Peanut hull flour as a potential source of dietary fiber

The objectives of this investigation were to analyze a flour made from peanut hulls and to evaluate its potential as a source of dietary fiber. Hulls produced a mean 27.50 grams of toasted Virginia-type hull flour (TVHF) and a mean 42.4 grams of toasted Runner-type hull flour (TRHF) per 100 grams of cleaned hulls. The proximate composition of TVHF and TRHF was determined. The TVHF had 2.68 percent moisture, 6.74 percent crude protein, 0.83 percent ether extract, 2.94 percent ash, 47.33 percent crude fiber, and 39.34 percent nitrogen free extract. The TRHF contained 2.55 percent moisture, 7.19 percent crude protein, 0.52 percent ether extract, 2.07 percent ash, 47.23 percent crude fiber, and 40.33 percent nitrogen free extract. Six macroelements and eight microelements were determined in TVHF and TRHF. The hull flours represent a potential source for calcium, phosphorus, and potassium. The concentration of lead in both flours was below the sensitivity limit of the atomic absorption spectrophotometer. TVHF and TRHF yielded 7.64 percent and 9.06 percent soluble solids, respectively. The water holding capacities for washed, acetone-dried flours were lower than those of TVHF and TRHF. The water holding capacity increased as the soaking time and temperature increased. The oil holding capacity was affected by the type of material, but was not affected by soaking time and temperature. The fibrous components in TVHF and in TRHF were, respectively, 61.49 and 58.76 percent lignocellulose for acid detergent fiber, 24.52 and 26.47 percent lignin, 78.45 and 78.26 percent lignocellulose in buffered acid detergent, 80.51 and 77.63 percent cell wall constituents, 21.41 and 22.37 percent soluble cell material in neutral detergent, 2.51 and 1.83 percent insoluble ash in neutral detergent, 19.02 and 18.87 percent hemicellulose, and 36.97 and 32.29 percent cellulose. The washed, acetone-dried Virginia-type hull flour and the washed, acetone-dried Runner-type hull flour were, respectively, composed of 70.32 and 61.72 percent lignocellulose for acid detergent fiber, 28.28 and 25.22 percent lignin, 84.01 and 77.30 percent lignocellulose in buffer acid detergent, 81.94 and 76.57 percent cell wall constituents, 18.06 and 23.43 percent soluble cell material in neutral detergent, 2.10 and 1.67 insoluble ash in neutral detergent, 11.62 and 14.86 percent hemicellulose, and 42.04 and 37.16 percent cellulose. The emulsifying capacity for one gram of flour ranged from 27.57 ml oil/g to 25.27 ml oil/g of dried sample of the toasted and washed, acetone-dried flours. The cation exchange values ranged from 1.01 to 0.91 meq./g of dry sample weight. These values represent materials similar to resins of weak cation exchange capacity. The pH of the toasted flours were close to each other, ranging from 6.1 to 5.4. The gross energy values for TVHF and TRHF were 4.574 and 4.566 Kcal/g, respectively. Aflatoxins were not detected in either types of flour. The Hunter L, "a," and "b" color values were dependent on the type of flour (Virginia- vs. Runner-type flours) and the treatment (untoasted vs. toasted). The sensory panel did not show a preference for toasted or untoasted flours when evaluated for taste or aroma.