... Address correspondence to: Dr. Egidijus Dauk as, SINTEF, Fisheries and Aqua-culture, N-7465 T... more ... Address correspondence to: Dr. Egidijus Dauk as, SINTEF, Fisheries and Aqua-culture, N-7465 Trondheim, Norway. ... bitter than hydrolysates obtained using Flavourzyme® (A1, A7 and A2, A8, Figure 2). The type of enzyme had a significant influence (Table 2, p = 0.0018) on ...
ABSTRACT Both the food industry and the health authorities have increased their focus on salt red... more ABSTRACT Both the food industry and the health authorities have increased their focus on salt reduction in food, due to the known negative health effect of high sodium intake. For this reason, there is great interest in developing products with reduced salt content without affecting properties related to sensory parameters, texture, yield and shelf-life. Whey and milk based permeates with favorable combinations of milk minerals and lactose can be used as natural ingredients in for instance meat and fish products and work as salt replacers. The aim of this study was to investigate how two different types of milk minerals; low mineral permeate, based on whey obtained in cheese production, and high mineral permeate, based on milk, affect the quality of comminuted fish products, using fish pudding as a model. Results showed that low mineral permeate can improve textural and water-holding properties of puddings at salt concentrations down to 0.8%, while it does not affect salt flavor. High mineral permeate contributes to changes in the textural and water-holding properties, and also increases salt flavor. Based on investigated factors, high mineral permeate is regarded as a promising salt replacer allowing for considerable salt reduction in fish puddings.
The main products of hydrolysis of fish by-products are hydrolysed protein and oil. The aim of th... more The main products of hydrolysis of fish by-products are hydrolysed protein and oil. The aim of this work was to study the effect of initial heat inactivation of endogenous enzymes, addition of water prior to hydrolysis, use of different commercial enzymes and combination of enzymes on the yield and purity of the protein and oil fractions after enzymatic hydrolysis of
... Dependent on the methods, two to six replicates were used. The programmes Guideline (Camo ASA... more ... Dependent on the methods, two to six replicates were used. The programmes Guideline (Camo ASA, Oslo, Norway), MatLab (MathWorks Inc., USA) and Microsoft Excel were employed for data processing and statistical analysis. Confidence level was set at 95% (p = 0.05). ...
The aim of this work was to study how different raw material mixtures from cod (Gadus morhua) by-... more The aim of this work was to study how different raw material mixtures from cod (Gadus morhua) by-products influenced the composition of the substrate for hydrolysis, yield and chemical composition of the different fractions after the enzymatic hydrolysis using endo-peptidase (Flavourzyme) or exo-peptidase (Neutrase).The most important factor influencing the yield of the different fractions was added water rather than type
An average production of 10,000 kg cod fillets (gadiform species) will generate by-products with ... more An average production of 10,000 kg cod fillets (gadiform species) will generate by-products with more than 1000 kg marine lipids. More than 30% of these lipids are the health beneficial n-3 fatty acids, which have commercial value. To increase the industrial utilization of these lipids different sources of raw material need to be evaluated in respect to available amounts and chemical composition. The present work presents such data on four gadiform species caught in the Barents Sea (Gadus morhua (cod), Pollachius virens (saithe), Melanogrammus aeglefinus (haddock) and Brosme brosme (tusk)) evaluated at three seasons during 1 year. Both seasonal and inter-species differences were found in the amount of by-products and the lipid composition. The levels of polyunsaturated fatty acids were significantly higher in haddock liver and significantly lower in tusk liver compared to saithe and cod. However, regardless of the variations found, the lipids from all samples analysed contained significant quantities of health beneficial fatty acids. Liver was the best lipid source containing between 43 and 69% total lipids. The viscera contained between 2 and 9% lipids and trimmings contained approximately 1% lipids. While the lipids from liver generally contained more than 90% triacylglycerols, the lipids from the other byproducts contained higher levels of phospholipids making up more than 60% of the total lipids in muscle and gonads. #
... The survey of proteolytic activity in crude muscle extract (Fig. 1) showed that slightly alka... more ... The survey of proteolytic activity in crude muscle extract (Fig. 1) showed that slightly alkaline proteases dominate. ... Elsevier, Barrett, AJ 1972. Lysosomal enzymes. ... Purification and characterization of serine proteinase from white croaker skeletal mus-cle. Bull. Jap. Sot. Sci. ...
