| Abstract: | Quality of raisins is affected by various factors like variety, pre-treatment of grape bunches, drying conditions etc. Considering the importance of raisin colour as an important quality attribute, the present study was conducted. Grape bunches were treated with different doses of ascorbic acid and sodium metabisulfite after harvesting. Applications of ascorbic acid concentrations to grapes before pretreatment of bunch by alkaloid solution on the second day of drying reduced colour intensity. Moisture content in raisins was also reduced up to 12.35 % in T3. It was an indicator of faster drying. The concentration of 300 ppm was found effective in producing quality raisins. Less colour intensity was observed when ascorbic acid was applied on bunches placed for drying than application before dipping in alkali solution in each treatment. Minimum colour intensity (6.356) was noted in T2 followed by T3 when ascorbic acid was applied on bunches placed for drying while maximum (7.344) was noted in control. The polyphenol oxidase (PPO) activities was decreased by increasing the drying duration. Lower PPO content was noted in treated grapes than control. While, no significant differences were observed for browning and colour intensity in raisins with different doses of ascorbic acid and sodium metabisulfite. However, applications of ascorbic acid and sodium metabisulfite influenced the other parameters. The present study reveals that the application of ascorbic acid is suitable for retaining good colour of raisins with faster drying and 300 ppm ascorbic acid spray on second day of drying can be adopted. |
