Optimization of Lutein Extraction from Pistachio Waste Using Experimental Design and Ultrasonic Method

Agricultural by-products rich in lutein such as pistachio hull can be applied in pharmaceutical, cosmetics and food manufacturing. The development of rapid and cost-effective extraction methods of lutein from pistachio hull to optimize lutein recovery is of great interest to transpose to an industrial scale. Herein, we optimized the extraction protocol of lutein from the Iranian pistachio hull using experimental design and ultrasonic method. Fresh raw un-hulled pistachios were harvested and dehulled, then hulls were dried and finely powdered to use for further analysis. Soxhlet process was carried out to obtain pistachio hull oleoresin and response surface methodology (RSM) was used for the optimization of saponification and ultrasonic methods. The lutein contents were quantitatively analyzed and validated using LC-MS/MS system. Our results showed that lutein in pistachio hull is mainly in free form, therefore the saponification method is not necessary for its extraction. Under optimal experimental design conditions, the maximum amount of lutein predicted and observed was 7.90 and 7.97 mg/100 g, respectively. Ethyl acetate was applied as an extraction solvent with the ultrasonic method followed by the setting up of the extraction time, temperature and solvent/sample ratio as variables. Under optimal experimental conditions corresponding to 45 min extraction time at 50 °C and 35.5 mg/ml of the solvent/sample ratio, the amount of lutein obtained from dried pistachio hull was 5.14 mg/100 g. Pistachio waste products are rich in lutein which is in free from, so the administration of ultrasonic extraction using Ethyl acetate as a green and cost-effective method can be applied for lutein extraction from other plant materials and suggested for application on an industrial scale.