Determination and validation of dietary fiber in food by the enzymatic gravimetric method

An adequate and validated method for the analysis of any nutrient is a fundamental step in achieving a good analytical result. The purpose of this study was to analyze dietary fibers (DF) and validate the results without the availability of a standard reference material (SRM). Ten samples of cracker biscuits in duplicate were analyzed using the enzymatic–gravimetric method. To validate, cracker biscuit was used as a matrix food and a fiber-rich product (47.63%) was used as a secondary reference standard (SRS). Three aspects were evaluated: (1) Precision—Samples from 10 assays in two lots of cracker biscuits and in the RS; (2) Accuracy—recovery test on biscuit plus three quantities of SR: 1.5, 2.5 and 5.0 g in 50 g of biscuit, (3) Linearity—recovery curve, through the correlation coefficient (R2). Results obtained for coefficient of variation were 4.89 and 4.10% for biscuits and 1.37% for the RS, showing a good precision of approximately 20%. The accuracy values obtained were 4.10, 4.90 and 6.55 g/100 g, which represents recoveries of 101, 108 and 110%. These results indicate acceptable accuracy, since the replicates of the fortified samples showed analyte recovery within the acceptance range of 70–120%. The correlation coefficient (R2) was 0.9999 indicating an excellent linearity in the methodʹs response. The conclusion is that DF results obtained through the EGM method are reliable, considering the cracker biscuit sample parameters analyzed.