Preparation Of Barley Resistance Starch And Its Protective Effect On Alcohol-induced Gastric Injury

Hulless barley is a feature crop in the plateau of China and is the main food of the Tibetan people.It has nutritional characteristics of high protein,high soluble cellulose,low fat and low sugar.Resistant starch is the sum of starch and its degradation products that cannot be absorbed by the small intestine of healthy humans.It is often used as a prebiotic or functional food in the food industry.In this paper,hulless barley flour was used as the research object to extract hulless barley starch.Two methods were used to prepare barley resistance starch,and the preparation process was optimized.The physical and chemical properties,thermal properties and crystal structures of four flour samples(hulless barley flour,HF;hulless barley starch,HS;autoclaving-retrograded starch,ARS;debranching-retrograded starch,DRS)were measured and compared.Finally,combined with animal experiments to verify the protective effect of resistant starch on acute alcoholic gastric injury and preliminarily explore the mechanism of action,the purpose was to provide a theoretical basis for the development of high value-added hulless barley products.The main research results are as follows:(1)The optimum process conditions for preparing hulless barley resistance starch by autoclaving-retrograding cycle method were as follows:mass fraction of hulless barley starch 10%,refrigerating time 24 h,4 times of autoclaving-retrograding cycles.By this way,the maximum resistant starch yield was 8.57±0.10%.The optimum process conditions for preparing barley resistance starch by enzymatic-debranching method are as follows:50? enzymolysis temperature,4 U/g pullulanase addition,6 h enzyme treatment time.The resistant starch content of DRS under the optimum process conditions was 11.28±0.27%.(2)Using simulated gastrointestinal fluid to determine the digestibility of four samples,the results showed that the digestibility of the four samples in gastric juice was less than 5%,the intestinal digestibility of DRS is the lowest.And the total digestibility in the gastrointestinal tract of ARS and DRS is significantly lower than HS,which indicates that the starch after strengthening treatment has strong digestion resistance.The ?-amylase was used to determine the digestion rate of the four samples.The results showed that the fast digestible starch content of ARS and DRS was not significantly different from that of HS,but the slow digestible starch was significantly reduced.This indicates that the digestion rate of the starch after the resistance-enhance treatment is lower and the resistance is stronger.(3)The four samples have significant differences in water solubility,water holding capacity,emulsion capacity,and oil absorption capacity.Among them,ARS has strong water-holding ability,and DRS has better water solubility and oil absorption ability.After the resistance-enhance treatment,the amylose dissolves,the apparent structure of the starch is destroyed,and the granular structure collapses to show an irregular block shape.The crystal structure changed from a typical A-type crystal to a V-type crystal,changed from a polycrystalline state to an amorphous state,and the crystallinity also decreased from more than 30%to less than 5%.These crystals are mostly dense anti-enzymatic structures,which also caused changes in the thermal properties of the starch.According to the thermodynamic analysis,the gelatinization enthalpy and peak temperature of ARS and DRS are significantly increased,which indicated that they have higher thermal stability.It can be known from the analysis of the gelatinization characteristic curve that the peak viscosity,gelatinization temperature,and final viscosity of the starch after the strengthening treatment are significantly reduced.(4)Acute alcoholic gastric injury model was established by intragastric administration of high concentration alcohol,and the preventive and protective effects of resistant starch on acute alcoholic gastric injury were explored.The results show that resistant starch has a certain preventive effect on ethanol-induced acute alcoholic gastric injury.Apparent analysis of gastric tissue showed that ARS and DRS pretreatment can significantly reduce the degree of gastric damage and improve the bleeding and erosion of gastric mucosa.The highest dose of DRS in the high dose group can reach a gastric protection rate of 50.77%.The preventive mechanism may be related to the regulation of oxidative stress,inflammatory factors and neutrophil infiltration.The experimental results showed that the SOD and GSH levels in gastric tissues were increased and the MDA content was reduced after four sample pretreatments,indicating that barley can reduce the body's oxidative stress response.The levels of TNF-? and IL-6 in gastric tissues of mice pretreated with ARS and DRS were significantly reduced,but there was no significant change in HF and HS groups,indicating that resistant starch can reduce gastric mucosal damage by improving inflammatory factor levels.The four samples had limited effects on improving MPO levels.Only the DRS group was significant,indicating that the damaged gastric tissue had been infiltrated by neutrophils.DRS can attenuate the inflammatory response by reducing inflammatory cell infiltration.