fatty acids in Yangcheng Lake, Gucheng Lake, and Tai Lake crabs were higher than those in Xinghua crabs. In conclusion, the results indicate differences in the edible yield and flavor of Chinese mitten crabs from different locations. Overall, Yangcheng Lake crabs had the most prominent sweet flavor. Tai Lake crabs had the highest edible yield and their flavor profiles included a marked degree of umami; however, they also had a bitter flavor. Umami flavor was present in female crab meat and crab yolk from Yangcheng Lake and Gucheng Lake, in addition to male crab meat and crab paste of Tai Lake and Xinghua.
This study aimed to compare the edible yield and flavor characteristics of Chinese mitten crabs (Eriocheir sinensis) from four regions in Jiangsu Province, China, to provide a theoretical basis and guidance for understanding consumer preference. For this, representative authentic Chinese mitten crabs from Yangcheng Lake, Gucheng Lake, Tai Lake, and Xinghua were used. The edible yield, flavor profiles, free amino acids, flavor nucleotides, and free fatty acids were measured, and the degree of flavor was evaluated using the taste activity value and equivalent umami concentration (EUC). The results showed that Tai Lake crabs had the highest edible yield [(33.08±0.31)% in male crabs, (37.65±1.09)% in females]. Yangcheng Lake and Gucheng Lake crabs had similar flavor profiles, as did Tai Lake and Xinghua crabs; however, Yangcheng Lake and Gucheng Lake crabs were sweeter, whereas Tai Lake and Xinghua crabs had a better umami flavor, although their bitterness and astringency were also high. Yangcheng Lake crabs had the highest sweet amino acid content in whole edible parts, male crab meat, female crab meat, and crab yolk: (676.65±1.30) mg/100 g, (899.00±2.88) mg/100 g, (950.34±4.78) mg/100 g, and (309.86± 0.73) mg/100 g, respectively. Whole edible parts and male crab meat from Tai Lake crabs had the highest umami amino acid content [(98.06±4.07) mg/100 g and (123.76±6.72) mg/100 g, respectively] and the highest EUC values [(11.62±0.66) g MSG/100 g and (15.29±2.58) g MSG/100 g, respectively]. Finally, total free fatty acids in Yangcheng Lake, Gucheng Lake, and Tai Lake crabs were higher than those in Xinghua crabs. In conclusion, the results indicate differences in the edible yield and flavor of Chinese mitten crabs from different locations. Overall, Yangcheng Lake crabs had the most prominent sweet flavor. Tai Lake crabs had the highest edible yield and their flavor profiles included a marked degree of umami; however, they also had a bitter flavor. Umami flavor was present in female crab meat and crab yolk from Yangcheng Lake and Gucheng Lake, in addition to male crab meat and crab paste of Tai Lake and Xinghua.
CHEN Yiping
,
CUI Wenxuan
,
GAO Ruichang
,
LI Jianpeng
,
ZENG Mingyong
,
TANG Shuwei
,
FENG Qiufeng
,
ZHAO Yuanhui
2020, 41(1):178-186.
DOI: 10.19663/j.issn2095-9869.20181017001
Abstract:
In this work, changes in the quality and storage life of sturgeon fillets were compared during 3℃ partial freezing storage and 4℃ storage in order to develop a method that will improve the storage quality of sturgeon fillets. Several indicators including sensory evaluation, total visible colonies (TVC), pH value, volatile base nitrogen value (TVB-N), thiobarbituric acid (TBA), texture, volatile substances, moisture distribution state, and microstructure changes of muscle fibers were studied and were later used to evaluate the effect of two temperature storages on the quality of sturgeon fillets. The results showed that the proportion of free water and combined water, TVB-N, TBA, and TVC of sturgeon fillets stored at 4℃ and 3℃ increased with the extension of storage time, whereas texture indices such as hardness and springiness and the score of sensory evaluation showed a decreasing trend. Microstructure observations illustrated that stickiness appeared between the muscle fibers, and the sarcomere gradually became blurred with the extension of storage time, especially during the later period of 3℃ partial freezing storage. Interestingly, its chemical indicators including TVB-N and TBA did not exceed the hygienic limits, whereas sensory evaluation rates were unacceptable. Taking all these indicators into consideration, it was observed that the storage life of sturgeon fillet was 6 days at 4℃ and 18 days at 3℃. It can therefore be concluded that partial freezing temperature storage (3℃) maintained the quality of sturgeon fillets much longer compared with storage at 4℃. Microbes have a small effect on the decay process of sturgeon fillets, whereas ice crystal formation and endogenous cathepsin may be the main influencing factors that led to the destruction of its structure during 3℃ partial freezing storage. Results of this study will enrich the basic theory of aquatic products and provide a technique for sturgeon fillets storage.
