Effects of physical refining process on quality and stability of argan oil (Argania Spinosa (L.) Skeels)

Abstract

Subquality argan kernels are 30% cheaper than the regular kernels mandatory used to prepare edible argan oil. The use of these argan kernels for the preparation of argan oil intended to be a cosmetic ingredient, after bleaching and deodorization, is therefore particularly economically appealing. The oxidative stability of Argan oil prepared from subquality kernels is unknown. It was evaluated over a period of storage of 12 weeks at 60 °C, then compared with that of argan oil stored under the same conditions and originating from the same initial batch, but which had subsequently been simply bleached and deodorized (physical refining). Physical refining led to an increase in initial oil quality due the loss of free fatty acids (up to 30% for refined argan oil), primary and secondary oxidation products but also to a dramatic decrease of the oxidative stability of argan oil caused by the loss of tocopherols, witnessed by the up to 94% loss after 12 weeks under accelerated storage conditions. As a conclusion, the oxidative stability of argan oil prepared from subquality argan kernels remains difficult to be adequately and efficiently evaluated since the initial quality of the argan kernels is the subject of great variations.