Study On The Quality And Mechanism Of Ldpe/Calcined Shell Powder Function Film Packaging On Fresh-Cut Apple During Storage

Fresh-cut apples have been considered to have great commercial prospects as a ready-to-eat type of processed apple product with rich nutritional value.In this work,fresh-cut apples were used as research objective to study the effects of conventional LDPE films（thickness:15,40,60μm）and LDPE/calcined shell powder functional films（thickness:60μm）packaging on the quality deterioration of fresh-cut apples under different storage temperatures（23℃,4℃）.The effect of LDPE/calcined shell powder functional film packaging on the softening characteristics and cell wall material degradation of fresh-cut apples during storage was deeply studied.The mechanism of the preservation effect of this functional film was initially investigated.This research could provide guidance for fruit and vegetable preservation and film packaging technology.The main study contents and results are divided as follows:（1）In order to better study the effect of films and their functional components on the quality of fresh-cut apples during storage,the performance of packaging films was tested and characterized which revealed that:LDPE/calcined seashell powder functional films have lower water vapor transmission（WVT）,oxygen transmission（OT）and light transmission rates than conventional LDPE films.LDPE/calcined shell powder functional film exhibits better antibacterial properties than conventional LDPE films.Optical microscope test results showed that the addition of calcined shell powder reduced the surface smoothness and flatness of the LDPE material.（2）LDPE/calcined shell powder functional film packaging combined with 4℃storage resulted in better quality（physicochemical and nutritional quality）of fresh-cut apples,effectively inhibited the increase in p H,the decrease in total phenolic content and the rise in relative conductivity,delayed the softening of the texture of the fruit and maintained the storage quality of fresh-cut apples.Correlation analysis showed that the addition of calcined shell powder particles enhanced the correlation between the firmness of fresh-cut apples in LDPE film packaging and its weight loss（23℃）,total phenolic content（23℃）,p H（4℃）,and relative conductivity（4℃）.（3）The effects of LDPE/calcined shell powder functional film packaging on the softening quality of fresh-cut apples during storage were further investigated by measuring and analyzing the cell wall substance content,infrared spectrum of pectin,total calcium content and morphological changes of flesh cells in four test film packages during 8 d storage（23℃,4℃）.The results showed that LDPE/calcined shell powder functional film packaging combined with4℃storage reduced the hydrolysis rate of starch in fresh-cut apples,inhibited the conversion of raw pectin to soluble pectin,increased the content of water-soluble pectin（WSP）and ion-bound pectin（ISP）,and decreased the content of covalently bound pectin（CSP）as well as hemicellulose and cellulose.Fourier infrared spectroscopy（FTIR）scans showed that the soluble pectin of fresh-cut apples inside the LDPE/calcined shell powder functional film package was low methoxylated pectin,which was easily cross-linked with Ca²⁺.Scanning electron microscopy（SEM）observation of LDPE/calcined shell powder functional films before and after storage showed that the calcined shell powder embedded,semi-embedded or free on the film surface after preservation storage swells due to hydration reaction and its irregular surface porous structure changes,and that hydration may lead to calcium migration and the reaction of calcined shell powder particles with CO₂ inside the package to avoid excessive CO₂ concentration in the microenvironment inside the package.Atomic absorption spectroscopy（AAS）test results showed that LDPE/calcined shell powder functional film packaging increased the total calcium content of the fruit.Microscopic observation of apple flesh cells before and after storage showed that LDPE/calcined shell powder functional film packaging reduced the occurrence of cell wall rupture and other phenomena in fresh-cut apples during storage and maintained the structural integrity of fruit cell walls.Correlation analysis showed that the addition of calcined shell powder particles enhanced the correlation between the firmness of fresh-cut apples in LDPE film packaging and the content of its starch and cell wall components（23°C,4°C）.