Development Of Edible Nanoemulsion Composite Coating And Its Preservation Effect On Blueberry

Blueberries are well known for their unique flavor,rich bioactive compounds,and health functions.However,fresh blueberry fruits are very susceptible to postharvest changes due to water loss and mold decomposition.The shelf life of blueberry fruits could be prolonged by using UV irradiation,modified atmosphere packing,High voltage electrostatic field and so on.However,it is restricted to be widely used due to high cost and energy consumption.The edible coating materials enriched with functional ingredients is a green preservation method,which could improve the microenvironment around the fruit by establishing a selective barrier.However,current composite coating still has some shortcomings,such as poor physical and chemical properties,poor functional characteristics.Composite edible coating material was widely applied for its excellent physical and chemical properties and encapsulation.Plant essential oil nanoemulsion is an excellent food additive with good stability and bioactive.Hence,a new type of edible composite coating was prepared by combining plant essential oil nanoemulsion with edible composite matrix in this work.The new edible composite coating was applied for conserving the quality of cold-stored blueberry.The main research works are summarized as follows:(1)Study on the preparation and properties of plant essential oil nanoemulsion.The different species of plant essential oils(Neem oil,Baobab oil,Moringa oil)were selected to prepare the different essential oil nanoemulsions.Physicochemical and phytochemicals property of the essential oil nanoemulsion was measured to evaluate their Functional characteristics.The results indicated that Neem oil nanoemulsion(NNE)showed the smallest particle diameter(99.3),best whiteness index(34.51),antimicrobial ability and storage stability.(2)Study on the preparation and properties of edible nanoemulsion composite coating.Edible composite material based on different mass ratios(0:1,1:0,1:1,1:2,1:4)of chitosan(CS),gum arabic(GA)were prepared.The NNE as the functional ingredient was added to the different coating materials to develop different edible composite coatings.All the coatings showed good stability,antioxidant capability and antimicrobial capability.The edible composite coating based on mass ratios of CS,GA at 1:2 showed the best stability,antioxidant capability(54.8%),antimicrobial capability and NNE retention(62.4%).The results indicated that the edible material based on mass ratios of CS,GA at 1:2 was the ideal composite matrix due to its best physicochemical properties and wrapping property.(3)Study on the effect of different coating materials on postharvest quality of blueberries during cold storage.The different concentrations(0%,1%,2%,4%)of NNE as the functional ingredient was added to the coating materials based on 1:2 mass ratios of CS/GA to develop different edible nanoemulsion composite coatings.The different composite coatings were applied for conserving the quality of cold-stored blueberry.In comparison with the control group,all the coating treatments improved the postharvest quality of blueberry.The CS/GA composite coating enriched with 2% NNE showed the better performance on inhibiting microbial growth and enzyme activity,maintaining polyphenol content(280.8 mg/100g)and anthocyanins content(102.2 mg/100g),and as well as reducing fruit browning index(1.55)and decay percentage(5.6%).The above results showed that the CS/GA composite coating enriched with 2% NNE show the optimal performance.The above results indicated that edible nanoemulsion composite coating based on 1:2 mass ratios of chitosan CS,GA enriched with 2% NNE was the ideal coating material.This coating effectively improved the postharvest quality of cold-stored blueberry.This composite coating was expected to be a new biomaterial for conserving the quality of blueberries.