An explanation for the natural de-bittering of Hurma olives during ripening on the tree

E Susamci,M Brenes,O Tuncay,C Romero

doi:10.3989/gya.1161162

Abstract

Harvested olives require further processing to make them edible due to their content in the bitter substance oleuropein. However, some olives of the Erkence cultivar naturally de-bitter on the tree giving rise to the so-called Hurma olives. In this study, the evolution of the chemical characteristics of Erkence and Hurma olives harvested from the northeast and southwest area of trees located in the Karaburun Peninsula was assayed. It was confirmed that the oleuropein content in Hurma olives was much lower (< 2000 mg/kg fresh weight) than Erkence, which reached 35.000 mg/kg fresh weight at the beginning of the season. In addition, no free or polymerized anthocyanins were found in Hurma fruit in contrast to ripened Erkence fruit. The concentration of glucose was also lower in Hurma than Erkence olives. These results suggest that the enzymatic oxidation of oleuropein could be responsible for the natural de-bittering of Hurma olives during their ripening on the tree.

Highlights

Olives are generally produced in Mediterranean countries, where there are about 8 million hectares of cultivated olives trees
The concentration of glucose was lower in Hurma than Erkence olives. These results suggest that the enzymatic oxidation of oleuropein could be responsible for the natural de-bittering of Hurma olives during their ripening on the tree
It must be noted that previous studies reported a very much lower concentration of oleuropein in Erkence olives that the content which is depicted in Figure 1 (Arslan, 2012; Aktas et al, 2014a)

Summary

Introduction

Olives are generally produced in Mediterranean countries, where there are about 8 million hectares of cultivated olives trees. There is an olive cultivar in Turkey, called Erkence, which can become edible naturally while still on the tree, when it is grown in the Karaburun Peninsula This “natural de-bittering” gives rise to olives called Hurma (Susamci, 2011). Hurma olives that fall to the ground are continuously collected by growers, and they can be directly consumed without any post-harvest processing. These olives are a healthy food product suitable for people seeking salt-free table olives

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Results

Conclusion