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    Effect of pH and ionic strength on functional, structural, and interfacial rheological properties of aquafaba
    (Elsevier B.V., 2025) Parlak, Mahmut Ekrem; Ozmen, Duygu; Toker, Omer Said; Inan, Mehmet; Sarıcaoğlu, Furkan Turker
    This study explored the nuanced influence of pH and ionic strength on aquafaba and investigated its viability as a plant-based alternative in food formulation. Functional assessments, including foaming capacity (FC), foam stability (FS), emulsifying activity index (EAI), and emulsifying stability index (ESI), underscore the critical role of pH. FC and FS peaked at pH 4, whereas EAI was highest at pH 5, highlighting the significant impact of protein net charge on aquafaba functionality. However, although increasing the ionic strength decreased the absolute zeta potential, the foaming and emulsifying properties differed. Rheological analysis confirmed non-Newtonian shear-thinning behavior, which shifted toward Newtonian-like behavior near the isoelectric point. The increasing ionic strength significantly increased the ?-helix content by decreasing the ?-structure content, which increased the adsorption rate of aquafaba at the air/water (A/W) interface. The pH-dependent adsorption rates highlight the importance of the net surface charge of the adsorbed molecules. The interfacial shear rheology results showed that while the foaming properties of aquafaba are dominated by the adsorption rate, the emulsifying properties are mainly dominated by the interactions between adsorbed molecules rather than the adsorption rate at the oil/water (O/W) interface. In summary, this study provides comprehensive insights into the intricate interplay between pH and ionic strength in aquafaba, which is crucial for the formulation of sustainable plant-based alternatives in the food industry. © 2025 Elsevier B.V.
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    Influence of seed concentration and storage time on the rheological, textural, and microscopic crystallization attributes of Apis mellifera honey
    (Elsevier, 2025) Ozmen, Duygu; Demircan, Huseyin; Yildirim, Rusen Metin; Waseem, Muhammad; Basdogan, Hakan; Toker, Omer Said; Osei Tutu, Crossby
    This study aimed to evaluate the impacts of seed honey supplementation at concentrations of 5, 10, and 15 % (w/w) and storage time (up to 12 days at 14 degrees C) on the rheological, textural, crystallization, and colour attributes of honey. The rheological properties, including the apparent viscosity, loss modulus, and storage modulus, were assessed using a rheometer. Textural properties, such as hardness and spreadability, were measured using a texture analyzer. The L* values were determined to assess the crystallization process, and microscopic imaging was used to observe the size and formation of the sugar crystals. Results showed that the apparent viscosity increased significantly (p < 0.05) from 13.1 Pa.s to 38.5 Pa.s (194 % up arrow) as both the seed concentration and storage time increased from 0 %-15 % and 0-12 days, respectively. The highest G value (2756 Pa) was observed on the 9th day for the 15 % seed concentration. The work of shear decreased with increasing seed concentrations but increased over storage time. L* values, an indicator of crystallization, showed a significant increase across concentrations and storage time. Microscopic examination of seed crystals anticipated zero crystals at 0-12th day in control; however, 6th and 12th days of storage at 10 % and 15 % addition of seeds increased size and magnitudes of crystals than 5 %. Conclusively, adding seed honey at levels up to 10 % and allowing 9 days of storage effectively promotes the shear-thinning behaviour desirable in spreadable honey products. Creamed honey offers improved texture and user convenience, enhancing product versatility without compromising flavour. These results provide a practical basis for optimizing processing conditions in commercial honey formulation to meet diverse consumer and market needs.
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    Textural, rheological, and structural properties of turkey and chicken gelatins from mechanical deboning residues
    (Wiley, 2024) Kurt, Abdullah; Toker, Omer Said; Akbulut, Mehmet; Coklar, Hacer; Ozmen, Duygu; Ozcan, Yilmaz; Argun, Mustafa Samil
    Large amounts of collagen-rich by-products are generated in poultry processing. In particular, gelatin from the by-products of turkey processing is limited. Gelatin extraction from turkey and chicken MDRs (mechanically deboning residue) was the purpose of this study. Both materials were modified at the highest swelling pH for chemical denaturation of collagen and hot water extraction of gelatin was performed at the optimum temperature-time, which was determined to be pH 1.0 and 80 degrees C-6 h, respectively. In these conditions, yields of 9.90% turkey gelatin (TG) and 13.85% chicken gelatin (CG) were produced. They demonstrated similar viscosity, gel strength, and lightness values of 72-73 g, 2.5-2.7 mPas, and 31, respectively. These results are close to those of bovine gelatin (BG). TG with 239.78 g Bloom exhibited higher strength than CG (225.27 g) and BG (220.00 g). The melting and gelation temperatures of CG and BG were 21 and 30 degrees C, respectively, while those of TG were 19 and 28 degrees C. Imino acids (proline + hydroxyproline) of TG (22.82%) were higher than those of CG (20.73%). Fourier transform infrared spectroscopy (FTIR) analysis revealed secondary structure and functional groups of CG and TG similar to those of BG. CG displayed a higher thermal transition temperature than BG, while TG exhibited the highest temperature sensitivity, according to the differential scanning calorimetry (DSC) analysis. In conclusion, TG showed higher potential for effective utilization with higher bloom and imino acids. Overall, turkey and chicken MDRs are a promising and potential alternative source to produce gelatin with comparable properties to bovine gelatin for intended food applications as well as for pharmaceutical and cosmetic fields. This is a novel research paper on the production of gelatin from alternative sources, turkey and chicken MDRs (mechanically deboning residues), as by-products of poultry processing. The findings of this study will be useful to the literature and the food science and technology.image