No abstract

The effect of particle size, acid and alkali on the composition of processed and unprocessed wheat bran, purified corn pericarp, and peanut hulls was studied. Van Soest's method for fiber analyses was used to measure hemicellulose, cellulose, lignin, and cutin. Hemicellulose values for wheat samples ground through a 60-mesh screen of Wiley Mill were 20% lower than samples ground through a 20-mesh screen. Shaking red wheat bran for 24 hr at 25°C solubilized 17% of the hemicellulose at pH 11.5 and 9% at pH 2.2. Refluxing for 60 min reduced the hemicellulose content by 62% at pH 11.5 and by 52% at pH 2.2. Similar losses were observed for purified corn pericarp while little change was found for peanut hulls. Variation in sample particle size and exposing plant fiber to acid and alkali may change fiber composition as measured by the Van Soest procedure.

The intake of crude fiber in the American diet was assessed for 7 time periods between 1909 and 1975 using food consumption and composition tables. Crude fiber intake dropped 28% from 6.8 g/day in 1909 to 4.9 g/day in 1957 to 1959 and has remained at that level until the present. The intake of fiber from vegetables has remained relatively constant from 1909 to 1975 while potatoes, fruit, cereals, dry peas, and dry bean consumption have declined. The trends shown for crude fiber consumption in the United States support the hypothesis that fiber intake has decreased coincidentally with increases in degenerative diseases.