Investigation on walnut kernel oil extraction using different methods

Extraction of oil from walnut kernel as raw material was explored using the method of pressing. Soxhlet and ultrasonic-assisted extractions of walnut oil, its evaluation index, the extraction process optimization by single factor experiment, the physical and chemical properties of oil, fatty acid composition, element composition, and the main functional group analysis were studied. The results showed that walnut kernel could be extracted effectively with petroleum ether. The optimal extraction conditions of walnut oil by ultrasonic assisted extraction were as follows: solid/liquid ratio of 1:11 (g/mL), ultrasonic power 180 W, extraction time 60 min, and the extraction efficiency of walnut oil was 59.13%. The optimal extraction conditions of walnut oil by Soxhlet were solid to liquid ratio of 1:7, temperature of 76 °C, time of 4 h, and the extraction efficiency of walnut oil was 58.3%. The extraction efficiency of pressing was 43.2%. Walnut oil mainly contains phosphorus, zinc, magnesium, potassium, calcium, and other elements. The fatty acids of walnut oil mainly consist of palmitic acid, palmitoleic acid, cis-linoleic acid, cis,cis,cis-9,12,15-octadecanotrienoic acid and other fatty acids. The cis linoleic acid accounted for the highest proportion in GC content, and the content of both was more than 90%.