Study On Absorption And Diffusivity Of1-MCP In Postharvest Fruit And Maintaining Its Quality

Absorption and diffusion of1-MCP in apple (Malus domestica Borkh.) and tomato(Solanum lycopersicum L.) fruit were studied, and changes in surface wax composition of‘Red Fuji’ apple (Malus domestica Borkh.‘Red Fuji’) during development (30d and10dbefore harvest) and during storage at (0±1)℃after1-MCP treatments were investigated, andphysiological quality of ‘Red Fuji’ apple during storage at (0±1)℃after1-MCP treatmentswas evaluated, and effects of combination of1-MCP and HH on tomato (Solanumlycopersicum L.‘Tasti-Lee’) were identified. The main results of this study were exhibited asfollows:1. Eight varieties of apple ‘Honeycrisp’,‘Cameo’,‘Gala’,‘Delicious’,‘Empire’,‘Rome’,‘McIntosh’ and ‘Redcort’ were studied. It accumulated the relative maximum amount ofinternal1-MCP with treatment12h for whole apple, and1h for fresh-cut apple slices. Ingressof gaseous1-MCP varied significantly among the apple varieties tested.‘Honeycrisp’accumulated the highest internal1-MCP, followed by ‘Cameo’ and ‘Gala’.‘Delicious’ and‘Empire’ had the moderate internal1-MCP. However,‘Rome’,‘McIntosh’ and ‘Redcort’accumulated the lowest internal1-MCP. The content of internal1-MCP in ‘Honeycrisp’ was69-fold high compared with ‘Redcort’. Wax treatment caused significant declines in1-MCPingress among all cultivars. Ingress/accumulation of gaseous1-MCP did not occur infresh-cut tissue. However,1-MCP in the jar was nearly delepted. Accumulation trends of1-MCP in fresh-cut tissue of the different varieties treated with antioxidants closely paralleledthose of intact fruit, and it was significant different among eight apple varieties. Varietydifferences in ingress of gaseous1-MCP could reflect differences in intercellular diffusivity,and capacities for physical sorption or metabolism. Excised fruit tissues are likely not suitablesystems for estimating1-MCP diffusivity in fresh-cut fruits, possibly due to1-MCP wasdestroyed by reactive oxygen species (ROS) induced by wounded. However, it is anappropriate model after apple slices were treated with tissue aging, anoxia, and theantioxidants ascorbate and hypotaurine to alleviate wound-related oxidative metabolism.2. Disks from tomato epidermis and stem-scar were used to examine ingress of gaseous1-MCP using a dual-flask system. Changes in1-MCP concentrations in the dual-flask system showed different patterns between tomato epidemis and tomato stem-scar. For tomatoepidermis tissues,1-MCP and ethylene in the top (source) flask did not deplete, and in thebottom flask it did not accumulate. However, for tomato stem-scar,1-MCP declined as muchas70%in source flasks with negligible accumulation in sink flasks, the pattern of ethylenedistribution was markedly different from that of1-MCP, which approached equal distributionwith tomato stem-scar.1-MCP ingress was further addressed by exposing whole tomato fruitto20μL L-11-MCP followed by sampling of internal fruit atmosphere (1-MCP). Tomato fruitaccumulated internal gaseous1-MCP rapidly, reaching approximately7to9μL L-1within3to6h at20℃. Internal1-MCP declined around74%and94%at1h and3h after exposure,respectively. Ingress was similar at all ripening stages and reduced by45%in fruit coatedwith commercial wax. Blocking1-MCP ingress through stem-scar and blossom-scar tissuesreduced accumulation by around60%, indicating that ingress also occurs through epidermaltissue. Fruit preloaded with1-MCP and immersed in water for2h retained about45%ofpost-exposure gaseous1-MCP, indicating that1-MCP is not rapidly sorbed or metabolized bywhole tomato fruit. Rapid ingress of gaseous1-MCP was also observed in tomato fruitexposed to aqueous1-MCP. Both accumulation and post-exposure decline in internal gaseous1-MCP are likely to vary among different fruits and vegetables in accordance with inherentsorption-capacity, surface properties (e.g., waxes, stoma), volume and continuity of gas-filledintercellular spaces and tissue hydration.3. Wax composition of ‘Red Fuji’ apple (Malus domestica Borkh.‘Red Fuji’) duringdevelopment and during storage at (0±1)℃after1-MCP treatment was studied by means ofgas chromatography-mass spectrometry. Total waxes were chromatographically separatedinto nonpolar and polar components. There were11nonpolar components and22polarcomponents. Nonacosane was the most abundant nonpolar wax, comprising95.0%of totalhydrocarbons, followed by heptacosane, which was1.6%of total hydrocarbons. Polar waxcomponents were comprised of a series of fatty acids and derivatives and nonacosan-10-oland nonacosan-10-one, the latter two comprised29.0%and16.0%of polar component,respectively. Hexadecanoic acid (16.8%) was the most abundant saturated fatty acid and9,12-octadecadienoic acid (0.4%) was the richest polyunsaturated fatty acid.Total wax, nonacosane, heptacosane and nonacosene increased during development anddecreased over seven months of fruit storage at (0±1)℃. Declines were delayed or slightlysuppressed in1-MCP–treated fruit. By contrast, hexadecanoic acid,9,12-octadecadienoicacid, nonacosan-10-ol and nonacosan-10-one showed variable accumulation trends duringdevelopment, but significant increases during late storage that were strongly suppressed in1-MCP–treated fruit.1-MCP delayed the decline in flesh firmness, titratable acid and sosluble solid content and reduced ethylene and respiration rates and weight loss.1-MCP was moreeffective than control for suppressing changes wax composition and maintaining storagequality.4. The effect of gaseous1-MCP of500nL L-1applied to turning tomato fruit under HH(10kPa,2.1kPa O2) for1h. Application of500nL L-11-MCP under NbC had little effect onsoftening and timing and magnitude of peak ethylene production, and moderate effects onrespiration and lycopene and PG accumulation. By contrast, turning fruit exposed to500nLL-1gaseous1-MCP under HH for1h showed acute disturbance of ripening. Firmness and hueangle declines were delayed for ten days and peak ethylene production for eleven dayscompared with trends for the other treatments. Maximum ethylene production did not exceed50%of maxima for the other treatments and a definitive respiratory climacteric was notobserved. Without1-MCP treatment under HH or NbC had the same effect on tomato qualityand physiology, indicating that HH had minimal effect on tomato ripening and the significantdelay of the fruit softening was the result of the combination of1-MCP and HH, not just byHH alone.In order to further demonstrate the effect of1-MCP under HH, the internal atmosphere1-MCP of the tomato fruit after treatment with20μL L-11-MCP under HH was measured.Internal1-MCP under HH doubled compared with under NbC for treatments1h and10min,internal1-MCP under HH showed a9-fold increase compared with under NbC for treatment2min, indicating that1-MCP can immediately diffuse to fruit under HH. However, oxygencontent in the container under HH had no difference for internal1-MCP.1-MCP under HHtreatment can significantly diffuse to fruit and delay their ripening. The high efficacy of1-MCP applied under HH is due to rapid ingress and accumulation of internal gaseous1-MCP.