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.