Effects of pre-treatments on browning of lemon peels during drying

Effects of pre-drying treatments such as blanching and dipping (soaking) in a sucrose solution on browning of lemon peel during drying were investigated. A color analysis method using a digital camera and computer software based on the HSL color system was employed for determination of the degree of browning of lemon peels. Hue (H) value decreased as the browning increased. Other two parameters, saturation (S) and lightness (L), were not sensitive to the browning reaction monitoring. The browning rate was faster at the beginning of the drying and became slower when the water content became low. The pre-treatments resulted in less browning during drying. In order to examine the browning rate as a function of water content, the samples of different water contents were incubated in an airtight container (no water loss during incubation), and the H values were determined as a function of incubation time. The browning became faster when the water content was high. Sample pre-treatments such as blanching and dipping in a sucrose solution slowed down the browning rate compared with non-pre-treated samples. The browning during drying was significant when the air temperature was above 318K. The pre-drying treatments (blanching and soaking in a sucrose solution) resulted in much slower browning.