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    Effect of UV-C light on anthocyanin content and other quality parameters of pomegranate juice
    (Academic Press Inc Elsevier Science, 2011) Pala, Cigdem Uysal; Toklucu, Aysegul Kirca
    Pomegranate juice (PJ) was subjected to UV-C irradiation as a non-thermal technology and changes in major quality characteristics of juice such as anthocyanins, polymeric colour, antioxidant activity and total phenol content were determined. The results were compared with control (untreated) and heat treated (at 90 degrees C, 2 min) juice samples. UV-C treatment preserved the major quality characteristics of pomegranate juice better than heating process. After UV-C treatment, total monomeric anthocyanin content of pomegranate juice did not change significantly and decrease in individual anthocyanin pigments were between 8.1% and 16.3%. However, anthocyanin content of PJ was significantly affected by heat treatment (P < 0.05) and 15.4% and 28.3% of individual anthocyanin pigments were lost after this process. Also, differences between the control and UV-C treated PJ samples were small in terms of polymeric colour values (P > 0.05) while polymeric colour of PJ were significantly affected by heat treatment (P < 0.05). There were no significant changes in antioxidant capacity evaluated by trolox equivalent antioxidant capacity (TEAC) assay and total phenol contents of PJ after UV-C and heat treatments. The effectiveness of the UV-C system on the aerobic plate count, yeast and mould count and Esherichia coli ATCC 25922 as a surrogate microorganism of E. cola O157:H7 in PJ resulted in 1.8, 1.45 and 6.15 log reductions, respectively. (C) 2011 Elsevier Inc. All rights reserved.
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    Effects of spontaneous fermentation on Karalahna and Cabernet Sauvignon young red wines: volatile compounds, sensory profiles and identification of autochthonous yeasts
    (Springer, 2020) Uzkuc, Nesrin Merve Celebi; Sisli, Burcu; Ay, Mustafa; Togay, Sine Ozmen; Yuceer, Yonca Karagul; Bayhan, Asli; Toklucu, Aysegul Kirca
    t The purposes of the present study were to evaluate the volatile compounds and sensory characteristics of young red wines produced by spontaneous and inoculated fermentations of Karalahna (KL) and Cabernet Sauvignon (CS) grapes and to identify the yeasts responsible for spontaneous fermentation by molecular methods. A total of 28 volatile compounds in KL wines and 35 compounds in CS wines were identified and quantified by GC-MS. The concentration of higher alcohols and esters differed significantly among spontaneously fermented and inoculated wines. Spontaneous fermentation resulted in greater amount of higher alcohols in KL wines, while inoculated wines had greater amount of higher alcohols in CS wines. Spontaneously fermented KL and CS wines showed greater amounts of esters than inoculated wines. KL wines obtained by spontaneous fermentation had significantly higher scores than inoculated wines based on fruity and green aromas, body and overall impression. Spontaneously fermented CS wines were found significantly higher in fruity and floral aromas than inoculated wines.
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    Effects of UV-C Light Processing on Some Quality Characteristics of Grape Juices
    (Springer, 2013) Pala, Cigdem Uysal; Toklucu, Aysegul Kirca
    White and red grape juices (GJs) were subjected to ultraviolet C (UV-C) light as a non-thermal preservation technology using a coiled tube UV-C reactor with nine lamps. The effects of UV-C light on microbial (total aerobic count and yeast and mould count) and some chemical quality characteristics (total phenolics, antioxidant capacity, anthocyanin and polymeric colour, etc.) of white and red GJs were investigated. The results were compared with control (untreated) and heat-treated juice samples. Single-pass UV-C treatment (12.6 J/mL) of white and red GJs resulted in 3.51 and 3.59 log reductions in total aerobic count and, 2.71 and 2.89 log reductions in yeast and mould counts, respectively. The microbial loads of both GJs were completely eliminated after two passes through the reactor (25.2 J/mL). After UV-C and heat treatments, there were no significant changes in antioxidant capacity, total phenolics, titratable acidity, soluble solids and pH of white and red GJs (P > 0.05). The losses in monomeric anthocyanins were 6.1% and 8.7% after UV-C treatment of 12.6 and 25.2 J/mL doses, respectively. However, anthocyanin level of red GJ was significantly affected by the heat treatment with an 11.8% loss (P < 0.05). The percent polymeric colour of the red GJ with heat treatment was significantly higher compared to the colour with the UV-C treatment.
