What is the effect of konjac flour on myofibrillar protein gel properties?

The gel properties of myofibrillar proteins are important functional properties of surimi products, which are the decisive factors for the formation of unique texture, water retention and other properties of surimi products.
Due to the excessive marine fishing and the further aggravation of marine pollution in recent years, seawater fish can no longer meet the large market demand. In recent years, the global freshwater fish aquaculture production has been increasing, and the production of surimi and surimi products from freshwater fish as raw materials will become a new trend in the surimi processing industry.
In order to improve the textural properties of surimi gels, exogenous ingredients such as inulin, konjac flour, soybean isolate protein, starch, phosphate, etc. are added to surimi to improve gel strength, elasticity and water retention.
The main component of konjac flour is glucomannan (KGM), the chemical structure of which is a polymeric heteropolysaccharide consisting of D-glucose and D-mannose residues with a molecular ratio of about 15:23 polymerized into a backbone through β-1,4 glycosidic bonds. Konjac flour has the prevention and improvement of constipation, increase intestinal probiotics, lower fat and sugar, weight loss and slimming, improve human immunity and other health functions.
Konjac flour itself has a strong ability to bind water, is commonly used in food processing thickener, protein gelatinization of meat products as well as water binding shows synergistic effect, is also commonly used to improve the quality of low-fat emulsified meat products. So how does konjac flour affect the gelation properties of myofibrillar protein?
The effect of konjac flour on the hardness and elasticity of myofibrillar protein gels at different heating temperatures.
Under the same temperature conditions, the konjac flour additive amount of 0.10g/100mL when the hardness of myofibrillar fibrin gel is the largest, and 80 ℃ for the maximum value of 129g, than 70 ℃ gel hardness is higher than about 20g; when the konjac flour additive amount continues to increase, the hardness of myofibrillar fibrillar fibrillar protein gel decreases.
Under the condition of the same konjac flour addition, the gel elasticity formed by myofibrillar protein at 80℃ was significantly higher than that formed at 70℃, but there was no significant difference with the gel elasticity formed at 90℃.
Under the same temperature conditions, with the increase in the amount of konjac flour, the elasticity of the gel is also gradually enhanced, but increasing the mass concentration of konjac flour instead of the hardness of myofibrillar fibrin gel decreased, probably because the higher mass concentration of konjac flour impedes the cross-linking of myofibrillar fibrillar fibrillar proteins to each other, which affects the formation of the gel. With the increase in the amount of konjac flour, the elasticity gradually increased, probably because the konjac flour dissolved in water and protein cross-linking, and the konjac flour dissolved in water to form a gel, the higher the mass concentration of the formation of the elasticity of the gel will be greater.
80 ℃ conditions myofibrillar protein gel hardness and elasticity of the best, probably because actin and myosin and other internal subunits are more fully exposed, the protein subunits re-interact with each other to form the network structure of the protein gel. At 70 ℃ protein did not fully reach its denaturation temperature, part of the protein is not fully denatured and crosslinked with each other; at 90 ℃ myofibrillar proteins due to high temperature failed to fully polymerize with each other after denaturation to form a three-dimensional network structure of proteins, the hardness and elasticity of the gel is also relatively low.
The effect of konjac flour addition on the hardness and elasticity of myofibrillar protein gels under different salt concentrations
Under the condition of the same amount of konjac flour, the hardness of the gel was enhanced with the increase of sodium chloride concentration, when the amount of konjac flour added was 0.20g/100mL and the concentration of sodium chloride reached 0.20 mol/L, the hardness of the gel was significantly enhanced, and the elasticity of the gel increased with the increase of sodium chloride concentration, and the elasticity change was significant at 0.05 mol/L sodium chloride.
Under the same conditions of sodium chloride concentration, the hardness of the gel was enhanced with the increase of konjac powder addition, and the elasticity of the gel was increased with the increase of konjac powder addition, but the elasticity of the gel did not change significantly at 0.20 mol/L NaCl concentration, and it changed significantly at 0.05 mol/L NaCl concentration.
The increase in elasticity may be due to the formation of tough colloid after dissolving konjac flour in water, which increased the elasticity of the gel, and another possibility is that fish contains a large amount of transglutaminase, and there may be a synergistic effect between konjac flour and transglutaminase at low ionic strength. In polysaccharide/protein hybrid systems this effect may be the result of chemical (e.g. hydrogen bonding) and physical (molecular entanglement) interactions.
Effect of konjac flour addition on the whiteness of myofibrillar protein gels at different heating temperatures
At the same temperature, the whiteness of myofibrillar protein gel decreased with the increase of konjac flour addition, the whiteness of myofibrillar protein gel was the lowest when the mass concentration of konjac flour was 0.15g/100mL, and the whiteness increased slightly as the mass concentration of konjac flour continued to increase. the whiteness of myofibrillar protein gel at 80℃ was significantly lower than that at 70℃ and 90℃, which was 77.54. At 90℃, the whiteness of myofibrillar protein gel was 77.54, and that at 90℃ was 77.54, and that at 90℃ was 77.54. ℃, myofibrillar protein gel with the increase in the mass concentration of konjac flour decreased significantly, while at 70 ℃ and 80 ℃, myofibrillar protein gel whiteness with the increase in the mass concentration of konjac flour downward trend is relatively slow. Because of the light yellow color of konjac flour itself, it will not have a significant effect on the chromaticity of the gel.
The effect of konjac flour on the whiteness of myocardin gels under different salt concentrations
Under the condition of the same konjac flour addition, the whiteness of myofibrillar protein gel increased with the increase of sodium chloride concentration. Under the same sodium chloride concentration, the whiteness of the gel decreased with the increase of konjac powder addition.
Without the addition of sodium chloride, the whiteness of the gel decreased slowly, which indicates that the sodium chloride concentration has a large effect on the whiteness. After the addition of sodium chloride, sodium ions can promote the formation of protein gels, while sodium ions can be combined with amino acids inside the protein, hindering the fructose and protein to have a Melad reaction, so the whiteness of the gel with a larger concentration of sodium chloride is higher.
Changes in water retention of myofibrillar protein gels by konjac flour at different heating temperatures
At the same temperature, with the increase of konjac flour, the water retention of myofibrillar protein gels showed an increasing trend. 80 ℃ and 90 ℃, the same amount of konjac flour added to the water retention of the gel compared to the difference is not significant, 70 ℃ water retention of gel compared to the water retention of 80 ℃, 90 ℃ gel compared to the difference is significant.
As the konjac flour itself has a strong ability to combine water, the increase in the mass concentration of konjac flour, the more water can be combined, the greater the water retention of the gel. Changes in water retention of myofibrillar protein gels caused by the addition of konjac flour at different salt concentrations
The water retention of myofibrillar protein gel was enhanced with the increase of sodium chloride concentration at the same konjac flour addition; at the same sodium chloride concentration, the water retention of the gel showed an upward trend with the increase of konjac flour addition. Because after adding a certain concentration of sodium chloride, the protein solution has a certain ionic strength, which makes the solubility of the protein enhanced, thus promoting gelation and the ability to combine with water. In summary the hardness and elasticity of myofibrillar protein gel formed when heated at 80 ℃ is the best, and the addition of konjac powder can significantly improve the hardness, elasticity and water retention of myofibrillar protein gel, but it will not have a significant effect on the whiteness. The addition of sodium chloride can significantly improve the hardness, elasticity, water retention and whiteness of the gel.