Effect Of Polyols On The Quality And Anti-retrogradation Of Spicy Wheat Gluten Sticks

Spicy wheat gluten sticks is a very popular snack food.According to statistics,the annual output value of Spicy wheat gluten sticks enterprises in China is nearly 60billion RMB.However,the oil holding capacity was weak and the oil was easy to separate from the Spicy wheat gluten sticks.Moreover,the hardness of Spicy wheat gluten sticks gradually increased due to starch retrogradation,water loss,which seriously restricted the development of Spicy wheat gluten sticks industry.In this study,the quality of Spicy wheat gluten sticks is improved by adding polyols,and the effects of polyols on water migration and the inhibition of Spicy wheat gluten sticks retrogradation were studied,which would make great contributions to improve the quality of Spicy wheat gluten sticks and promote the development of the industry.The effect of mannitol,erythritol,isomalt,lactitol,xylitol,sorbitol,maltitol on the quality of Spicy wheat gluten sticks was investigated through moisture content,water activity,radial expansion rate,oil holding capacity and texture,and three kinds of polyols were selected to be more effective.The results are as follows.In different storage time,all polyols were effective in reducing the moisture loss and hardness of the Spicy wheat gluten sticks.3%of mannitol,isomalt,and xylitol significantly improved the radial expansion rate and oil holding capacity of Spicy wheat gluten sticks(p<0.05).And excessive addition of polyols would bring negative effects.Moreover,with the increase of erythritol,lactitol,and sorbitol content,the radial expansion rate and oil holding capacity of Spicy wheat gluten sticks showed a trend of first decreasing and then increasing,but the addition of maltitol could significantly reduce the radial expansion rate and oil holding capacity of Spicy wheat gluten sticks(p<0.05).Effects of different concentrations of mannitol,isomalt and xylitol on the quality of wheat flour and Spicy wheat gluten sticks were studied.The results showed that the addition of mannitol,isomalt,and xylitol significantly reduced the water absorption ratio and softening degree,increased the stability time,but had no significant effect on the dough development time(p<0.05).And the extensograph text showed that the energy,the resistance to extension and the maximum resistance to extension all increased significantly with the addition of mannitol,isomalt and xylitol(p<0.05).The addition of mannitol,isomalt and xylitol significantly reduced the peak viscosity,through viscosity,final viscosity,breakdown viscosity and setback viscosity of wheat flour(p<0.05).In the dynamic rheological experiments,the storage modulus G'and loss modulus G''of the dough with addition of mannitol,isomalt and xylitol were significantly increased compared with the blank group(p<0.05).Moreover,the water content of Spicy wheat gluten sticks increased compared with the blank group.The water content was the highest with addition of 4%mannitol,2%isomalt,and 4%xylitol.And with the increase of mannitol content,the water activity of the Spicy wheat gluten sticks kept decreasing.However,with the increase of isomalt and xylitol content,the water activity showed a trend of first decreasing and then increasing,and the water activity was the lowest with the addition of 2%isomalt and 4%xylitol.The gelatinization rate of Spicy wheat gluten sticks was also significantly reduced with the addition of mannitol,isomalt and xylitol,but the radial expansion rate of Spicy wheat gluten sticks showed a trend of increasing first and then decreasing,and the oil holding capacity was maintaining the same changes as the radial expansion rate.And the radial expansion rate and oil holding capacity were highest with addition of 2%mannitol,3%isomalt and 3%xylitol.Polyols could also effectively protect the surface structure of Spicy wheat gluten sticks and make the surface smooth.The improvement was highest with addition of 5%polyols.And the hardness was the lowest after storage for 4 weeks with addition of 2%mannitol,4%isomalt and 3%xylitol.The hardness was 460 gf,497 gf and 462 gf,respectively.And the trend of chewiness was consistent with the hardness.In addition,sensory experiments showed that the sensory evaluation scores of the Spicy wheat gluten sticks were the highest with addition of 2%mannitol,3%isomalt and 4%xylitol,respectively.Subsequently,this study further explored the effect of polyols on the retrogradation of Spicy wheat gluten sticks.The results showed that the addition of mannitol,isomalt and xylitol could significantly reduce the setback value and increase the gelatinization temperature of wheat starch(p<0.05).The G'values of wheat starch/polyols pastes were lower than that of wheat starch paste,and the change rate of the G'value of wheat starch over time is significantly greater than that of the wheat starch/polyols pastes.And the peaks at 3385 cm^-1 and 1081 cm^-1 in the infrared spectra of the freeze-dried powder of Spicy wheat gluten sticks and wheat starch gels became wider and higher with the addition of polyols.The texture results also showed that the hardness of the Spicy wheat gluten sticks and wheat starch gels were significantly reduced with addition of polyols.Especially for mannitol and xylitol,the hardness of Spicy wheat gluten sticks with mannitol and xylitol were reduced by 42.0%and 42.3%,and the hardness of wheat starch gels were reduced by 41.6%and 45.6%,respectively.Compared with the blank group,the Avrami rate constant(k)of the Spicy wheat gluten sticks and wheat starch gels were significantly decreased with addition of polyols,which indicated that polyols reduced the retrogradation rate of starch.In addition,differential scanning calorimetry(DSC)experiments showed that polyols could effectively reduce the transition peak temperatures(T_p)and total transition enthalpy(?H)of the Spicy wheat gluten sticks and wheat starch gels.Moreover,after storage at 4°C for 4 weeks,the?H of the sample adding mannitol and xylitol was significantly lower than that of the sample adding isomalt,which showed that mannitol and xylitol was significantly better than isomalt in inhibiting starch retrogradation(p<0.05).And the position of the diffraction peak had not changed,but the crystallinity of Spicy wheat gluten sticks and wheat starch gel were significantly reduced with addition of polyols,which was showed in X-ray diffraction(XRD)experiments(p<0.05).NMR results showed that the water in the Spicy wheat gluten sticks was mainly semi-bound water,and the water in the wheat starch gels was mainly free water.Moreover,polyols could inhibit the migration of water and reduce the loss of water.In summary,the addition of polyols can effectively improve the quality of Spicy wheat gluten sticks,inhibit the retrogradation and reduce the water loss of the product.It provides a theoretical basis for the application of polyols in Spicy wheat gluten sticks,and effectively promotes the development of the Spicy wheat gluten sticks industry.