Screening of the Volatile Composition of Moroccan Olive Oils by Using SPME/GC-MS-FID over a Two-Year Period: A Pedoclimatic Discrimination

The volatile profile of an olive oil is a crucial attribute indicating its sensory quality. Hence, to elucidate the impact of geographical origin (including edaphoclimatic conditions) and the crop season on the volatile composition of monovarietal Moroccan olive oil "Picholine Marocaine", over a two-year harvest period (2018/19 and 2019/20), thirty-eight olive oil samples were obtained from nineteen Moroccan areas well-known by the abundance of olive tree cultivation. By using SPME/GC-FID-MS, 229 and 215 volatile compounds were characterized in olive oils produced during the 2018/19 and 2019/20 crop years, respectively. The identified compounds belong to nine volatile groups: terpenes, hydrocarbons, furans, esters, alcohols, acids, ketones, aldehydes, and nitrogen compounds. The one-way ANOVA and interactive heatmap revealed significant differences in the volatiles proportion in oils from different geographical origins. Our results imply that environmental (edaphoclimatic) conditions considerably influence the volatile compounds' biosynthesis, e.g., when soil granulometry decreases (from sand to silt), alcohols become esters due to the activity of alcohol dehydrogenase (ADH) and alcohol acetyl transferase (AAT) enzymes. Moreover, our findings exhibit a significant influence of the crop season on the volatile composition of Moroccan olive oils.