Study On Soil Nutrients And Fruit Quality Of Pitaya And Its Drying Technology In The Karst Region

Exploring distribution of soil nutrient,characteristics of fruit quality about Pitaya,relationship between the soil nutrient quality and characteristics of fruit quality about Pitaya,and the processing technology applicable to the fruit of Pitaya in karst area to provide a scientific basis for restoring the soil environment in karst rocky desertification area and improving the quality of Pitaya.Selecting Zhenfeng-Guanling Huajiang area of Guizhou Province which represents the overall structure of the karst ecological environment in southern China as the survey area.The samples of soil and Pitaya fruit were were taken in the study area in 2017 and relevant indicators were determined.,respectively and tested the corresponding index.Exploring the soil nutrient status of Pitaya,the fruit quality of Pitaya and the relationship between them under different slope,slope position,intercropping mode and sampling time in Pitaya planting area of karst.Vacuum freeze-drying technology was used to study Pitaya fruit.Conclusion as below:(1)Slope position,slope gradient,intercropping mode and sampling time all have certain effects on soil nutrient.The comprehensive nutrient quality of Pitaya sample plot affected by different factors is obtained by using membership function.Generally,there is no significant difference in the comprehensive fertility evaluation results of soil nutrients in different sampling areas of pitaya,but in different sampling areas of pitaya,there is a middle slope position > lower slope position.The soil nutrient comprehensive nutrient law of slope position > uphill position;with the increase of slope degree,the soil nutrient comprehensive quality score showed a trend of first increasing and then decreasing.The soil nutrient comprehensive quality law of different slopes was 12 > 5>18.Among them,the soil nutrient comprehensive quality of uphill position was the worst.In order to ensure the normal demand of nutrient for the growth and development of Pitaya fruit,the uphill position needed to increase artificial nutrient.Amount of fertilizer.Intercropping of pitaya fruit is beneficial to improving soil nutrients.The quality of soil nutrients in different intercropping types is as follows: pitaya fruit(0.6402)< pitaya fruit + sweet potato(0.7384)< pitaya fruit + pepper(0.7934);from 2016 to 2018,the soil nutrients in pitaya fruit sample decreased year by year.Principal component analysis and stepwise regression analysis were used to analyze and evaluate the related quality indicators of pitaya fruit under four different soil conditions.11 quality indicators including soluble solids,protein,total sugar,total acid,sugar-acid ratio,proanthocyanidins,calcium,magnesium,potassium,Vc and total dietary fiber were determined and analyzed.The results showed that the ratio of sugar to acid,soluble solids,calcium and magnesium was 4.Each representative index contributes most to the comprehensive evaluation.(2)Principal component analysis and stepwise regression analysis were used to analyze and evaluate the related quality indicators of pitaya fruit under four different soil conditions.11 quality indicators including soluble solids,protein,total sugar,total acid,sugar-acid ratio,proanthocyanidins,calcium,magnesium,potassium,Vc and total dietary fiber were determined and analyzed.The results showed that the ratio of sugar to acid,soluble solids,calcium and magnesium was 4.Each representative index contributes most to the comprehensive evaluation.The relationship between soil nutrients and fruit quality in Pitaya plantation in karst area was preliminarily revealed by correlation and redundancy analysis.The results of correlation analysis showed that there was a significant negative correlation between organic matter and total acid and total nitrogen content,and a significant positive correlation with organic matter;protein and total nitrogen had a very significant positive correlation;protein and organic matter content had a significant negative correlation;total dietary fiber and total nitrogen content had a significant positive correlation.Redundancy analysis showed that total phosphorus had a significant positive effect on total dietary fiber,which was the dominant factor affecting total dietary fiber.Organic matter was an important factor affecting soluble solids.Hydrolyzed nitrogen mainly affected total sugar,and available potassium mainly affected Vc content.The order of importance of soil nutrients on nutrient composition of pitaya fruit was total phosphorus > available phosphorus > pH > total nitrogen > available potassium > total potassium > organic matter > hydrolyzed nitrogen.(3)The quality of the dragon fruit in the uphill position is inferior to the mid-slope position and the downhill position,while the total dietary fiber content tends to decrease with the decrease of the slope position.With the increase of slope,the nutrient composition of dragon fruit in the fruit of dragon fruit first increased and then decreased,but the nutrient content of dragon fruit collected under the maximum slope was higher than the minimum slope.When the slope is 18°,the nutrient composition of dragon fruit is the best.The main nutrient content of dragon fruit collected under different sets of methods showed the regularity of Pitaya <fire Pitaya + sweet potato < Pitay + pepper.With the increase of the planting time of Pitaya,the nutrient content of dragon fruit showed a decreasing trend.Among them,the total sugar and vitamin C content increased first and then decreased;the ratio of sugar to acid showed a downward trend.The content of soil organic carbon decreased first and then increased.The content of nutrient components in other fruits decreased with the increase of planting month.In general,the harvest time has little effect on the quality of Pitaya.(4)Pitaya vacuum freeze-drying experiment,the results show that the temperature of eutectic point of dragon fruit is(-18±2)°C,and the temperature of eutectic point is(-11.1±2)°C.On the basis of single factor experiment,three factors affecting vacuum freeze drying were analyzed by orthogonal test.The optimum process parameters of vacuum freeze drying of dragon fruit were 10 mm thick and sublimation.The temperature was 25 °C and the analytical temperature was 50 °C.The sensory score,vitamin C content,protein content,total dietary fiber content and sugar-acid ratio of the Pitaya were 95,74 mg/100 g,9 g/100 g,22.5 g,respectively./100 g,64.37.This study provides a theoretical reference for the intrinsic quality retention of Pitaya after drying,and is an effective technical means to improve the added value of Pitaya fruit.