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    Effects of Elevated Temperature and Carbon Dioxide Concentrations on Aromatic Compounds of Stevia rebaudiana
    (Springer India, 2021) Tursun, Ayse Ozlem; Jabran, Khawar; Gurkan, Hacer; Telci, Isa
    A global rise in CO2 concentration and temperature levels can impact the living part of the earth including the plants. Stevia or candy leaf (Stevia rebaudiana Bertoni) is a medicinal aromatic plant that produces several useful chemical compounds. Studies were carried out in a fully automated greenhouse in order to determine the response of aromatic compounds of stevia leaves to different CO2 concentrations and temperature levels. This study had four treatments including (1) 26 +/- 1/16 +/- 1 degrees C day/night temperature plus 400 +/- 50 ppm CO2 concentration [control], (2) 29 +/- 1/19 +/- 1 degrees C day/night temperature plus 600 +/- 50 ppm CO2 concentration, (3) 32 +/- 1/22 +/- 1 degrees C day/night temperature plus 800 +/- 50 ppm CO2 concentration and (4) 35 +/- 1/25 +/- 1 degrees C day/night temperature plus 1000 +/- 50 ppm CO2 concentration. Results of the study showed that yield of total aromatic compounds ranged between 12.65 and 13.65 mu g/g for stevia . Generally, concentrations of the compounds such as ketones, aldehydes and alcohols were decreased with increase in concentration of CO2 and temperature. Terpenes were the compounds whose concentrations were increased with increase in concentration of CO2 and temperature. The climatic conditions did not cause a significant change in the aromatic compounds of stevia.
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    Floral authentication of some monofloral honeys based on volatile composition and physicochemical parameters
    (Springer, 2022) Yildiz, Oktay; Gurkan, Hacer; Sahingil, Didem; Degirmenci, Atiye; Kemal, Mehtap Er; Kolayli, Sevgi; Hayaloglu, Ali Adnan
    Twenty four honey samples of eight distinct botanical origins obtained from different regions of Turkey were analyzed in this study. Various physicochemical (glucose and fructose content, color, diastase activity, electrical conductivity, optical rotation, moisture and proline content), biochemical (total phenolic content, total flavonoid content, FRAP antioxidant capacity and DPPH radical scavenging activity) and volatile analytical methods were used for floral authentication of the honeys. Identification of 103 volatile compounds from different chemical classes was carried out using SPME/GC/MS. The availability of physicochemical and volatile identification methods, instead of melissopalynology which is dependent on the researcher's ability and judgment regarding honey classification, was investigated. The results were statistically processed, and principal component analysis (PCA) was applied. The first two principal components explained 98.10% of the total variance, and the PCA produced eight different groups rhododendron, chestnut, lavandula, astragalus, chaste tree, polyfloral, oak, and pine honeys, each corresponding to a distinct botanical origin. Polyfloral honeys formed a cluster, although those samples were rather widespread. The studied honeys exhibited specific volatile compounds and biochemical properties which may be capable of use as floral markers.
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    Influence of purple basil extract (Ocimum basilicum L.) on chemical composition, rheology and antioxidant activity of set-type yoghurt
    (Croatian Dairy Union, 2019) Gurkan, Hacer; Boran, Osman Seracettin; Hayaloglu, Ali Adnan
    Four different types of yoghurt were manufactured using purple basil which was added to milk as water extract or powder forms at levels of 1.0 % and 0.4 % (w/w). Physicochemical and rheological properties, antioxidant capacity, color and total phenolic contents of yoghurt samples were measured during 21 days of storage. None of changes were observed for titratable acidity, pH and hardness parameters of yoghurt samples; however, some changes were observed during storage. The contents for total phenolic compounds and antioxidant activity [2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid diammonium salt (ABTS(+)*) and 22-Diphenyl-1-picrylhydrazyl (DPPH*) values] were dramatically higher in powder-added yoghurt samples than those of its water extract counterparts, while the lowest total phenolics and ABTS(+)* were observed in control sample during storage. The values for storage and loss modulus were higher in water extract-added samples than powder-added counterparts. In conclusion, no significant effect of the addition of powder or water extract of basil was observed on gross chemical characteristics of yoghurt, while use of basil powder positively contributed to antioxidant activity and changed the rheological behavior of yoghurt gel.