Development Of Frozen Black Rice Pudding And Evaluation Of Their Nutritional And Digestive Properties

Pudding is widely welcomed by consumers because of its delicate taste,smoothness and strong fragrance.However,at present,domestic pudding products have problems such as low nutritional value,lack of novelty,and serious water separation after thawing.In addition,in order to maintain the sweet taste of pudding,more sucrose is added in the production process.The potential harm of long-term high-sugar diet to the body,such as obesity,diabetes,and dental caries,is attracting the attention of many consumers.Black rice is rich in nutritional value and has many physiological functions,such as anti-oxidation,maintaining vascular osmotic pressure,inhibiting the growth of cancer cells and so on,but it is not easy to be accepted by consumers because of its poor palatability.Combining the nutritional characteristics of black rice with pudding to construct a functional black rice pudding is of great significance for the comprehensive utilization of black rice and the development of new type pudding.In this paper,konjac gum and xanthan gum were used as basic gel materials,and the best synergistic ratio was explored by means of rheology.to explore the effects of total gel concentration,protein concentration,black rice addition and soybean oil addition on the texture,water holding capacity,syneresis rate,chromaticity and other basic physical properties of black rice pudding gel,so as to construct a black rice pudding with good elasticity,toughness and good freeze-thaw stability.Then,in order to solve the problem of excessive addition of sucrose in pudding production,three functional sweeteners:fructose,inulin and erythritol,were used to replace sucrose to explore the effect of sucrose addition on the texture properties and freeze-thaw stability of black rice pudding.FTIR spectroscopy,LF-NMR and scanning electron microscope were used to explore the reasons for the changes of texture properties and freeze-thaw stability.Finally,the nutrition and digestive characteristics of black rice pudding were evaluated by simulated in vitro digestion model.The main results of this paper are as follows:1.Research and development of functional black rice pudding.In the first part,the best synergistic ratio of konjac gum and xanthan gum was studied,on the basis of which the effects of total gum concentration,protein concentration,black rice addition and soybean oil addition on the basic physical properties of black rice pudding were studied.The results showed that different ratios of konjac gum and xanthan gum showed different synergistic effects,in which the ratio of konjac gum to xanthan gum at 6:4 had the highest apparent viscosity and elastic modulus.The gel strength and freeze-thaw stability of black rice pudding could be improved by the increase of total gum concentration,protein concentration and black rice addition in a concentration-dependent manner,but under these conditions,soybean oil as an inactive filler had little effect on the texture properties of black rice pudding.The results of orthogonal experiment showed that the order of influence of various factors on the sensory score of black rice pudding was as follows:total gum concentration>black rice concentration>protein concentration>soybean oil concentration.The pudding produced according to the optimal formula(1%total gum concentration,3%black rice,4%protein,2%soybean oil)tastes delicate,smooth and fragrant with black rice.2.Study on processing technology and sugar reduction of black rice pudding.In this part,the effects of four different processing techniques on the texture properties of black rice pudding were compared,and on this basis,the effects of crystalline fructose,inulin and erythritol on the physical properties of black rice pudding were studied.The results are as follows:after pre-emulsification,high pressure microfluidization emulsification and post-emulsification,the gel strength of black rice pudding increased by 24.00%,49.64%and 11.90%,respectively.The filled sweetener has an important effect on the texture properties and freeze-thaw stability of black rice pudding,and the addition of sweetener has a"soft modification"effect on black rice pudding.The SEM results show that the pore size of black rice pudding without sweetener is larger,but the porosity is smaller and the grid wall is thicker;after adding 10%sweetener,the porous structure of black rice pudding becomes smaller and the network structure is denser,but the grid wall is thinner,which makes it change from"hard and brittle"to"soft and elastic".The texture properties of black rice pudding prepared by adding 10%crystalline fructose,inulin and erythritol are close to those of commercial pudding.The low-field NMR results show that the free water content in black rice pudding accounts for about 95%.The increase of filled sweetener will change the internal water proportion and distribution of black rice pudding gel and improve its freeze-thaw stability;compared with the FTIR spectroscopy of pudding gel without sweetener,it is found that there is no new absorption peak,indicating that no new substance is formed,but the red shift of hydroxyl vibration peak indicates the formation of hydrogen bond.3.Evaluation of nutritional and digestive properties of black rice pudding.Temperature and p H have great influence on the stability of anthocyanins in black rice.After black rice anthocyanins were treated at 70°C for 1h,2h,and 3h,the anthocyanin concentrations decreased by 12.97%,30.12%,and 55.64%,respectively,and the degree of degradation further increased with the increase of heat treatment temperature and time;As the p H increased from 2 to 8,the degradation of anthocyanins in black rice was 31.63%;as the p H continued to increase to 12,the decrease was more than75.00%.At the same concentration,the scavenging rate of black rice anthocyanins for DPPH free radicals and ABTS free radicals is higher than that of V_c,especially at low concentrations,black rice anthocyanins show better antioxidant effect;use the simulated in vitro digestion model to compare different chewing degrees Regarding the influence of black rice pudding on the digestive characteristics,it was found that konjac gum and xanthan gum were basically not digested in the stomach and small intestine,and the release rate of fatty acids in high chewiness pudding was 3%higher than that of low-chewiness pudding.