Drying is a process to convert grape berries into raisins. The waxy cuticle on the surface of grapes acts as a barrier against moisture evaporation during the drying process. Therefore, an effective pretreatment and drying method is necessary to remove the waxy layer to accelerate the drying rate. A study was conducted to standardize the effect of pretreatments viz., K2CO3 with ethyl oleate and olive oil, hot water treatment and no dipping along with three drying methods viz., cabinet tray dryer, solar tunnel dryer and open sun drying on drying time, instrumental color value (L*, a*,b*) and texture (N) of raisins. Grapes berries (var. Thompson seedless) pretreated with ethyl oleate 1.5% + K2CO3 3% and dried in cabinet tray dryer took lesser (26.08h) drying time and appeared lighter (47.04 L*), bright green (4.03 a*), intense yellow (27.98 b*) and were soft (4.91 N). Sun dried raisins without pretreatment took maximum (169h) drying time, more dark (25.87 L*), and observed to be stiff (6.44 N). The findings emphasize the pretreatment and drying method in minimizing the drying time with desirable color, nutritional qualities, organoleptic attributes. Therefore, the production of raisins using the above said treatment and drying method will have scope from both the industrial and health points of view, because of the remarkable reduction in the processing time and drying time.

Raisin, Drying methods, Drying time, Pretreatment, Color, Texture

The combination of pretreatments and drying methods are critical factors for production of good quality raisins. The raisin produced from the combination of a pretreatment i.e. potassium carbonate and ethyl olate and drying methods viz., cabinet tray dryer and solar tunnel dryer accelerated the drying rate, had appealing colour and soft texture in short period of time saving energy and manpower, acceptable sensory attributes and better marketability.

Foshanji Ahmad Shafiq, Krishna, H.C., Sadanand K. Mushrif, Ramegowda, G.K., Bhuvaneswari S., Shankarappa T.H. and Sahel Nasir Ahmad (2022). Effects of Pretreatments and Drying Methods on Drying Kinetics and Physical properties of Raisins. Biological Forum – An International Journal, 14(4a): 155-160.