Effects Of Hydrocolloids On The Quality Properties Of Glutinous Dumplings And Their Interaction Mechanism

As a traditional glutinous rice product in China,rice dumpling is loved by people.However,the rice dumplings made from glutinous rice flour have undersired quality,such as poor ductility,loose organization,difficult to shape,high freeze-crack rate,weak gel structure and other quality problems.Hydrocolloids can improve the quality of glutinous rice dumplings by regulating the water distribution and gel properties of food systems.The effects of hydrocolloids(flaxseed gum;FG and Artemisia Sphaerocephala Krasch gum;ASKG)on the quality of rice dumplings were systematically studied in this study.Glutinous rice starch was compounded with hydrocolloids to study the effects of hydrocolloids on the physicochemical property,aggregation structure and to explore the change law of the interaction between hydrocolloids and glutinous rice starch system.To reveal the mechanism of hydrocolloids affecting the quality of rice dumpling can provide theoretical basis and technical guidance for the rational use of hydrocolloids in rice dumpling.The main conclusions are as follows:Firstly,studying the effects of hydrocolloids on the quality and sensory of glutinous dumplings by adding hydrocolloids.The results showed that hydrocolloids increased the content of bound water and increased water stability of glutinous dumplings during frozen storage.FG reduced the water loss rate and cracking rate of glutinous dumplings by 1.57% and25% respectively,while the water loss rate and frost crack rate of glutinous dumplings decreased by 2.6% and 33.34% after the addition of ASKG.FG and ASKG increased the transmittance by 23.95% and 28.53%,respectively(P < 0.05).FG and ASKG increased the hardness of the system from 745.4 g to 965.7 g and 922.3 g,and decreased the adhesiveness by about 46.07 g·s and 31.19 g·s,respectively.Adding hydrocolloids improved the sensory score of glutinous dumplings.When the amount of ASKG is 0.9%,the highest sensory score is 84.56,while without hydrocolloids,the lowest sensory score is 77.43.The addition of hydrocolloids reduced the digestion rate of glutinous dumplings,resulting in the decrease of RDS content and the increase of RS content.Secondly,the effects of hydrocolloids on the physicochemical properties of glutinous rice starch were studied by means of DSC,RVA,texture and LF-NMR.The results showed that the addition of hydrocolloids resulted in a significant increase in the gelatinization enthalpy and gelatinization viscosity of the system(P < 0.05).The swelling degree of the complex system increased with the increase of temperature and hydrocolloids concentration.The addition of FG increased the gel strength of glutinous rice starch,while the addition of ASKG reduced the gel strength and formed a soft gel.In addition,the addition of hydrocolloids reduced the relaxation time and reduce the water mobility of the gel.The addition of hydrocolloids reduced the content of RDS,increase the content of SDS and RS,and reduced the digestion rate of the system.Thirdly,the rheological properties of hydrocolloids-glutinous rice starch complex were measured by rotational rheometer,and the interaction between hydrocolloids and glutinous rice starch was simulated and analyzed based on the rheological properties.The results showed that the hydrocolloid and rice starch paly a synergistic role in thickening,and the apparent viscosity,shear stress,G' as well as G" of compound system.The tan ? of the composite system was decreased by FG,which indicated that flaxseed gum enhanced the gel network structure of the system.However,ASKG increased the tan ?,which might be caused by the intensified phase separation between ASKG and glutinous rice starch.The interaction force test showed that hydrogen bond was the main molecular force in the formation of glutinous rice starch with FG.However,the effects of ASKG on secondary bonds in glutinous rice starch were not obvious.Lastly,the effects of hydrocolloids on the microstructure,molecular ordering structure,helix structure and nano-aggregate structure of glutinous rice starch were studied by using modern analytical techniques from multiple angles and multiple scales.The results showed that the addition of FG resulted in a uniform and tight network of gel networks and an increase in mesh thickness in the network structure.After gelatinization of the complex system,the original lamellar structure of starch granules was destroyed,and the semi-crystalline layer structure of starch was gradually disordered,resulting in the increasing density of aggregation and the increase of the degree of heterogeneity and the relative crystallinity of the gel system.After adding FG,there was no new groups were formed in compound system,and the interaction was mainly through hydrogen bond,which resulted in the short-range ordering degree of the system increased and the double helix content decreased.