Development and performance evaluation of grape debunching machine for production of raisins and stemless table grapes

Abstract

Chemical pretreatment before drying is a practice in raisin making which has many limitations and use of chemical shall be discouraged. A new process is being developed with physical pretreatment. The process requires intact grape berries for further processing. Therefore, a grape debunching machine has been developed for separation of intact berries from the bunch. The machine consists of central rotor with helical fingers. The rotor assembly is surrounded by perforated trough through which the detached berries drop. The performance of the machine was evaluated with “Thompson Seedless” table grape for debunching efficiency and damage to berries. The rotor speed (80–120 rpm) and concave clearance (5–25 mm) were selected as independent parameters. The debunching efficiency and percentage of damaged berry were in the range of 77.17–98.73% and 5.75–11.82%, respectively. The maximum debunching efficiency (94.33%) and minimum berry damage (7.10%) was obtained at rotor speed of 100 rpm and concave clearance of 15 mm. The capacity of grape debunching machine was found to be 145.2–150.2 kg/hr for different grape varieties, namely Thompson Seedless, Manik Chaman, and Fantasy Seedless. The developed machine will be useful in production of raisins without use of chemicals and stemless table grapes.