Aromatization of virgin olive oil by seeds of Pimpinella anisum using three different methods: Physico-chemical change and thermal stability of flavored oils

Abstract

Knowing that flavored products would increase the use of olive oil by non-traditional consumers and enhance the added value of this valuable agricultural product, the virgin olive oil (VOO) was flavored with the seeds of Pimpinella anisum (Green anise) using three different methods: classic maceration, ultrasonic assisted maceration and direct addition of the essential oil (EO). These methods were compared under two main criteria: time and level of aromatization. The physico-chemical parameters and the thermal stability of flavored oils prepared by the three methods were determined by AOAC titration method and GC–MS analysis so as to compare the aromatization effect of the three methods. The trans-anethole is the major component of the EO of anise seeds as well as the indicator of the level of aromatization. GC/MS analysis results of the flavored oils showed that the diffusion of trans-anethole in the flavored oil by direct addition of EO was very important (36.3% of the total volatile fraction of the flavored oil) in comparison to the oil flavored by ultrasonic assisted maceration or classic maceration (respectively 26.59% and 23.85%). These different aromatization methods ensure an improvement in the quality of VOO with an enrichment in polyphenols estimated at 35% in the case of ultrasonic flavored oil, an increase in the content of carotenoids and chlorophylls (67% and 21% respectively) in the event of aromatization by classic maceration, and a decrease in specific absorbency at 232 nm estimated at 29% during aromatization by addition of EO as well as a decrease in the peroxide value estimated at 26% in oil flavored by classic maceration unlike in oil flavored by ultrasound which has seen an increase of around 20%. The aromatization was able to maintain the stability of the oils and its qualification as VOO with a gain in induction time in the case of treatment at 60 °C estimated at 29 and 27.5 d respectively in oils flavored by addition of EO and by conventional maceration, an improvement resistance to degradation concerning K₂₃₂ and K₂₇₀ of all flavored oils which varied from 15 to 40 d in the case of treatment at 60 °C and 3 h resistance to degradation of oils treated at 130 °C for K₂₃₂. Polyphenols, chlorophyll pigments and carotenoids play an important role in oxidative stability due to their antioxidant nature and their degradation during heating is very complex. All of these physico-chemical changes have increased the thermal stability of flavored oils with better resistance to oxidation of flavored oil by classic maceration in compared to oil flavored by adding EO and the oil flavored by using ultrasound.