International Journal of Food Science & Technology, 2011
Page 1. Invited review Possibilities for the utilisation of marine by-products Turid Rustad,1* Iv... more Page 1. Invited review Possibilities for the utilisation of marine by-products Turid Rustad,1* Ivar Storrø2 & Rasa Slizyte2 1 Department of biotechnology, Norwegian University of Science and Technology, Trondheim, Norway ...
The most important factor for increasing shelf life is the product temperature, and since fish is... more The most important factor for increasing shelf life is the product temperature, and since fish is more highly perishable than meat, the temperature is even more important. In the present study, portions of fillets of farmed Atlantic salmon (Salmo salar) were superchilled at two temperature levels, −1.4 and −3.6°C. Texture, drip loss, liquid loss, cathepsin activities and protein extractability were
Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 1995
A high molecular mass alkaline proteinase was purified by DEAE-Sepharose and Mono Q chromatograph... more A high molecular mass alkaline proteinase was purified by DEAE-Sepharose and Mono Q chromatography. The mol. wt was estimated to be about 600,000. Under denaturing conditions, the enzyme dissociated into a cluster of subunits with mol. wt ranging from 25,000 to 30,000. The isoelectric point of the enzyme was about pH 7.3. The proteinase was able to hydrolyse N-terminal-blocked 4-methyl-7-coumarylamide substrates for either trypsin- or chymotrypsin-like activity. It was also able to hydrolyse haemoglobin and myosin at temperatures of about 60 degrees C. The activities responded to pH and some chemicals in different ways. The trypsin-like activity was clearly inhibited by several serine protease inhibitors. These results suggest that the enzyme is multicatalytic, having at least two different active sites.
Combining atmospheric freeze-drying (AFD) with a properly designed heat pump system (HP) results ... more Combining atmospheric freeze-drying (AFD) with a properly designed heat pump system (HP) results in an energy-efficient drying process. This combination makes HP-AFD competitive with vacuum freeze-drying (VFD). The advantages of AFD compared to VFD are lower production costs and the ability to manufacture a similar porous product. The zooplankton species Calanus finmarchicus (CF) is attractive for use as aquaculture feed due to its high content of valuable marine lipids and proteins. Atmospheric freeze-drying in a fluidized bed has been evaluated as preservation method for CF. Three different trials of drying techniques were conducted with CF. The drying temperatures were -5ºC, -10ºC and a combination of -5ºC/+20ºC (initial -5ºC for 4 hours and final drying at +20ºC). This paper evaluates the effects of drying conditions on proteolytic and lipolytic activities, and describes particle size distribution and sorption isotherms. Proteolytic activity was reduced for CF dried at a combine...
a b s t r a c t Salting is one of the basic procedures in food processing. The NaCl concentration... more a b s t r a c t Salting is one of the basic procedures in food processing. The NaCl concentration influences water hold-ing properties, viscosity, texture, emulsification, etc. It is important to study and model mixing pro-cesses by mathematical methods to predict properties of the matrix and the food quality. The objective of this study was to develop a mathematical model of mixing of salt and meat in a bowl cut-ter and verify this with experimental data. The bowl cutter is described as a continuous stirred tank reactor, combined with a plug flow reactor in a repetitive series-model. The theoretical model shows that 30 rounds are sufficient to get a salt concentration in the whole bulk of meat with a deviation between maximum and minimum values of about 5%. The comparison of the theoretically predicted salt gradient and the experimental results showed that the mathematical equation developed is appro-priate to describe the process.
ABSTRACT Cooked minces made from both fresh and frozen haddock with NaCl, KCl, or MgCl2 at concen... more ABSTRACT Cooked minces made from both fresh and frozen haddock with NaCl, KCl, or MgCl2 at concentrations from 0.07 to 0.34 mol/kg fish mince were prepared and analysed for physicochemical properties. The properties of the minces varied both with the type and amount of added salt. Minces added the same molar amount of NaCl or KCl had fairly similar properties, but pH in minces made with KCl was slightly higher. Minces made with MgCl2 had lower pH than the corresponding minces made with NaCl. Minces made from fresh raw material with 0.07 mol/kg MgCl2 had significantly lower WHC than the rest of the minces, while minces made with 0.34 mol MgCl2/kg had lower moisture and breaking force than the corresponding minces with KCl or NaCl. Low field NMR T2 relaxation data indicated differences in the protein structure as an effect of addition of small amounts of salt. Cooking loss decreased with increasing salt content both when fresh and frozen raw materials were employed, and the results indicate that this could be due to the increased ionic strength. WHC for minces made with NaCl decreased significantly, whereas WHC did not change much for minces made with KCl or MgCl2.
