Effect Of Plant Peptides On Retrogradation Properties Of Wheat Starch And Its Application In Fermented Flour Products

With the increasing popularity of wheat products,fermented flour products are widely used as staple foods.However,fermented flour products are also affected by factors such as starch retrogradation and water loss,which led to problems such as hardening of texture and shortening of shelf life,which seriously restricted the development of fermented flour products.This topic aimed to investigate the effects of plant peptides on starch and dough properties,so as to understand the effects of plant peptides on water migration and texture changes during the processing of fermented flour products.The improvement effect of two plant peptides on the quality of fermented flour products was studied by mixing them,which provided new theoretical insights for expanding the application range of plant peptides and promoting the development of fermented flour products.Starch accounts for approximately 70%to 75%of the total weight of wheat flour,so changes in starch properties can easily affect product quality.The effects of different proportions of plant peptides on the retrograde characteristics of wheat starch gel were studied by Rapid viscosity analysis（RVA）,dynamic rheology,solubility and swelling power,water holding capacity,hardness,X-ray diffraction（XRD）,Flourier transform infrared spectroscopy（FTIR）,Low field nuclear-magnetic resonance（LF-NMR）,Scanning electron microscopy（SEM）,etc.The specific results were as follows:compared with the blank group,the pasting results showed that the addition of plant peptides significantly improved the pasting temperature of wheat starch,while also significantly reducing the peak viscosity,breakdown value,and setback value.Among them,1%wheat oligopeptides（WOPs）and 0.3%garlic peptides（GPs）had the most significant effect（P<0.05）.At this time,the water holding capacity of starch gel was also significantly improved（P<0.05）.The elastic modulus G’and viscous modulus G”of wheat starch gel added with plant peptides were lower than those of the blank group.The tanδincreased as the frequency increased,it was higher than the blank group.With the addition of plant peptides,the solubility of wheat starch gel increased,while the swelling power decreased.After 20 days of storage,the starch gel added with 1%WOP and 0.3%GP showed a softer texture.With the addition of plant peptides,XRD and FTIR patterns showed that the addition of plant peptides had no effect on the position of diffraction peaks,but could significantly reduce their crystallinity（P<0.05）.The results of LF-NMR showed that the water in starch gel was mainly free water,and with the increase of storage time,A₂₁in the test group was larger than the blank group.The SEM results indicated that the network structure remained relatively continuous after storage with the increase of the content of two plant peptides.Dough production was a key step in the processing of fermented flour products.Therefore,the effects of plant peptides on the rheological properties of wheat flour and dough were studied.The results showed that the addition of WOPs and GPs inhibited the swelling and gelatinization of starch,and the water absorption of dough increased with the increase of the ratio of the two plant peptides.The farinograph and extensograph qualities showed that the effects of WOPs and GPs were significantly different,and significantly affected the viscoelasticity of dough（P<0.05）.At the same time,as the proportion of plant peptides increased,T₂in the dough decreased,indicating that plant peptides limited the fluidity of water molecules.The results of fermentation rheology and SEM showed that the addition of plant peptides could effectively increase H_m,V_r,V_t,and R,promoting the development of gluten networks.However,when the addition of WOPs and GPs exceeded 1%and 0.3%,respectively,it had a negative impact on the above parameters.Subsequently,this paper further studied the influence of plant peptides on the stalling of fermented flour products and combined with the determination of basic indicators of complex plant peptides.The results showed that plant peptides could reduce the hardness of fermented flour products,but the high proportion led to negative effects.After 7 days of storage,the hardness of bread was the lowest when1%WOP and 0.3%GP were added to bread,and 2%WOP and 1%GP were added to steamed bread,respectively.They were 301.23 gf,316 gf,995.56 gf,and 1248.05 gf,respectively.The LF-NMR results showed that the relaxation time of fresh fermented flour products was not significantly affected by the presence of plant peptides.However,with the increase of storage time,they effectively resulted in a gradual decrease in water fluidity,while T₂₃showed a fluctuation trend.XRD and FTIR experiments showed that adding different proportions of plant peptides could reduce the crystallinity of freeze-dried flour from fermented flour products after storage period.At the same time,there were significant differences in the infrared spectral bands of freeze-dried flour from fermented flour products added with plant peptides,which indicated that an appropriate amount of WOPs and GPs were beneficial to reducing the formation of internal ordered structures in fermented flour products,slowing down the recrystallization rate of wheat starch,and delaying stalling.The SEM results showed that the gluten network structure of fermented flour products was well stretched after adding different levels of plant peptides,which could limit alleviate the negative effects of stalling.With the addition of compound plant peptides,the hardness and specific volume of bread improved,while the hardness of steamed bread was lower than that of the blank group,but the improvement of specific volume was not good.Combined with sensory evaluation experiments,various indicators of the product were comprehensively considered,and the recommended optimal addition amounts of WOPs and GPs in bread were 1%and 0.3%.The optimum addition levels of WOPs and GPs in steamed bread were 2%and 1%,and the sensory evaluation of bread was better than that of steamed bread.The above results indicated that the addition of plant peptides could effectively improve the quality of fermented flour products,and significantly inhibit the adverse effects of stalling and water loss.This not only provided a theoretical basis for the application of plant peptides in fermented flour products,but also promoted the development of fermented flour products.