| The dietary structure of"refined rice and wheat flour"makes the intake of dietary fiber insufficient,which will cause disorders of the human metabolic system.Highland barley and chickpea kernels are rich in dietary fiber,especially rich in non-starch polysaccharides,and their nutritional composition is complementary,which has the potential to develop high-fiber foods.However,the dense cortex and cell wall structure in the kernels makes it less suitable for processing.Based on this,our research studied the puffing effect of microwave(MW),steam explosion(SE)and dynamic precision microfluidic control(DPM)on the highland barley and chickpea kernels and the destruction effect of fiber structures,as well as the influence of puffing and wall breakage behavior on the components and components’interactions.The coarse highland barley-chickpea milk was prepared by high-speed turbulence shearing technology,which provided an innovative way for the easy-to-eat processing of coarse cereals.The puffing and wall breakage effects of microwave(MW),steam explosion(SE)and dynamic precision microfluidic(DPM)on the highland barley and chickpea kernels were studied.The results showed that MW,SE and DPM induced the apparent puffing of highland barley and chickpea kernels,with DPM having the most significant puffing effect,followed by MW and SE.With the increase of DPM and MW treatment time and SE vapor pressure,the puffing degree of highland barley and chickpea kernels increased significantly(p<0.05),the maximum was 1.95 and 2.23 caused by DPM,respectively.However,the treatment time of DPM and MW exceeded 7 min and 1.5 min,and the vapor pressure exceeded 0.8 MPa,the kernels produced a charred black appearance and burnt odor.Combined with sensory analysis,the optimal parameters for the treatment of highland barley kernels were:MW(power:700 W,time:1 min);SE(vapor pressure:1.0 MPa,residence time:80 s);DPM(temperature:170°C,surface air flow rate:3.0 m/s,time:7 min).The optimal parameters for the treatment of chickpea kernels were:MW(power:700 W,time:3 min);SE(vapor pressure:0.8 MPa,residence time:80 s);DPM(temperature:170°C,surface air flow rate:6.0 m/s,time:12 min).After the kernels were treated with the above parameters,scanning electron microscopy(SEM)found that DPM tore the cortex structure of highland barley,separated the pericarp,testa and aleurone layer and their cross-sectional structures were broken,and the aleurone layer cells were broken due to collapse.MW and SE endowed the cortex surface of highland barley with different number and size of pores.The parenchyma cells in the cortex structure of chickpea suffered different degrees of compression and broken into pieces with different shapes.Confocal laser scanning microscopy(CLSM)found that the cell walls of the aleurone layer,endosperm and cotyledon were disrupted to varying degrees,and these findings demonstrated that MW,SE,and DPM induced the puffing and wall breakage behavior of kernels.Particle size distribution and nuclear magnetic resonance imaging(MRI)showed that DPM-induced the puffing and wall breakage behavior of kernels were the most significant,resulting in the highest micronization degree of dietary fiber,and the proportion of particle size less than 96μm increased from 5.3%to 30%.Meanwhile,the time of complete water absorption of highland barley and chickpea kernels were shorted from 20 h and 320 min to 200 min and 160min,respectively.Based on the puffing and wall breakage behavior of kernels induced by MW,SE and DPM,the changes of non-starch polysaccharide components in highland barley and chickpea kernels were further investigated.The results showed that the extractability ofβ-glucan and pectin increased significantly,and their molecular weight decreased significantly with the increase of the degree of kernels puffing and wall breakage(p<0.05),and the DPM-induced kernels puffing and wall breakage behavior could increase the maximum extractability ofβ-glucan and pectin to 4.30 g/100 g and 3.76 g/100 g,respectively,and their molecular weight decreased to 0.50×10~6 g/mol and 0.41×10~6 g/mol,respectively.Fourier transform infrared spectroscopy(FTIR)and atomic force microscopy(AFM)found that the puffing and wall breakage behavior of the kernels severed the molecular chains of non-starch polysaccharides,exposed more free hydroxyl groups,induced hydrogen bond association between the short chains and entangled the molecular chains into a network structure,which increased the maximum ABTS radical scavenging capacity ofβ-glucan and pectin to 84.98%and 88.79,respectively.SEM images showed that DPM-induced kernels puffing and wall breakage behavior transformedβ-glucan from large spherical aggregates to alveolate gel network structures,and pectin from rod-like molecular aggregates to continuous nanofiber cluster structures,which increased the apparent viscosity ofβ-glucan and pectin to 0.484 Pa.s and0.136 Pa.s,respectively,and provided them the most stable viscous solution characteristics.Based on the puffing and wall breakage behavior of kernels induced by MW,SE and DPM,the changes of