Abstract:

The aim of this study was to study the effects of three browning inhibitors, citric acid, L-cysteine and sodium
pyrosulfite on color and polyphenols of longan puree treated in model systems at 60 ℃ for 24 h and to correlate color
difference (ΔE*) with polyphenol retention. A three-level orthogonal array design was employed to select the optimal
blend of the three browning inhibitors. The results showed that a better inhibitory effect on enzymatic browning of
longan puree was indicated by a higher amount of polyphenols retained and smaller ΔE* values. The importance of
the browning inhibitors in affecting ΔE*, all at a significant level, decreased in the following order: citric acid ＞
L-cysteine ＞ sodium pyrosulfite, while the decreasing order of their effect on the retention of polyphenols was sodium
pyrosulfite ＞ L-cysteine ＞ citric acid, with the effects of sodium pyrosulfite and L-cysteine being extremely significant
and that of citric acid being not significant. A formulation composed of 1.0 g/kg citric acid, 0.35 g/kg odium pyrosulfite and
0.8 g/kg L-cysteine was found to be optimal for inhibiting enzymatic browning of longan puree.

Key words: longan puree, citric acid, sodium pyrosulfite, L-cysteine, total color difference, polyphenols