| K-Carrageenan is a polysaccharide gel which is extracted from red algae with excellent gel characteristics and rheological properties. But its performance show brittleness, small elasticity, easy water separating and other issues. Konjac gum (KGM) has excellent viscosity and dispersion. The mixture of konjac gum and K-carrageenan can improve the existence issues of K-carrageenan gel which maintains small brittleness, high elasticity, benefiting from the interaction between the polysaccharide molecules. The mixture of konjac gum and K-carrageenan has an important application value in the food industry.This thesis was focused on the mixture of K-carrageenan and konjac gum. To discuss relationship between K-carrageenan and mixture, the gel properties and rheological behavior of them, and the texture properties and structural analysis of mixture were investigated. Main results obtained from this study were summarized as follows:(1) The gel properties ofκ-carrageenan.The gel properties ofκ-carrageenan were studied under different experimental conditions. The results showed that the viscosity ofκ-carrageenan solution and gel strength increased linearly with the increase of concentration. Concentration of 1.0 g/100 mLκ- carrageenan in 70℃water for 30 min, then removed at room temperature for 6 h had the maximum strength. The appropriate storage temperature (-5-0℃) could increase the storage time ofκ-carrageenan, but long-term cryogenic storage could make a great impact on structures and patterns ofκ-carrageenan. With the concentration of the KCl, CaCl2, NaCl increasing, the gel strength firstly increased and then reduced. The maximum gel strength was found when the concentration of KCl, CaCl2 and NaCl were 0.3 g/100 mL,0.2 g/100 mL and 0.8 g/100 mL respectively. The low ionic strength (0.1 mol/L) could enhance the strength ofκ-carrageenan, but the excessive salt ion could make gel accelerate aging. So we should control concentration of salt ion and the ionic strength in solution. The sucrose (≤1.5 g/100 mL) might enhance the strength, but a large number of sucrose could interfere withκ-carrageenan molecules itself around and caused the strength to decline; when pH value was 5.0-7.0, the strength ofκ-carrageenan was stable; citric acid decreased the strength.(2) Study on the synergy ofκ-Carrageenan and Konjac gum properties.κ-Carrageenan and konjac gum showed cooperative synergism in mixture system. so we investigated the mixture viscosity, strength and texture under different experimental conditions. The results were as follows:the viscosity of mixture was larger than single gel and the largest viscosity was at 70℃heating. When the w (K-carrageenan):w (KGM) was 5.5:4.5 mass ratio, concentration of 1.0 g/100 mL mixture got the largest strength on the experimental condition that 80℃water for 30 minutes, and then at room temperature for 6 h. The strength of mixture increased linearly with the increasing of total gel concentration. Low temperature storage chronically would destroy the structure of mixture, and the appropriate storage temperature (-5-18℃) and time would lengthen the gel quality, a certain amount of K+, Ca2+, Na+ could enhance strength under the storage conditions, and the existed of K+ could form greater strength than Na+.When the mass ratio between K-carrageenan and konjac gum was 5.5:4.5, the mixture gained maximum hardness, chewiness and gumminess, with the konjac gum increased in compound proportion, the adhesiveness and flexibility increased accordingly. When PH value was between 5.4-7.0, the mixture texture parameters (hardness, chewiness, gumminess and so on) would remain stable. The mixture was stable to alkali and sensitive to acid. The appropriate amount of sucrose(≤0.8 g/100 mL) could improve texture characteristics such as hardness, chewiness and gumminess, a large number of sucrose could improve the viscoelastic; When we added citric acid to mixture, the hardness, chewiness and gumminess were decreased while adhesiveness and springiness increased. Moderate ionic strength (0.1 mol/L due to presence of K+, Ca2+, Na+ cations) could increase the mixture gel hardness and viscoelastic, but the large ionic strength was not conducive to gel formation, so we should control the dosage of K+, Ca2+ cations to avoid overdosage.According to the concentration, pH, ionic strength, KCl, and CaCl2, we conducted the five factors, four levels of the orthogonal test (i), and discussed the influence of the key factors of mixture gel on the confrontation:the factors which affected the hardness of mixture were in the order of concentration, KCl, pH value, ionic strength, and CaCl2 from major to minor; the factors which affected the springness of mixture were in the order of pH value, CaCl2, concentration, ionic strength, and KCl from major to minor; the factors which affected the cohesiveness of mixture were in the order of concentration, pH value, CaCl2, ionic strength, and KCl from major to minor; According to the citric acid, sugar, NaCl, KCl and CaCl2, we conducted the five factors, four levels of the orthogonal test (ii), and discussed the influence of the key factors of mixture gel on the confrontation:the factors which affected the hardness of mixture were in the order of citric acid, sugar, KCl, CaCl2 and NaCl from major to minor; the factors which affected the springness of mixture were in the order of citric acid, sugar, KCl, NaCl and CaCl2 from major to minor; the factors which affected the cohesiveness of mixture were in the order of citric acid, sugar, NaCl, KCl and CaCl2 from major to minor.(3) The rheological properties ofκ-carrageenan and konjac gum compound.1.0 g/100 mL K-Carrageenan water solution has the viscoelasticity and pseudo-plastic at 30℃, In the low-frequency region, they mainly exhibited elasticity, displaying the weak colloidality. The solution viscosity increased with the shear rate reduces; The stored energy module G' was bigger than consumed energy module G", which showed elastic to be higher than viscidity. Moreover with the temperature increased, G' and G " increased. G' and G " presented suddenly change at 60℃, possibly the gel started transform to the sol.It could be concluded thatκ-carrageenan was compatible with konjac gum, the mixture have high elasticity module value compared to the aloneκ-carrageenan. Blends solution has a good pseudo-plastic behavior at low concentrations, viscosity declined rapidly with shear rate increased. The increase proportion of konjac gum in mixture might enhance the sol temperature, which explained that coordination synergized action existed between K-carrageenan and konjac gum. KCl and CaCl2 enhanced the gel sol temperature approximately 3-5℃, which explained that K+ and Ca2+ participated in the gelatin process and under the controlled condition might enhance force among moleculars. With konjac gum increasing, G' and G " were first increased and then decreased. Whenκ-carrageenan and konjac gum mass ratio of 5.5:4.5, G' and G " were largest. With the temperature increasing G'and G " increased, and G' and G " presented suddenly change at 60-70℃, possibly the gel started transform to the sol. Small amplitude oscillatory tests in the linear domain of viscoelasticity showed thatκ-carrageenan played the major role in the viscoelasticity of the mixture, and konjac gum strengthened the gel-net configuration and stability.(4) Structural analysis of theκ-carrageenan and konjac gum mixture gel.FT-IR results showed that -OH peak shifted to lower wave number direction in mixture. DSC endothermic peaks of compound gel were wider thanκ-carrageenan alone, which indicated that there were some interactions between the two polymers. SEM images showed that the mixture gel seemed more compact thanκ-carrageenan. According to the experimental results, we can conclude thatκ-carrageenan builds up the continuous network construction and konjac gum particulated that seemed to adhere to the network, which caused the network to be more compact. Theκ-carrageenan has more contribute to the network in mixture. |
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