Study On The Inhibition Effect Of Chitosan/nano TiO₂ Composite Coating On Spoilage Molds Of Mango

Mango,a valuable fruit crop grown throughout the tropical region,is rich in nutrients,delicious,and loved by consumers.In China,mango has a large planting area and high yield,and is one of the main cash crops in the planting area.The mango industry plays an important role in hot zone agriculture and rural economy.However,mangoes are susceptible to microbial infection after harvest.Most of the pathogens that cause mango rot are latently infectious,which will cause the fruit to rot during storage,transportation and sale.Postharvest rot seriously restricts the development of the mango industry.In recent years,studies have shown that the chitosan/nanomaterial composite coating film has an effective fresh-keeping effect on fruits and vegetables,but the application of chitosan/nano-titanium dioxide to the preservation of mangoes after harvest has not been reported.This article addresses the problem of mango being prone to spoilage.First,the spoilage mold of mango was isolated and identified.Then,Chitosan/nano-titanium dioxide is used as a bacteriostatic agent to explore the bacteriostatic effect of different concentrations of composite membrane solution on mold under in vitro conditions.Next,the effect of antibacterial agent on preventing post-harvest mango rot and its resistance induction were studied.Finally,the effect of compound coating on post-harvest physiology and quality of mango was studied,which provided a theoretical reference for mango storage and preservation.The main findings are as follows:（1）Isolation and identification of mango spoilage bacteria and in vitro bacteriostasis experiment of chitosan composite nano-TiO₂.Three strains of mold were isolated by tissue separation method and Koch’s law.Through morphological and molecular biological analysis,the three strains were: Colletotrichum gloeosporioides,Cladosporium oxysporum and Penicillium steckii.The experimental results show that chitosan has a certain bacteriostatic effect on Colletotrichum gloeosporioides,Cladosporium oxysporum and Penicillium steckii,and there are some differences in the bacteriostatic effect on different rot-causing bacteria.Compared with chitosan,chitosan/nano-TiO₂ composite coating has better antibacterial effect.When the content of nano-TiO₂ is 0.3%,it shows a stronger bacteriostatic rate for three kinds of molds,which can effectively inhibit the growth of mycelium,destroy the integrity of the cell membrane,and extravasate intracellular proteins and nucleic acids,and cause the conductivity of the bacterial suspension to increase,cause the death of mold.（2）Chitosan/nano-TiO₂ composite coatings induced resistance to mango spoilage bacteria.Treat the inoculated mango with a composite coating to study the effect of the composite coating on preventing post-harvest mango rot and its resistance induction.The measurement results of physiological and biochemical mechanisms in mango found that: compared with chitosan,the chitosan/nano-TiO₂ composite coating can better inhibit the incidence and the expansion of the lesion diameter,increase the total sugar content and soluble protein content,and induce PPO and POD activity increased,increased the accumulation of total phenols and flavonoids,inhibited the increase in MDA content.（3）Study on chitosan/nano-TiO₂ composite coating for preservation of mango.Through the measurement of various physiological and biochemical indicators in the preservation process,it is concluded that the effect of the chitosan composite membrane is better than that of the chitosan single membrane.Compound coating treatment can better maintain fruit hardness,Vc and titratable acid content,inhibit fruit rot and respiration rate,delay the degradation rate of pectin,and maintain the functional activity of cell membranes.On the 20 th day of storage,the yellowing index of mango was 58.16%,and the weight loss rate was 6.72%,indicating that the chitosan / nano-TiO₂ composite coating played a good role in keeping mango fresh at 13 ℃.