| Glycemic index(GI)is a indicator to reflect the elevated blood glucose level caused by food,long-term consumption of low GI food can effectively control diabetes.Diet therapy is the basic method for diabetes treatment,GI theory as a guide,the development of food products for patients with diabetes has practical significance.The aim of this study is to combine fermented milk with whole grain to develop a low-GI and hypoglycemic whole grain fenrmentation milk,to providing more dietary choices for diabetic patients.The main findings are as follows:(1)Study on preparation technology of whole grain enzymatic hydrolyzate.The optimum baking process of oats,barley and highland barley was studied.After crushing,I mixed with a certain percentage of water through the colloid mill.The whole grain juice was liquefied and saccharified by a-amylase and glucoamylase which can resistant high temperature,the full grain enzymatic solution was made.The results shows that the optimum baking conditions for oat,barley and barley are 180 ℃/10min,180 ℃/15min,180 ℃/25min,and the three kinds of grains are mixed in a ratio of 1:1:1,ration of water is 1:10.The optimum temperature for a-amylase is 65℃,add amount is 70 U/g,the time of liquefaction is 60 min;the optimum temperature for glucoamylase is 65 ℃,add amount is 100 U/g,the time of saccharification is 80 min.(2)Screening of lactic acid bacteria with adjuvant hypoglycemic function.Screening lactobacillus with higher ability to hypoglycemia and better functional characteristics from 5 strains of lactic acid bacteria with auxiliary hypoglycemic function,by measuring their ability to inhibit a-glucosidase,antioxidant capacity,gastric acid resistance,intestinal resistance,resistance to bile salt and post-acidification;further filter the combination of strains by curd time,acidity,viable count experiments.The results show,the five Lactobacillus:Lactobacillus plantarum s7,Lactobacillus delbrueckii subsp.d12,L.casei g9,L.casei m11,L.casei r9 all have hypoglycemic function,inhibitions are all above 60%and s7 is the highest one with 75.48%;s7,d12 and g9have good tolerance to simulated gastric juice(pH3),simulated intestinal fluid(pH8.0)and 0.5%bile salt,and the degree of acidification was low.Which the curd time of d12 and s7 is shorter,8.3h and 9.5h respectively,so choose d12 and s7 for the next experiment.Considering that the addition of whole grain juice will reduce the stability of fennented milk,so add a better cohesive Streptococcus thermophilus 937 to coupe with d12 and s7,the ratio of which is 1:1:1,which can short the curd time,and the number of viable cells is higher.Therefore,s7,d12 and 937 were chosen to prepare the whole grains fermented milk,the mixing ratio of which is 1:1:1.(3)The impact of the addition amount of whole-grain enzymolysis liquid in products.The effects of different total grain hydrolyzate on the pH,acidity,viscosity,sensory properties,texture characteristics,rheological properties,volatile flavor,β-glucan content,viable count,antioxidant capacity and a-glucosidase inhibition rates of fermented milk were studied.Results shows that,With the increase of total grain hydrolyzate,the pH of whole-grain fermented milk was increasing,up to 4.26,the acidity and viscosity decreased,and the lowest was 71,76T 0 and 2320 pa · s-1.With the increase of total grain hydrolyzate,the hardness,adhesion and chewiness of fermented milk decreased,and the gel stability and mechanical resistance are reduced,when the total amount of enzyme hydrolyzate is more than 20%,it is easy to under the action of external force demulsification,therefore,the whole amount of grain enzyme solution should be controlled at 20%or less.There are acids,esters,ketones and alkanes in the whole-grain fermented milk.With the increase of the total amount of the enzyme,the content of the acid is lower,the total amount of esters,ketones and alkanes remained essentially unchanged.With the increase of total grain hydrolyzate,the content of P-glucan in fermented milk increased,but the number of viable bacteria of lactic acid bacteria decreased.When the whole-grain hydrolyzate is 20%,the DPPH scavenging rate and hydroxyl radical scavenging rate of the whole-grain fermented milk are the highest,65.12%and 54.37%respectively.When the total amount of hydrolyzate was 30%,the inhibitory rate of a whole-grain fermented milk was the highest,46.21%.When the total amount of hydrolyzate was 20%,the sensory score was the highest 81.40.Based on the above indicators,the optimal amount of whole-grain hydrolyzate was determined to be 20%.(4)Study on the optimization of production technology and storage characteristics of the whole-grain fermented milk.The types and additions of sweeteners were determined by measuring the antioxidant capacity,a-glucosidase inhibition rate and sensory characteristics of whole-grain fermented milk.And the response surface optimization method was used to determine the amount of whole-grain hydrolyzate,lactic acid bacteria inoculation and sweetener addition in whole-grain fermented milk.And the pH,acidity and viability of whole-grains fermented milk were studied at 4℃ storage 15d.The results shows that xylitol was more suitable for the preparation of whole-grain fermented milk than sorbitol and maltitol,and its optimum amount was 7%.Surface optimized to get whole-grains fermented milk formula for optimal:The amount of enzyme solution was 20.45%,the amount of lactic acid bacteria was 3.15%,and the content of xylitol was 6.98%.Experiments show that the model is well fitted with the actual situation.During the storage at 4 ℃,the pH of whole-grain fermented milk decreased,the lowest was 3.926,the acidity increased,the highest was 114.2T °,the number of viable cells increased first and then decreased,but in the 15d storage period is always maintained at 106 CFU/mL or more,in line with the requirements of national standards for fermented milk.(5)Study on blood glucose production index and hypoglycemic function in vitro of whole-grain fermented milk.With glucose as the control,the GI value of whole-grain fermented milk was determined,and the hypoglycemic function in vitro was studied by measuring the antioxidant capacity and a-glucosidase inhibitory ability.The results showed that the GI value of whole-grain fermented milk was 22.97,48.59%and 69.48%lower than that of plain yogurt and black rice bread.the fermented milk with whole-grains has a good antioxidant capacity after 15 days storage at 4 ℃,and the inhibition rate of a-glucosidase was always above 44.9%. |
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