Effects Of Ultrasonic Assisted Freezing Combined With Cassava Starch On Gel Properties Of Konjac Glucomannan And Research On Its Application

Konjac Glucomannan(KGM)can form a thermal irreversible gel after the acetyl group is removed.Freezing can regulate the gel properties of konjac gel.After freezing treatment,the gel strength is improved and special texture is formed.However,dehydration and shrinkage are easy to occur during thawing,which not only reduces the yield,but also affects the quality of the gel,which is the key problem restricting the development of konjac gel industry.In this paper,by optimizing the freezing methods: comparing air freezing,immersion freezing and ultrasonic assisted freezing,adding different cassava starch,and investigating their synergistic effects on the properties and structure of konjac gel,and explored its potential application,in order to provide theoretical basis and technical support for the production of konjac gel.The results are as follows:(1)The effects of different freezing methods on the properties and structure of KGM gel were explored.The results show that compared with the air freezing and immersion freezing,ultrasonic assisted freezing can speed up the cooling rate of KGM gel,reduce drainage rate and thawing temperature,increase the water holdup,gel strength and gel eutectic point,make KGM gel internal moisture distribution more even.The morphology of ice crystal of KGM gel was improved,and the effect on deacetylation,molecular structure and crystallinity of konjac glucomannan was weak.When the ultrasonic power was 300 W,the water extraction rate was lowest(22.61%),and the gel strength was highest(744.91 g).Compared with air freezing,the water extraction rate decreased by 23.56%,and the gel strength increased by 61.23%.(2)The effects of different cassava starch on the properties and structure of freezingthawing KGM gel were explored.The results showed that cassava starch(CS),starch acetate(SA),acetylated di-starch adipate(ADA)and acetylated di-starch phosphate starch(ADP)can improve the water retention,thermal stability and anti-dehydration shrinkage of freezingthawing KGM gel.KGM/ADP gel showed the best water retention and gel strength,the best thermal stability,the most uniform microstructure,the lowest water extraction rate of 8.71%,the highest gel strength of 361.44 g.Compared with KGM gel,KGM/ADP gel showed the best water retention and gel strength.The water extraction rate of KGM/ADP gel decreased by70.72%,but the gel strength decreased by 21.27%.(3)The effects of ultrasonic-assisted freezing combined with ADP starch on the characteristics of KGM gel were explored.The results showed that the lowest water extraction rate of KGM gel prepared by ultrasonic-assisted freezing combined with ADP starch at 300 W power was 6.67%,and the highest gel strength was 609.97 g.Meanwhile,the proportion of binding water in the gel was increased.Compared with ultrasonic assisted freezing alone and ADP starch addition,the combination of ultrasonic assisted freezing and ADP starch can better use ultrasonic assisted freezing process to improve the gel strength,ADP starch can reduce the water separation rate,improve the dehydration shrinkage phenomenon during gel thawing,and improve the gel quality.(4)The influence of ultrasonic-assisted freezing combined with ADP starch on KGM composite emulsion gel was explored.The results showed that ultrasonic-assisted freezing combined with ADP starch could also improve the gel properties of KGM composite emulsion gel.The KGM composite emulsion gel prepared by ultrasonic-assisted freezing coupled with ADP starch at 300 W had the most similar color,whiteness and texture to the animal fat,lower cooking loss than animal fat,and the most similar rheological properties to the animal fat.At about 73 °C,the storage modulus and loss modulus coincided with the animal fat.And the compound emulsion gel does not appear fat melting phenomenon when heating up.