Efficacy of Ascorbic Acid Treatments in the Production of Green Raisins

The quality of raisins is mainly perceived by their colour. Green-coloured raisins are considered as the best quality raisins whereas brown/dark-coloured raisins possess poor quality. Raisin colour is affected by different factors like grape variety, pre-treatments to grape berries, drying method, drying conditions, etc. The present study was conducted to produce greencoloured raisins through two different treatments of ascorbic acid – dipping and spraying. These treatments were applied to Thompson Seedless grapes independently with different doses (100–500 ppm) of ascorbic acid. Results indicated that lesser darkening of raisins was observed when ascorbic acid was sprayed on bunches during drying than the dipping treatment. In all the samples, polyphenol oxidase (PPO) activity decreased with drying duration. Lower PPO content was noted in dipped and sprayed grapes than control. However, application of ascorbic acid influenced the other parameters. The present study revealed that ascorbic acid spray is suitable for retaining green colour in raisins with faster drying. Overall, 200 ppm ascorbic acid spray was found appropriate in the production of green raisins.