starch components in highland barley and chickpea kernels were further investigated.The results showed that the kernels puffing and wall breakage induced by MW,SE and DPM degraded highland barley and chickpea starch to varying degrees.Among them,DPM-induced kernels puffing and wall breakage exhibited the greatest degradation effect on highland barley and chickpea starch,and their long chains content(B1,B2 and B3 chains),crystallinity and molecular weight decreased to 39.46%and 36.94%,1.8%and 1.5%,0.25×10~8 g/mol and 0.33×10~8 g/mol,respectively,and their amylose/amylopectin ratio increased to 0.71 and 0.78,respectively,and gelatinization degree increased to 100%.Polarized light microscopy(PLM),small-angle X-ray scattering(SAXS),SEM and CLSM found that the degradation effects of highland barley and chickpea starch caused by MW and SE-induced kernels and wall breakage were manifested in different hierarchical structures as follows:the reduction of lamellar crystal thickness(5.99,6.30 nm and 5.17,6.23 nm),expansion of amorphous region,weakening of birefringence intensity,fracture of growth ring and deformation and fracture of starch granules.DPM-induced kernels puffing and wall breakage exhibited the greatest damage to the hierarchical structures of highland barley and chickpea starch,resulting in the disappear of lamellar crystal,birefringence,growth ring and intact starch granules,with 20.1%and 20.9%of slow digestion starch(SDS)transforming to rapid digestion starch(RDS),and the component’interactions effect(V-type crystals and starch-protein polymers)caused by DPM-induced kernels puffing and wall breakage imparted 42.1%and 47.9%resistant starch(RS)to highland barley and chickpea starch,respectively.Furthermore,the gelatinized starch increased the apparent viscosities of highland barley and chickpea starch to 3.564 Pa.s and 66.487 Pa.s,respectively,and highland barley starch showed typical strong gel rheological characteristics,and chickpea starch showed weak gel rheological characteristics.Based on the puffing and wall breakage behavior of kernels induced by MW,SE and DPM,the changes of protein components in highland barley and chickpea kernels were further investigated.CLSM and SEM found that the denaturation degree of highland barley and chickpea protein increased,and the multi-microporous structure was gradually formed,and the in vitro digestibility respectively increased to 91.77%and 89.61%with the increasing degree of kernels puffing and wall breakage induced by MW,SE and DPM.Meanwhile,β-glucan(0.67%-4.02%)and pectin(0.55%-3.58%)in highland barley and chickpea proteins interacted with proteins through a gradually penetrating manner,forming protein-non-starch polysaccharide multi-microporous network structures.Size-exclusion high performance liquid chromatography(SE-HPLC)and sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE)showed that the cross-linking of proteins contained covalent and non-covalent patterns,and the interaction product between highland barley protein andβ-glucan were eluted earlier,and its molecular weights was more than 200 k D.The interaction product between chickpea protein and pectin was eluted late with a molecular weight of 60-70 k D.The interaction between proteins and non-starch polysaccharides caused by DPM-induced kernels puffing and wall breakage increased the initial apparent viscosity to 6.87 Pa.s and 1.11Pa.s,respectively,and provided them the best resistance ability to shear and oscillation.Based on the puffing and wall breakage of highland barley and chickpea kernels,component modification and component’interaction induced by MW,SE and DPM,the highland barley-chickpea milk were prepared by high-speed turbulence shearing technology.The results showed that the increase in the rotate speed,pulping time,solid-liquid ratio,material ratio and water temperature could improve the apparent condition and taste of the highland barley-chickpea milk,and the increment of water temperature exhibited the most significant improvement effect.The puffing and wall breakage behavior of kernels reduced the water temperature needed for the highland barley-chickpea milk preparation by 25-55℃.The best highland barley-chickpea milk was prepared by the DPM-induced puffing and wall breakage kernels through the following conditions:a material ratio of 3:2,a pulping time of 3min,a rotate speed of 48,000 r/min,a solid-liquid ratio of 1:14,and a water temperature of70℃,which exhibited the highest sensory score(95.8),smallest particle size(108.4μm),and delicate and smooth taste.Light microscopy(LM)and CLSM showed that there was no cortex structure in the highland barley-chickpea milk prepared by DPM-induced puffing and wall breakage kernels,and the presence of component’s interactions formed a continuous dense network structure.Therefore,this highland-chickpea milk could maintain the characteristics of viscous solution well within the shear rate of 0.1-1000 1/s and the oscillation frequency of 0.1-100 rad/s,and was stored 21 days without delamination at 4℃. |
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