| Peanut is one of the most important oilseeds and an important protein resource in the world. The oil content of peanut is about50%and the protein content is24%-36%. Peanut protein is an ideal food protein resource, which accounts for11%of the total protein in the top three plant protein resources. The classical processing methods for peanut oil include mainly pressing and soaking with organic solvent. However, both the main methods are of imperfection, the pressing way with high residual oil rate, labor intensive and energy consumption, and the solvent extraction with residual organic solvents and the protein under-utilization. It’s necessary to find a new method that could extract oil from peanut with high oil extraction rate and no residual organic solvents. The supercritical carbon dioxide fluid extraction technology is known as green technology, which could solve the problems of the traditional methods with huge market potential. The main conclusions of this paper were as follows:A method utilizing supercritical CO2fluid extraction (SFE-CO2) technology to extract peanut oil was described. The optimum technological conditions were obtained by single-factor and response surface experiments, and parameters that affect extraction rate, such as peanut granularity, extraction pressure, time, temperature and supercritical CO2flow were investigated. The order of factors that influenced the oil extraction rate was as follows:extraction temperature> extraction time> extraction pressure. The highest extraction rate96.16%was achieved in the optimum extraction conditions with20mesh peanut at20L/h CO2flow in the pressure of24MPa for110min at43℃.12compositions had been extensively determined in peanut oil by SFE-CO2method on the basis of gas chromatograph-mass spectrometer (GC-MS,NIST10spectral database) detection methods. Saturated fatty acids (mainly palmitic acid,11.27%) and unsaturated fatty acids (oleic,45.68%and linoleic,32.42%) in the SFE-CO2extracts were20.11%and79.32%, respectively. While,9compositions were identified by GC-MS in the organic solvent extracts. The saturated fatty acids and unsaturated fatty acids in the extracts were21.07%(palmitic acid,11.30%) and78.14%(oleic,44.79%and linoleic,32.31%), respectively. Compared with the organic solvent extraction method, the peanut oil by SFE-CO2method with higher content of unsaturated fatty acids, lower acid value and peroxide value, was obviously superior in quality.Peanut protein isolate was prepared through alkali extraction and acid precipitation from low variability peanut meal. The optimal values of theoretical parameters including extraction temperature, ratio of liquid and material, extraction time and extraction pH were investigated by Box-Behnken surface response design method. The optimum conditions of alkaline extraction:extraction temperature57.5℃, pH9.2, ratio of liquid and material12:1and extraction time100min, based on the single-factor test, the optimum pH4.5of acid precipitation were determined. Under these conditions, a maximum protein extraction rate of87.57%was obtained. The relative error with predicted value was0.4%.Peanut protein milk powder was prepared by the ultramicro-porwderized protein isolate residues and low-denature peanut meal, mixing with whole milk powder. The products had the peculiarity of both milk flavor and peanut-specific flavor with high solubility, good dissolving ability, smooth taste and balanced nutrition. |
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