In this work, changes in the quality and storage life of sturgeon fillets were compared during 3℃ partial freezing storage and 4℃ storage in order to develop a method that will improve the storage quality of sturgeon fillets. Several indicators including sensory evaluation, total visible colonies (TVC), pH value, volatile base nitrogen value (TVB-N), thiobarbituric acid (TBA), texture, volatile substances, moisture distribution state, and microstructure changes of muscle fibers were studied and were later used to evaluate the effect of two temperature storages on the quality of sturgeon fillets. The results showed that the proportion of free water and combined water, TVB-N, TBA, and TVC of sturgeon fillets stored at 4℃ and 3℃ increased with the extension of storage time, whereas texture indices such as hardness and springiness and the score of sensory evaluation showed a decreasing trend. Microstructure observations illustrated that stickiness appeared between the muscle fibers, and the sarcomere gradually became blurred with the extension of storage time, especially during the later period of 3℃ partial freezing storage. Interestingly, its chemical indicators including TVB-N and TBA did not exceed the hygienic limits, whereas sensory evaluation rates were unacceptable. Taking all these indicators into consideration, it was observed that the storage life of sturgeon fillet was 6 days at 4℃ and 18 days at 3℃. It can therefore be concluded that partial freezing temperature storage (3℃) maintained the quality of sturgeon fillets much longer compared with storage at 4℃. Microbes have a small effect on the decay process of sturgeon fillets, whereas ice crystal formation and endogenous cathepsin may be the main influencing factors that led to the destruction of its structure during 3℃ partial freezing storage. Results of this study will enrich the basic theory of aquatic products and provide a technique for sturgeon fillets storage.
2020, 41(2):191-199.
DOI: 10.19663/j.issn2095-9869.20190124002
Abstract:
To reduce the wastage of aquatic resources and improve the additional value of cod swim bladder, we determined the optimum technological conditions for antioxidant peptides from the cod swim bladder and observed the changes in antioxidant activities after being digested in vitro. Six kinds of proteases, namely, acid proteinase, dispase, pepsin, papain, compound proteinase, and trypsin, were used to hydrolyze the cod swim bladder in order to select the optimal protease by determining the degree of hydrolysis and DPPH radical scavenging rate. Combining the single factor method and response surface methodology, the optimum process was ensured at the hydrolysis temperature of 58.56℃, hydrolysis time of 6 h, pH of 7.21, and enzyme addition of 200 U/ml. The results of the confirmatory experiment showed that the scavenging rate of DPPH was 61.1%, which agreed with the predicted value of 62.0%, and the results proved that the optimized extraction process was stable and reliable. The free radical scavenging rates of peptides were detected, and the results showed that swim bladder peptides have good abilities of scavenging free radicals of DPPH, OH, O2-, and chelating Fe2+. Besides, the half maximal inhibitory concentration (IC50) of these was 8.29 mg/ml, 5.03 mg/ml, 5.43 mg/ml, and 1.35 mg/ml, respectively. After being digested in vitro, the degree of hydrolysis increased while the free radicals scavenging abilities and chelating power of Fe2+ decreased. This might have occurred because the changes of reaction conditions in the simulated gastrointestinal digestion process such as the change of pH value lead to the changes of composition and structure of the peptides. Meanwhile, the changes of composition and structure lead to the changes in antioxidant activities. In conclusion, swim bladder peptides had potent antioxidants and could serve as useful ingredients in the food industry.