... weeks. Jeremiah, Gibson, and Argnosa (1995) found a shelf life of 9 weeks at the same tempera... more ... weeks. Jeremiah, Gibson, and Argnosa (1995) found a shelf life of 9 weeks at the same temperature. Jeremiah and Gibson (2001) concluded that storage life could be more than doubled at −1.5 °C compared to at +2 and 5 °C. ...
European Journal of Lipid Science and Technology, 2015
ABSTRACT The aim of this work was to understand the effect of pH and chelators on free iron (Fe2+... more ABSTRACT The aim of this work was to understand the effect of pH and chelators on free iron (Fe2+/Fe3+)-mediated oxidation in liposome dispersions made of marine phospholipids. Consumption of dissolved oxygen was used to follow lipid oxidation. The highest oxygen uptake rates were found at pH 4 - 5. Increase in pH (> 5.7) enhanced autoxidation rate of Fe2+ to Fe3+ and lowered solubility of Fe3+ causing decrease in oxygen uptake rates. Simultaneously, the negative charge on the liposome vesicles increased with increasing pH improving the attraction between iron and liposomes. Retention of Fe3+ ions by phospholipids is suggested to prevent complete precipitation of Fe3+ at pH > 5, which facilitates a pro-oxidative activity of iron even at higher pH. The tested chelators reduced Fe2+ (10 µM) mediated oxidation at pH 5.5 and at 2:1 chelator-to-iron ratio in the following order: EDTA casein > citric acid > oxalic acid. However, when pH was reduced below the pKa of the EDTA carboxylic groups, EDTA lost its chelating abilities. The stability constants for complexes between the chelators and iron followed the same sequence as efficacy of the chelators at pH 5.5, making it an additional factor determining the efficacy of chelators. This study shows that the final oxidation rate is dependent on the overall dissolved iron in the system and the degree of attraction between iron and the surface of liposome vesicles at a given pH.Practical applications For successful addition of marine polyunsaturated lipids into emulsified food, it is important to understand how physicochemical conditions affect the pro-oxidative activity of iron and antioxidant activity of metal chelators. This work addresses the role of pH in oxidation of marine liposomes and the knowledge may help to characterize effective hurdles for lipid oxidation. This study shows that pH has an impact on iron solubility and attraction between iron and liposome surface and also affects the efficacy of EDTA. This study also shows that by quantification of the dissolved oxygen consumption it is possible to screen and evaluate the impact of surrounding conditions (pH, chelators) on iron-mediated oxidation in a water-based system.
High resolution NMR technique has been used to monitor post-mortem changes in salmon (Salmo salar... more High resolution NMR technique has been used to monitor post-mortem changes in salmon (Salmo salar) fillets upon storage at 4 and 0°C. Thirty-one different fish metabolites influencing freshness and taste properties have been unequivocally assigned by NMR using either available standard compounds or ad hoc acquired 2D (1)H-(1)H TOCSY and (1)H-(13)С HSQC spectra. The monitored fish metabolites include amino acids, dipeptides, sugars, vitamins, biogenic amines, as well as different products of the ATP degradation. The detection and monitoring of biogenic amines by NMR, upon fish storage, is information of interest for consumers, since some of these compounds are toxic. The data from this study shows that NMR spectroscopy also provides the amount of all metabolites necessary for the calculation of the K-index used to express fish freshness. A good correlation was found between the K-index increase and the formation of the undesired biogenic amines. The metabolite concentrations and the ...
The aim of this study was to investigate endogenous proteolytic activities in a cod product and t... more The aim of this study was to investigate endogenous proteolytic activities in a cod product and their impact on muscle proteins and textural properties during fermentation and storage. The result of specific proteolytic activities showed that cathepsins, especially cathepsin B, had the highest activities during fermentation and storage. SDS-PAGE indicated more degradation of myofibrillar proteins by cathepsin L than other proteases and that the hydrolysis by cathepsins was pronounced in the last stage of fermentation. Texture analysis showed that cathepsins had a negative impact on gel strength and this impact increased in the last stage of fermentation. However the product still had a firm texture. During storage (4 °C) for one week, no significant changes were seen in the gel strength. In conclusion, cathepsins had more impact on muscle proteins and textural properties than other proteases during fermentation but had little impact on gel strength during storage at 4 °C.
