Solvent Extraction of Oil
The pecan kernels were baked at 95 ℃ for 8 min, cooled, pulverized for 30 s using a BJ-150 pulverizer (made by Baijie Jingdong Company, China), ground to pass through a 100-mesh sieve with a ceramic grinding rod by hands, and extracted for 10 h at 85 ℃ in a water bath by Soxhlet extractor with n-hexane as solvent. The extract was evaporated in a rotary evaporator until n-hexane was completely removed. Free oil was vacuum dried at 50 ℃ to a constant weight. Oil content in de-oiled meal was determined. Oil extraction efficiency (OEE) was calculated by the method similar to that described in “2.2.2 ” for calculating OR (= OEE) of NAM. Crude oil obtained was refined by method similar to that optimized by Ma et al. (2017). OR of solvent extraction (SE) was calculated by: [total refined oil obtained (g)/total crude oil in original pecan kernels (g)] x 100.