Studies On The Optimal Techniques On Extraction And Decolouration Of Dietary Fiber From Alfalfa Dregs

In the experiments, firstly, the content of the soluble and insoluble dietary fiber (SDF and IDF for short) of alfalfa sampled in different period of their life was determined. Secondly, after the dregs after extracting leaf protein from fresh alfalfa was selected as raw materials and a number of single-factor and orthogonal experiments were designed, the optimal techniques on producting of SDF and IDF from alfalfa dregs and decoloring of IDF were studied.The results showed as follows, (1) It is better to extract DF by selecting alfalfa at the beginning of florescence, because the content of SDF declined while IDF increased with the growing of alfalfa.(2).The optimal condition for extracting SDF were 90℃, pH1.0, 90min, water volume 1:10; temperature,pH value,taking-time and water volume were all significant factors contributing to the production ratio of SDF(P<0.01). (3). The optimal conditions for extracting IDF with papain were: sodium hydroxide concentration 5%, soda-soaking temperature 60℃, soda-soaking time 50min and the amount of used papain 0.3%; among these factors, the amount of used papain was the most significant affecting factor to the IDF content(P<0.01); sodium hydroxide concentration and soda-soaking time were also important considerations to the IDF content(P<0.05); Soda-soaking temperature worked inconspicuously. (4). The optimal conditions for extracting IDF with soda and acid were: soda-soaking temperature 80℃, soda-soaking time 70min, acid-soaking temperature 50℃, and acid-soaking time 4h. Among these factors, soda-soaking temperature was most sensitive factor to the IDF content(P<0.01);soda-soaking time had significant effect to the IDF conten(tP<0.05); acid-soaking temperature and acid-soaking time were of little significance. (5). The optimal conditions for extracting IDF with lactobacillus and facultative thermophile were: inoculants size 6%, the ratios between the two reagents 1:2, fermentation temperature 37℃, fermentation time 15h; fermentation temperature and fermentation time were significant effecters to the IDF content(P<0.05); inoculums size and the ratio between the two reagents were of little significance. (6). Among these three methods of extracting IDF, the content of protein in the production obtained by papain hydrolysis was much less than by chemical process or fermentation method(P<0.01), however, the content of IDF, water maintenance ability and expansibility in the production obtained by papain hydrolysis was much more than by the other two methods. So papain hydrolysis was the most effective among the three methods. (7).There was better effect in decoloring IDF with NaClO than with H2O2 or Na2SO3; the suitable conditions for decoloring IDF were: NaClO concentration 5%, time 1h, temperature 20℃.