| Cotton is a kind of major agricultural product in our country. Cottonseed as an component of it is not only an important plant oil,but also an important source of plant protein, second only to soybean in the world. After the oil extracted and gossypol removed,there was a high protein content in the cottonseed meal,usually being33.21%-45.09%. Cottonseed protein without beany flavor will not make people feel flatulent after eating.So it is a better plant protein than soy’s,worth of developing and utilizing in food and feed resources.The phenol and fat-removed cottonseed as rew material to extract cottonseed protein, uses the method of alkali extraction and acid precipitation,determining the extraction process conditions and different decolorization methods. And after studying the thermal stability, water holding capacity, oil absorption ability and other physical and chemical propeties of cottonseed protein, the alkali-extraction conditions of the polysaccharides in cottonseed meal are confirmed. The results are as follows:1. The optimum conditions of alkali-extraction of cottonseed protein were determined as follows:the pH was10,the temperature was50℃,the solid-liquid ratio was1:20,the time was90min, the crushing mesh of the raw material were100and the extraction times were2.Choosing three main factors including pH, temperature and solid-liquid ratio for response surface experiments, the results were as follows:the pH was10.5,the temperature was47.5℃and the solid-liquid ratio was1:20(m/v).Under above conditions, the extraction rate of alkali-soluble cottonseed protein was up to53.78%.2.Cottonseed protein contains two kinds,which are storage protein and non-storage protein.The maximum amount of protein precipitation was5.21mg in non-storage protein at pH4.5,while4.85mg in storage protein at pH6.3. By SDS-PAGE determines cottonseed protein in the supernatant on molecular weight of22.30,20.80,14.20kDa;Precipitation of the protein molecular weight were53.70kDa, b50.10kD, alkali soluble acid sinking method can effectively separate the high molecular weight and low molecular weight protein.4. Two different decolorization methods, utilizing activated carbon and hydrogen peroxide, were compared on the decolorization effect of alkali-extraction of cottonseed protein solutions and the results were as follows:the best decolorization rate of the first one was65.53%and the protein retention rate was54.89%,with the comprehensive score being58.08.However, the best decolorization rate of the second one was64.53%and the protein retention rate was97.61%,with the comprehensive score being81.07.Obviously,the second method is far superior the first one.5. The physicochemical properties of cottonseed protein(1)Thermal stability:the denaturated temperature of the protein extracted from high temperature meal is82.89℃and the enthalpy value is0.139J/g;while the denaturation temperature of low temperature one is87.64℃, enthalpy value is0.845J/g.So the thermal stability of the protein extracted from low temperature meal is significantly higher than the one’s extracted from high temperature meal.(2)Dissolution rate:the dissolution rate of the protein extracted from both high and low temperature meal tends to change slowly under acidic condition.But it is significantly increased under neutral to alkaline condition. And the dissolution rate of the protein extracted from low temperature meal is significantly higher than the one’s extracted from high temperature meal.(3)Study the impact on water-holding capacity of protein extracted from both high and low temperature meal with different pH,temperature,concentration of NaCl and sucrose.What’s more,as the value increases, water-holding capacity of both kinds of meal appear to be a significant increasing trend.The water-holding capacity were2.54g/L and2.94g/L respectively at pH7.The hygroscopicity reached to a balance, without a significant increasing trend when pH was higher than7.With the increasing temperature,the hygroscopicity of both kinds of meal appears to be a significant increasing trend.The highest water-holding capacity were2.54g/L and2.94g/L respectively when the temperature is60℃.And the hygroscopicity began to decrease when temperature was higher than it. With the increasing concentration of NaCl, the hygroscopicity of both kinds of meal appears to be a significant increasing trend.The highest water-holding capacity were4.01g/L and4.65g/L respectively when the concentration of NaCl was0.8mol/L.And the hygroscopicity began to decrease when concentration was higher than it. With the increasing concentration of sucrose, the hygroscopicity of both kinds of meal appears to be a significant increasing trend.The highest water-holding capacity were4.07g/L and4.90g/L respectively when the concentration of sucrose was10%.And the hygroscopicity lost the significant increasing trend when concentration was higher than it.In conclusion, the physicochemical property of low temperature meal were superior to high temperature one under different factors.(4)Study the impact of temperature on the oil-holding capacity of cottonseed protein,and low temperature meal performs,significantly,better than high temperature meal under different temperatures.Both have a highest oil-holding capacity at30℃,being3.44g/and3.75g/L respectively.6.The factors of alkali-extraction of cottonseed protein in decreasing order were alkali concentration,temperature, solid-liquid ratio and time.The optimal conditions of alkali-extraction of cottonseed protein are as follows:the aikali concentration was0.15mol/L,the temperature was80℃, the solid-liquid ratio was1:20,and the time was90min. Under above conditions, the extraction rate of cottonseed polysaccharide was9.17%... |
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