Various amounts of apple fiber and cellulose were added to wheat gluten and water-holding capacities (WHC) of the different mixtures were determined. A linear relationship between concentrations of two kinds of fiber and WHC was not observed, indicating a possible interaction between fiber and gluten which reduced the WHC of mixtures. Mixograph studies of wheat flour and fiber mixtures demonstrated that the dilution of gluten by fiber could not account for all of the observed changes in mixing properties of the wheat flour/fiber blends. This is further evidence for a possible interaction of fiber and gluten which may explain the poor baking properties of apple fiber bread. INTRODUCTIONDIETARY FIBER is defined as the nondigestible components in foods which include cellulose, hemicellulose, lignins, pectins, gum and mucilages (Williams, 1985); The lack of dietary fiber in the American diet has been associated with constipation, diverticulosis, cardiovascular diseases and cancer (Spiller et al., 1978).Many forms of dietary fiber have been added to bread and other cereal-based products. Pomeranz et al. (1977) replaced wheat flour with up to 15% cellulose, wheat bran, and oat bran in bread baking. D'Appolonia and Young (1978) added lO-20% wheat and oat brans to bread dough. Toma et al. (1979) baked bread with 5--15% potato peel.The chemical and baking properties of apple fiber used in this study were previously evaluated (Chen et al., 1987). The chemical analyses of apple fiber showed that apple fiber contained 31% cellulose, 1.5% lignin, 12% water-insoluble hemicellulose as well as 9% water-insoluble pectin. In addition, apple fiber also contained 18% water-soluble hemicellulose. In the baking property study, loaf volume of bread decreased by 21% when 4% wheat flour was replaced by apple fiber. As the concentration of apple fiber increased, the loaf volume decreased markedly. The main problem in apple fiber bread baking is "weak" or "crippled" dough with a reduced ability to retain gas during the baking processing (Chen et al., 1987).The poor baking quality of certain fiber cereal products has been attributed to several factors. Pomeranz et al. (1977) reported that at 5% fiber the loaf volume decreased to an extent expected from the dilution of the functional gluten proteins. At levels above 7%, however, fibrous materials decreased the loaf volume more than could be explained by the dilution of gluten. These authors further demonstrated with electron microscopy that fibrous materials inhibit the formation of thin sheets and fibers in the crumb which are present in nonfiber containing bread. These authors stated the inhibition of fine structure formation in the crumb was not due to dilution of gluten. It was the purpose of this study to further investigate the effect of fibrous materials on the physical properties of gluten and the mixing properties of wheat flour.

Salt and combinations of salt with phosphates and antioxidants were investigated for their role in lipid oxidation and discoloration in restructured beef, pork, and turkey steaks during storage at -10°C for 16 wk, 8 wk and 8 wk, respectively. Lipid oxidation and discoloration occurred simultaneously in pork and turkey, but beef color loss occurred much earlier than did lipid oxidation. Phosphates were effective in inhibiting lipid oxidation in beef (4 wk), pork (8 wk) and turkey (6 wk). Tertiary butylhydroquinone inhibited lipid oxidation in pork and turkey steaks, but, overall, neither prevented discoloration. Results indicate discoloration and lipid oxidation are interrelated, and pigment oxidation may catalyze lipid oxidation.

To evaluate the type of binding involved, thermodynamic analysis of the temperature dependence of proanthocyanidin binding to bovine serum albumin (BSA) and bean glycoprotein G-l (G-l) was investigated. Binding was analyzed with tritiated proanthocyanidin by ultrafiltration to separate free ligand and protein-bound ligand. Binding constants were determined from Scatchard plots. Van't Hoff plots indicated proanthocyanidin binding to BSA was spontaneous and entropy driven. Analysis with cis-parinaric acid supported the conclusion drawn from the thermodynamic analysis that the binding of proanthocyanidin to BSA was a hydrophobic interaction. Van't Hoff plots indicated proanthocyanidin binding to native G-l protein was also spontaneous but, in contrast to BSA, enthalpy driven. Analysis with cis-parinaric acid confirmed the hydrophilic character of proanthocyanidin binding to native G-l. Evaluation of proanthocyanidin binding to heat-denatured G-l with cis-parinaric acid indicated hydrophobic interactions.

A new model system was developed for the study of autoxidation of thin films of neat lipid and the effect of relative humidity on the oxidation reaction. In the model system, the surface-to-volume ratio of lipid was large and measureable, and the relative humidity (RH) and oxygen partial pressure were controlled. Methyl linoleate, oxidized at six different RH as a thin film in an atmosphere of pure oxygen, exhibited a maximum rate of oxidation at 32% RH and minimum rates at 0% and 100% RH. The rates of oxygen uptake, determined manometrically, were linear and reproducible at all six RH. The maximum rate at 32% RH was attributed to solvation and stabilization of the propagation transition state by water. Increasing the RH beyond 32% resulted in solvation of the peroxy radical, sterically hindering the radical from entering the propagation transition state.

The inhibitory effect of water on the decomposition of methyl linoleate hydroperoxides (MLHP) catalyzed by Co2+ and Cu2+ was studied in a model system using proton nuclear magnetic resonance (NMR) spectroscopy. MLHP were prepared by photoxidation and purified by chromatographic methods. Proton NMR spectroscopy was used to measure reaction rates by monitoring changes in the intensity of the OOH signal. The rate constant of the reaction was obtained by plotting the natural logarithm of MLHP concentration vs time. In the first part of the study, no transition metals were added to the model system, so that the effect of water could be attributed to the interaction between water and MLHP only. The rate constant of the reaction (K) was found inversely proportional to the concentration of water. There was a downfield chemical shift of both hydroperoxide and water peaks in the NMR spectra when water was added. As temperature increased to 40 degrees C, the difference in K between the systems with 0% and 2% water disappeared. It is proposed that the hydroperoxides were solvated with water which retarded their decomposition. When Co2+ was added to the model system, K decreased as the concentration of water increased from 0% to 1.5%. As temperature increased from 18 degrees C to 40 degrees C, differences between the K for 0% and 2% water disappeared. A similar phenomenon was observed in reactions catalyzed with Cu2+. These findings would support a mechanism in which the protective effect of water involves both the solvation of OOH and hydration of the metal catalyst.