Application Of Low-frequency Magnetic Field Modified Soy 11S Globulin In Low-fat Pork Batter

In the new consumption situation,the theory of"four reductions"（salt reduction,fat reduction,sugar reduction,and hazard reduction）has been put forward to meet the demand for new and diversified meat products.In the traditional emulsified meat processing,about 20%-30%animal fats need to be added to maintain the stability of the emulsified system.However,animal fat contains a large amount of saturated fatty acids,excessive consumption may lead to obesity and a variety of cardiovascular and cerebrovascular diseases.Therefore,"fat reduction"has become a major challenge for the meat processing industries.A vari-ety of fat substitutes（mainly including proteins,lipids and carbohydrates）are also being explored.Safflower seed oil is rich in vitamin E and linoleic acid,which has the effect of reducing blood cholesterol content and antioxidation.So,it can be used as a lipid substitute in emulsified pork batter products.However,directly replacing solid animal fat with liquid vegetable oil will change the rheological properties,and adversely affect texture and taste of the products.Emulsify is a common method of vegetable oil modification.Liquid oils can be endowed with plastic solid-like properties.Soy protein is a commonly used edible emulsifier,which can be used to emulsify safflower seed oil.However,soy 11S globulin is one of the most important components of soy protein,its functions（such as emulsify,foaming and gelation）are often limited by its own structure,so it is of great significance to introduce low-cost and efficient plant protein modification technol-ogy.As a new type of physical processing technology,low-frequency magnetic field could change the struc-ture of protein by changing the arrangement of charged molecules in the field.However,there are few studies on the application of low-frequency magnetic field in plant proteins.In addition,there are some gaps in the development of safflower oil O/W emulsion as a substitute for pork fat.Therefore,this work first studied the modification effect of low-frequency magnetic field on soy 11S globulin,then prepared O/W emulsion with safflower seed oil and modified protein,and finally explored the feasibility of using O/W emulsion to replace pork back fat in emulsified pork batter.In order to provide a new idea for the modification of plant proteins and provide a theoretical basis for the development of new low-fat emulsified meat products.The results are as follows:1.Effects of low-frequency magnetic field on the structure and functional properties of soy 11S globulinThe conformation,physicochemical properties,surface characteristics,and gel properties of soy 11S globulin were studied to investigate the effects of low-frequency magnetic field（5 mT,50 Hz）treatment times（30,60,90,and 120 min）.Compared with the native soy 11S globulin,the free-SH content and absolute Zeta-potential values significantly increased（P<0.05）after low-frequency magnetic field treatment,average particle size significantly decreased（P<0.05）.Accordingly,low-frequency magnetic field treated soy 11S globulin showed the higher emulsifying activity,foaming activity,foaming stability,and gel quality.Accord-ing to the analysis of rheological properties,low-frequency magnetic field treatment increased the viscosity of soy 11S globulin dispersions and the G′of gels.After comprehensive analysis,90 min is the optimum treatment time for soy 11S globulin modification.Overall,low-frequency magnetic field treatment is an ef-fective method to improve various functional properties of soy 11S globulin,and this study provides a refer-ence for the development of plant-based proteins in the food industry.2.Preparation and characterization of low-frequency magnetic field modified soy 11S globulin-based saf-flower oil O/W emulsionThe oil-in-water（O/W）emulsions with different safflower oil phase fractions（0.4-0.7）and different concentrations（1%-5%）of magnetic field-modified soy 11S globulin were prepared.According to apparent observation,the O/W emulsions prepared with low and high oil phase fraction（0.4-0.5,≥0.7）showed obvi-ous delamination in a short time,while prepared with medium oil phase fractions（0.6-0.65）and suitable magnetic field-modified soy 11S globulin concentrations（3%-5%）could form solid-like emulsion gel.In order to optimize the formulation of emulsion gel,the microstructure,droplet size distribution,storage sta-bility,macro-and micro-rheological were studied.The results showed that the increase in oil fraction signif-icantly increased（P<0.05）the apparent viscosity,storage stability,gel puncture force,and L^*value of the emulsion.Moreover,the droplet size decreased significantly（P<0.05）,and the emulsion viscosity,storage stability,and b^*value increased significantly（P<0.05）with the increase in magnetic field-modified soy 11S globulin concentration from 3%to 5%.Overall,the O/W emulsion prepared with the 5%magnetic field-modified soy 11S globulin and 0.65 oil phase fraction had the highest storage stability and rheological prop-erties.3.Application of pre-emulsion safflower seed oil based on magnetic field modified soy 11S globulin as animal fat in pork batterThe changes in gel quality,oxidational sensitivity,rheological and sensory properties of pork batters with different pork back-fat and/or safflower oil O/W emulsion with magnetic field modified soy 11S globulin were studied.Compared to the sample without safflower oil O/W emulsion,pork batter with 25-100%pre-emulsified safflower oil showed higher emulsion stability,apparent viscosity,L^*value,springiness,cohesiveness,and expressible moisture,while had lower a^*value and cooking loss.Moreover,added saf-flower oil O/W emulsion could be more uniformly distributed into the meat matrix with smaller holes.As revealed by sensory evaluation and TBARS,using safflower oil O/W emulsion to substitute for pork back-fat decreased the lipid oxidational sensitivity of pork batter,and without negative effects on the apparent,juiciness and overall evaluation.However,with the increase in the replacement proportion of pork back-fat,the hardness,water-and fat-holding capacity,P₂₁,and flavour intensity of pork batter significantly decreased（P<0.05）.Overall,it is feasible for applying safflower oil O/W emulsion as pork-fat replacer to produce the reduced-fat pork batter with good gel and sensory properties.