To reduce the wastage of aquatic resources and improve the additional value of cod swim bladder, we determined the optimum technological conditions for antioxidant peptides from the cod swim bladder and observed the changes in antioxidant activities after being digested in vitro. Six kinds of proteases, namely, acid proteinase, dispase, pepsin, papain, compound proteinase, and trypsin, were used to hydrolyze the cod swim bladder in order to select the optimal protease by determining the degree of hydrolysis and DPPH radical scavenging rate. Combining the single factor method and response surface methodology, the optimum process was ensured at the hydrolysis temperature of 58.56℃, hydrolysis time of 6 h, pH of 7.21, and enzyme addition of 200 U/ml. The results of the confirmatory experiment showed that the scavenging rate of DPPH was 61.1%, which agreed with the predicted value of 62.0%, and the results proved that the optimized extraction process was stable and reliable. The free radical scavenging rates of peptides were detected, and the results showed that swim bladder peptides have good abilities of scavenging free radicals of DPPH, OH, O2-, and chelating Fe2+. Besides, the half maximal inhibitory concentration (IC50) of these was 8.29 mg/ml, 5.03 mg/ml, 5.43 mg/ml, and 1.35 mg/ml, respectively. After being digested in vitro, the degree of hydrolysis increased while the free radicals scavenging abilities and chelating power of Fe2+ decreased. This might have occurred because the changes of reaction conditions in the simulated gastrointestinal digestion process such as the change of pH value lead to the changes of composition and structure of the peptides. Meanwhile, the changes of composition and structure lead to the changes in antioxidant activities. In conclusion, swim bladder peptides had potent antioxidants and could serve as useful ingredients in the food industry.
2020, 41(4):190-197.
DOI: 10.19663/j.issn2095-9869.20191218001
Abstract:
Aquatic products may be contaminated by microorganisms during storage and transportation, leading to product spoilage and quality deterioration. Aquatic products are prone to deterioration by decomposition, putrefaction, degradation of proteins and amino acids, and production of basic amines. Pretreatment by sterilization is required to reduce the effects of microorganisms on the quality and shelf life of aquatic products during processing and storage. The mechanisms, main advantages, and disadvantages of common water treatment methods, including electrolysis or ozonation of water and use of chlorine dioxide solution were compared and analyzed. The research focused on the application of ozonated water in the sterilization and preservation of aquatic products. Ozone exhibits strong oxidizability as well as bacteriostatic and bactericidal effects. In addition, treatment with ozonated water is convenient and plays an important role during storage and preservation by spraying, immersion, and flowing water treatment. Ozonated water is widely used to bleach and decolorize fish fillets and surimi products and to remove strong scents. Additionally, it is also used for product sterilization and preservation, and for cleaning and disinfection of processing equipment. However, ozonated water is associated with poor stability, which may affect its sterilization ability. Therefore, the combination of ozonated water with other preservation technologies may prolong the shelf life of aquatic products to a greater extent than that by ozonated water alone. The combination of ozone water with slurry ice, modified atmosphere packaging, and other freshness preservation methods were described. Researchers should consider using orthogonal experiments or response surface methodology to identify the optimal treatment concentration and duration, and to develop optimal process parameters based on the individual characteristics of different aquatic products.
