Optimization of microwave assisted extraction parameters of neem (Azadirachta indica A. Juss) oil using the Doehlert's experimental design

Demand for neem oil for use in cosmetics, pharmaceutics and biodiesel formulations has been on a steady increase and is expected to rise even more in the future. In order to meet increasing demand, it is important to define optimum conditions that can increase volumes and quality of oil produced. Parameters for microwave assisted extraction (MAE) of neem oil were optimized using the Doehlert design. Quantity of oil extracted, fatty acid profiles and acid number were used to evaluate the effect of microwave heating time, temperature and solvent/biomass ratio on the MAE process. Second order models were generated and used to establish optimum MAE parameters of heating time (24 min), temperature (80 °C), solvent/solute ratio (3:1). Under these conditions, close to 80% of the oil was extracted in comparison to 10 h required for the Soxhlet process. Scanning electron microscopy revealed that structure degradation of the kernels by microwaves was the main driving force behind the rapid and efficient extraction process, but had no significant effect on the fatty acid profiles and acid numbers, respectively. MAE process can therefore be used to extract high volumes of oil within short intervals without significant degradation of the oil quality. This paper presents for the first time, to the best of our knowledge, a study on the microwave extraction process of neem oil.