... Address correspondence to: Dr. Egidijus Dauk as, SINTEF, Fisheries and Aqua-culture, N-7465 T... more ... Address correspondence to: Dr. Egidijus Dauk as, SINTEF, Fisheries and Aqua-culture, N-7465 Trondheim, Norway. ... bitter than hydrolysates obtained using Flavourzyme® (A1, A7 and A2, A8, Figure 2). The type of enzyme had a significant influence (Table 2, p = 0.0018) on ...
ABSTRACT Both the food industry and the health authorities have increased their focus on salt red... more ABSTRACT Both the food industry and the health authorities have increased their focus on salt reduction in food, due to the known negative health effect of high sodium intake. For this reason, there is great interest in developing products with reduced salt content without affecting properties related to sensory parameters, texture, yield and shelf-life. Whey and milk based permeates with favorable combinations of milk minerals and lactose can be used as natural ingredients in for instance meat and fish products and work as salt replacers. The aim of this study was to investigate how two different types of milk minerals; low mineral permeate, based on whey obtained in cheese production, and high mineral permeate, based on milk, affect the quality of comminuted fish products, using fish pudding as a model. Results showed that low mineral permeate can improve textural and water-holding properties of puddings at salt concentrations down to 0.8%, while it does not affect salt flavor. High mineral permeate contributes to changes in the textural and water-holding properties, and also increases salt flavor. Based on investigated factors, high mineral permeate is regarded as a promising salt replacer allowing for considerable salt reduction in fish puddings.
The main products of hydrolysis of fish by-products are hydrolysed protein and oil. The aim of th... more The main products of hydrolysis of fish by-products are hydrolysed protein and oil. The aim of this work was to study the effect of initial heat inactivation of endogenous enzymes, addition of water prior to hydrolysis, use of different commercial enzymes and combination of enzymes on the yield and purity of the protein and oil fractions after enzymatic hydrolysis of
... Dependent on the methods, two to six replicates were used. The programmes Guideline (Camo ASA... more ... Dependent on the methods, two to six replicates were used. The programmes Guideline (Camo ASA, Oslo, Norway), MatLab (MathWorks Inc., USA) and Microsoft Excel were employed for data processing and statistical analysis. Confidence level was set at 95% (p = 0.05). ...
The aim of this work was to study how different raw material mixtures from cod (Gadus morhua) by-... more The aim of this work was to study how different raw material mixtures from cod (Gadus morhua) by-products influenced the composition of the substrate for hydrolysis, yield and chemical composition of the different fractions after the enzymatic hydrolysis using endo-peptidase (Flavourzyme) or exo-peptidase (Neutrase).The most important factor influencing the yield of the different fractions was added water rather than type
An average production of 10,000 kg cod fillets (gadiform species) will generate by-products with ... more An average production of 10,000 kg cod fillets (gadiform species) will generate by-products with more than 1000 kg marine lipids. More than 30% of these lipids are the health beneficial n-3 fatty acids, which have commercial value. To increase the industrial utilization of these lipids different sources of raw material need to be evaluated in respect to available amounts and chemical composition. The present work presents such data on four gadiform species caught in the Barents Sea (Gadus morhua (cod), Pollachius virens (saithe), Melanogrammus aeglefinus (haddock) and Brosme brosme (tusk)) evaluated at three seasons during 1 year. Both seasonal and inter-species differences were found in the amount of by-products and the lipid composition. The levels of polyunsaturated fatty acids were significantly higher in haddock liver and significantly lower in tusk liver compared to saithe and cod. However, regardless of the variations found, the lipids from all samples analysed contained significant quantities of health beneficial fatty acids. Liver was the best lipid source containing between 43 and 69% total lipids. The viscera contained between 2 and 9% lipids and trimmings contained approximately 1% lipids. While the lipids from liver generally contained more than 90% triacylglycerols, the lipids from the other byproducts contained higher levels of phospholipids making up more than 60% of the total lipids in muscle and gonads. #
... The survey of proteolytic activity in crude muscle extract (Fig. 1) showed that slightly alka... more ... The survey of proteolytic activity in crude muscle extract (Fig. 1) showed that slightly alkaline proteases dominate. ... Elsevier, Barrett, AJ 1972. Lysosomal enzymes. ... Purification and characterization of serine proteinase from white croaker skeletal mus-cle. Bull. Jap. Sot. Sci. ...
