Physicochemical and sensory properties of a chip-type snack food based on defatted peanut and soy flour
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Raw peanuts contain 45% oil, and mechanical extraction leaves 12-14% fat in the press cake. Peanut press cake is rich in protein and relatively low in fat; however, almost all of it is currently used as animal feed or fertilizer since the peanuts used in the oil extraction process are not edible grade. The goal of this research was to develop a chip-type snack food based on partially defatted flour processed from edible grade peanuts. In a preliminary experiment, chips were produced from a mixture of peanut flour and either soy or corn flour. A consumer test showed that the panelists did not consider the chips completely acceptable. However, peanut-corn chips had a higher rating than peanut-soy chips for overall liking (4.9 versus 4.4, on a 9-point hedonic scale) and acceptability (46.7% considered the peanut-corn acceptable, compared with 40.7% for peanut-soy chips). A second generation of peanut chips was produced by mixing 3 parts of peanut flour with 1 part of soy flour or wheat flour, cornstarch, peanut butter and sugar. A trained panel characterized the sensory attributes of the peanut chips in an analytical sensory test. Only a few significant differences in sensory quality were found between the peanut-soy chips and the peanut-wheat chips. However, the hardness appeared to be the biggest concern about the new product, with shear stress values close to 1000 N/g. In a third experiment a new series of peanut chips was produced, containing peanut flour and soy in the ratio of 3:1, in addition to variable amounts of sugar, starch and peanut butter. A factorial design was used, with sugar, starch and peanut butter at three different levels. Twenty-seven formulations were produced in replicate. Kramer shear force, instrumental color and consumer acceptability were analyzed. The Kramer shear value was 441 N/g chip in formulations with high percentages of sugar, starch and peanut butter. Response surface methodology (RSM) was applied to investigate the optimum levels of each ingredient in the chips. Contour plots were built for each physical and sensory characteristic. They showed that chips made with the highest level of sugar, starch and peanut butter were about half as hard as chips made with the lowest level of each ingredient.