Loss of fatty acid esters from grape surfaces during drying

Abstract

Fatty acid esters have been shown to reduce the drying time of grapes by interacting with the waxy surface of the grapes. Laboratory scale procedures were developed to determine the fate of esters during dehydration. Thompson seedless grapes were dipped in a water emulsion containing 2% fatty acid ester, 2% potassium carbonate and an emulsifier. Grapes were dried at ambient, 43 C and 71 C. Drying rates vs. fatty acid ester concentration on the grape surfaces were plotted. The fate of fatty acid esters during dehydration was determined by running the dryer exhaust through a cold trap and extracting the condensate. These studies showed that the large loss of esters during drying lowered the drying rate considerably. An additional dip during drying reduced the drying time significantly. The ester losses appeared to be caused by vapor distillation of the esters during drying.