EFFECTS OF ORANGE JUICE FORTIFICATION WITH THIOLS ON P-VINYLGUAIACOL FORMATION, ASCORBIC-ACID DEGRADATION, BROWNING, AND ACCEPTANCE DURING PASTEURIZATION AND STORAGE UNDER MODERATE CONDITIONS

Pasteurization of orange juice produced sub-taste-threshold levels of p-vinylguaiacol (PVG) and induced ascorbic-acid degradation but had al most no effect on browning. Fortification with glutathione, L-cysteine , or N-acetyl-L-cysteine at concentrations below 4.0 mM had no effect on PVG formation and browning but inhibited ascorbic-acid degradation during pasteurization and improved juice acceptance. Storing the orang e juice for 12 weeks at 25 degrees C resulted in a PVG; content that r eached its taste threshold; fortification with the above concentration s of thiols reduced PVG formation and browning. Storage at 35 degrees C resulted in a PVG level about 10-fold above its taste threshold, 25% degradation of ascorbic acid, and significant browning. Fortification with thiols at concentrations below 4 mM reduced PVG formation, ascor bic-acid degradation, and browning. Sensory evaluation tests indicated increased hedonic scores due to thiol fortification during pasteuriza tion and storage (though not statistically significant for the latter) , and aroma-similarity tests performed on juice stored at 35 degrees C indicated that fortification with 1.0 mM glutathione results in an ar oma similar to that of the control juice stored at 4 degrees C.