Kinetics of olive oil fortification with helichrysum and laurel in a model system

Aromatization of olive oil with herbs and spices is a typical practice in the Mediterranean region, representing a fortification process that influences both sensory and functional properties of the resulting oil. Infusion is the most common and traditional technique for oil aromatization, nonetheless, it involves complex mass transfer mechanisms from the flavouring agents to the oil. Understanding these mechanisms is crucial for optimizing the infusion process and the characteristics of the final product, in particular when unconventional flavouring agents are used. This research aims at monitoring and modelling the kinetics of oil aromatization using two underutilized herbs, helichrysum (HEL) and laurel (LAU), in a model system represented by a purified olive oil (PO). After drying and initial chemical characterization, the herbs were infused into PO (1:9, w/w). The evolution of bioactive compounds (phenols, tocopherols, pigments), oxidative stability, and volatile compounds, was monitored over time, and the kinetics of aromatization were mathematically modelled. HEL was richer in phenolic compounds, chlorophylls and tocopherols respect to LAU, while, in both, the volatile fraction was dominated by mono- and sesquiterpenes and their derivatives. The results highlighted how the mechanisms of fortification are agent-dependent, regardless of the initial herb characteristics, except for chlorophylls and volatile compounds which were always excellently described by a quadratic model. The oxidative stability improved by +37% and +90% with HEL and LAU, respectively. The latter also caused an outstanding α-tocopherol transfer. Under the experimental conditions, an infusion period of about 30 days ensures optimal enrichment of the base oil.