Studies on utilization of hard shelled walnuts for extraction of kernel oil.

摘要

The suitability of hard shelled walnuts (Juglans regia L.) found in Himachal Pradesh for utilization for kernel oil extraction on a semi-commercial scale was evaluated. Mean nut weight in medium and hard-shelled walnuts ranged from 9.6 to 13.3 g and 9.5 to 23.5 g, respectively. The respective hardness values of 0.39 to 0.65 KN and 0.80 to 3.16 KN were observed for medium and hard shelled walnuts, respectively. Though kernel recovery in hard shelled nuts was low (20.3-39.3%) as compared to medium shelled nuts (29.0-46.0%), the kernel oil yield in both types of nuts was almost the same (62.0-70.7%). Use of a mechanical decorticator was found to be optimum, with a crushing capacity of 13.2-16.7 kg/h as against manual crushing of only 2 to 5.8 kg/h. Dipping crushed nuts in 7.5% salt solution (specific gravity 1.059) and collecting the floated kernels resulted in good kernel separation (78.0-88.7%), while shells sank to the bottom of the solution. Use of an oil expeller was optimized for operation at semi-commercial scale with an oil yield of 58.3-62.5%. The quality of oil from both medium and hard shelled walnuts was within the minimum specifications prescribed under the English Walnut Oil Standards. On the basis of lipid profiling, the extracted oil contained an appreciably higher proportion of unsaturated fatty acids consisting of oleic (31.0%), linoleic (45.6%) and linolenic acid (15.9%), thus exhibiting good nutritional and pharmaceutical significance..