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    Development of Stable Microemulsions Containing Laurel Essential Oil Using Amylopectin and Gum Arabic as Natural Emulsifiers
    (Wiley-V C H Verlag Gmbh, 2025) Berber, Mehmet Mert; Uzkuc, Nesrin Merve Celebi; Uzkuc, Hasan; Kuzu, Kubra Tarhan; Hosoglu, Muge Isleten; Togay, Sine Ozmen; Toklucu, Aysegul Kirca
    This study aimed to develop food-grade microemulsions of laurel essential oil (L-EO) (MEs) stabilized with amylopectin (L-AP) and gum arabic (L-GA) and to determine characteristic properties of the MEs at different pH and temperatures during storage. L-EO was extracted using the microwave-assisted hydrodistillation technique. The prepared ME droplets ranged in size range from 328 to 347 nm in L-AP (pH 6.0) and from 327 to 432 nm in L-GA (pH 3.0). The total phenolic content and antioxidant capacity were 170.60 mg/L gallic acid equivalent (GAE) and 0.93 mM Trolox/mL in L-AP, respectively, while total phenolic content was 243.10 mg/L GAE and antioxidant capacity was 1.19 mM Trolox/mL in L-GA. Additionally, the MEs demonstrated relatively potent antimicrobial activity against Escherichia coli, Bacillus cereus, and Staphylococcus aureus strains. The main volatile compounds of L-EO were identified as 1,8-cineole (33.4%), sabinene (8.4%), and linalool L (6.6%).
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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 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.