http://hdl.handle.net/20.500.12566/31 2026-04-06T03:25:44Z 2026-04-06T03:25:44Z Öziyci, Hatice Reyhan Okutucu, Aleyna Or, Hamide Sena Karhan, Mustafa http://hdl.handle.net/20.500.12566/2321 2025-12-01T17:32:54Z 2024-01-01T00:00:00Z

Contribution of stevia to the perception of sweetness and bitterness in fruit drinks Öziyci, Hatice Reyhan; Okutucu, Aleyna; Or, Hamide Sena; Karhan, Mustafa The rise of healthy living trends has increased the popularity of natural sweeteners like stevia, derived from the Stevia rebaudiana plant. This study aimed to examine stevia’s impact on the sweetness and bitterness perceptions of apricot and sour cherry drinks. Initially, fruit drinks with 0% stevia (control group sugar source: saccharose) were produced using an optimal formulation (100 g sugar, 20% fruit puree, 0.3% citric acid, 1 L distilled water) based on Karhan et al.’s experiment (2024). In the earlier panel reviews, a 75% stevia substitution ratio was found to be the best. This study also tested that ratio, and all stevia-substituted fruit drinks (75 and 100%) were made using Karhan et al.'s formula. In the post-production stage, the drinks underwent pH and total soluble solids (Cemeroğlu, 2007), and sensory analyses with panelists (N = 12) using intensity scale (1: Very low, 9: Very high) and ranking (1: Most liked, 6: Least liked) tests (Lawless & Heymann, 2010). Results showed that increasing stevia concentrations decreased the pH values of apricot drinks more than sour cherry drinks. High stevia levels significantly lowered soluble solids in both drinks. Sensory analysis indicated that higher stevia concentrations reduced sweetness perception, especially in apricot drinks, and increased bitterness as sucrose-derived sugar content decreased. This shift in the balance between sweetness and bitterness resulted in a less sweet and more bitter flavor profile. The apricot drink with 0% stevia was the most favored, but the 75% stevia apricot drink also performed well, suggesting effective harmonization with apricot at appropriate ratios. However, drinks totally sweetened with stevia, particularly apricot, were least favored, indicating high stevia doses might adversely affect the authentic taste of apricot. Sour cherry drinks with 100% stevia received slightly better scores than their apricot counterparts. Overall, acceptance of stevia as a sweetener varied by fruit type and concentration. Apricot drinks were preferred more with 75% stevia, while sour cherry drinks were less preferred at the same concentration. The data suggest that stevia can create a favorable taste profile when used in suitable compositions and ratios. In summary, panelists rated sweeter drinks as less bitter, indicating sweetness masks bitterness. The effect of stevia on bitterness was less pronounced in sour cherry drinks, suggesting a better blend with sour cherries. The findings of this study highlight that 20 Uluslararası Tüketici ve Duyusal Bilimler Konferansı Bildiriler Kitabı stevia has good potential when applied in the right proportions. The desired amount of this natural sweetener should be specifically designed for each product. The study also emphasizes the significance of optimizing stevia concentrations to effectively balance sweetness and bitterness. To ensure consumer acceptability, it is essential to maintain this balance, as an excessive amount of bitterness can diminish the overall enjoyment of the drink.

2024-01-01T00:00:00Z Kapi, Yeşim Öziyci, Hatice Reyhan Karhan, Mustafa http://hdl.handle.net/20.500.12566/2287 2025-11-25T15:54:53Z 2024-01-01T00:00:00Z

