The Effect Of Hydrocolloids On The Quality Of Par-baking Chiffon Cake

Chiffon cake is sensitive to breed bacteria at room temperature,thus cause starch aging,which severely limit its shelf life.The cold storage of Par-baking is a new technology which is designed to heat the starchy food to a half cooked degree and cool it.The Par-baking products made in this way requires anather simple reheating process before eating,and this technology can effectively inhibit the growth of microorganism,slow down the aging of starch and prolong the storage period of starchy products.However,,local desiccation would occur during the refrigerating storage of Par-baking chiffon cake,due to the heterogeneous internal moisture migration and redistribution,and the formation and growth of the ice crystals in the Par-baking cake which destroys the structure of the starch and gluten network and deteriorates its quality.Therefore,it worthy of studying how to improve the quality of chiffon cakes with refrigerated Par-baking technology.Two kinds of commonly-used edible gums,xanthan gum and hydroxypropylmethyl cellulose(HPMC),were used in this study as quality improvers for refrigerated Par-baking cakes.The effect of addition of hydrocolloids on soft wheat farinograph property,gelatinization properties,cake batter viscosity and density were studied.Then relation between the addition of hydrocolloids and the baking loss,moisture content,specific volume,textural properties,sensory evaluation of chiffon cake during Par-baking process were investigated.After that,X-ray diffraction(XRD)and scanning electron microscopy(SEM)were used to explore the mechanism underlying the effesct of hydrocolloids on Par-baking process from a microscopic perspective.The main findings are as follows:(1)Effect of the addition of hydrocolloids on properties of soft wheat and cake batter were studied.Compared with soft wheat farinograph property of the control,xanthan gum and HPMC significantly increased the water absorption of soft wheat,xanthan gum increased the formation and stabilization of soft wheat whereas HPMC decreased them.Xanthan gum and HPMC are shown to increase the gelatinization of starting temperature,peak temperature and final temperature of soft wheat,which help to extend the volume expansion time of cakes.Meanwhile,the reduction of the gelatinization enthalpy of soft wheat resulted in reduced degree of gelatinization,and the effect of xanthan gum on the gelatinization characteristics of soft wheat was more significant that that of HPMC.Both hydrocolloids are shown to increase the viscosity and density of the cake batter while indacate a dose-dependant relationship.(2)The effects of Par-baking process and addition of hydrocolloids on the quality of chiffin cakes were studied in this section.Cooling process of the Par-baking technique was shown to cause the contractive volume of the 0-day pre-baking cakes,and lead to the increase in moisture content and hardness and decreased crust moisture,baking loss,specific volume and the sensory score of the final cakes.The refrigerated process resulted in baking loss,increased hardness,decreased moisture contents and specific volumes significantly,and the sensory scores of the re-baked cakes after 14 days frozen-storage process were proved to decrease.In addition,by comparing the effect of hydrocolloids on the quality of the cakes at full baking and par-baking stages,hydrocolloids were proved to have an adverse effect on the quality of the fully baked cake.The thire sensory score was lower than the control ones(without improver),while the quality of the re-baked cakes(0 and 14 days)were improved.These finding indicate that the hydrocolloids could reduce the adverse effect of cooling and refrigerating on the quality of par-baking cakes,especially by adding the hydrocolloids in a amount of 0.45 g/100 g flour.(3)The effects of hydrocolloid on the quality and microcosmic characteristics of chiffin cake in each stage of Par-baking process were studied using oil oxidizer,XRD and microstructural observation assays.Results show that the cold storage could decrease the lipid oxidation in chiffin cakes,and the addition of hydrocolloids could further limit the lipid oxidation process.The 0-day rebaked cakes of blank groups(without adding hydrocolloid)show increase in the crystallinity and a more compact appearance than the full-baking cakes.The frozen-storage are shown to increase more significantly the crystallinity,biggest cavities and internal structural failure.By adding hydrocolloids,the crystallinity was reduced,and the microstructure became more intact and showed no large cavities.The hydrocolloids had strong water absorption and dispersed evenly in the gluten protein,thus helped the gluten to form a more uniform network structure and could act as a water retention agent and antifreezer in the process of freezing-thawing.Therefore,addition of hydrocolloids was beneficial for the melting of microcrystalline structure and the integrity of the microstructure.