DETERMINATION OF SOLUBLE DIETARY FIBER IN FOODS AND FOOD-PRODUCTS - COLLABORATIVE STUDY

A collaborative study was conducted to determine the soluble dietary f iber (SDF) content of foods and food products by using a combination o f enzymatic and gravimetric procedures. The method was basically the s ame as that employed for determining total dietary fiber (TDF), 985.29 , and the method for insoluble dietary fiber (IDF), 991.42. Ten labora tories were each sent 13 test samples (6 blind duplicates and 1 standa rd [green beans] containing 29-33% TDF, 19-23% IDF, and 8-13% SDF) and were instructed to assay for IDF, SDF, and TDF independently. Include d in the package were the 3 enzymes, namely alpha-amylase, amyloglucos idase, and protease, and the filter aid Celite, which was thought to b e the major cause of high reproducibility relative standard deviation (RSD(R)) values for SDF obtained in a previous collaborative study. Th e foods to be analyzed were apricots, carrots, chickpeas, onions, rais ins, and the sugar beet fiber Fibrex(TM). IDF, TDF, and SDF were calcu lated as the weight of residue minus the weight of protein and ash on a dry weight basis. RSD(R) values of the IDF results averaged 8.02%, w ith only 1 food having an RSD(R) >10%. The RSD(R) values for the TDF r esults averaged 4.97%, and all foods had an RSD(R) <7%. Although the R SD(R) values for SDF averaged 14.17%, 4 of the 6 foods had an RSD(R) < 10%, and 1 of the 2 remaining foods that had a high RSD(R) had an SDF content of only 1.2%. In all cases, the RSD(R) values of the SDF conte nt of the foods were less than the values for the same foods analyzed in a previous collaborative trial. The enzymatic-gravimetric method fo r the determination of SDF was adopted first action by AOAC INTERNATIO NAL.