Metabolomic analyses of dry lemon slice during storage by NMR

Abstract

Lemon is a fruit with delicious taste and attractive flavor, which has been widely accepted by people over the world. Dry lemon slice is a classical processed product of lemon. It is readily to be browning during storage. Which chemicals are responsible for the browning behavior remains unclear. Therefore, in this work, nuclear magnetic resonance spectroscopy is used to analyze the metabolites changes in dry lemon slice during storage. Nineteen metabolites were identified and their related levels were statistically calculated by principal component analysis. The first principal components were represented by glutamic acid, α-amino-butyric acid, γ-amino-butyric acid, alanine, limonoid, citric acid, glutamine, and phosphocholine. The changes of browning degree during storage and its correlations with the levels of polyphenol, ascorbic acid, amino acid nitrogen, and 5-hydroxymethylfurfural were analyzed. The results indicated that Maillard reaction and oxidation of phenolics were two main processes contributing to the nonenzymatic browning during storage.