Study On The Controlled Gelatinization Coupled Hotextrusion 3D Printing To Adjust Starch Digestibility

Hot-extrusion 3D printing technology has the advantage of being able to personalize the appearance and customize the nutrition ratio according to the needs in the food field.Rice,wheat,and potatoes are important staple foods in the diet of residents.The digestion,absorption,and metabolism of starch,the main nutrient ingredients,play an important role in human health.Studies have shown that slowly-digestible starch（SDS）and resistant starch（RS）are beneficial to human health.Therefore,hot-extrusion 3D printing technology can be used to change the multi-scale structure of starch and then to manipulate the digestibility,give it new nutritional functions,and ultimately to manufacture personalized and nutritious starch foods,which will provide new ideas and new ways for the creation of healthy foods.However current research in this area is rarely reported.In this paper,according to the characteristics of slow digestion starch and resistant starch structure,it is proposed to control the digestibility of starch by controlling gelatinization coupled hot-extrusion 3D printing technology.On the basis of establishing a method for controlling starch gelatinization and obtaining starch gel materials with different gelatinization degrees,SAXS,XRD,¹³C NMR and other modern analytical techniques were used to explore crystalline and amorphous domain evolution,starch molecular chain unwinding and rewinding behavior for starch gel material with different gelatinization degrees and concentrations within the controlled gelatinization and hot-extrusion 3D printing system.The effect of structural evolution on printability and digestibility was analyzed.The relationship between controlled gelatinization coupled hot-extrusion 3D printing-starch material domain evolution-printing formability optimization-digestion performance manipulation was clarified.The design method for regulating the anti-digestion properties of starch by hot-extrusion 3D printing was established.The specific research and conclusions were as follows:The starch material gelatinization function was established by DSC method to obtain the conditions for quantitative control of gelatinization degree.Rice,wheat and potato starch gel materials with gelatinization degrees of 30%,40%,50%,60%,70%were prepared.Modern analytical techniques were used to clarify the effect of gelatinization on the multi-scale structure and digestibility of starch materials.The results showed that as the gelatinization degree increased,the starch granules continued to swell and break,and the polarized cross gradually disappeared;the layered structure was gradually destroyed,and the arrangement density of nano-aggregates was significantly reduced;the relative crystallinity was continuously reduced;double and single helix content decreased significantly,and the proportion of amorphous structure increased significantly;the proportion of bound water in the gel system decreased,and the proportion of semi-bound water increased.It showed that the increase of gelatinization degree would cause the ordered structure of the starch gel material to become disorder,which resulted in an increase of RDS content,decrease of the SDS and RS content.For completely gelatinized rice,wheat and potato starch gel material,the RDS content increased from 29.52%,31.16%and 46.62%to 94.97%,96.23%and 94.36%,respectively.Above all,controlling the gelatinization degree and retaining crystalline domain and the ordered structure in amorphous domain could inhibit the digestibility of starch.The evolution of crystalline and amorphous domains,the behavior of starch molecular chain unwinding and rewinding,the regulation effect on printing formability and digestibility for starch gel materials with different gelatinization degrees were investigated within the process of hot-extrusion 3D printing.The results showed that after hot-extrusion 3D printing,the layer structure,crystalline structure and double helix structure of three kinds of starch gel materials with different gelatinization degrees were further damaged,and the arrangement density of nanoaggregates was significantly reduced.The content of semi-bound water increased,the content of bound water decreased,and the trend became more obvious as the gelatinization degree increased.The content of the single helix structure showed a trend of increasing firstly and then decreasing,changing from V₆ type to curlier V₈ type;new V-type crystals were formed in rice and wheat starch materials printed samples.As the gelatinization degree increased,the width of the printed filament decreased firstly and then increased,and the number of printed layers increased firstly and then decreased;the RDS content increased significantly,the SDS and RS content decreased significantly,and the samples with good printability had a relative high SDS+RS content.Although hot-extrusion 3D printing caused the aggregation of starch molecular chains to form some new ordered structures,it led to a further transformation of the overall structure of starch materials into disorder.Starch gel materials with a low degree of gelatinization could resist structural disorder and improve resistant digestible property.When the gelatinization degree of rice,wheat and potato starch materials were 50%,40%and 30%respectively,ideal printing formability and resistant digestible property of printed objectives could be successfully obtained.Setted the concentration range of starch gel materials with suitable gelatinization as 10-30%.The evolution of the crystalline and amorphous domains,the behavior of starch molecular chain unwinding and rewinding,the regulation effect on printing formability and digestibility for starch gel materials with different concentrations were investigated within the process of hot-extrusion 3D printing.It was found that increasing the concentration of starch gel material in printing system could effectively resist the damage of water molecules,heat energy and shear forces to the starch crystalline domain and the ordered structure in amorphous domain.It also could promote the starch molecular chain rearrangement to form new ordered structure,improve the formability of the printed samples and thus increase the SDS and RS content.Besides,the rice,wheat and potato starch gel materials could obtain the best printing formability,and SDS+RS content of them increases significantly,reaching 29.59%,28.43%and 48.82%,respectively when their concentration reached 25%（w/w）.Therefore,it showed that the concentration of starch gel material was an important factor to adjust the digestibility of starch samples under hot-extrusion 3D printing.Based on the above research results,a physical model and related molecular mechanisms for controlled gelatinization coupled hot-extrusion 3D printing to regulate starch domain and digestibility were established.It is believed that the regulation of starch digestibility by hot-extrusion 3D printing depends on the starch domain evolution.Maintained low gelatinization degree and high material concentration under the premise of ensuring ideal printing formability,which was conducive to reducing the damage on the starch material ordered structure caused by the synergistic effect of water,heat and shear force,then promoting the orientation and regathering of starch molecular chains to form new ordered structures,thereby effectively improving the resistant digestion performance of printed products.These obtained research results had good academic value and practical significance which could provide new design ideas and methods for personalized creation of nutritious and healthy starch foods by using hot-extrusion 3D printing technology.