Regulation Of Post-harvest Quality And Softening Of Blueberries By Microenvironmental Modified Atomosphere Packaging During Storage And Transportation

In this experiment,"Legacy" blueberries were used as experimental material and treated with microenvironmental modified atmosphere packaging(mMAP),1-methylcyclopropene(1-MCP)and modified atmosphere packaging combined with1-methylcyclopropene(mMAP+1-MCP)to explore the effects of mMAP on the quality of storage under controlled freezing point(-0.5 ± 0.3℃)and shelf life under low temperature(7 ± 1℃)after storage.The effects on cell wall substances and cell wall degrading enzymes and the regulation on softening of mMAP factors of transportation and storage of blueberries during storage and shelf life were also explored.The results were as follows:1、To study the influence of mMAP on the quality of blueberries during storage,the gas composition,sensory quality,firmness index,nutritional quality,physiological index and volatile substances were measured separately,and the principal component score of physicochemical indicators and characteristic volatile substances during storage were applied.The results of the comprehensive scores of the physicochemical indicators and characteristic volatile substances from different treatments were as follows: m MAP+1-MCP > m MAP > 1-MCP > CK,which showed that mMAP+1-MCP treatment had the best preservation on blueberries during storage.The mMAP+1-MCP and the other three treatments were analyzed by orthogonal partial least squares(OPLS-DA)to screen differential indicators and the conclusions were that mMAP+1-MCP could maintain a lower soft fruit rate and ethylene production rate but higher anthocyanin content than the other three treatments.Meanwhile,the content of 2-hexenal,which was the main fragrance substance of blueberries,was suppressed as a whole.2、To study the effect of mMAP on the quality of blueberries during shelf life at low temperature after storage,the sensory quality,firmness index,nutritional quality,physiological index and volatile substances were measured.The comprehensive scores of each treatments during shelf life in order from high to low were that mMAP+1-MCP > 1-MCP > mMAP > CK,which showed that the effect of mMAP+1-MCP on the preservation of blueberries was better than that of mMAP or1-MCP alone.The mMAP+1-MCP treatment and the other three were subjected to OPLS-DA and the conclusions were that mMAP+1-MCP could have higher values offirmness than the others,while at the same time,the content of 2-hexenal would decrease.3、Compared with the control,the three treatments could delay the degradation of cell wall polysaccharides to varying degrees during both storage and shelf life.The blueberries of mMAP and 1-MCP had higher cellulose content at the beginning of storage,which had a direct effect on the cellulose of blueberries during storage.Firmness and cell wall materials during storage or shelf life were analysed by multivariate statistical analysis and the results were that mMAP+1-MCP was separated from the other three treatments and had higher values of cellulose,hemicellulose,propectin and firmness,which were beneficial for fruit quality,during both storage and shelf life.Cellulose and soluble pectin had the highest correlation with firmness during storage and hemicellulose,protopectin and soluble pectin had the highest correlation with firmness during shelf life.The mMAP+1-MCP treatment could maintain higher content of cellulose and hemicellulose during both storage and shelf life,and maintain a better texture.4、Compared with the control,the three treatments could inhibit the activity of cellulase(Cx),polygalacturonase(PG),pectin methylesterase(PME)andβ-galactosidase(β-Gal)during storage and shelf life effectively.Multivariate statistical analysis was performed on the firmness and cell wall degrading enzymes of blueberries during storage or shelf life.mMAP+1-MCP was clearly distinguished from the other three treatments with higher values of firmness and PG had the highest negative correlation with firmness regardless of storage or shelf life.The texture of mMAP+1-MCP was the best.During storage,it showed stronger inhibition of Cx andβ-Gal.During shelf life,it showed better inhibition of PG and PME,which echoed the previous analysis of polysaccharides.