Effect Of Coating Treatments On Quality And Postharvest Physiology Of Pitaya

Red pitaya is a new tropical fruit,which has high nutritional value and health value.The fruit contains high water,has a high metabolism and a short shelf-life.Currently,the reseach reports on postharvest physiology and storage of pitaya are rare.In this study,several tests were studied on effects of different coating substances on fruit quality,and effects of combined coating agents on quality and postharvest physiology of red pitaya.The study was aimed at providing theoretical-basis and reference for preservation of red pitaya.The main research contents and results were as follows:1.Fresh red pitaya were treated with sucrose-based polymers,sodium alginate, chitosan, konjak gum,carrageenan,xanthan gum,sodium carboxymethylcellulose coatings for room temperature storage(30-32℃).After 11 days of storage,sucrose-based polymers,sodium algi-nate,chitosan had the lowest percentage of weight loss of 6.53%,6.31%,7.82%,respec-tively;and the lowest percentage of rot of 47.22%,43.89%,59.40%,respectively.The three coating substances significantly affected (P<0.05) the percentage of weight loss,rot rate. Whereas.the preservation effect of sucrose-based polymers and sodium alginate coating were significantly better compared with the chitosan coating.2.Sucrose-based polymers,sodium alginate with different concentrations were evaluated for maintaining red pitaya postharvest quality under ambient temperature storage.The results indicated that the concentration of sucrose-based polymers below 5% showed a lower weight loss percentage and rot percentage.3% sucrose-based polymers gave the best preservation effect in that it had the lowest percentage of weight loss 7.65%. After 11 days of storage. Concentration of sodium alginate below 1.5% showed a positive effect on maintaining quality of fruit.Fruit treated with 1% sodium alginate had the best preservation.After 11 days of storage,1% sodium alginate had the lowest rot rate and weight loss rate,but weight loss rate was not significantly different compared to 0.5%.3.The effects of combined coating agents on weight loss rate and decay rate of red pitaya fruit were investigated under ambient temperature storage.The result showed that combined coating agents more effectively reduced the weight loss and decay,and maintained a better freshness appearance of fruit.Coating with 3% sucrose-based polymers+1.5% sodium alginate had the best preservation effect.After storage 11 days,the treatment had the lowest percentage of weight loss and decay was 5.03% ,23.21%,respectively.Whereas,there was not significantly different (P<0.05) among 3% sucrose-based polymers+1.5% sodium alginate,3% sucrose-based polymers+1.0% sodium alginate and 5% sucrose-based polymers+1.0% sodium alginate.4.The effects of combined coating agents on storage quality and postharvest physiology of red pitaya fruit were investigated under ambient temperature and cold storage (10±1℃), respectively.The result indicated that combined coating agents effectively maintained higher postharvest quality of fruit,including soluble sugar,titratable acidity,soluble protein,vitamin C,and maintained higher percentage in water,pigment,insoluble pectin of peel,and thereby maintained freshness appearance and firmness.In addition, combined coating agents effectively reduced MDA content,activity of polygala-cturonase(PG),and improved the activity of(POD),thus, combined coating agents significantly reduced respiratory intensity,and thereby extending storage life. Coating combined treatment significantly extended pitaya postharvest life which stored at 10±1℃, and thereby maintained quality of pitaya fruit for up to 45days of storage.