Quality Deterioration And Its Laws Of Navel Orange Granulation

Granulation is a kind of physiological disorders during the storage of citrus fruit,and it affects the quality of citrus fruit seriously.It is easy happened during the storage of citrus fruit.Its typical symptom is that juice vesicles become granulated,tough,dry,and taste yucky.There has been no comprehensive and systematic conclusion on the deterioration mechanism of citrus fruits caused by granulation.Quality of granulated citrus fruit decline a lot,and it is very important to analyze the quality changes of citrus fruit under granulation systematically for unraveling its mechanism.However,there is still no systematic study on the deterioration of fruit quality about citrus granulation.In this research,navel orange from Chongqing was used as research materials.Samples was collected during storage,and sample tissues were then used for sensory evaluation and experiments about different indicators.To make the quality deterioration and mechanism of granulation clear,the disorder degree of the fruit was concerned from the results of sensory evaluation,and changes of substances determining those sensory indexes were tested in kinds and contents.Results suggested that:(1)Fruit granulation were accompanied by quality deterioration with overall flavor drops,sensory qualities like acceptability of sweetness,sourness,aroma and chewing performance were extremely low,and these parts could not be eaten any more.The total soluble solids(TSS),titratable acid(TA),ascorbic acid content,juice yield and water content of granulated pulp were significantly lower than those of un-granulated parts.(2)A total of 11 kinds of sugars and 11 kinds of organic acids were identified in either normal or disordered fruits by metabolomics analysis,.And the kinds between both fruits were the same.Sugars like sucrose,glucose,fructose,D-galactose,arabinose,glucopyranose,mannose,maltose and sorbitol were identified to be decreased during granulating,ribose content is relatively stable,and xylose content increased significantly.Organic acids like citric acid,2-keto-D-gluconic acid,?-ketoglutaric acid,gluconic acid,pentonic acid and L-ascorbic acid were significantly decreased during the deterioration,the content of fumaric acid,oxalic acid and propionic acid was relatively stable,and the content of malic acid was significantly increased.Loss of sucrose,glucose,fructose,citric acid and most other kinds of sugars and organic acids made the drop of sweetness and sourness of fruit.(3)Soluble pectin,propectin,cellulose and lignin content in granulated parts were significantly higher than normal ones,this significant lignification phenomenon brought navel orange a rough slag of the taste,and its sensory quality dropped sharply.(4)A total of 27 kinds of volatile components were identified in the fruit by Gas chromatography-mass Spectrometry(GC-MS)analysis.Normal fruit was without ?-guaiacene,while disordered fruit was without carvone and eremophilene.Contents of 15 kinds of volatiles were significantly different between normal and granulated fruit.Terpenes(monoterpenes,sesquiterpenes)had the most contents in the fruit both in the normal and granulated ones,and monoterpenes was the highest in normal while sesquiterpenes was the highest in granulated ones.The contents of monoterpenes,esters and aldoketones decreased significantly when fruits were granulated,and the degradation of these substances could directly lead to the loss of fruit aroma.The content of alcohols material did not change significantly,while the content of sesquiterpenes was significantly increased.In summary,the deterioration of fruit quality leads to the deterioration of all aspects of its sensory quality of navel orange under granulation.The degradation of sugars and organic acids and also the lignification in the juice sacs leads to fruit sweetness,sourness loss and its rough taste.Our study also found that navel orange granulation is also accompanied by a significant reduction in the volatiles content in the fruit,which leads to fruit loss of aroma.This research will provide important references for revealing the mechanism of citrus granulation.