Effect Of Alfalfa Ice Structure Proteins On Frozen Glutenin And Frozen Dumpling Skins

The ice structuring proteins(ISPs),mainly produce from insects,fish,bacteria,fungi and plants and other organisms,are kinds of special proteins in living organisms in order to adapt to the low temperature environment,which have the characteristics of thermal hysteresis activity,ice crystal morphology effect,inhibiting ice crystal recrystallization and antifreezing activity.In our study,Alfafla ice structuring proteins(AISPs)were extracted from the raw materials of alfalfa hay,in order to investigate the protective effects resisted to degradation of AISPs on frozen glutenin,and on the secondary structure,disulfide bonds and free sulfhydryl group of wheat gluten.Additionally,AISPs were in practical application in dumpling skin,to detection the quality of Quick-frozen dumpling skin.The AISPs were extracted using ice extraction,by our study group improved,with phosphate buffer solution method.The identification results of the characteristics in AISPs showed that the maximum absorption peak is appared in UV visible 280nm,molecular weight is 52kD and 33kD,thermal hysteresis activity is 0.54℃;Ice crystals are small in volume and large in quantity,forms are mostly single small diamond in the solution of AISPs.These data indicating that AISPs are really ice structuring proteins with well antifreeze activities.To confirm the components of glutenin,we extracted the glutenin from wheat gluten by ethanol method.SDS-PAGE electrophoresis analyses were carried out using Quantity One software.The results showed that glutenin contained 10 components whose relative molecular weight was 145 kD,103 kD,80 kD,52 kD,47 kD,33 kD,28 kD,25 kD,20 kD,19 kD,respectively.Including A subunit,HMW-GS,was composed by 148.83 kD and 104.67 kD,B subunit consist of 47.36 kD only,C subunit was composed of 33.31 kD,28.76 kD,25.29 kD,20.11 kD,19.07 kD,and D subunit was composed by 79.74 kD and 52.23 kD.To investigate the antifreeze protection effects of AISPs under freeze and thaw,adding different concentrations of AISPs to glutenin,and the frozen and freeze-thaw treatments were carried out.The results suggested that all of the HMW-GS were degraded,and the part of LMW-GS disappeared and degraded.After 1,3,5,7 weeks of frozen storage,the A subunits of Glutenin were all degraded,B subunits and C subunits were more stable,but D subunits increased in varying degrees.The anti-degradation protection effect was obviously in Adding AISPs’s group,comparing with the control group,in varying degrees.In 0.5%group of adding AISPs,The molecular weight of D subunit is much larger and more components.In addition,after 1,3,5,7 weeks of freeze-thaw treatment time,all of A subunit were degraded,so were B subunit except freezing and thawing 3 times a week group,so were C subunit including components below 30 kD only,so were D subunit but for adding 0.5%AISPs group in freezing and thawing 1 week and 5 weeks group,with components no more than 60kD.This result indicated that the components of glutenin,including protein and molecular weight,were impacted significantly under the treatment of freezing thawing than frozen storage.And the components were less degraded in adding AISPs group compared to control group.Therefore,AISPs play nobly antifreeze protection effects on glutenin,especially added with 0.5%AISPs group.To study the effect of AISPs on disulfide bonds,Ellman’s reagent method was employed to measure the fracture between disulfide bonds.The content of disulfide bonds of glutenin at normal temperature was 155.094 μmol/g,and the content of free sulfhydryl group was 49.122 μmol/g.When the amount of AISPs was 0.7%,the contents of disulfide bonds in frozen glutenin were increased by 24%,25.6%,34.7%and 41.5%than those in control group,respectively,after multiple frozen storage cycles.While after freezing and thawing treatment,disulfide bonds were increased by 62.9%,56.8%,46.8%,41.7%and 41.7%than those in control group.The results revealed that AISPs could be prevent the fracture of the disulfide bond effectively,adding 0.7%AISPs.Fu Liye infrared spectroscopy showed that the content of alpha helix in the secondary structure of glutenin was 15.48%,the beta fold was 39.08%,the beta rotation angle was 29.40%,and the irregular coil was 16.04%.AISPs play the best protective effect on secondary structure of glutenin,adding the amount of 0.5%,compared with by 0.7%.Therefore,we characterized the functional role of AISPs adding to Quick-frozen dumpling skin.The results showed that the appearance of frozen dumplings was largely intact without distinct cracking,the water holding capacity was decreased slowly,the textural properties was improved obviously.Together,these results indicated that AISPs effectively modified the elasticity and hardness of frozen dumplings,which was added with amount of 0.5%,dealing with different freeze-thaw cycles.