Evaluation of bioactive compounds in fermented black table olives.

Table olives have been a component of the Mediterranean diet for centuries and their consumption is increasing worldwide. They contain several nutritional components such as unsaturated fatty acids, vitamin E, triterpenic acids, sterols, polyphenols and carotenoids [1]. The content of these bioactive molecules depends on the olive variety, the ripening stage of the olive fruit, the cultivation conditions and the processing method [2]. There are numerous commercial preparations of table olives and in a recent work we have developed and validated a new procedure for table olive production based on the use of selected autochthonous microbial starters and a productive process optimized to mimic the microbial evolution observed during spontaneous fermentations. [3]. In this work, we characterized some bioactive compounds and coloring pigments of fermented black table olives, belonging to two Italian (Cellina di Nardò and Leccino) and two Greek (Kalamàta and Conservolea) cultivars. Greek table olives resulted richer in carotenoids, vitamin E and triterpenic acids (maslinic and oleanoic acids) than Italian cv, contents ranged from 2.28 to 6.91 µg/g fw (edible portion), 53.64 to 59.15 µg/g fw and 2.19 to 3.28 mg/g respectively. Polyphenol compounds are known to be responsible for the bitter taste of the olive fruit and most of them are involved in table olives colour changes. In all tested black table olive cultivars, polyphenols content ranged from 0.87 mg/g fw (in Conservolea) to 23.49 mg/g fw (Cellina di Nardò). Moreover, we analysed the content of tyrosol, hydroxytyrosol, oleuropein aglycone, verbascoside, isoverbascoside, rutin, pyrocathecol, luteolin glucoside, quercetin, cyanidine rutinoside and cyniadine glucoside. In particular, Cellina di Nardò is characterized by the highest levels of anthocyanin pigments such as cyanidin 3-O-glucoside (14.77 mg/g fw) and cyanidin-3-O-rutinoside (3.17 mg/g fw) responsible for the characteristic black color. The results indicated that fermented black table olives are an excellent natural source of bioactive compounds and can represent a potential important functional food.