Cellulose, Hemicellulose and Lignin Content of Raw and Cooked Spanish Vegetables

The content in NDF, ADF, cellulose, hemicellulose, and lignin of 22 raw and 19 cooked vegetables (14 boiled, and 5 fried) widely consumed among the Spanish population was determined according to the method of Van Soest. Cooking generally increases the NDF, ADF and cellulose content on a dry weight basis. Normal size servings of the vegetables were prepared and their NDF, cellulose, hemicellulose and lignin contents calculated. We observed that, with vegetables of common use, a total amount of 15–20 g/day of these fiber components can be obtained; according to current knowledge this implies beneficial physiological effects for a broad human pathology.     

EVALUATION OF DIETARY FIBER IN POTATO CRISPS: INFLUENCE OF THE ANALYTICAL METHOD USED

Dietary fiber in ready salted potato crisps was determined by two methods, i.e., the official AOAC method, and the modified method of Englyst, recommended in the U. K. The ultimate aim was to compare the results and to evaluate the advantages and limitations of each method for the analysis of this food in order to obtain a figure to be included on the package. The AOAC method is an enzymatic-gravimetric procedure to determine the total dietary fiber (TDF). The Englyst method consists of an enzymatic-chemical extraction and fractionation of the nonstarch polysaccharides (NSP) and their subsequent determination as neutral sugars by GLC. We modified the original chromatographic method. The AOAC method gave a value of 5.39 g/100g (dry matter) for TDF, and the Englyst method of a value of 1.70 g/100g (dry matter) for NSP. It is assumed that the gravimetric method gives a higher fiber value than the Englyst method due to a contribution from retrograded starch. For this particular food, the AOAC method is faster and much easier to carry out and does not overestimate dietary fiber, if the resistant starch is regarded as part of it.