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    Investigation of the traditional organic vinegars by UV-VIS spectroscopy and rheology techniques
    (Pergamon-Elsevier Science Ltd, 2021) Yalcin, O.; Tekgunduz, C.; Ozturk, M.; Tekgunduz, E.
    Optical, rheological and metabolic properties of the apple, hawthorn, artichoke, grape, rosehip and blackberry organic vinegar produced by deep culture method (handmade traditional method) were analysed using UV-Vis spectroscopy and rheology techniques. Flow behaviours for all samples were analysed in the shear rate range of 10(-3) to 10(3) 1/s and in frequency range of 10(-3) to 10(3) rad/s, respectively. Absorption spectra for six organic vinegars was observed two peaks around 215 and 285 nm due to the presence of phenolic compounds and organic acids such as acetic. The effects of optical transitions of organic molecules on the absorption coefficient values for vinegars were determined. Optical energy band gaps of all samples were found to be consistent with Planck's radiation approach known as Rayleigh-Jeans law and Tauc law. The rheological/flow properties of the all vinegars were found to be relevant with non-Newtonian flow behaviour and Ostwald-de Waele model. From the results of optical and rheological analysis, which determines the quantity and quality characteristics of all organic vinegars, it was concluded that these vinegars are in a level that people can drink easily. (c) 2020 Published by Elsevier B.V.
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    Origin of the effects of optical spectrum and flow behaviour in determining the quality of dry fig, jujube, pomegranate, date palm and concentrated grape vinegars
    (Pergamon-Elsevier Science Ltd, 2022) Ozturk, M.; Yalcin, O.; Tekgunduz, C.; Tekgunduz, E.
    In this study, we focused on physical characterization and quality control of dry fig, jujube, pomegranate, date palm and concentrated grape vinegars using UV spectroscopy method and rheology technique. The optical spectra and flow behaviour of the vinegars were analysed in detail in the selected specific wavelength, shear rate and frequency ranges, respectively. It was determined that the peak values seen in the UV spectra of the vinegars were caused by the organic acid and phenolic compound concentration. The peak values in the UV spectra of the vinegars wavelength range of 190 nm to 240 nm and 250 nm to 300 nm were caused by the organic acid and phenolic compound concentration, respectively. In this context, it was predicted that concentrated grape vinegar, which has the highest absorbance value, has higher organic acid content and more antibacterial/antioxidant properties compared to the others. It is thought that the optical energy gaps of vinegars are related to the organic acid concentration and the release time. Flow properties of the vinegars were non-Newtonian thickening fluids (dilatant fluids) and compatible with the Power law model. The stable flow of the vinegars in the high shear rate region was interpreted as having a successful production process and being of good quality. (C) 2021 Published by Elsevier B.V.