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    Change in major fatty acid composition of vegetable oil depending on phenolic incorporation and storage period
    (Codon Publications, 2016) Toker, O. S.; Ozturk, I.; Karaman, S.; Yalcin, H.; Kayacıer, Ahmed; Dogan, M.
    In the present study, response surface methodology was conducted for the determination of effects of some phenolics (gallic acid, ellagic acid and quercetin) on the major fatty acid composition of vegetable oil prepared by mixing of sunflower and hazelnut oil (50:50, v/v) during storage at a constant temperature (50 degrees C). In this respect, major fatty acid composition (palmitic, stearic, oleic and linoleic acid) of vegetable oil was determined. Predictive regression equations were constructed for the estimation of each studied parameter (R-2>0.735). Storage period caused a significant increase in palmitic acid, stearic acid and oleic acid content of oil while it caused a decrease in the linoleic acid content of the oil (P<0.01) because of the reactions that occurred in the structure of the oil during storage. In general, gallic acid and quercetin were found to be effective on the preservation of oil against oxidation and addition of gallic acid that retarded the change of major fatty acids composition due to oxidation. Multiple response optimisation was performed by considering the change in all major fatty acids simultaneously. According to the results, addition of ellagic acid, gallic acid and quercetin at the concentrations of 20, 46.7 and 33.3%, respectively, in a phenolic mixture (0.1 g) to the oil sample is convenient for decreasing oxidation.
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    Effect of apple fibre on textural and relaxation properties of wheat chips dough
    (Wageningen Academic Publishers, 2016) Karaman, S.; Yilmaz, M. T.; Toker, O. S.; Yuksel, F.; Kayacıer, Ahmed; Dogan, M.
    In this study, the effect of apple fibre with different levels of fibres (5, 10, 15 and 20%) was investigated on viscoelastic nature and the textural properties of wheat chips dough using stress relaxation test and texture profile analysis. Apple fibre addition changed the stress relaxation properties of wheat dough, depending on fibre concentration. Increase in the fibre concentration increased resistance of the dough samples to the deformation by increasing their elasticity. Hardness and gumminess values increased while springiness, cohesiveness and resilience values decreased as apple fibre level increased. Significant correlations were found between stress relaxation and texture profile analysis parameters. In order to describe the effect of apple fibre on the viscoelastic properties of wheat dough, generalised Maxwell, Nussinovitch and Peleg models were fitted to experimental stress relaxation data. All three models were found to be efficient in describing the stress-relaxation behaviour of wheat dough; but, the Maxwell model was the most effective. In addition, power-law and exponential functions were successfully used to describe the effect of apple fibre concentration on the constants related with stress relaxation data and textural parameters.