Effect Of W/O/W Double Emulsion On Quality And Physiology Of Postharvest Broccoli During Storage

Broccoli is rich in nutrients and is loved by consumers,however it has a short storage period due to its strong respiratory metabolism after harvest and its yellowing and browning reactions.In order to improve the quality of broccoli during storage and prolong the shelf life,the method of film preservation is generally applied.In this paper,a novel water/oil/water(W/O/W)double emulsion was selected as the study object to explore its effects on the storage and preservation quality and physiological characteristics of broccoli as a film preservative.W/O/W double emulsion was able to be used to load functional ingredients enabling simultaneously encapsulate and transport two substances with hydrophilic and lipophilic properties.Coating it on the surface of fruits and vegetables was proven to be a safe and effective measure for their storage and transportation.The main content and conclusion of the paper are as follows:(1)The method of preparing the W/O/W double emulsion was studied.The double emulsion was characterized for different polysaccharide materials and ratios in the compound.The effects of different protein-polysaccharide complexes as embedding wall materials on the morphological structure,stability,particle size,viscosity and other indexes of the double emulsion were analyzed.The research results showed that the two-step method was the proper measure to prepare the W/O/W double emulsion.And the double emulsion prepared by the compound of whey protein concentrate(WPC):pectin(PEC)=1:3 had the tightest microstructure and the best storage stability,which also made its particle size and viscosity become large.(2)In order to fully understand the value of W/O/W double emulsion in practical application,the preservation effects of W/O/W double emulsion coating film on broccoli fruit were studied.Simultaneously,the fresh-keeping effects of W/O/W double emulsion on broccoli color,relative conductivity,malonic dialdehyde(MDA),antioxidant activity,total colonies and nutrients were analyzed.It was found that broccoli treated with W/O/W double emulsion coating was able to maintain a brighter color during storage.Moreover,the double emulsion treatment significantly delayed the decline in relative conductivity,MDA content(p<0.05),and the yellowing and browning reactions of broccoli during storage period.The double emulsion also made broccoli retain relative high total phenol content,total flavonoid content and 1,1-diphenyl-2-picrylhydrazyl(DPPH)free radical scavenging activity.And it helped broccoli keep a low total number of colonies and high glucosinolates(GSL)content,which showed that it had a significant effect on the preservation of broccoli.(3)The effects of W/O/W double emulsion coating on broccoli chlorophyll and energy metabolism related indexes were further studied.W/O/W double emulsion coating treatment was capable of keeping broccoli maintain low chlorophyllase content and demagnesium chelatase activity and inhibit chlorophyll degradation leading to prevent premature yellowing reaction of broccoli.Study showed that the emulsion was excellent in maintaining energy levels,delaying the decline of adenosine triphosphate(ATP),adenosine diphosphate(ADP)content and energy charge,inhibiting the rising of adenosine monophosphate(AMP)content.Apart from that,the protected broccoli acquired high activities of H⁺-ATPase,Ca²⁺-ATPase,cytochrome C oxidase(CCO)and succinate dehydrogenase(SDH).What's more,high activity of these enzymes not only had a significant positive effect on maintaining the quality of broccoli,but also further verified the good preservation properties of the W/O/W double emulsion.