Study On The Regulation Of Water Retention Capacity And Texture Property Of Frozen Composite Konjac Glucomannan Gel

It is known that the removal of acetyl groups on the molecular chains of konjac glucomannan?KGM?via addition of alkaline coagulant results in the formation of high elasticity gel.Freezing can regulate the physical properties of KGM gel with special texture.However,the gel is prone to dehydrate and shrink during the freezing thawing process,thus reducing the output of gel products and making the taste too hard.This is a problem to be solved urgently in the industry.In this paper,polysaccharides?amylose,amylopectin and guar gum?,soybean oil and emulsifiers are added to KGM to prepare composite gel,exploring the impact of these compounds on the water retention capacity?WRC?and texture properties of frozen KGM gel.The main results of this study are as follows:1 Amylose?AS?and amylopectin?AP?were added in KGM to prepare KGM/starch composite gel.The impact of the types and concentrations of starches on the eutectic point,WRC,texture properties,moisture distribution and microstructure of frozen KGM gel have been studied.The addition of starches decreased eutectic point of KGM gel;The water syneresis rate?SR?decreased and water holding capacity?WHC?increased;The proportion of P₂₁in composite gel increased and the proportion of P₂₂decreased;Thus,these results indicated that the addition of starches could improve the FT stability of KGM gel.The hardness and chewiness of frozen KGM/starch composite gel increased and the network structure tended to be dense,but the springiness and cohesiveness decreased with the concentration of starches increased.Meanwhile,the difference of the addition of AS or AP in KGM gel has been compared.It was found that the frozen KGM/AS composite gel had higher SR,WHC,hardness and chewiness then frozen KGM/AP composite gel with the same concentration of starches.The proportion of P₂₁of the frozen KGM/AS composite gel was higher than frozen KGM/AP composite gel,and the water distribution of frozen KGM/AS composite gel was more homogeneously.2 The effects of different frozen condition?frozen storage time,frozen temperature and FT cycles?on WRC and texture properties of KGM/starch composite gels have been studied.WRC and texture properties of frozen composite gel had no obvious changes during 28 days of frozen storage time at a freezing temperature of-18°C,indicating that composite gel has good FT stability.There were no obvious changes in SR and WHC when the the composite gel have been frozen at different temperature?-10°C?-20°C?-30°C?-40°C?for 12 h,but SR was slightly reduced and WHC was slightly increased when frozen temperature decreased.Meanwhile,the hardness and chewiness increased and the network structure of gel became denser with the lower temperature.One to five FT cycles were applied in the composite gel.The increase in FT cycles resulted in the increase of SR,the decrease of WHC and the decrease of the bound water ratio and the larger pore size in gel network structure,which indicated FT cycles could weaken WRC and FT stability of the composite gel.3 Emulsification system was used to achieve the purpose of higher WRC of frozen KGM gel.Guar gum?GG?,soybean oil?SO?and emulsifiers were added to frozen KGM composite gel to study the effect of single or compound addition of these compounds on the freeze-thaw stability of frozen KGM/starch composite gel.Single factor experiment results showed that the addition of GG to frozen KGM gel could increase WRC and hardness.The SR was further improved when SO and glyceryl monostearate?GM?were composite added in KGM/GG composite gel to form frozen KGM emulsification gel,but the hardness of the composite gel decreased.The composite gel had the minimum SR and maximum WHC when the concentration of GG,SO and GM were 0.1%,5%,0.1%,respectively.Furthermore,0.1%GG,5%SO and 0.1%GM were composite added in two frozen KGM/starches composite gels,the hardness and chewiness decreased,the springiness and cohesiveness increased and WRC substantially improved with these compounds addition.The SR of frozen KGM/AS composite gel decreased from 21.74%to 9.34%and the SR of frozen KGM/AP composite gel decreased from 15.68%to10.78%.