Rice bran extrusion is divided into dry and wet methods. Dry extrusion is to directly feed the rice bran from the rice production line into a dry extruder to puff it. Wet puffing is to inject a small amount of direct steam into the casing during the rice bran expansion process to increase the temperature and humidity of the material in the extruder. The dry expansion equipment has low investment and simple process. It can not regulate the moisture and temperature of the expanded rice before puffing and the expanded material after puffing, but the processing capacity of the equipment is relatively small, the electricity consumption is several times higher than the wet expansion, and the machine parts are worn.
Fast, and the passivation of enzymes in rice bran is not thorough enough, generally only suitable for small-scale production. The advantage of wet expansion is that the oil cells in the expansion process are completely destroyed, the mechanical strength, particle size and capacity of the expanded material are large, the internal cavity has more voids, the outer surface has more free grease, and the oil leaching is better.
The extrusion process completely inactivates the enzymes such as lipolytic enzyme, lipoxygenase and phospholipase in rice bran, which makes the acid value of leaching olein decrease, the content of non-hydrating phospholipid decreases, and the acid value rises slowly during storage, leaching hair The quality of the oil is good. In addition, the introduction of direct steam in the expansion process increases the temperature and moisture of the rice bran, softens it, thereby increasing the output of the extruder, slowing down the wear of the parts, and reducing the power consumption, generally at 15 KW.h/t.
However, the moisture content of the wet-expanded pellets is relatively high, up to 13-15%. It is necessary to equip the cooling equipment to adjust the temperature and moisture of the bulking material, and reduce the moisture to 5%-7% for leaching, so it is dry. The investment cost of the extrusion process is large. Wet extrusion is a widely used process for large and medium-sized rice bran oil extraction plant.
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