Aquatic products may be contaminated by microorganisms during storage and transportation, leading to product spoilage and quality deterioration. Aquatic products are prone to deterioration by decomposition, putrefaction, degradation of proteins and amino acids, and production of basic amines. Pretreatment by sterilization is required to reduce the effects of microorganisms on the quality and shelf life of aquatic products during processing and storage. The mechanisms, main advantages, and disadvantages of common water treatment methods, including electrolysis or ozonation of water and use of chlorine dioxide solution were compared and analyzed. The research focused on the application of ozonated water in the sterilization and preservation of aquatic products. Ozone exhibits strong oxidizability as well as bacteriostatic and bactericidal effects. In addition, treatment with ozonated water is convenient and plays an important role during storage and preservation by spraying, immersion, and flowing water treatment. Ozonated water is widely used to bleach and decolorize fish fillets and surimi products and to remove strong scents. Additionally, it is also used for product sterilization and preservation, and for cleaning and disinfection of processing equipment. However, ozonated water is associated with poor stability, which may affect its sterilization ability. Therefore, the combination of ozonated water with other preservation technologies may prolong the shelf life of aquatic products to a greater extent than that by ozonated water alone. The combination of ozone water with slurry ice, modified atmosphere packaging, and other freshness preservation methods were described. Researchers should consider using orthogonal experiments or response surface methodology to identify the optimal treatment concentration and duration, and to develop optimal process parameters based on the individual characteristics of different aquatic products.
2019, 40(5):175-184.
DOI: 10.19663/j.issn2095-9869.20180813002
Abstract:
Heat treatment is the leading and most traditional means of cooking and sterilizing meats from aquatic products and poultry product for the processing industry. The meat protein composition and structures are briefly described in this manuscript and the denaturing of the different proteins during the heat treatments are discussed. Most of the sarcoplasmic proteins either from aquatic or poultry meat aggregate between 40℃ and 60℃, but some coagulation can occur at up to 90℃. The unfolding of myofibrillar proteins in solution begins at 30℃~32℃, followed by protein–protein associations at 36℃~40℃, and subsequent gelation at 45℃~50℃ (conc.>0.5% by weight). At temperatures between 53℃ and 63℃, collagen denaturation occurs, followed by collagen fibre shrinkage. If the collagen fibres are not stabilised by heat-resistant intermolecular bonds, they dissolve and form gelatine on further heating. In addition, the structural changes and quality changes of different kinds of meat due to the heat treatment are discussed. In most cases, after meat is heated to a certain temperature, its microscopic structure shrinks, the sarcomere length shortens, the water holding capacity decreases, and the shear force which represents hardness rises once or twice. Minced meat products including surimi products, hamburger patties and emulsified sausages have disordered muscle system structures due to the effect of heat processing. Compared with emulsified sausage, hamburger patties have a higher occurrence rate of whole fiber and fiber fragments, and their content is as high as 50%~70%, and resulting in greater shrinkage after heating. Compared to poultry product, surimi products showed to be much more complicated. Salt soluble proteins in fish muscle would reform a cubic network containing water when it was heated to be surimi products due to the formation of disulfide bridge, hydrophobic interaction and hydrogen bond, etc. In emulsified sausage, the myofibrillar protein is extracted due to the crushing and stirring of muscle, resulting in a dense protein network gel during heat treatments, and water can be effectively maintained through capillary force. Understanding the structural changes of different meat proteins and the mechanism of quality changes during heat treatments can provide a theoretical basis for formulating a more reasonable meat processing methods.
