Influence Of High Voltage Electrostatic Field On The Preservation Effect Of Cherry Tomatoes And Design Of Experimental Equipment

Cherry tomato,which belongs to Solanaceae and Lycopersicon Mill,is rich in taste and contains a variety of essential nutrients for human.However,due to its physiological properties and high water content,it is easy to produce quality degradation,which seriously affects sales radius of cherry tomatoes and income of fruit farmers.The preservation treatment of cherry tomatoes is an effective solution to extend its shelf life.The current commonly used preservation technology has high-performance requirements for the equipment.In addition,there are exist problems such as environmental pollution and low efficiency.Recently,radiation,ultrasonic waves,high-voltage pulse electric field,and other emerging preservation methods are also facing with high investment,technological immaturity,and difficulty in adjusting the process parameters,which have not gained widespread acceptance by the industry.As a non-thermal processing technology that can better meet the requirements of high-quality products and low energy consumption in dustry,high voltage electrostatic field(HVEF)has many advantages and is developing rapidly in the field of food preservation.Aiming at prominent problems such as the rapid deterioration of quality in the storage process of cherry tomatoes,this study studied the influence of HVEF treatment on the storage quality of postharvest cherry tomatoes and optimized processing parameters.On the basis of optimizing the electric field processing parameters,the dynamic models and shelf life prediction models of quality deterioration of cherry tomatoes were established and verified.Finally,the structure of the experimental treatment device was optimized to improve the treatment effect.This study provides more references for the development of the process of fruit and vegetable treatment with HVEF.The main research results are as follows:(1)The effects of electric field intensity and treatment time on storage quality of cherry tomatoes were clarified,and the process parameters of HVEF were optimized.HVEF treatment delayed the loss of nutritious components of cherry tomatoes during storage,led to stronger antioxidant capacity,less weight loss and color change,lower microbial loads and better microstructure.In the range of 50～250 k V/m and 30～120 min,the greater the electric field intensity,the longer the treatment time,the better the preservation effect.However,there was a threshold of treatment time,beyond which the improvement effect was no longer obvious.In summary,the best electric field conditions were:150 k V/m,60 min.(2)Influence of ambient temperature on storage quality of cherry tomatoes pretreated by HVEF was studied,and the shelf-life prediction models based on physicochemical indicators and aerobic plate count of cherry tomatoes were established and verified.Low temperature was beneficial to the storage of cherry tomatoes and significantly reduced the quality change rate.During storage,the change of weight loss,color change,p H,Vitamin C content and total phenolic content of cherry tomatoes were more consistent with the zero-order kinetic model,while the change of hardness,soluble solid content and DPPH radical-scavenging capacity were more consistent with the first-order kinetic model.Through Pearson correlation analysis,hardness was selected as the key factor of to establish the shelf-life prediction model of cherry tomatoes.It was verified that the relative errors of the shelf-life prediction model based on the hardness changes were-6.854,3.878 and 7.343%at 6,10,and 20°C,respectively.Compared with Baranyi and Huang model,the modified Gompertz model had a higher degree of fitting with the growth curve of microorganisms in cherry tomatoes(R~2>0.900)with relative errors of-8.146,2.956 and 8.314%,respectively.(3)The optimized design of HVEF preservation test equipment was completed and its treatment effect was evaluated.It was mainly divided into two parts:hardware and software.The hardware part included the design of the mechanical structure,key components,electronic and related components,etc.The software included related control programs,which could realize the automatic adjustment of electrode spacing and complete the continuous turning of cherry tomatoes.Finally,principal component analysis was used to reduce data dimension and establish a comprehensive evaluation model of cherry tomatoes.The results showed that the storage quality of cherry tomatoes treated by this test deviced was better,and the final comprehensive quality score was-1.02,while the final comprehensive quality score of cherry tomatoes treated by common test devices(Static processing system)and stored under low temperature were-1.07 and-1.13,respectively.