The impact of debittering methods on black table olive quality

This study intends to determine the impact of freezing techniques on breaking of bitterness material (oleuropein). For this reason, Gemlik black olive that was harvested on 2016 and 2017 january are used as materials. Two different freezing methods were applied that individualy quick frozen method (IQF) then stored in different frozen storage temperatures (frozen storage conditions were -18°C and -25°C) for 90 days period and slow freezing method in -18°C and -25°C frozen storage for 90 days period. 2016 harvested Gemlik variety black olives were evaluated for their sensory characteristics after freezing and 3 months of frozen storage period. As a result of sensory analysis, it was cleared that different freezing methods and frozen storage were decreased the bitterness but softened the texture of olives. Because of this, 2017 year harvested olives were held on 15 hours period in % 0,5 calcium chloride solution before freezing. After the frozen period, olives were processed by two different methods that were treated with dry salt and brine. Statistical analysis revealed that calcium chloride treatment effect on firmness (g) and toughness (g.sn) values of raw material were significant (p<0,01). Different freezing methods, different frozen storage temperatures and storage period effects on, dry matter (g 100 g-1), protein (g 100 g-1), ash (g 100 g-1), oil (g 100 g-1), reduced sugar (g 100 g-1), oleuropein (mg kg-1), antioxidant capacity (mmol GAEAC g-1), firmness (g) , toughness(g.sn) values and sensory properties were significant (p<0,01) but on fruit / stone ratio values were not significant (p>0,05). Freezing methods and frozen storage temperature effect on total phenolic content values were not significant (p>0,05) but storage period effect on were significant (p<0,05). The number of olive fruit per one kg values are showed differences between 2016 and 2017 January harvested olives. Freezing method and frozen storage temperature effect on 2016 January harvested black olives' the number of olive fruit per one kg values were not significant (p<0,05) but frozen storage period effect on were significant (p<0,01). Different freezing methods, different frozen storage temperatures and storage period effects on 2017 january harvested black olives' the number of olive fruit per one kg values were significant (p<0,01). As a result of analyses, it was indicated that different freezing methods and frozen storage have not negatively affected the material, in spite of this bitternes decreases, thus is affects positively to the decreasing of olive ripening period. For overall acceptability of sensorial properties sample that after calcium chloride treatment slow freezing in -25°C frozen storage, at the end of the 90 days storage period, processed as sele olives (treatment with dry salt) was preferred by panellists.