Heat treatment is the leading and most traditional means of cooking and sterilizing meats from aquatic products and poultry product for the processing industry. The meat protein composition and structures are briefly described in this manuscript and the denaturing of the different proteins during the heat treatments are discussed. Most of the sarcoplasmic proteins either from aquatic or poultry meat aggregate between 40℃ and 60℃, but some coagulation can occur at up to 90℃. The unfolding of myofibrillar proteins in solution begins at 30℃~32℃, followed by protein–protein associations at 36℃~40℃, and subsequent gelation at 45℃~50℃ (conc.>0.5% by weight). At temperatures between 53℃ and 63℃, collagen denaturation occurs, followed by collagen fibre shrinkage. If the collagen fibres are not stabilised by heat-resistant intermolecular bonds, they dissolve and form gelatine on further heating. In addition, the structural changes and quality changes of different kinds of meat due to the heat treatment are discussed. In most cases, after meat is heated to a certain temperature, its microscopic structure shrinks, the sarcomere length shortens, the water holding capacity decreases, and the shear force which represents hardness rises once or twice. Minced meat products including surimi products, hamburger patties and emulsified sausages have disordered muscle system structures due to the effect of heat processing. Compared with emulsified sausage, hamburger patties have a higher occurrence rate of whole fiber and fiber fragments, and their content is as high as 50%~70%, and resulting in greater shrinkage after heating. Compared to poultry product, surimi products showed to be much more complicated. Salt soluble proteins in fish muscle would reform a cubic network containing water when it was heated to be surimi products due to the formation of disulfide bridge, hydrophobic interaction and hydrogen bond, etc. In emulsified sausage, the myofibrillar protein is extracted due to the crushing and stirring of muscle, resulting in a dense protein network gel during heat treatments, and water can be effectively maintained through capillary force. Understanding the structural changes of different meat proteins and the mechanism of quality changes during heat treatments can provide a theoretical basis for formulating a more reasonable meat processing methods.
2019, 40(2):83-90.
DOI: 10.19663/j.issn2095-9869.20180813001
Abstract:
This study was done to assess regional differences among abalone from different habitats and develop a new and efficient method to identify abalone from different habitats of origin. To do this, the content and composition of 13 major elements and trace elements (Na, K, Mg, Ca, Fe, Zn, Cu, Ni, As, Al, Mn, Cr, and Se) in the muscle tissue of 18 kinds of abalone samples from the four major breeding provinces of Guangdong, Fujian, Shandong, and Liaoning, China, were determined and analyzed using principal component analysis (PCA). The results showed that the elemental content differed among the 18 abalone samples. The variation in Manganese (Mn) was the largest [the coefficient of variation (CV) was 74% among samples], followed by Nickel (Ni) (CV = 65%), and then by Selenium (Se) (CV = 60%); all the rest of the analyzed elements had CVs higher than 10%. At the same time, after using the PCA method to reduce the dimensions of these data, six elements were effectively extracted from among the 13 elements examined that cumulatively explained 89.87% of the variance among samples. These characteristic elements of abalone from different habitats were Ca, Se, Na, Fe, Mn, K, and Ni, and a comprehensive model of the six principal components including them was established as follows: F = 0.2777F1 + 0.2652F2 + 0.1295F3 + 0.1066F4 + 0.0656F5 + 0.0541F6, where F1 represents the first principal component, and F2~F6 represent the second to sixth principal components, respectively. On the basis of the comprehensive PCA score, the top six samples were samples No. 2, 6, 17, 13, 7, and 15, and the lowest one was sample No. 5. Among these, sample No. 2 had a higher content of all characteristic elements and better quality than all others. The PCA approach was found to be quite suitable for the evaluation of the nutritive quality of abalone. The establishment of this PCA model provided an empirical basis for the theoretical determination of the origin of abalone samples.
This study was done to assess regional differences among abalone from different habitats and develop a new and efficient method to identify abalone from different habitats of origin. To do this, the content and composition of 13 major elements and trace elements (Na, K, Mg, Ca, Fe, Zn, Cu, Ni, As, Al, Mn, Cr, and Se) in the muscle tissue of 18 kinds of abalone samples from the four major breeding provinces of Guangdong, Fujian, Shandong, and Liaoning, China, were determined and analyzed using principal component analysis (PCA). The results showed that the elemental content differed among the 18 abalone samples. The variation in Manganese (Mn) was the largest [the coefficient of variation (CV) was 74% among samples], followed by Nickel (Ni) (CV = 65%), and then by Selenium (Se) (CV = 60%); all the rest of the analyzed elements had CVs higher than 10%. At the same time, after using the PCA method to reduce the dimensions of these data, six elements were effectively extracted from among the 13 elements examined that cumulatively explained 89.87% of the variance among samples. These characteristic elements of abalone from different habitats were Ca, Se, Na, Fe, Mn, K, and Ni, and a comprehensive model of the six principal components including them was established as follows: F = 0.2777F1 + 0.2652F2 + 0.1295F3 + 0.1066F4 + 0.0656F5 + 0.0541F6, where F1 represents the first principal component, and F2~F6 represent the second to sixth principal components, respectively. On the basis of the comprehensive PCA score, the top six samples were samples No. 2, 6, 17, 13, 7, and 15, and the lowest one was sample No. 5. Among these, sample No. 2 had a higher content of all characteristic elements and better quality than all others. The PCA approach was found to be quite suitable for the evaluation of the nutritive quality of abalone. The establishment of this PCA model provided an empirical basis for the theoretical determination of the origin of abalone samples.
