Effect of irradiation on total biophenol and antioxidant activity during storage of natural black table olives obtained using starter culture

In this study, it was aimed to determine the effects of different production and preservation methods on the shelf life and quality of the Gemlik variety of natural black table olives produced with low salt (2%). For this purpose, olives were processed by the traditional Turkish style dry salted black olive by using a starter culture. The MAP (Modified atmosphere packaging, 60% N₂ and 40% CO₂), vacuum and for the first time gamma irradiation methods (1, 3 and 5 kGy) were applied in the preservation of table olives. The 5 kGy irradiation treatment reduced the total phenolic amount and DPPH antioxidant activity of olives more than other irradiation doses. The pH (4.3–4.83) and titratable acidity (0.68–1.02%) of the samples changed in accordance with the legal regulations during the storage period (pH max. 5 and acidity min 0.3%). At the end of the fermentation and storage, total phenolic content and antioxidant activity decreased significantly (p-value <0.05). During the storage period, the total phenolic content in natural fermented olives (without starter culture) decreased from 232 to 144 mgCAE/100 g and in starter culture added table olives from 200 to 138 mgCAE/100 g. In addition, the antioxidant activity was changed between 60.94 and 47.14 μmolTE/100 g oil. As a result of the study, it was ensured that black table olives produced with less salt (2%) could be stored on the shelves for 6 months without using any preservatives. In addition, radiation effect on quality was relatively similar to other treatments (vacuum and MAP).