| The cottonseed meal produced through an extracting process using two-phasesolvent (TPS) (named TPS meal therein after) , is a good protein resource because ofthe high protein and low gossypol content contained in it. TPS meal has some especialproperties which are different from that of the meals produced through other methods,and not been studied carefully yet. In order to develop and use this important resourceeffectively, it is necessary to explore the properties of TPS meal, especially theproperties relevant to extraction and precipitation.In this work cottonseed protein concentrates, precipitated protein isolate andsoluble protein were prepared from TPS meal. Some key steps of the preparation,such as extraction, precipitation and ultrafiltration were studied. The mathematicalmodels for extraction and ultrafiltration flux were developed, and the functionalproperties from TPS meal were determined.1. Preparation of the cottonseed protein concentratesA method named density fraction was used to prepare the cottonseed proteinconcentrates which was based on the principle that there is difference between thedensity of cottonseed kernel and that of cottonseed hull, and a liquid medium, i.e. asolution with suitable density could make them apart. In this work the K2CO3 solutionwas chosen through experimental comparison. The influence of concentration andpretreatment method of it on the separation of the kernel and hull were investigated.(1) The optimum K2CO3 concentration was 43% for the density fraction. To wetthe cottonseed meal with methanol was necessary before the density fraction. Thecottonseed protein concentrates produced by this method contained 75% protein. Itwas even higher than that of dehulled cottonseed meal(protein content 68.72%). Theprotein yield was 66%.It's clear that: the larger loss of protein (28%) is the main drawback for thismethod.(2) By sieving, 25% cottonseed meal was removed before density fraction iABSTRACTbecause of the low protein content (only 15%) in it. Then the rest was processed bydensity fraction with K2CO3 solution. For those that the diameter was in 0.105-0.22,0.22-0.355,0.355-0.45mm and bigger than 1mm, the suitable K2CO3 concentrationswere 35%,37%,40%and 42% respectively. By this way, the protein yield (75.2%)was higher, but the protein content (66.7%) was lower than former (density fractionwithout sieving).2. Preparation of the precipitated protein isolateThe optimum conditions for extraction and precipitation were investigated aspreparing cottonseed precipitated protein isolate. The dissolved property of phyticacid was also studied in order to decrease the content of phytic acid in protein isolate.(1) Orthogonal experiments and monofactorial analysis were used to determinethe optimum extraction conditions. The influence of pOH, extraction temperature(T),particle-size, extraction time(t), ratio of liquid and meal and stir strength on theextractability were studied. The optimum conditions for protein extraction were: pOH= 2.3, T =30 ℃, t =1h, the ratio of liquid and meal =15. The protein extractability was73.52%.(2) The influence of pH on the phytic acid extractability was measuredexperimentally in order to reduce the content of phytic acid in the protein isolate. Inthe range of pH=11-11.5 the protein extractability was high (73.52%). But thesolubility of phytic acid was minor (22%). The extractability of phytic acid wasmaximum (88.7%) when pH=5.0.(3) The influences of pH, temperature, flocculation time on precipitability wereinvestigated by the orthogonal experiments. The precipitability was maximum whenpH=5.0—the isoelectric point of cottonseed protein. Lower temperature and longerflocculation time were beneficial to the protein precipitability. The suitable proteinprecipitation condition was: lower temperature (5℃ in this work), flocculation time>10minutes, pH=4.8. The precipitability was 77.5%.(4) Compared with traditional extraction with alkali solution...
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