INTRODUCTION
Table olives are the traditional fermented product of Mediterranean countries, but today the production and consumption of table olives has spread around the world (Arroyo-Lopez et al., 2008). Turkey is the third biggest producer of table olives in the world, with a production of 399,9 tons in 2022 (IOC, 2022).
The Gemlik cultivar itself has a distinguished place among the olive cultivars grown in Turkey and its cultivation area continues to expand across the country (Ben Ghorbal et al, 2018), and almost constitutes half of the olive tree presence in Turkey (Ozaltas et al., 2016).
Among the 94 local olive variety, due to its high flesh/stone ratio, good shape, texture and excelent organoleptic characteristics “Gemlik” is the most important and economically valuable variety for black table industry in Turkey and mostly processed with naturel fermentation known as Gemlik style traditionally. In this method, Gemlik olives produced with high amount of salt (10-12% salt for winter days and 12-18% salt in summer) and preserved in this way. In recent years, consumers have developed an attitude towards low sodium intake because the sodium-rich diet causes higher blood pressure. The recommended daily intake of salt has been established as 5 g/day (~2000 mg Na+/day) by the World Health Organization (WHO) (Bautista Gallego et al., 2011).
Good process control is necessary to improve fermentation and produce standard and quality final products. The main drivers of fermentation are the availability of fermentable substrates, salt content, pH, aerobic/anaerobic conditions and temperature control. In order to avoid these disadvantages, the use of starter cultures in the modern table olive industry is recommended (Aponte et al., 2012).
The fermentation process, generally performed by indigenous microorganisms, is one of the best and oldest procedures of treating food products to preserve them and produce other products. Spontaneous fermentations are uncontrolled and not predictable. These spontaneous processes are inefficient since they do not ensure the expected quality and safety characteristics of the final product, the sensorial and structure features, the limitation, or absence of growth of harmful or undesired spoilage organisms. In order to obtain a more controlled process and to improve the quality and safety levels of table olives, the selection and use of starter cultures is diffusing. In fact, several studies demonstrated the usefulness and the benefits of starters in table olives production (Boskou and Clodoveo, 2016).
Besides, the use of starter culture in black olive fermentation was found to be important in terms of LAB dominance on yeast (Montet et al, 2014). Although the starter culture inoculation rate varies depending on the variety and process, it is usually around 1%. The final concentration of inoculated microorganisms in the brine is between 106-107 cfu/ml (Erten et al., 2016).
Vacuum and MAP preservation techniques and are widely used in the table olive industry. Gamma irradiation is another preservation method applied to several food products. Food irradiation is a processing technique applied to decontaminate and extend the shelf life of foods by exposing them to ionizing radiation in order to increase the shelf life and safety of the food. Ionizing radiation is highly effective in inactivating micro-organisms in various vegetables and it offers a safe alternative as a food decontamination method. There has been a number of research studies directed at examining the effects of irradiation against fresh vegetables and fruit aimed at delaying the ripening, control of the pathogen and pest (Kader, 1986; Niemira et al., 2001).
Black olive production constitutes 80% of the table olive production in our country and consumers prefer black olives for consumption. It was aimed to improve the traditional production method by using starter culture and less salt and to increase the shelf life by irradiation. It is important to find appropriate technologies for table olive preservation. It is seems that irradiation is a potential tool in extending shelf-life of table olives.
To our knowledge, no studies have shown the effect of gamma irradiation on the antioxidant capacity and phenolic compounds of table olives. The aim of this study was to evaluate and compare the effects of different preservation methods (irridation, MAP, vacuum) on some quality paratmeters and antioxidant properties of less salted and starter culture added black table olives during storage. Our secondary aim was to evaluate the effect of starter culter adding on the some quality paraö-meters and total phenol phenolic content of Gemlik olive.