Application of Osmotic Dehydration and Ultrasound to Enhance Hazelnut Oil Extraction

Abstract

Hazelnut oil is a valuable product which can be used in various applications not limited to food processing, cosmetic product, and pharmaceutical industry. Traditionally, heating process is used to remove the moisture in various nuts and seeds prior to oil extraction stage in the industry which is relatively energy consuming. In this study, osmotic dehydration which is normally used as a pretreatment in fruit dehydration process was applied as a low-energy moisture removal method during the ultrasound-assisted extraction of oil from hazelnut. The effects of ultrasound amplitude, concentration of osmotic solution, and dehydration time on the yield and characteristics of hazelnut oil obtained were investigated in this study. Concentration of osmotic solution and dehydration time showed more significant effects on water removal as compared with ultrasound amplitude. Higher oil yield of 93% was achieved with the introduction of osmotic dehydration as pretreatment without negative impacts on quality of oil as compared with 88% oil yield in extraction without dehydration aid. The values for quality of oil obtained were in the range of 25–40 g/100 g oil, 0.5–1.1 g/100 g oil, and 2–6 mEq/kg for iodine, free fatty acid, and peroxide values, respectively. All the values were in the range of edible oil standard. Therefore, osmotic dehydration is a promising pretreatment method to enhance oil yield during extraction process in food industry.