Pilot-plant-scale test of cold-pressed oil extraction with twin-screw pressing for camellia seeds

Abstract: The oil camellia (Camellia oleifera Abel., Theaceae) is notable as an important source of edible oil (known as tea oil or camellia oil) obtained from its seeds in China. Camellia oil with high oleic acid content is coming more into the focus of interest in recent years since the fatty acid composition is more comparable to olive oil. Another important aspect is that the high content of oleic acid results in a high oxidative stability, making this oil interesting for a wide range of applications. Traditional processing of camellia oil extraction is carried out by seed preparation, cooking, hot pressing, solvent extraction, and refining. This results in the loss of some nutritional component and peculiar flavor due to high temperature. A cold-pressed production process for camellia seeds oil was developed for high-quality, tasty, and natural camellia oil, including storage of raw materials, dehulling, twin-screw pressing, and the purification of crude oil.The developed cold pressing process for camellia oil was investigated in a pilot plant. The results indicated that the residual oil rate in press-cake of 3.6% and oil recovery of 90% over were found while the dehulled camellia seed material contained 8.0% of hulls in the kernels at a moisture content of 6.0% which was expressed in the developed twin-screw press. The maximum barrel temperatures of the twin-screw press during pressing didn't exceed 60℃, which assured production of a good quality oil and the de-oiled cake. The quality of obtained cold-pressed tea seed oil reached the one-level edible oil standard (GB/T11765-2003) for pressing camellia oil. Under these process conditions, a better balance was found between oil yields and quality. Compared with the traditional refined tea seed oil, the Vitamin E content of cold-pressed tea seed oil, which is 2.6 times that of refined oil, is much higher than that of refined oil (P<0.05), and unsaponifiable matter content (1.27 g/kg) was significantly higher than those of refined oil (0.65 g/kg) (P<0.05). As well, unsaturated fatty acid (81.91%) was significantly higher than those of refined oil (79.71%) (P<0.05). These indicate that the nutrition and physiological active component present in camellia oil were more sufficiently extracted from the raw material because of the cold-pressed processing without pre-heating or exposure to any other supply of heat. The quality of cold- pressed camellia cake is significantly better than that of deoiled meal by solvent extraction of pre-pressing cake from unhulled camellia seeds. Crude protein, soluble sugar, and starch content of cold-pressed camellia cake were twice as high as those of the deoiled meal, while mass fraction of crude fiber decreased 55.16%. Mass fraction of tea saponin contained in cold-pressed cake was also about double that of the deoiled meal (P<0.05). Therefore, the cold-pressed cake not only had higher feeding validity, but also would be advantageous to further developing for extraction of tea saponin.An economic feasibility analysis for a cold press oil mill with processing capacity of 30 t/d indicated that a net annual profit of RMB 92.65 million Yuan can be earned, providing a Benefit to Cost Ratio of 1.28:1, with a Pay-Back Period of 0.78 years. Hence, installation of such medium- and large-scale enterprise processing cold-pressed camellia oil in China particularly around mountain areas planting oil camellia could be a profitable proposition.