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Rev Nutr 43-4

and nutritious baked products. Peanut flour could improve the nutritional quality and the functionality of wheat flour based products. Breads and cookies are valuable vehicles for nutritional improvement to target areas, such as child-feeding programmes. Bakery products containing peanut flour are scarce or are not available in most of the world´s countries. Scientific 382 information about chemical composition and functional properties of peanut flour is needed to optimize its potential application in bakery products. The objectives of the current study were a) to obtain partially defatted peanut flour; b) to evaluate some of the most important chemical, nutritional and functional properties; and c) to assess peanut flour incorporation on nutritive value and sensorial acceptability of breads and cookies. MATERIALS AND METHODS Raw material and peanut flour obtention De-hulled seeds from Runner market type peanut were used to prepare partially defatted peanut flour (PF). Seeds were ground using a home-made stainless steel roller crusher and particles between 2.4 and 4.8 mm (mesh 8-4, Tyler standard screen scale) were selected using an automated screen. The oil was partially removed with n-hexane by cross flow extraction at room temperature using a continuous lixiviation apparatus acording to a procedure described previously (19). The resulting meal was desolventized under reduced pressure at 30 °C. Peanut flour was obtained by grinding the peanut meal to very fine particles, so that 90 % of the product passed through 100-mesh screen. Proximate composition of peanut flour Total protein content of PF was evaluated using a Kjeldahl nitrogen analyzer and it was calculated as % N x 5.46 (20). Fat, moisture, ash and fiber contents were determined using standard AOAC methods (20). All chemical analyses were run in triplicate and results were expressed on dry matter basis (DB). Functional properties of peanut flour Protein solubility. Protein solubility was determined as described previously (21). Triplicate determinations were carried out and solubility profile was obtained by plotting average of protein solubility (%) against pH. The soluble protein content was determined according to the Lowry method (22). Water holding capacity (WHC). The WHC determination was carried out according to Bernardino-Nicanor et al. (23). Briefly, PF was dispersed in distilled water (1 % w/v) by magnetic stirring, and vortex agitation every 10 minutes, for 1 h at room temperature. The final pH reached for the sample was 7.2. The sample was finally centrifuged at 5000 g for 30 min, and the WHC was expressed as milliliters of water retained per gram of flour. Fat absorption capacity (FAC). FAC was determined as described previously (21), with slight modifications. A sample (0.1 g) of PF was weighed into a pre-weighed 1.5 ml eppendorf tube. One ml of sunflower oil (density = 0.9241 g ml--1) was added, vortex mixed for 1 min and then allowed to stand for 30 min at ambient temperature. The mixture was centrifuged (3000 g, 20 min), the supernatant removed and the weight of the tube was recorded. Fat absorption capacity (milliliters of oil per gram of sample) was calculated as follow: FAC = (W2-W1) / (Wo D) Where W2 is the weight of the tube plus the sediment (g), W1 is the weight of the tube plus the dry sample (g), W0 is Labuckas D. y cols. the weight of the dry sample (g) and D is the density of the oil. Emulsion properties. Emulsifying activity (EA) and emulsion stability (ES) were investigated by the methods described by Pearce and Kinsella (24) with some modifications. For the emulsion formation, a volume of 50 ml of a 0.5 g/dl aqueous protein solution was blended with 50 ml vegetable oil for 45 s with Brown mixer at maximum speed. An aliquot of 200 ul of the emulsion was taken and diluted to 10 ml with 0.1 g/ dl sodium dodecyl sulfate. The absorbance of the resulting sample was read at 500 nm using a UV/VIS Spectrophotometer (Perkin Elmer Lambda 25). The absorbance at time zero was taken as EA, and the time required for the EA to decrease by half as ES (25). Preparation of peanut flour products Preparation of breads. Three types of breads were prepared and coded WB (100 % wheat flour), PFB1 (replacement 10 % wheat flour by PF), and PFB2 (replacement 20 % wheat flour by PF). Other basic ingredients were shortening, brewer´s yeast, salt and water. The percentage amounts of each ingredient were as follow: 63.4 % flour, 0.65 % shortening, 0.65 % brewer´s yeast, 1.0 % salt, and 34.3 % water. Flours were mixed with water and salt using a wire whip during 5 min. Shortening and brewer´s yeast were added and all the blend mixed for 35 min. After 3 hours fermentation, the dough was cut in cylinders of 10 cm diameter, and baked in gas-fire oven (190 ºC, 1 hour). Preparation of cookies. The basic ingredients used for peanut flour cookies (PFC) and wheat flour cookies (WFC) were: 10.5 % flour, 15.7 % shortening, 2.2 % water, 42.0 % corn fecula, 11.8 % egg yolk, 15.7 % sugar and 2.1 % baking powder. Shortening, egg yolk and sugar were mixed thoroughly with whip for 5 min. Fecula, flour (peanut or wheat) and baking powder were added and mixed 5 min. Water was added and rubbed in until uniform. The dough was rolled to 5 mm thickness, cut to 60 mm diameter and baked in gas-fired oven (180 ºC, 12 min). Chemical composition of peanut flour products Total solids content of breads and cookies was calculated by drying 50 g samples at 50 °C for 3 days. The nitrogen, oil, ash and crude fiber contents were determined from dehydrated material using standard methods (20). Protein content was calculated as % N x 5.46 or 5.7, for peanut or wheat products, respectively. Oils from PF, breads and cookies were extracted separately with n-hexane in a Soxhlet apparatus during 12 hours. The extracted lipids were dried over anhydrous sodium sulphate and the solvent was removed by vacuum distillation at 40 ºC. The fatty acid methyl esters of oils were prepared and analysed by gas chromatography (26). Mineral analysis was carried out by digestion of dry samples (2 g) with a mixture of 25 ml of 19 g/dl HCl and 5 ml of concentrated HNO3. The mineral constituents were determined by atomic absorption spectrophotometry (27). Sensory evaluation Breads and cookies were subjected to sensory evaluation using fourteen panelists drawn within the University community. Breads products were evaluated for crust and crumb color, aroma, taste, crust and crumb texture and overall acceptability. Cookies were evaluated for color, aroma, taste, texture and overall acceptability. The ratings were carried on a 9-point hedonic scale form 9 (like extremely) to 1 (dislike extremely).


Rev Nutr 43-4
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