Use of castor oil cake and castor oil in improving the nutritional characteristics and peroxidase activity of eggplant (solanum melongena l.)

Polyphenol oxidases (PPOs) are enzymes involved in the oxidation of polyphenols into quinones under the action of molecular oxygen, causing certain vegetables to brown. They also participate in essential biological processes such as cellular respiration, photosynthesis, and plant defense systems. Faced with agricultural challenges, including the proliferation of pests, the harmful effects of chemical inputs on the production chain, and the short shelf life of eggplants, the search for sustainable solutions is intensifying. This study aims to evaluate the impact of combining castor meal and castor oil on improving the nutritional and enzymatic properties of eggplants. The experiment was conducted using a randomized block design (4x4), with four treatments: a negative control, the application of cake (1.9 t/ha), castor oil (5 l/ha), and a combination of the two (0.95 t/ha + 2.5 l/ha). Analysis of the results reveals that the fiber content of the fruit reached 7.45% for the control, followed by 7.02% for castor oil, and 6.68% and 6.85% for oil alone and the meal-oil combination, respectively. In terms of protein, castor meal achieved 21.26%, compared to 17.55% for castor oil, while the meal-oil mixture and the negative control showed 13.30% and 0.18% respectively. In terms of enzyme activity, castor oil induced peroxidase of 15.18 IU, while the other treatments showed values of 11.95 IU (control), 10.96 IU (cake-oil) and 10.15 IU (cake alone). The polyphenol oxidase rate was slightly higher in the control (12.15 IU) and lower with the meal-castor oil combination (11.97 IU). The integration of meal and castor oil into eggplant cultivation is therefore an innovative approach to optimizing the nutritional value of the fruit while enhancing peroxidase activity and reducing polyphenol oxidase activity.