Preparation Of V-Starch And Its Application In Ethylene Encapsulation And Controlled Release

Ethylene,a natural ripening agent for fruits and vegetables,is widely used in food and agriculture.However,it is usually stored and transported in cylinders.It is exposed to risks such as leakage and explosion,and has no sustained release effect.The subject uses different alcohol-induced V-starches as carriers to carry ethylene,studying the relationship between different molecular structures and ethylene loading,revealing the adsorption mechanism of ethylene,and finding the sustained release properties of ethylene in complexes and at different temperatures and relative humidity.The research results have theoretical guiding significance for the development of new ethylene carrier materials.Using native potato starch as raw material,V-starches with different single helix content?6.35²5.31%?and cavity size?V₆ and V₇?was prepared by methanol,ethanol,n-propanol,isopropanol and tert-butanol.The ethylene was carried by solid adsorption method.Fourier transform?FT-IR?infrared spectroscopy and Raman spectroscopy confirmed that the presence of ethylene gas in the V-starches,and the ethylene concentrations in inclusion complexes followed the order of n-propanol?13.46%?>isopropyl alcohol?13.26%?>ethanol?11.86%?>tert-butanol?9.28%?>methanol?6.66%?.The release kinetics study shows that under different temperature and relative humidity conditions,the ethylene release rate increases with the increase of temperature and humidity.Avrami's equation was used to analyze the release mechanisms from inclusion complexes,and the result showed that the ethylene release conforms to the diffusion release mechanisms in temperatures experiment,whereas the release mechanism in relative humidity experiments resembled first-order kinetics.Among the five V-starches,V-starch prepared by ethanol has higher adsorption rate and better controlled release characteristics.V-starch prepared by tert-butanol has lower ethylene adsorption rate and best controlled release characteristics,because tert-butanol occupies a part of the starch single-helical cavity and the binding is relatively stable.In order to further increase the ethylene concentration in the inclusion complexes and achieve lower release rate,the V-starch prepared by ethanol is respectively combined with butyric acid,caprylic acid and lauric acid,and the free fatty acid is removed by ethanol.The results of headspace gas chromatography showed that the concentration of ethylene in the complexes increased by about 2 to 3%?w/w?after removal of fatty acid.The long carbon chain of saturated fatty acid enters the starch granule through the surface crack of starch granule.¹³C nuclear magnetic spectroscopy proves that the fatty acid does not form a type I or type II complex with starch.FT-IR spectroscopy proves that the fatty acid can be completely removed by ethanol,which make ethylene binding sites in the starch particles increase,and the ethylene concentration increases.The release kinetics of ethylene gas in the inclusion complexes showed that the ethylene diffused from the solid phase to the gas phase under different temperature conditions,whereas different relative humidity conditions had a significant effect on release kinetics of ethylene.The fatty acid was coated on the surface of starch granules,which helped to improve the controlled release characteristics of ethylene gas under different temperature conditions.