2019, 40(5):185-194.
DOI: 10.19663/j.issn2095-9869.20180814001
Abstract:
Antarctic krill (Euphausia superba) is a species of krill found in the Southern Ocean, and an important strategic resource of China, whose growth and reproduction are susceptible to the Antarctic water environment. Due to their huge biomass (estimated to be 125 to 725 million tons), nutrient contents, and active ingredients, Antarctic krill can be widely used in functional food, aquaculture, medicine, and other fields. As an important extractive, astaxanthin has high antioxidant activity and could play an important role in anti-oxidation, anti-inflammatory, anti-tumor, and immunity enhancement treatments, as well as in the prevention of cardiovascular diseases. However, astaxanthin has poor stability and poor water solubility, as the molecules are easily damaged by oxygen, light, and heat. In order to reduce the oxidation rate of astaxanthin and improve the storage stability of astaxanthin, the use of maltodextrin and hydroxypropyl-β-cyclodextrin (HP-β-CD) as the wall material for the microencapsulation of the Antarctic krill astaxanthin by spray drying and the physical and chemical properties of the product after microencapsulation were studied. The results showed that when the mass ratio of maltodextrin to HP-β-CD wall material was 1:3, the mass fraction of astaxanthin was 4.76%, the mass fraction of polysorbate-80 was 0.87%, and the solids concentration was 0.20 g/ml; the microencapsulation efficiency of astaxanthin microcapsules was 98.77%. The water content of the prepared astaxanthin microcapsule was (3.11±0.11)%, the solubility was (94.32±0.08)%, and the angle of rest was (34.16±0.24)°. Stability experiments showed that compared to the non-microencapsulated astaxanthin crystals, astaxanthin microcapsules at high temperatures, the retention rate of astaxanthin increased from 28.72% to 78.32%; under natural light conditions. The astaxanthin retention rate increased from 45.27% to 84.88%; under aerobic conditions and the retention rate of prime increased from 20.76% to 74.97%. The above-mentioned results indicated that microencapsulation can significantly improve the solubility and stability of astaxanthin, which can provide technical support for the preparation of astaxanthin microencapsulated products.
Antarctic krill (Euphausia superba) is a species of krill found in the Southern Ocean, and an important strategic resource of China, whose growth and reproduction are susceptible to the Antarctic water environment. Due to their huge biomass (estimated to be 125 to 725 million tons), nutrient contents, and active ingredients, Antarctic krill can be widely used in functional food, aquaculture, medicine, and other fields. As an important extractive, astaxanthin has high antioxidant activity and could play an important role in anti-oxidation, anti-inflammatory, anti-tumor, and immunity enhancement treatments, as well as in the prevention of cardiovascular diseases. However, astaxanthin has poor stability and poor water solubility, as the molecules are easily damaged by oxygen, light, and heat. In order to reduce the oxidation rate of astaxanthin and improve the storage stability of astaxanthin, the use of maltodextrin and hydroxypropyl-β-cyclodextrin (HP-β-CD) as the wall material for the microencapsulation of the Antarctic krill astaxanthin by spray drying and the physical and chemical properties of the product after microencapsulation were studied. The results showed that when the mass ratio of maltodextrin to HP-β-CD wall material was 1:3, the mass fraction of astaxanthin was 4.76%, the mass fraction of polysorbate-80 was 0.87%, and the solids concentration was 0.20 g/ml; the microencapsulation efficiency of astaxanthin microcapsules was 98.77%. The water content of the prepared astaxanthin microcapsule was (3.11±0.11)%, the solubility was (94.32±0.08)%, and the angle of rest was (34.16±0.24)°. Stability experiments showed that compared to the non-microencapsulated astaxanthin crystals, astaxanthin microcapsules at high temperatures, the retention rate of astaxanthin increased from 28.72% to 78.32%; under natural light conditions. The astaxanthin retention rate increased from 45.27% to 84.88%; under aerobic conditions and the retention rate of prime increased from 20.76% to 74.97%. The above-mentioned results indicated that microencapsulation can significantly improve the solubility and stability of astaxanthin, which can provide technical support for the preparation of astaxanthin microencapsulated products.
