Studies Of Effects And Mechanism Of Soybean Protein Isolate And Carrageenan On Qualities Of Prepared Pork Products

Prepared meat products are defined as those products using livestock and poultry meat as the main raw materials which can be consumed after simple processing.Prepared meat products have been developing fast in recent years,while they have many quality problems.For example,protein denaturation could change the texture,fat oxidation could bring the flavor loss and freezing thawing instability could produce ice crystals and result in worse taste.These quality problems are caused by many factors including raw meat quality,processing technology and conditions,and associated additives.Supplementation of additives in prepared meat products receives much attention recently.Protein and polysaccharide are two major ingredients in food additives and studies on the interaction between two components have gradually become hot topic.At present,many researches study the influence of either protein or polysaccharide on the quality of meat products,but the mechanism of combation impact of soybean protein isolate and carrageenan on the meat products are unclear.Therefore,this research was aimed to study the effects of the interaction of soy protein isolate,starch,hydrophilic colloid and raw meat and their influences mechanism on meat processing performance and product quality.This study chose pork patties as meat product to selecte appropriate additives and put forward the combination scheme based on quality requirements.The main results arc as follows:1.Determination of optimization conditions for pork patties productThe research determined the optimum amount of different additives by studying the influence of different additives on the quality of chopping pork patties.Based on preliminary experiments,the single factor experiment and response surface optimization experiment was performed to study the effects of different additives on the quality and flavor of pork patties.The best ratio of various factors was determined including glutinous rice flour,soybean protein isolate and carrageenan.Cooking yield,texture and sensory evaluation were chosen to study the effects of additives on patty quality and obtain the best level in chopped pork patties for optimal formula.Compared with control,soy protein isolate,carrageenan,glutinous rice flour,potato starch and corn starch could improve the quality of pork patties.Based on single factor experiment and response surface experimental results,as well as the objective and sensory evaluation indexes,the combination of 5.7%soy protein isolate,0.7%carrageenan and 20%fat significantly improved the product quality including cooking yield,water and oil holing capacity,texture characteristics,and sensory scores.Due to higher amylopectin easily to form gel network and influence the interaction with meat proteins after heating,3%glutinous rice flour can also be used as an effective additive in pork patties.2.The interaction of soy protein isolate with carrageenan in pork patties and effects on pork protein retention capacity of water and oil.The effects of 5.7%soybean separation protein and 0.7%carrageenan combination on the water and oil holding ability of pork patties were studied.Four treatments inlcuded control,5.7%soy protein isolate,0.7%carrageenan and combined 5.7%soy protein isolate and 0.7%carrageenan.Cooking loss,water and oil holding capacity,vacuum loss and textural characteristics were measured.Scanning electron microscope,low field nuclear magnetic and sensory evaluation were used to investigate the influence of combined additives on the quality of pork patties.Before 40 min of heating,water loss trend of each group of products was similar to control group.However,water loss rate of control remained unchanging,and the moisture loss rate curve inflection point of other three groups tended to be stable after 40 min.The results showed that individual soy protein isolate and carrageenan or combination of them could improve the water stability of meat products and increase the water retention.With the prolonging of heating time,fat loss occurred with different levels at pork patties.During 60-90 min,the fat loss of control group was significantly higher than that in other three groups,and combined additive group had the least fat loss rate.Cooking yield of all samples with additives was higher than control significantly.Vacuum purge of SPI adding group and combined group were significantly lower than control group?P<0.05?.Low field nuclear magnetic results showed that soy protein isolate and carrageenan affected proton relaxation time T₂₁?proton closely combined with protein molecules?and the T₂₂ of combined group was significantly lower than that in other groups.The results indicate that the combination of additives significantly affected the retention capacity of water and fat in emulsion gel of large molecules combined state of proteins and other components.Compared with control group,the combination of soy protein isolate and carrageenan resulted in increased T₂₂/T₂₁ ratio of peak area in cooked meat patties than that in raw batters.It could be explained by that the combination of soy protein and carrageenan was more conducive to promote protein to combine with more water and fat in the swollen state than in heating gel.This suggests that heating treatment could lead to part of combined water and fat into water and fat easily flowed in the gel matrix.Added alone or mixed additives significantly increased the hardness and chewiness of cooked patties?P<0.05?,while there were no significant difference for elasticity and adhesiveness among all treatments?P>0.05?.Scanning electron microscope results showed that raw meat formed different state in the processing and heating process after adding different additives which produced different effects on protein gel matrix.The samples with combined additives presented the most compact and fine compound structure.Except for color,groups with all additives significantly improved the sensory quality score of patties compared with the control group and the treatment with combined additives obtained the highest score of juiciness and mouth taste.3.Effects and mechanism of soybean protein and carrageenan on the functional properties of low-fat chopped pork battersThe effects of 5.7%soy protein isolate and 0.7%carrageenan on the functional properties of low fat chopped pork batters were investigated.Results show that compared with control group,samples with combined additives in low-fat chopped pork batters significantly decreased cooking loss,improved emulsifying stability and microscopic structure.A-helice in combined groups was significantly lower than the control group,while the ?-sheet content increased significantly?P<0.05?.Moreover,the content of?-sheet,?-turn and random coil of combined groups were higher than other groups,which showed combined additives promoted protein conformational changes which were better to emulsify fat.Increasing ?-sheet content and reducing a-helical content in chopped pork patties were directly related to increased hardness and reduced cooking loss.The combined additives effectively improved the functional properties of low fat ground pork batters without affecting the quality.However,no new bands were detected in electrophores indicating no new substance to be formed which could be indirectly explained that there were no chemical reactions between the additives and meat protein.4.Molecular forces of interaction among carrageenan,soy protein isolate and salt soluble pork proteinsIn order to explore the essence of interaction between carrageenan/soy protein isolate and salt soluble pork protein,the effects of combined carrageenan and soybean protein isolated on dynamic rheological properties,particle size,texture and molecular forces of interaction between them with salt soluble pork protein were studied.The results showed that centrifuge loss of samples with combined 5.7%soy protein isolate and 0.7%carrageenan additives was significantly lower than samples from control group and the two groups treated with propyl glycol gained the largest losses?P<0.05?.Therefore,it could be concluded that hydrophobic forces played key roles in water retention of salt soluble protein gels which was similar to the results in hardness.The samples without chemical reagent presenting the largest gel strength indicated that the addition reduced gel hardnes of salt soluble protein.During the main temperature range of gel formation?except for treatments of hydrogen bonds were destroyed?,the elastic modulus of all combined additives were significantly higher than control?P<0.05?.The combined additives enhanced the gel forming ability of salt soluble protein even under the same chemical destruction.In treatment group,in addition to destroy hydrogen bonds,the other groups of carrageenan/soybean separation protein processing accessories add elastic modulus were higher than the control group even with adding the same chemical destruction reagents.Hydrogen bond force significantly affected the gel forming ability.SDS-PAGE strip analysis showed that the thermal stability of myosin light chain was good and combined soy protein isolate/carrageenan promoted the stability.Myosin heavy chain is known to be important in the salt soluble protein aggregation and gel forming process.In this study,myosin heavy chain degraded obviously under the effect of propyl glycol,and it had significant effect on water retention capability and hardness of gels.Raman spectroscopy analysis showed that,the addition of combined additives resulted in reduced a-helix and increased ?-sheet under the same conditions.This affected the structure of protein molecules including hydrophobic groups exposed,hydrogen bond and two sulfur bond cleavage and the rearrangement which further changed the protein conformation in different degree.