Comparative study on volatile compounds, fatty acids, squalene and quality parameters from whole fruit, pulp and seed oils of two tunisian olive cultivars using chemometrics

Abstract

The oils of olive fruits, pulps and seeds of two main Tunisian cultivars of olive trees (Chemlali and Oueslati) were extracted at two different indices of maturity. The free acidity, peroxide value, spectrophotometric indices, chlorophyll content, squalene, fatty acids, aroma, and sensory profiles of oils were analyzed. Fruit and pulp oils had similar fatty acid compositions. While, seed oils have fatty acid profiles that are different from both varieties. For the first time in this work, squalene content in the fruit, pulp, and seeds oils were measured by gas chromatography and it decreased during maturation. Its concentration in the seed oils were lower than those found in fruit and pulp oils. The volatile profiles of twelve Tunisian olive oils obtained from different parts of fruits were established by solid phase micro‐extraction (SPME) coupled with gas chromatography (GC) and gas chromatography‐mass spectrometry (GC‐MS). Sixty‐six compounds were identified and characterized, representing 92.4 and 97.6% of the total volatiles. Principal component analysis showed that olive oil quality is strongly affected by olive cultivar, maturity index and the different olive parts.Practical applications: Nowadays, extractions of olive oil processes require grinding of the whole olives. The proposed method is useful alternative process for olive oil production involves olive destoning before extraction of the oil. although destoning lowers olive oil yields, manufacturing plants for stone removal and milling of pulp have been recently set up, showing good oil yield. Interest in this technology is increasing, and some producers believe that oils obtained from destoned olives are of better quality than oils extracted from the whole fruit. Indeed, oils extracted from destoned olives had a better sensory property than oils obtained from the traditional milling of entire fruits and is very important from a marketing point of view for the olive oil company.The different parts of the olive (seeds, pulps and whole fruits) seem to play a very significant role for the qualitative characteristics and the sensory attributes of Chemlali and Oueslati olive oils. In addition, these results have proven that the cultivar and the olive parts influence the quali‐quantitative production of volatiles and consequently the final aroma of the oil.