2019, 40(6):196-202.
DOI: 10.19663/j.issn2095-9869.20180818002
Abstract:
The hairtail (Trichiurus haumela) is rich in protein and high in nutrition. In this study, the effects of chilling storage on the muscle protein of hairtail were studied by measuring a series of physical and chemical indicators that characterize changes in the fish quality, including TCA-soluble peptides, sulfhydryl group content, surface hydrophobicity, Ca2+-ATPase activity, and Mg2+-ATPase activity, as well as SDS-PAGE patterns of total soluble proteins, water-soluble proteins, low-salt-soluble proteins, and high-salt-soluble proteins. The effects of 0℃ and 4℃ chilling on the fish muscle protein were observed after 15 days of storage, and the oxidation, denaturation, and degradation of the fish protein under the two storage temperatures were compared. The results showed that after 0℃ and 4℃ storage for 15 days, the TCA-soluble peptides increased from 1.446 μmol/g to 6.717 μmol/g and 7.595 μmol/g, respectively. The Ca2+-ATPase activities were lower than the initial values, decreasing from 0.99 U/mg prot to 0.092 U/mg prot and 0.134 U/mg prot, respectively. The Mg2+-ATPase activities also decreased from 0.76 U/mg prot to 0.199 U/mg prot and 0.125 U/mg prot, respectively. In addition, the sulfhydryl group content decreased from 38.15 μmol/g MP to 35.82 μmol/g MP and 30.36 μmol/g MP, respectively. The surface hydrophobicity first increased and then decreased, but the values were higher than those of the fresh samples. The changes in the values of this series of physical and chemical indicators indicated that the refrigerating conditions of 0℃ and 4℃ were not conducive to the long-term storage of the hairtail. Prolonged storage time destroyed the freshness and quality of the hairtail owing to protein oxidation, which caused a bad odor and rendered the fish inedible. From the microstructure perspective, there were almost no changes in the total soluble proteins and water-soluble proteins. However, the high-salt-soluble proteins degraded under storage, indicating that the myofibrillar protein had degraded gradually, decreasing the fish quality. Moreover, the rate of myofibrillar protein degradation and corruption of the fish was slower at 0℃ than at 4℃ on the same day during storage.