Phenolic acid profile alterations in aqueous and ethanolic stevia extracts across sequential purification stages Kapi, Yeşim; Öziyci, Hatice Reyhan; Karhan, Mustafa Stevia extracts are valued for their health benefits, primarily due to the phenolic acids they contain, which contribute to the antioxidant properties of stevia. This study investigated the alterations in the phenolic acid composition of aqueous and ethanolic stevia extracts across several purification stages. Accordingly, dried stevia leaves were mixed with distilled water or ethanol, centrifuged, filtered, clarified at 50°C with aids, and then passed through stepwise membrane filtration using 30 kDa ultrafiltration and 5 kDa nanofiltration membranes. The phenolic acid composition was analyzed by extracting samples with a 75% methanol and formic acid solution, followed by centrifugation. Detection was performed using an LCMS/ MS device equipped with a C18 column. Chlorogenic acid was the most prevalent in both aqueous and ethanolic stevia extracts. However, the ethanolic extract exhibited a higher concentration (approx. 600 mg/kg) compared to the aqueous extract (approx. 100 mg/kg). After centrifugation and clarification, the phenolic acid concentrations in both extracts significantly decreased. The 30 kDa retentate phase was crucial for the enrichment of chlorogenic and caffeic acids. The aqueous extract reached approximately 120 mg/kg chlorogenic acid, while the ethanolic extract reached about 400 mg/kg. Nanofiltration phases (5 kDa permeate and retentate) significantly reduced the levels of these acids. Other phenolic acids, such as luteolin, apigenin, and rutin, remained at low levels throughout all phases. The solvent used had a significant impact on the phenolic profile, with ethanol being more effective in retaining chlorogenic acid. While the 30 kDa retentate phase concentrated phenolic acids, the type of solvent used played a key role in shaping the overall profile.

2024-01-01T00:00:00Z Kütük, Yüksel Alper Öziyci, Hatice Reyhan Karhan, Mustafa http://hdl.handle.net/20.500.12566/2286 2025-12-01T15:57:07Z 2024-01-01T00:00:00Z

Electrocoagulation for D-pinitol enrichment from carob extract: Plate selection. Consulting and Training Centre KEY. Kütük, Yüksel Alper; Öziyci, Hatice Reyhan; Karhan, Mustafa D-Pinitol (3-O-methyl-D-chiro-inositol), a bioactive compound holds promise for its anti-diabetic properties. However, synthesizing D-pinitol in laboratory settings is prohibitively expensive, prompting research to focus on extracting and purifying it from natural sources. This study introduces electrocoagulation (EC) as an innovative technique not previously explored for D-pinitol extraction from carob extract. EC facilitates the removal of charged compounds in colloidal suspensions by inducing collisions and neutralization with ions of opposite charges. The efficiency of this process largely depends on the types of plates used, as they vary in effectiveness based on the colloidal compounds in the solution. In this context, this study evaluated aluminum (Al) and stainless-steel (SS) plates, commonly employed in EC research, to ascertain their effectiveness in the extraction process. Four distinct trials were designed, positioning each plate type at the anode and cathode ends within the EC system. The experiments maintained fixed operational parameters (Electrode interval: 3 cm, current density: 60 mA/cm², voltage: 30 V, and time: 60 min) in the carob extract produced from cultivated carob fruits grown in Antalya, Türkiye. The effectiveness of EC was assessed by determination of D-pinitol content (using HPLC separation and refractive index detection), colorimetric analysis of total phenolic content (using a spectrophotometer), color measurement (using a colorimeter), and turbidity measurement (using a turbidimeter) in the post-treatment The study found that the Al (-) and SS (+) plate combination significantly enhanced D-Pinitol yield by 23%, increasing it from 17 to 42.36 g/100 g dry matter. Additionally, there were reductions in total phenolic content and turbidity, along with an improvement in color (L value). The results indicate the success of EC as an intermediate process for D-Pinitol purification.

2024-01-01T00:00:00Z Başer, Gözdegül Mutlu, Eda Evla Ramalhosa, Elsa http://hdl.handle.net/20.500.12566/1995 2024-03-25T13:04:52Z 2023-01-01T00:00:00Z

Ethical food entrepreneurship: a review of the literature and a case analysis based on ethical matri Başer, Gözdegül; Mutlu, Eda Evla; Ramalhosa, Elsa Uluslararası Gastronomi, Turizm ve Kültür Çalışmaları Sempozyumu (4. : 2023 : Çeşme, Türkiye)

2023-01-01T00:00:00Z