Study On Ultrasonic Assisted Sodium Tripolyphosphate To Improve The Gel Properties Of Minced Pork Under Low Salt Conditions

Myofibrillar protein is an important component of muscle protein,accounting for 55 ～65% of the total muscle protein content,and plays an important role in determining the texture and functional properties of meat products.During the processing of meat products,salt is often used as a flavoring agent and flavor enhancer,which can promote the dissolution of salt-soluble myofibrillar protein,enhance the water binding capacity of protein,and improve the textural properties of meat products.According to statistics,the current daily salt intake of adults in China is about twice the recommended intake of the U.S.Food and Drug Administration.Numerous studies have shown that a long-term high-salt diet increases the risk of cardiovascular disease,hypertension and other chronic diseases,seriously endangering human health.However,directly reducing the salt content in meat products can affect the texture and sensory characteristics of the product and shorten the shelf life of the product.Sodium tripolyphosphate is often used as a water retention agent in meat processing to improve the quality of meat products,which has the advantages of green,safe and economic.Sodium tripolyphosphate can react with protein side chains to introduce phosphate groups into myofibrillar proteins,changing the electronegativity of the protein surface and enhancing electrostatic repulsion between proteins,thus affecting the functional properties of myofibrillar proteins.Ultrasound has been shown to modify myofibrillar proteins and improve the functional properties of myofibrillar proteins by modulating the folding and depolymerization of myofibrillar proteins,effectively reducing the amount of salt added to meat products.However,high concentration of sodium tripolyphosphate and high power ultrasonication can cause protein aggregation and negatively affect the functional properties of proteins.Therefore,when reducing the salt content in meat products,the concentration of sodium tripolyphosphate and the conditions of ultrasonic treatment need to be regulated to avoid negative effects on proteins due to excessive treatment.In this experiment,from the perspective of reducing the salt content in minced meat gel products,the effects of adding different concentrations of sodium tripolyphosphate(0,2.5,5,10,15,45 m M)on the gel characteristics of myogenic fibrin under low salt conditions(0.3M Na Cl)were firstly investigated,and then,based on this,different power(0,100,200,300,400,500 W)of Ultrasonic treatment was then performed to investigate the effect of ultrasonic power on the gel characteristics of myogenic fibrin at different sodium tripolyphosphate concentrations,and finally it was applied to ground pork products(pork sausage)to investigate the effect of ultrasonic-assisted sodium tripolyphosphate treatment on the quality characteristics of pork sausage.The specific results of the study are as follows:(1)Effect of sodium tripolyphosphate on physicochemical,structural and gel characteristics of myogenic fibrin.The results showed that the solubility of myogenic fibrin increased from 5.46% to 39.58%,the turbidity value decreased from 1.61 to 0.45,the particle size value decreased from 2164.50 nm to 1169.50 nm,the absolute value of zata potential increased from 1.87 m V to 7.43 m V,and the α-helical structure content increased from 49.08% to 67.77%.At the same time,the sulfhydryl content and surface hydrophobicity of myogenic fibronectin increased with the increase of sodium tripolyphosphate concentration(p < 0.05),and the decrease of fluorescence intensity occurred subsequently.Fourier infrared spectroscopy revealed two characteristic peaks of P=O and P-O near 1100 cm-1 and 900 cm-1 in the sodium tripolyphosphate treated group,demonstrating the successful introduction of phosphate groups in sodium tripolyphosphate into myogenic fibronectin.The highest gel strength(34.49 g)and the best rheological properties of myogenic fibrin gel were obtained when the concentration of sodium tripolyphosphate was 10 m M,and its gel network structure was the most uniform and dense with the lowest porosity,which was close to that of the control(0.6 M Na Cl).This is because the introduction of phosphate groups enhanced the myogenic fibrin protein-water interaction and electrostatic repulsion and promoted protein cross-linking,resulting in protein gels with high gel strength and high water retention.(2)Effect of ultrasound-assisted sodium tripolyphosphate on physicochemical,structural and gel properties of myogenic fibronectin.The myofibrillar proteins treated with different concentrations of sodium tripolyphosphate were then subjected to different power(0,100,200,300,400 and 500 W)ultrasound treatments to further modify myofibrillar proteins.The results showed that sonication alone had limited effect on the improvement of physicochemical,structural and gel properties of myogenic fibrin under low salt conditions,and the quality of the gels formed was still poor.The effect of sonication on the gel properties of myogenic fibrin was not significant at sodium tripolyphosphate concentrations of 2.5,5 and 45 m M.There was a significant synergistic effect of ultrasound-assisted sodium tripolyphosphate when the sodium tripolyphosphate concentration was 10 m M and 15 m M and the ultrasound power was 100 W and 200 W.The solubility of MP further increased,turbidity and particle size as well as zeta potential decreased after ultrasound treatment compared to that without ultrasound treatment.Moreover,the surface hydrophobicity,fluorescence intensity and sulfhydryl content of myogenic fibronectin were enhanced,and a significant increase in α-helical structure content was also promoted.When the concentration of sodium tripolyphosphate was 10 m M and the ultrasonic power was 100 W,the myogenic fibrin gel had the strongest gel strength(37.78 g)and the strongest rheological properties,and could form a thermally induced gel with good viscoelasticity and showed a three-dimensional network liaison structure with the lowest uniform dense porosity,and its gel quality was close to that of the control group.(3)Effect of ultrasound-assisted sodium tripolyphosphate treatment on the quality of pork sausage meat.Sodium tripolyphosphate at concentrations of 0 and 10 m M was added to the low-salt-treated ground pork,and then the ground pork was treated with ultrasonic waves at 0,100 and 500 W.Finally,the treated ground pork was prepared into pork sausage to investigate the effects of different treatments on the quality of pork sausage.The results showed that both ultrasonic treatment alone and sodium tripolyphosphate treatment alone could improve the cooking loss,color and gel strength of pork sausage.At a concentration of10 m M sodium tripolyphosphate and an ultrasonic power of 100 W,the synergistic effect of ultrasound-assisted sodium tripolyphosphate had the strongest effect on the quality of pork sausage,and the textural properties of pork sausage were significantly improved,with an increase in hardness from 1852.88 g to 2702.18 g(p < 0.05),elasticity from 0.77 to 1.15(p <0.05),and chewiness from 1175.80 to 1673.19(p < 0.05),and the pork sausage had the lowest cooking loss(3.77%)and the highest sensory evaluation score,and the meat quality of the pork sausage treated under this condition was the closest to that of the control group.In summary,the ability of sodium tripolyphosphate alone and ultrasound treatment alone to improve the gel properties of MP under low salt conditions was limited.At a sodium tripolyphosphate concentration of 10 m M,there was a synergistic effect with 100 W ultrasound,which significantly improved the gel characteristics of myogenic fibrin.It was shown that ultrasonic-assisted sodium tripolyphosphate treatment effectively solved the problem of poor gel quality of ground pork under low salt conditions.This experiment provides theoretical basis and technical support for the processing and development of high-quality low-salt meat products.