Ohmic Heat Treatment Of Oil-bearing Biomass Materials

The processing or utilization of oil-bearing biomass resources usually involves a series of heat treatment processes,which have a key impact on the extraction efficiency and processing quality of the target products.Due to its inherent characteristics such as low thermal conductivity,weak fluidity and poor homogeneity,it is difficult for oil-bearing biomass materials to obtain uniform and accurate heat supply under the current mainstream exogenous heating approaches,thus facing problems such as loss of target components,generation of processing hazards and time consumption of ineffective energy consumption.In order to realize precise heat treatment of oil-bearing biomass,the application potential of ohmic heating technology based on endogenous heating pathway in heat treatment scenarios such as distillation of volatile plant essential oil,steaming and frying of oil and thawing of frozen meat was explored.The research results are as follows:1.In order to achieve efficient and low-consumption extraction of essential oil from Artemisia argyi leaf,key devices and operating methods for the extraction of essential oil from Artemisia argyi leaf based on ohmic heating distillation were developed.Artemisia argyi leaves were wet-crushed into slurry with water content of 87.5%,and distilled under electric field intensity and frequency of 14 V/cm and 50 Hz,respectively.The total extraction of volatile essential oils from the raw materials could be achieved in 120 min.The extraction efficiency and energy efficiency were far better than that of traditional steam distillation method.A rapid method for the determination of volatile essential oils was developed by combining ohm heating distillation with refractive index.For artemisia argyi samples,the relative standard deviation of this method was not more than 3.33%,and the recovery rate was 95%-100%.The determination accuracy was similar to that of the National Pharmacopoeia method,and the determination time was shortened by more than 60%.For low essential oil samples such as moxa,which are difficult to be determined by pharmacopoeia method,this method can still be used for reliable determination and greatly reduce sample consumption and energy consumption.At the same time,the chemical composition and content of essential oil extracted by the two methods are basically the same,which reflects the superiority of ohm heating method in the extraction of essential oil.2.In order to solve the problems of low efficiency,high consumption and the generation of processing hazards in the pre-processing of steaming and frying oil by pressing oil,the feasibility of accurate steaming and frying oil based on ohmic heating was explored by taking rice bran as a typical sample.The results showed that the thermal efficiency,apparent heat transfer coefficient and heating rate of rice bran ohm heating increased by 9 times,3705 times and 14 times,and the coefficient of temperature variation decreased by 16.81% compared with the mainstream indirect heating method.On this basis,a continuous rice bran heat treatment device with spiral propulsion combined with ohmic heating was developed.The device was used to steam and fry rice bran and press the cooked rice bran to produce oil.The results showed that when the feed moisture content of rice bran was 40%,the heat treatment temperature and time were 100℃ and50 min respectively,the residual oil rate of pressed cake was 10.42%,which was1.01% lower than that after steaming and frying for 3h.The obtained crude oleic acid value was 20.35 mg KOH/g,the peroxide value was 0.39mmol/Kg,the color was Y38.8R4.9,the content of millet was 1.90%,the content of vitamin E was10.20mg/100 g,and the quality was similar to that of traditional crude oil.This study confirmed that the pretreatment of rice bran steaming and frying based on ohmic heating can significantly reduce the heat treatment time consumption on the premise of ensuring the yield and quality of pressed crude oil.3.In order to solve the problems of traditional water thawing,such as long time consuming,large loss of nutrients and microbial contamination,a frozen meat rapid thawing device and process based on ohm thawing was developed.When the electrode plate area is 80% of the projected area of frozen meat in the direction of electric field,the spacing is 105-120% of the thickness of frozen meat in the direction of electric field,the electric field intensity is 23.68V/cm,and the soaking liquid contains 5% sucrose and 0.02% Na Cl,the thawing time of chicken breast is 10.85 min/200 g.Temperature difference between core and surface is not more than 5.5 ℃,thawing weight loss rate is not more than 1.05%.Under the conditions of the apparatus and technology,the thawing time of the hind leg meat with high adipose tissue content was 7.67 min/200 g.It has been proved that ohmic heat thawing can be widely used in frozen meat with various structure or composition,and a new thawing method is expected to be developed.