A simple on package indicator label for grapes (Vitis vinifera L.) ripeness has been developed based on chlorophenol red (CPR). The CPR was immobilized onto the filter paper via absorption method to make the CPR membrane. The membrane as a colorimetric label for grape ripeness works based on pH increase as the volatile organic acids decreased gradually in the package headspace due to the formation of sugars during berry ripening process. Subsequently, the color of the indicator label will change from white to beige then finally to yellow for over-ripe indication, which is easily detected by naked eye. The results show that the indicator label could be used to monitor the ripeness of grapes since the color changes of indicator label toward the ripeness of the grapes are in similar tendency and have a good linear correlation. Thus, the indicator label can be used as an effective tool for on-line ripeness monitoring of grapes packaging. Finally, the indicator label was successfully used as on-package indicator label for on-line ripeness monitoring of grapes in ambient and chilled conditions.
Sensor Research Group at Faculty of Pharmacy, University of Jember