Cereal Chem 59:440 - 443.  |  VIEW ARTICLE
In Vitro Interaction of 1-14C-Ascorbic Acid and 2-14C-Thiamin with Dietary Fiber.

S. T. Omaye, F. I. Chow, and A. A. Betschart. Copyright 1982 by the American Association of Cereal Chemists, Inc. 

Hard red spring (HRS), soft white winter (SWW) wheat brans, citrus pectin (CP), and alphacel cellulose (AC) were studied for their ability to influence the availability (not trapped by, bound to, or destroyed by the fiber matrix) of 1-14C-ascorbic acid or 2-14C-thiamin in vitro. HRS and SWW wheat brans seemed to have a stabilizing influence on preventing the degradation of ascorbic acid that diminished as the level of the fiber increased in the incubation mixture. The availablility of ascorbic acid decreased with increasing amounts of HRS, SWW, or CP incubated with saline and with HRS, SWW, or CP incubated with sodium taurocholate and saline (P less than 0.005). Availability of ascorbic acid was not related to increasing levels of AC, incubated with or without sodium taurocholate. The availability of thiamin decreased significantly with increasing HRS or SWW incubated with saline and with HRS, SWW, or CP incubated with sodium taurocholate and saline (P less than 0.05). Free thiamin in mixtures of AC incubated with or without sodium taurocholate was not significantly different from that of mixtures containing no AC. In general, the availability of ascorbic acid decreased at pH 5.5 and above in the presence of all fiber sources. The relationship between pH and thiamin availability was more pronounced than the relationship between pH and ascorbic acid in the presence of fiber sources. The interaction between ascorbic acid and selected sources of dietary fiber may be the result of ascorbic acid being trapped by water held in the fiber matrix or adsorption (binding) to the fiber matrix and some loss due to degradation. However, the loss of availability of thiamin is more consistent with binding or being trapped by water held in the fiber matrix.