Heat Transfer Analysis And Experimental Study Of Post-harvest Fruit And Vegetable Heat Treatment

Hot water treatment can effectively improve the storage quality and shelf life of postharvest fruits and vegetables.The essence of this method is the heat transfer process of heat transfer from high-temperature treatment media to low-temperature fruit and vegetable tissues.However,most studies currently only focus on the biological aspects of fruits and vegetables from heat treatment.The impact of heat treatment is unfolded.From the perspective of heat transfer,the internal mechanism of heat treatment affecting biological preservation is less,and most of the studies only discuss continuous heat treatment.Based on the above problems,this paper uses a combination of theoretical simulation analysis and experimental testing to analyze and verify the heat transfer factors that produce heat preservation effect,then provides a theoretical reference for exploring more differences from conventional continuous heat treatment schemes.The main work of the full text is as follows:This paper summarizes the hot water of 6 kinds of fruits and vegetables("Minle" apple pear,"Small Taiwanese Farmer" mango,Gannan navel orange,"Yongfeng" strawberry,"Ya Fu Rosa" grape and "Dasher3" cucumber)through literature research.Treatment temperature and time,and CFD two-dimensional non-steady-state heat transfer simulation of its hot water treatment process.This work explores the main reasons for heat preservation to produce freshness and heat damage from the perspective of heat transfer.Meanwhile provides a new idea for predicting the heat treatment temperature and time range of other fruit and vegetable varieties,which is the range of different fruit and vegetable heat treatment conditions should be based on their varieties as much as possible.Characteristics(physiological,physical characteristics,etc.)and heat transfer characteristics of the heat treatment process are derived together.The post-harvest cherries were used as samples,they were subjected to conventional continuous and intermittent hot water treatments.The weight loss rate,browning index,respiratory strength,soluble solids content,titratable acid,hardness,and cell microstructure were selectively tested during storage.After the storage index was obtained,the heat transfer characteristics of the two heat treatment processes were obtained.The results showed that intermittent hot water treatment can effectively improve the storage quality of cherry.At the end of storage,the intermittent treatment group reduced the weight loss rate,browning index and respiratory intensity by 16.6%,37.3% and 28.8%,soluble solids and titratable acid were 13.8% and 1.71%,and the hardness was 1.89 times that of the control group,and maintain a good cell structure and morphology.This work analyzes the internal reasons for intermittent hot water treatment to improve the storage quality of post-harvested cherries from the perspective of heat transfer,which is the appropriate temperature treatment during heat treatment can block the accumulation of thermal stress and avoid thermal damage.At the same time,the corresponding changes in temperature Heat transfer induced stress physiological changes in cherries.The post-harvest Nanfeng Tangerines were used as samples,they were subjected to conventional continuous and variable temperature hot water treatment.The weight loss rate,decay rate,soluble solid content,acid content,chewability,elasticity,sensory quality,skin perimeter structure during storage were selectively tested.And the heat transfer characteristics of the two heat treatment processes were obtained.The results showed that the temperaturechanging hot water treatment could effectively improve the post-harvest Nanfeng Tangerines storage.At the end of storage,the highest rate of rot and weight loss in the variable temperature treatment group were 26.6% and 79.7% of the control group,respectively.The soluble solids and acidity were 16.45% and 1.3g / 100 mL,respectively.The skin structure was smooth and full,which improved the overall acceptability.From the perspective of heat transfer analysis,the variable temperature hot water treatment significantly improves the post-harvest storage quality of Nanfeng tangerine,which may be related to the step temperature increase of the variable temperature treatment resulting in a higher heat transfer rate in the center of the fruit at the later stage of the treatment,effectively enhancing the accumulation of nutrients.