The hairtail (Trichiurus haumela) is rich in protein and high in nutrition. In this study, the effects of chilling storage on the muscle protein of hairtail were studied by measuring a series of physical and chemical indicators that characterize changes in the fish quality, including TCA-soluble peptides, sulfhydryl group content, surface hydrophobicity, Ca2+-ATPase activity, and Mg2+-ATPase activity, as well as SDS-PAGE patterns of total soluble proteins, water-soluble proteins, low-salt-soluble proteins, and high-salt-soluble proteins. The effects of 0℃ and 4℃ chilling on the fish muscle protein were observed after 15 days of storage, and the oxidation, denaturation, and degradation of the fish protein under the two storage temperatures were compared. The results showed that after 0℃ and 4℃ storage for 15 days, the TCA-soluble peptides increased from 1.446 μmol/g to 6.717 μmol/g and 7.595 μmol/g, respectively. The Ca2+-ATPase activities were lower than the initial values, decreasing from 0.99 U/mg prot to 0.092 U/mg prot and 0.134 U/mg prot, respectively. The Mg2+-ATPase activities also decreased from 0.76 U/mg prot to 0.199 U/mg prot and 0.125 U/mg prot, respectively. In addition, the sulfhydryl group content decreased from 38.15 μmol/g MP to 35.82 μmol/g MP and 30.36 μmol/g MP, respectively. The surface hydrophobicity first increased and then decreased, but the values were higher than those of the fresh samples. The changes in the values of this series of physical and chemical indicators indicated that the refrigerating conditions of 0℃ and 4℃ were not conducive to the long-term storage of the hairtail. Prolonged storage time destroyed the freshness and quality of the hairtail owing to protein oxidation, which caused a bad odor and rendered the fish inedible. From the microstructure perspective, there were almost no changes in the total soluble proteins and water-soluble proteins. However, the high-salt-soluble proteins degraded under storage, indicating that the myofibrillar protein had degraded gradually, decreasing the fish quality. Moreover, the rate of myofibrillar protein degradation and corruption of the fish was slower at 0℃ than at 4℃ on the same day during storage.
2018, 39(6):134-140.
Abstract:
Pyropia yezoensis at different harvest times were obtained from Jing Bay, and its nutritional and umami characteristics were analyzed. Crude protein, crude fat, ash, inorganic elements, and amino acid composition were determined to analyze its nutritional characteristics. Free amino acids and flavor nucleotides were determined to calculate the taste active value (TAV) and equivalent umami concentration (EUC), which indicated the umami of P. yezoensis. The results showed that P. yezoensis from Jing Bay had high protein and low fat content. The protein content exceeded 49% in the first and second harvest, indicating that the P. yezoensis had higher nutritional value in the early stage of the harvest. The K content was the highest among the constant elements, while the P content was the lowest. Fe content was the highest among the trace elements; Zn content was higher, and Co content was the lowest. Pb content was significantly lower than the limited requirements of GB 2762-2017. There were significant differences between P. yezoensis from the first, second harvest and the fourth, sixth harvest in terms of essential and total amino acid content (P<0.05). Glutamic acid and hypoxanthine nucleotide played a major role in the umami contribution; the Equivalent umami concentration (in dry basis) of P. yezoensis in the first, second, fourth, and sixth harvests was 239.71, 190.03, 108.05, and 51.56 g MSG/100 g, respectively. P. yezoensis from Jing Bay has high nutritional values and desirable umami characteristics in the early stage of harvest, and thus, has great market potential.
Pyropia yezoensis at different harvest times were obtained from Jing Bay, and its nutritional and umami characteristics were analyzed. Crude protein, crude fat, ash, inorganic elements, and amino acid composition were determined to analyze its nutritional characteristics. Free amino acids and flavor nucleotides were determined to calculate the taste active value (TAV) and equivalent umami concentration (EUC), which indicated the umami of P. yezoensis. The results showed that P. yezoensis from Jing Bay had high protein and low fat content. The protein content exceeded 49% in the first and second harvest, indicating that the P. yezoensis had higher nutritional value in the early stage of the harvest. The K content was the highest among the constant elements, while the P content was the lowest. Fe content was the highest among the trace elements; Zn content was higher, and Co content was the lowest. Pb content was significantly lower than the limited requirements of GB 2762-2017. There were significant differences between P. yezoensis from the first, second harvest and the fourth, sixth harvest in terms of essential and total amino acid content (P<0.05). Glutamic acid and hypoxanthine nucleotide played a major role in the umami contribution; the Equivalent umami concentration (in dry basis) of P. yezoensis in the first, second, fourth, and sixth harvests was 239.71, 190.03, 108.05, and 51.56 g MSG/100 g, respectively. P. yezoensis from Jing Bay has high nutritional values and desirable umami characteristics in the early stage of harvest, and thus, has great market potential.
