Mechanism For The Digestion Properties Of Starch Influenced By Lipid And Protein

Starch is the major components of human diet and plays an important role in the texture of food products and the glycemic response.Frequent consumption of rapidly digestible starchy food is associated with the development of insulin resistance and metabolic syndrome.Resistant starch and slowly digestible starch have been recommended for diets to prevent metabolic syndrome.A variety of macronutrients including proteins and lipids are commonly present in starchy foods.Interactions between starch,protein and lipid influence the physicochemical properties and nutritional properties,including texture,flavour,palatability,and digestion/absorption rate and extent.These interactions also further affect some physiological response such as postprandial blood-glucose response.This study provided a better understanding for digestion properties of lipid and protein on starch and the formation mechanism of the binary and ternary complex.And it will keep forward guidance for food design to control starch digestion as well as its real effect on postprandial glycemic response.The three-component blends?TCBs?containing swollen maize starch?MS?,maize oil?MO?and zein protein?ZP?were prepared using high-speed homogenization and thermal treatments at different heat temperatures?25,40,50,60,and 65°C,respectively?.The objective of this study was to understand the thermal treatment effect on the structural,physicochemical and digestion properties of the TCBs,providing guidance for designing low GI foods.Heat treatment had a pronounced effect on the physicochemical and in vitro digestion properties of the starch-containing food.Heat treatment at 40°C resulted in the highest levels of slowly digestible-and resistant-starch fractions.We proposed that the hydrophobic physical barrier of the ZP and the amylose-lipid complex together influence the starch digestion properties.Binary and ternary blends were prepared using corn starch?CS?mixed with corn oil?CO?and/or soy protein?SP?and incubated in a water bath at 50°C.The effects of physicochemical properties and digestive rates of annealed starch complex and mechanisms of interactions between CS,CO and SP were investigated.With the addition of CO and/or SP,the CS displayed a decreased pasting temperature,an increased peak viscosity and a decreased enthalpy change of amylose-lipid complex dissociation.The CO can reinforce but SP hinder the annealing phenomenon.Results also showed that CO decreased retrogradation of CS,whereas SP increased it.The digestibility studies showed that the addition of CO and SP decreased the content of rapidly digestible starch and increased the sum of slowly digestible starch and resistant starch contents.SP played more impact on the digestibility of the blends than CO.The physical barrier of CO,and amylose-lipid complex and protein-starch matrix can provide resistance to starch digestion.Physicochemical and digestive properties between wheat starch?WS?and wheat flour?WF?which had been modified by using heat-moisture treatment?HMT?were investigated.Reduced peak viscosity and increased pasting temperature were found in both WS and WF after HMT.With moisture content increasing,HMT significantly changed crystal structure of WS and WF,and patterns transferred from A to A+V,which was due to the formation of starch-lipid complex.And HMT wheat flour showed a higher resistant and slowly digestible starch content when compared to the other counterpart of WS.Compared with native counterparts,the RDS content of HMT wheat starch and flour decreased,and the RS content increased.The lower RDS content was associated with a higher moisture content of treatment.The 25%-WS and 15%-WF showed highest SDS contents and the 35%-WS and 35%-WF showed highest RS contents.Structural,in vitro digestion and physicochemical properties of normal rice starch?NRS?/flour?NRF?complexed with maize oil?MO?through HMT were studied.Results showed that non-starch components,including lipids,proteins and their interaction with starch,greatly affect the morphology,pasting,thermal,structural and digestive properties of NRS and NRF complexed with MO.The higher moisture content of HMT was also favorable for the amylose-lipid complex formation.Differences in starch digestion properties were found for NRS-MO and NRF-MO complex.All of the NRS/NRF complexed MO after cooking showed lower rapidly digestible starch?RDS?contents compared with the control sample,therein NRS-/NRF-MO20% exhibited the highest sum of the slowly digestible starch and resistant starch contents.In general,HMT had a greater impact on the in vitro digestion and physicochemical properties of flour samples compared with starch counterparts.The inhibitory activities of soy protein and wheat gluten protein against porcine pancreatic ?-amylase?PPA?were studied by measuring their half inhibitory concentrations(IC₅₀).The kinetics of inhibition by these proteins were investigated through Dixon,Cornish-Bowden,and Lineweaver-Burk plots.The results showed that both the soy protein and wheat gluten protein were mixed-type inhibitors with both competitive and uncompetitive inhibitory characteristics.For wheat gluten protein and soy protein,the competitive inhibition constants?Kic?were 4.975 and 38.197 mg/mL,and the uncompetitive inhibition constants?Kiu?were 5.923 and 33.125 mg/m L.Besides,the IC₅₀ of wheat gluten protein and soy protein were 3.080 and 32.246 mg/m L.For wheat gluten protein,the lower Kic than the uncompetitive inhibition constant for the mixed-type inhibitors suggests that they bind more tightly with free PPA than with the PPA-starch complex.On the contrary,the soy protein bind less tightly with free PPA than with the PPA-starch complex.In comparison with soy protein,wheat protein showed stronger inhibitory effect on alpha amylase.