| Spicy wheat gluten sticks is a very representative snack food in China,but the development of industry is at a low end and lags behind.There are few reports on the special flour research and quality improvement of spicy wheat gluten sticks at home and abroad.Thus,this project systematically selected and optimized the superior wheat flour for spicy wheat gluten sticks,and studied the quality improvement effect and mechanism on inulin for spicy wheat gluten sticks with different concentrations and different polymerization degrees.Our research provides the data for establishing quality standards of spicy wheat gluten sticks,but also provides a theoretical basis for the production of high-quality and long shelf-life spicy wheat gluten sticks.Taking hardness,radial expansion rate,oil holding capacity etc.of product as evaluation indicators,the correlation between the quality of wheat flour and the quality of spicy wheat gluten sticks and the establishment of a stepwise regression equation were used to clarify the characteristic components that affect the quality of spicy wheat gluten sticks.These results showed that the quality of spicy wheat gluten sticks is determined by multiple components in wheat flour.Among them,the quality of spicy wheat gluten sticks is extremely significant correlated with dry gluten content,wet gluten content,gluten index and starch composition in wheat flour(P<0.01).The product quality is also significantly correlated with initial water content(P<0.05).The recommended range of important indicators for spicy wheat gluten sticks are: ash 0.6% ? 0.8%,initial moisture 12.5% ? 13.5%,wet gluten content 28% ? 39%,dry gluten content 7.5% ? 10.5%,gluten index 60 ? 95,in which the amylose content is 13.0% ? 14.5%,and the amylose ratio is 0.16 ? 0.22.Through the analysis of rheological properties,gelatinization characteristics in wheat flour and spicy wheat gluten sticks quality,the effects of short-chain inulin and long-chain inulin with different concentrations on the quality improvement of spicy wheat gluten sticks.The results showed that when two inulin types were added in a range of 0% to 8%,the formation time and the farinograph quality number increased significantly(P<0.05),and the degree of softening decreased significantly(P<0.05);stability time reached its maximum value when 8% short chain inulin / 4% long chain inulin was added;dough water absorption reached its minimum value when 8% short-chain inulin / 6% longchain inulin was added.The area of tensile curve,the maximum tensile resistance(Rm),and the tensile ratio(Rm/E)increased significantly(P<0.05),and the extensibility(E)began to decrease significantly(P<0.05)when the short chain inulin and long chain inulin were added at 4% and 2%,respectively.The minimum viscosity,peak viscosity and final viscosity decreased significantly(P<0.05),and the thermal stability and gelatinization temperature of wheat flour increased significantly(P<0.05).The water content of spicy wheat gluten sticks increased significantly(P<0.05);the radial expansion rate decreased significantly(P<0.05);the hardness reached a minimum and the elasticity reached the maximum when the short chain inulin or long chain inulin was added at 4% or 2% respectively;the oil holding capacity reached the maximum when 2% inulin was added.The addition of two inulin types delay the retrogradation of starch,and increase the degree of protein polymerization,the content of high polymers,and the molecular weight of proteins in the spicy wheat gluten sticks system.The extrusion process resulted in the disappearance of the ?-helix in the secondary structure of the spicy wheat gluten sticks protein.The addition of inulin increased the ?-sheet and decreased the ?-turn,however,the random curl did not change significantly in spicy wheat gluten sticks.In general,both short chain inulin and long chain inulin improve the apparent characteristics of spicy wheat gluten sticks by enhancing the strength of protein gluten,protecting starch molecules,and maintaining moisture content.Comprehensive evaluation of various indicators,the recommended additive contents of short chain inulin and long chain inulin in spicy wheat gluten sticks are 4% and 2%,respectively.To evaluate the effect and mechanism of inulin on the hardness and internal components of the product during long-term storage(0 week?1 week?2 week?3week?4 week),the texture test,differential scanning calorimetry,X-ray diffraction,nuclear magnetic resonance,and magnetic resonance imaging analysis were used.The results showed that the starch crystal form in spicy wheat gluten sticks changed from the original type A to type B + V after extrusion.With the gradual extension of the storage time,starch was easy to retrogradate.The hardness of spicy wheat gluten sticks increased with the enthalpy change.When 4% short chain / 2% long chain inulin in spicy wheat gluten sticks was added,the characteristic diffraction peak intensity was smaller than that of the blank group,and the enthalpy change was equal to or greater than the enthalpy change of the blank group at the above addition amounts.This may be the reason of inulin inhibits starch retrogradation while increasing the strength of gluten,which leads to an increase in the enthalpy of the product compared to the blank group.Compared with the blank group,the experimental group had more tightly bound water,the initial water content increased significantly,and the total water loss was less during long-term storage.As the storage time increases,the content of tightly bound water and semi-bound water of spicy wheat gluten sticks gradually decreased,and the free water content increased first and then stabilized;the relaxation time corresponding to the tightly bound water gradually increased,and the relaxation time corresponding to the semi-bound water and free water gradually reduced;the water is mainly gradually diffused and lost to the outside of the product.From the overall point of view,the water in each state of spicy wheat gluten sticks was converted to each other,and the degree of water binding became gradually tighter.Inulin delayed the retrogradation rate of starch,and had an inhibitory effect on starch retrogradation.At the same time,by increasing the ability to bind water,increasing the water content and delaying the water loss in spicy wheat gluten sticks,it was conducive to delay the increase of hardness in spicy wheat gluten sticks during long-term storage.The shelf life of spicy wheat gluten sticks with 4% short chain inulin or 2% long chain inulin was significantly improved compared with the blank ones,but there was no significant difference between the two type of inulin.These results show that the addition of inulin has a positive effect on the quality of spicy wheat gluten sticks.Results also suggest that inulin with different degrees of polymerization can make the quality of spicy wheat gluten sticks reach the similar effect under certain condition.The research has a positive guidance for formulating standards of spicy wheat gluten sticks special flour,and provided a reference for wheat flour to produce high-quality products.By adding inulin to improve the quality of spicy wheat gluten sticks,the storage time of spicy wheat gluten sticks is prolonged to a certain extent,which provides a theoretical basis for the improvement of other natural additives in spicy wheat gluten sticks. |
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