Production and consumption of traditional groundnut oil in Thua Thien Hue province and effect of heat treatments on oil's initial quality

Abstract

Traditional production of groundnut in Thua Thien Hue province is small and non-uniform, mainly based on the experience of household producers, thus the oil quality is unstable. The household groundnut oil producers do not pay enough attention to the quality of raw materials, 61.3% did not sort groundnut seeds before pressing while 6.5% did not sediment nor filter the oil before selling for consumption. The groundnut flour was steamed for 28.38 minutes without drying before pressing. Among those surveyed, 89% chose to use traditionally produced groundnut oil because of its natural origin and concentrate while 88% chose based on its safety. Evaluation of the initial quality of groundnut oil by various heat treatments, including steaming groundnut flour for 20, 25, 30, and 35 min and drying the flour after steaming for 5, 10, 15, and 20 min based on the ratio obtained oil, color, and odor, insoluble impurities content, the water content in oil and values of iodine, peroxide, saponification and acid. Our study showed that steaming the groundnut flour for 30 minutes followed by 5 minutes of drying increased the oil expressing yield and produced oil with brighter color, less water content, and higher quality in comparison with the non-dried samples after steaming.