Effect Of Germination On Sorghum Properties And Its Application In Gluten-free Cake

Sorghum is an important grain crop in China,however due to its high content of anti-nutritional factors,poor protein quality,lack of lysine and rough taste,it still remains in the traditional processing methods.The research on processing quality and application characteristics of sorghum is not systematic and in-depth in China,and lags behind abroad.Sorghum is gluten-free and is an excellent raw material for preparing gluten-free food.In recent years,celiac disease caused by gluten allergy has been on the rise in China,and currently the only effective way to treat celiac disease is to strictly control the intake of gluten-containing foods.At present,there are mature gluten-free foods in foreign markets,but the research on gluten-free foods in China is still in the initial stage,and the research on gluten-free sorghum food is lacking.Therefore,in view of the above problems,this paper studies the effects of germination on the nutrients,physicochemical and functional properties of sorghum flour,and its application in gluten-free cake making.The aim is to provide scientific basis for the application of sorghum in food processing and the development of gluten-free food.The main research conclusions are as follows:1.In order to improve the nutritional quality of sorghum,white sorghum was used as raw material to germinate.The changes of amino acid composition,γ-aminobutyric acid(GABA)content,glutamic acid decarboxylase(GAD)activity,phytase activity,phytic acid and tannin content during sorghum germination were investigated.The results showed that with the extension of germination time,the total amount of sorghum amino acids increased significantly,reached the maximum value of 5.694g/100g at 60h,an increase of 28.50%;lysine content reached the maximum value of 0.157g/100g at 72h after germination,increased by 21.7%;GAD activity is enhanced,and GABA content increases,reached the maximum value of 13.406mg/100g at 60h,which increased nearly 5 times;phytase activity also increases with the extension of germination time,which promoted the phytic acid degradation,and the phytic acid content decreased from 94.85mg/100g to 52.44mg/100g,decreased by 44.71%;tannin content decreased by 86.92%from 1.07%to 0.14%.It can be seen that germination can significantly increase the nutritional content of sorghum,reduce the content of anti-nutritional factors,and improve the nutritional quality of sorghum.2.In order to clarify the effect of germination on the processing quality of sorghum flour,the changes of physicochemical and functional properties of sorghum flour during germination were investigated.The results showed that the amylase activity of sorghum increased significantly after germination;the contents of total starch,amylose and amylopectin decreased significantly;DSC results showed that germination increased the gelatinization enthalpy,improved the stability and crystallinity,and the initial gelatinization temperature(T_o)increased,while the peak(T_p)and the end gelatinization temperature(T_c)had no significant changes.With the extension of germination time,the viscosity of sorghum flour system decreased,and the stability of hot paste and cold paste increased;storage modulus(G’)and loss modulus(G")are reduced,with the fluidity of sorghum flour paste enhanced;the emulsification and emulsification stability,foaming and foam stability of sorghum flour were improved,the oil holding capacity was increased while water holding capacity decreased.3.In order to promote the application of sorghum in the field of gluten-free foods,germinated sorghum was used to make gluten-free cake.The viscosity and density of cake batter,as well as the specific volume,texture and sensory quality of cake were taken as the indexes,the quality difference of sorghum gluten-free cake at different germination stages was investigated.The results showed that with the extension of the germination time,the viscosity and density of sorghum cake batter,the specific volume of cake increased first and then decreased;and the cake made of sorghum germinated for 48 hours had the largest specific volume;the hardness,elasticity and chewiness of cake decreased with the extension of sorghum germination time;the best sensory quality is the cake made of sorghum germinated for 48 hours.However,compared with wheat flour cake,there are still differences in specific volume,sensory and texture characteristics.Therefore,sorghum cake made from germinated 48h sorghum was selected for further quality optimization.4.Aiming at the difference between germinated sorghum cake and wheat flour cake,rice flour,xylitol,hydroxypropyl methyl cellulose(HPMC)and soybean lecithin were chosen to improve the quality of gluten-free sorghum cake.Through single factor and orthogonal experiment,the best formula of gluten-free sorghum cake was selected as follows:rice flour40g,sorghum flour 60g,xylitol 20g,white granulated sugar 40g,HPMC 0.4g,soybean lecithin 0.5g,corn oil 30g,egg 200g,milk 50g.The specific volume and sensory acceptability of gluten-free sorghum cake prepared by this formula increased,and both of them were better than that of conventional wheat flour cake.The cake has same surface color and regular in shape;which tastes soft,delicate,has no rough sense,with slight aroma of rice.