International Journal of Food Science & Technology, 2011
Page 1. Invited review Possibilities for the utilisation of marine by-products Turid Rustad,1* Iv... more Page 1. Invited review Possibilities for the utilisation of marine by-products Turid Rustad,1* Ivar Storrø2 & Rasa Slizyte2 1 Department of biotechnology, Norwegian University of Science and Technology, Trondheim, Norway ...
The most important factor for increasing shelf life is the product temperature, and since fish is... more The most important factor for increasing shelf life is the product temperature, and since fish is more highly perishable than meat, the temperature is even more important. In the present study, portions of fillets of farmed Atlantic salmon (Salmo salar) were superchilled at two temperature levels, −1.4 and −3.6°C. Texture, drip loss, liquid loss, cathepsin activities and protein extractability were
Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 1995
A high molecular mass alkaline proteinase was purified by DEAE-Sepharose and Mono Q chromatograph... more A high molecular mass alkaline proteinase was purified by DEAE-Sepharose and Mono Q chromatography. The mol. wt was estimated to be about 600,000. Under denaturing conditions, the enzyme dissociated into a cluster of subunits with mol. wt ranging from 25,000 to 30,000. The isoelectric point of the enzyme was about pH 7.3. The proteinase was able to hydrolyse N-terminal-blocked 4-methyl-7-coumarylamide substrates for either trypsin- or chymotrypsin-like activity. It was also able to hydrolyse haemoglobin and myosin at temperatures of about 60 degrees C. The activities responded to pH and some chemicals in different ways. The trypsin-like activity was clearly inhibited by several serine protease inhibitors. These results suggest that the enzyme is multicatalytic, having at least two different active sites.
Combining atmospheric freeze-drying (AFD) with a properly designed heat pump system (HP) results ... more Combining atmospheric freeze-drying (AFD) with a properly designed heat pump system (HP) results in an energy-efficient drying process. This combination makes HP-AFD competitive with vacuum freeze-drying (VFD). The advantages of AFD compared to VFD are lower production costs and the ability to manufacture a similar porous product. The zooplankton species Calanus finmarchicus (CF) is attractive for use as aquaculture feed due to its high content of valuable marine lipids and proteins. Atmospheric freeze-drying in a fluidized bed has been evaluated as preservation method for CF. Three different trials of drying techniques were conducted with CF. The drying temperatures were -5ºC, -10ºC and a combination of -5ºC/+20ºC (initial -5ºC for 4 hours and final drying at +20ºC). This paper evaluates the effects of drying conditions on proteolytic and lipolytic activities, and describes particle size distribution and sorption isotherms. Proteolytic activity was reduced for CF dried at a combine...
a b s t r a c t Salting is one of the basic procedures in food processing. The NaCl concentration... more a b s t r a c t Salting is one of the basic procedures in food processing. The NaCl concentration influences water hold-ing properties, viscosity, texture, emulsification, etc. It is important to study and model mixing pro-cesses by mathematical methods to predict properties of the matrix and the food quality. The objective of this study was to develop a mathematical model of mixing of salt and meat in a bowl cut-ter and verify this with experimental data. The bowl cutter is described as a continuous stirred tank reactor, combined with a plug flow reactor in a repetitive series-model. The theoretical model shows that 30 rounds are sufficient to get a salt concentration in the whole bulk of meat with a deviation between maximum and minimum values of about 5%. The comparison of the theoretically predicted salt gradient and the experimental results showed that the mathematical equation developed is appro-priate to describe the process.
ABSTRACT Cooked minces made from both fresh and frozen haddock with NaCl, KCl, or MgCl2 at concen... more ABSTRACT Cooked minces made from both fresh and frozen haddock with NaCl, KCl, or MgCl2 at concentrations from 0.07 to 0.34 mol/kg fish mince were prepared and analysed for physicochemical properties. The properties of the minces varied both with the type and amount of added salt. Minces added the same molar amount of NaCl or KCl had fairly similar properties, but pH in minces made with KCl was slightly higher. Minces made with MgCl2 had lower pH than the corresponding minces made with NaCl. Minces made from fresh raw material with 0.07 mol/kg MgCl2 had significantly lower WHC than the rest of the minces, while minces made with 0.34 mol MgCl2/kg had lower moisture and breaking force than the corresponding minces with KCl or NaCl. Low field NMR T2 relaxation data indicated differences in the protein structure as an effect of addition of small amounts of salt. Cooking loss decreased with increasing salt content both when fresh and frozen raw materials were employed, and the results indicate that this could be due to the increased ionic strength. WHC for minces made with NaCl decreased significantly, whereas WHC did not change much for minces made with KCl or MgCl2.
