Study On Preparation And Deterioration Mechanism Of Quick-frozen Deep-Fried Dough Sticks During Freezing Storage

The rapid development of quick-frozen churros meets the modern consumption concept and food safety requirements,and is an important form of industrialized production of churros.Quick-frozen churros can be divided into direct fried type and pre-fried type,among which the direct fried churros can avoid the increase of oil content after deep-frying and the odor caused by oil oxidation in the process of freezing storage.However,the deterioration of quality in the process of frozen storage is an urgent problem to be solved in the industrial development of frozen fried dough sticks.Based on this,the effects of different wheat flour on the quality of deep-fried quick-frozen fried dough sticks were investigated on the basis of active dry yeast fermentation.And the effect of freeze-thaw cycle on the quality of quick-frozen fried dough sticks;From the Angle of starch and gluten protein,the quality deterioration of deep-fried quick-frozen fried dough sticks in the process of frozen storage was studied.Firstly,the effects of different wheat flour on the quality of deep-fried quick-frozen churros were studied.The results showed that the content of starch had a positive effect on the specific volume of deep-fried quick-frozen dough sticks and the resilience of their flesh.High protein content and wet gluten content(32.43% 35.35%)contribute to the improvement of the quality and structure of type of Fried dough sticks properties and sensory quality,but can lead to increased oil content of frozen type of Fried dough sticks;The oil content of quick-frozen fritters made from wheat flour with lower ash content is lower.Wheat flour with high gluten index can reduce the oil content of deep-fried quick-frozen churros.According to the comprehensive score of PCA analysis,wheat flour C with relatively high starch content,relatively low ash content,relatively high wet gluten content and relatively high gluten index was selected for follow-up study.Compared with the pre-fried type(control),the specific volume of the direct fried type frozen fryou sticks prepared by six kinds of wheat flour increased,the oil content,water content and sensory evaluation value decreased,the hardness and chewability of the fryou sticks increased,and the elasticity and resilience decreased.Secondly,the effect of freeze-thaw cycle on the quality of deep-fried quick-frozen churro was investigated.It was found that with the increase of freeze-thaw cycles,the viscoelasticity of dough decreases,the maximum creep increases,the deformation resistance weakens and the recovery ability decreases.The p H of youtiao dough decreases and the gas production ability weakens.The structure of gluten network of youtiao green dough is deteriorated,pores are gathered,and the size of holes is increased.Compared with the pre-fried type(control),under the same freeze-thaw cycle,the specific volume of the deep-fried type was increased,the comprehensive value of oil content,water content and sensory evaluation was decreased,the hardness and chewability of the deep-fried type were increased,and the elasticity and resilience were decreased.With the increase of freeze-thaw cycles,the specific volume,oil content,water content and sensory evaluation value of the direct-fried and pre-fried quick-frozen churro decreased significantly.10 After freeze-thaw cycle,the specific volume,oil content and water content of the direct-fried quick-frozen churro decreased by 21.2%,20.6% and 32.4%,respectively,while the hardness and chewability increased,while the elasticity and resilience decreased.At the same time,the effect of freeze-thaw cycle on the starch characteristics in the dough was studied.The results showed that after 10 freeze-thaw cycles,the damaged starch content and amylose content of green dough increased by 23.7% and 27.8%,the D10 and D50 values of starch particles decreased,and the specific surface area increased.The main reason was that the freeze-thaw cycle treatment destroyed the morphology and structure of starch particles,leading to the leaching of amylose and other internal soluble substances.The results showed that the solubility and swelling potential of starch in the dough increased by30.2% and 14.4%,but the gelatinization temperature had no significant effect on starch.In addition,the freeze-thaw cycle increased the peak viscosity,final viscosity,disintegration value and rebound value of starch particles,but decreased the ΔH value of starch particles,indicating that the thermal stability of starch particles became worse.With the increase of freeze-thaw cycles,the R1047/1022 ratio of starch in the dough increased,the R995/1022 ratio decreased,and the relative crystallinity of starch molecules decreased.Finally,the effect of freeze-thaw cycle on the properties of gluten protein in youtiao dough was studied.The results showed that the water holding capacity and oil holding capacity of gluten protein decreased significantly and the surface hydrophobicity increased after freeze-thaw cycle.SDS extractable protein content of gluten increased and glutenin macropolymer content decreased,which indicated that freeze-thaw treatment could depolymerize the high molecular protein of gluten in the dough.After 10 freeze-thaw cycles,the contents of α-spiral and random curl of gluten decreased by 9.73% and 44.39%,the contents of β-fold and β-turn increased by 30.49% and 12.03%,and the content of free sulfhydryl group increased by 47.4%,which indicated that freeze-thaw treatment could change the conformation of gluten in green dough.In addition,the elastic modulus and viscosity modulus of gluten decreased significantly,and the rheological properties of gluten deteriorated significantly during the freeze-thaw cycle,resulting in loose network structure,weakened deformation resistance,reduced recovery ability,and poor thermal stability of gluten.To sum up,this topic explored the effects of different wheat flour and freeze-thaw cycles on the quality of direct-fried quick-frozen fried dough sticks,and clarified the quality deterioration mechanism of direct-fried quick-frozen dough sticks during the freeze-thaw cycle from the perspective of comcomposition(starch and gluten protein),providing a reference for the quality improvement of other fermented quick-frozen flour products.