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    Formation kinetics of hydroxymethylfurfural and brown coloured compounds in goat milk during heating
    (Wiley, 2013) Guneser, Onur; Toklucu, Aysegul Kirca; Karagul-Yuceer, Yonca
    The formation of hydroxymethylfurfural, nonenzymatic brown coloured compounds and free sulphydryl groups in goat milk was studied during heating at 7595 degrees C. Analysis of kinetic data suggested that formation of hydroxymethylfurfural and nonenzymatic brown coloured compounds followed zero order reaction kinetics, while formation of free sulphydryl groups during heating varied depending on heating time. A good linear correlation (r = 0.839) was found between brown coloured compounds and hydroxymethylfurfural content in milk samples during heating. Activation energies (Ea) for the formation of hydroxymethylfurfural and nonenzymatic brown coloured compounds were 96.31 and 69.79 kJ/mol, respectively.
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    Kinetic Analysis of Anthocyanin Degradation and Polymeric Colour Formation in Grape Juice during Heating
    (Czech Academy Agricultural Sciences, 2015) Danisman, Gulsan; Arslan, Esra; Toklucu, Aysegul Kirca
    The degradation of total monomeric anthocyanins and changes in the proportion of polymeric colour (% PC) as well as antioxidant capacity of grape juice were studied during heating at 70-90 degrees C. Anthocyanin degradation fitted to a first order reaction model, while the formation of % PC followed zero order reaction kinetics. High correlations (r = 0.989-0.997) were found between anthocyanin degradation and % PC formation during heating. The activation energies for the degradation of anthocyanins and formation of % PC were 64.89 and 50.42 kJ/mol, respectively. Trolox equivalents antioxidant capacity (TEAC) values of grape juice slightly changed during heating.
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    Microbial, physicochemical and sensory properties of UV-C processed orange juice and its microbial stability during refrigerated storage
    (Elsevier, 2013) Pala, Cigdem Uysal; Toklucu, Aysegul Kirca
    The effect of the UV-C light on quality characteristics (microbiological, physicochemical and sensorial) and microbial stability of orange juice (OJ) during storage (4 and 10 degrees C) were investigated and the results were compared with untreated and heat treated (at 90 degrees C, 2 min) juice. UV-C treatment (36.09 kJ/L dose) of OJ resulted in 2.8 log and 0.34 log reductions in aerobic plate count and yeast & mould count, respectively. Also, a 5.72 log reduction in Escherichia coli ATCC 25922 after UV-C treatment (36.09 kJ/L dose) was achieved, which indicates an acceptable reduction of a potential pathogen in juices. Ascorbic acid content as a major quality parameter of OJ did not change significantly after the UV-C treatment (36.09 kJ/L dose). Differences between untreated and UV-C treated (48.12 kJ/L dose) OJ were small in terms of organic acids, antioxidant capacity and phenolics. Based on sensory analysis results, no significant differences were detected between fresh and UV-C treated juices, and UV-C treated OJ was preferred more than the heat treated juice. UV-C treatment partially extended the shelf life of fresh juice during storage at the refrigerated conditions. (C) 2012 Elsevier Ltd. All rights reserved.
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    Optimization of organogels prepared with turpentine oil and wax mixtures via response surface methodology and determination of vaporization kinetic parameters
    (Wiley, 2024) Ogutcu, Mustafa; Albayrak, Elif Dincer; Toklucu, Aysegul Kirca
    BACKGROUNDThe main aim of the study is to investigate the thermal, textural and vaporization behaviors of turpentine oil (representing essential oils) organogels prepared with wax mixtures (beeswax, BW; shellac wax, SHW) instead of a single wax. The second aim was to determine the optimum level of wax addition to minimize vaporization of volatiles using response surface methodology.RESULTSBoth weighing and thermogravimetric analyses showed that when the total wax concentration increased, the vaporization was decelerated. The variation of the hardness and melting point values depended on both wax types and amounts in the mixtures. Additionally, the kinetics of the vaporization of the volatile compounds at 37 degrees C were evaluated, and both first- and second-order reaction kinetic models fitted well for the vaporization with R2 values of 0.96-0.99. The organogelation increased the thermal stability and limited the release of volatiles. The multiple response optimization results showed that the melting point, the reaction rate constant and the weight loss of the organogels produced with 24.43% BW and 17.68% SHW were 44.40 degrees C, 4.00 x 10-3 day-1 and 30.02%, respectively.CONCLUSIONAs a result, essential oil organogels produced with a wax mixture instead of a single wax can provide controlled release of volatiles as well as tailored texture and melting range. (c) 2024 Society of Chemical Industry.