... weeks. Jeremiah, Gibson, and Argnosa (1995) found a shelf life of 9 weeks at the same tempera... more ... weeks. Jeremiah, Gibson, and Argnosa (1995) found a shelf life of 9 weeks at the same temperature. Jeremiah and Gibson (2001) concluded that storage life could be more than doubled at −1.5 °C compared to at +2 and 5 °C. ...
European Journal of Lipid Science and Technology, 2015
ABSTRACT The aim of this work was to understand the effect of pH and chelators on free iron (Fe2+... more ABSTRACT The aim of this work was to understand the effect of pH and chelators on free iron (Fe2+/Fe3+)-mediated oxidation in liposome dispersions made of marine phospholipids. Consumption of dissolved oxygen was used to follow lipid oxidation. The highest oxygen uptake rates were found at pH 4 - 5. Increase in pH (> 5.7) enhanced autoxidation rate of Fe2+ to Fe3+ and lowered solubility of Fe3+ causing decrease in oxygen uptake rates. Simultaneously, the negative charge on the liposome vesicles increased with increasing pH improving the attraction between iron and liposomes. Retention of Fe3+ ions by phospholipids is suggested to prevent complete precipitation of Fe3+ at pH > 5, which facilitates a pro-oxidative activity of iron even at higher pH. The tested chelators reduced Fe2+ (10 µM) mediated oxidation at pH 5.5 and at 2:1 chelator-to-iron ratio in the following order: EDTA casein > citric acid > oxalic acid. However, when pH was reduced below the pKa of the EDTA carboxylic groups, EDTA lost its chelating abilities. The stability constants for complexes between the chelators and iron followed the same sequence as efficacy of the chelators at pH 5.5, making it an additional factor determining the efficacy of chelators. This study shows that the final oxidation rate is dependent on the overall dissolved iron in the system and the degree of attraction between iron and the surface of liposome vesicles at a given pH.Practical applications For successful addition of marine polyunsaturated lipids into emulsified food, it is important to understand how physicochemical conditions affect the pro-oxidative activity of iron and antioxidant activity of metal chelators. This work addresses the role of pH in oxidation of marine liposomes and the knowledge may help to characterize effective hurdles for lipid oxidation. This study shows that pH has an impact on iron solubility and attraction between iron and liposome surface and also affects the efficacy of EDTA. This study also shows that by quantification of the dissolved oxygen consumption it is possible to screen and evaluate the impact of surrounding conditions (pH, chelators) on iron-mediated oxidation in a water-based system.
High resolution NMR technique has been used to monitor post-mortem changes in salmon (Salmo salar... more High resolution NMR technique has been used to monitor post-mortem changes in salmon (Salmo salar) fillets upon storage at 4 and 0°C. Thirty-one different fish metabolites influencing freshness and taste properties have been unequivocally assigned by NMR using either available standard compounds or ad hoc acquired 2D (1)H-(1)H TOCSY and (1)H-(13)С HSQC spectra. The monitored fish metabolites include amino acids, dipeptides, sugars, vitamins, biogenic amines, as well as different products of the ATP degradation. The detection and monitoring of biogenic amines by NMR, upon fish storage, is information of interest for consumers, since some of these compounds are toxic. The data from this study shows that NMR spectroscopy also provides the amount of all metabolites necessary for the calculation of the K-index used to express fish freshness. A good correlation was found between the K-index increase and the formation of the undesired biogenic amines. The metabolite concentrations and the ...
The aim of this study was to investigate endogenous proteolytic activities in a cod product and t... more The aim of this study was to investigate endogenous proteolytic activities in a cod product and their impact on muscle proteins and textural properties during fermentation and storage. The result of specific proteolytic activities showed that cathepsins, especially cathepsin B, had the highest activities during fermentation and storage. SDS-PAGE indicated more degradation of myofibrillar proteins by cathepsin L than other proteases and that the hydrolysis by cathepsins was pronounced in the last stage of fermentation. Texture analysis showed that cathepsins had a negative impact on gel strength and this impact increased in the last stage of fermentation. However the product still had a firm texture. During storage (4 °C) for one week, no significant changes were seen in the gel strength. In conclusion, cathepsins had more impact on muscle proteins and textural properties than other proteases during fermentation but had little impact on gel strength during storage at 4 °C.
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