Preparation and use of partially defatted peanut flour in breakfast cereal flakes

Abstract

This study investigated preparation of partially defatted peanut flours by extrusion, screw pressing, and use of the flours in breakfast cereal flakes. Release of oil by wet and dry extrusion was evaluated. Wet extrusion (using an Anderson International Company expander) was tried initially and abandoned in favor of dry extrusion (using an InstaPro International Company extruder). Thus, fewer samples of earlier product were observed. Dry extrusion, followed by screw pressing removed oil for a total recovery of 90.6% of the oil in peanut kernels. Press cakes prepared by dry extrusion had higher protein dispersibility index (PDI) than those made using wet extrusion. Trypsin inhibitor was quite stable to heat treatment, only 23% was inactivated by dry extrusion and 26% after screw pressing. Press cakes were roasted (166'C for 8 min) to develop flavor. Press cakes were ground and evaluated as protein supplement in flakes. Corn cones, ground corn of particle size intermediate between meal and flour, were replaced with unroasted partially defatted peanut flour (PDPF) and roasted flour (R-PDPF) at 0%, 10%, 20% and 30% levels. The mixtures were extruded using a Wenger Manufacturing Company twin-screw extruder to produce collets. The collets were flaked, then roasted at 171'C for 3 min. Flakes containing 30% PDPF had 16% protein. Increasing the peanut flour level decreased the product bulk density and hardness. Lightness and yellowness decreased as the peanut flour content increased. Water absorption (WAI) and water solubility (WSI) indices increased for flakes with addition of peanut flour. Bowl fife, the time for crispiness to disappear after soaking in milk, decreased with addition of peanut flour. Sensory evaluation was conducted for crispiness, color, flavor and overall acceptance using the 9-point hedonic scale (I = dislike extremely, 9 like extremely). Peanut flavor was also evaluated (I = none, 9 = strong). Untrained sensory panelists (n = 48) evaluated 5 samples of flakes (O%, 10%, 20%, 30% R-PDPF and 30% PDPF) I min after addition of milk. All flakes were rated acceptable (score > 5.0). Surprisingly, peanut flavor intensity was the highest for flakes containing 30% PDPF, rather than the R-PDPF.