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Öğe A new approach to enhance quinoa protein nano-aggregates: Combined pH shifting-High pressure homogenization(Elsevier Sci Ltd, 2023) Yildiz, Gulcin; Yildiz, GokcenThe physicochemical characteristics of soluble nano-sized quinoa protein isolates prepared by combined pH shifting and high-pressure homogenization were studied. Commercial quinoa protein isolates were exposed to pH shifting at acidic (pH 2-6) or alkaline (pH 8-12) conditions followed by high-pressure homogenization earlier than neutralizing of pH to 7.0. The pH method under pH 12 followed by high-pressure homogenization was found as the most efficient treatment in the reduction of protein aggregate sizes and transparency, improving soluble protein content and surface hydrophobicity. Quinoa protein isolates treated with pH 12 and high-pressure homogenization increased the solubility from 7.85% to 78.97%, creating quinoa protein isolate nano -aggregates with an average size around 54 nm. The quinoa isolate aggregates were used to produce oil-in-water nanoemulsions, which demonstrated the good stability for 14 d at 4 degrees C. This new approach might present an effective technique for the modification of functional features of quinoa protein isolates.Öğe Effect of high-intensity ultrasound-induced acoustic cavitation on enzymatic activity and quality attributes of granny smith apples during storage(Keai Publishing Ltd, 2025) Yildiz, Gulcin; Yildiz, GokcenThis study investigates the effects of high-intensity ultrasound (HIU), chemical treatments (ascorbic acid and calcium chloride), and thermal treatment (water bath at 65 degrees C) on metabolic, structural, and physical changes in Granny Smith apples during a 14-day cold storage period. HIU, a non-thermal physical processing method, utilizes acoustic cavitation and microstreaming to induce mechanical and oxidative stresses at the cellular level, thereby inhibiting enzymatic browning, reducing microbial load, and preserving bioactive compounds. Treated apples were stored at 4 degrees C and analyzed on Days 0, 7, and 14 for antioxidant capacity using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC) assays; total phenolic content (TPC); total flavonoid content (TFC); ascorbic acid levels; and enzymatic activities of polyphenol oxidase (PPO) and pectin methyl esterase (PME). Additional quality parameters included texture, colorimetric properties, microbial counts, and sensory quality. Compared to chemical and thermal treatments, HIU treatment significantly preserved firmness and color parameters, reduced enzymatic activity, and enhanced antioxidant retention (p < 0.05). Ultrasound-treated samples also exhibited minimized off-odor development and decay. These results demonstrate that HIU, through mechanisms such as acoustic cavitation and shear forces that alter cellular structure and inhibit enzymatic activity, offers a promising, non-thermal, scalable approach for extending shelf life and maintaining the nutritional and sensory quality of fresh produce, meeting the growing demand for clean-label, minimally processed foods.Öğe Effects of Ultrasound and Microwave-Hot Air Drying on the Drying Kinetics and Physicochemical Properties of Mango Powder(Wiley, 2025) Ahmed, Ahmed Abdirahman; Yildiz, GokcenThis study evaluated the effects of ultrasound (ULS) pretreatment (15 and 30 min) combined with different drying methods-hot air drying (HAD), microwave drying (MW), and hybrid microwave-hot air drying (MW-HAD)-on the drying kinetics and physicochemical attributes of mango powder. Results demonstrate that 30 min ULS pretreatment with MW-HAD (200 W + 70 degrees C) significantly enhanced drying efficiency, reducing processing time by 80% (p < 0.05). However, quality outcomes were method-dependent: MW drying at 200 W without pretreatment optimally preserved bioactive compounds, maintaining phenolic content (1431.86 mg/100 g GA dry weight) and antioxidant capacity (23.41 mu mol Trolox/g dry weight). Conversely, HAD at 70 degrees C without pretreatment produced powders with superior physical properties, including higher bulk density (0.35 g/cm3) and improved flow characteristics (CI = 33.35). Functional properties were most enhanced by ULS pretreatment, which increased water solubility index (42.32%) and swelling capacity (48.91 mL/g). These findings provide a framework for industrial process selection: MW drying for nutrient retention, HAD for powder handling, and ULS pretreatment MW-HAD for time-sensitive production. The study emphasizes the importance of method selection based on targeted quality parameters in mango powder processing. Furthermore, future research should focus on optimizing ULS parameters to simultaneously maximize efficiency and quality, facilitating the industrial adoption of this promising technology.Öğe High-intensity ultrasound treatment to produce and preserve the quality of fresh-cut kiwifruit(Wiley, 2022) Yildiz, Gokcen; Yildiz, Gulcin; Khan, Moazzam Rafiq; Aadil, Rana MuhammadIn this study, high-intensity ultrasound (HIU), antibrowning chemicals (calcium chloride and ascorbic acid), water bath were used to avoid the browning of kiwifruit pieces, and the shelf-life of fresh-cut was measured (two weeks). The treated fresh-cut kiwi samples were evaluated in terms of color, enzyme activities, bioactive compounds, microbial, and sensory studies. The study has shown that HIU treatment restricted (p < .05) the microbial growth (bacteria, yeast, and mold) in fresh-cut kiwi samples at 4 degrees C. Moreover, kiwi samples exposed to HIU exhibited significant (p < .05) enhancements in bioactive metabolites as well as improvements in the physical features with the comparison of all other applications. Similarly, the lowest browning index values were observed for kiwifruit samples by HIU at the end of storage (180.04). Furthermore, the lowest scores for decay (0.5/3.0 and 0.9/3.0 on days 7 and 14, respectively) and off-odor (1/7 and 2/7 on days 7 and 14, respectively) were determined for the fresh-cut kiwifruit subjected to HIU. It has been proposed that HIU application is a possible choice to take the place of chemical and physical approaches to extend the product life and maintain quality characteristics in fresh-cut kiwifruit at cold storage conditions. Novelty impact statements A significant improvement in the quality of HIU-treated fresh-cut kiwifruits with the comparison of other chemical and physical treatments was achieved. This study contributed a novel method to develop HIU-treated fresh-cut fruit and vegetables with enhanced product quality and extended shelf life. In overall, processing of fresh-cut kiwifruits with a HIU treatment might be applied to get a high-quality and browning-free product.Öğe Insights into Ultrasound-Assisted Postharvest Preservation: Metabolic, Structural, and Quality Changes in Strawberries During Storage(Springer, 2025) Yildiz, Gokcen; Yildiz, GulcinThis study investigates the effects of high-intensity ultrasound (HIU), chemical treatment (ascorbic acid and calcium chloride), and physical treatment (water bath at 65 degrees C) on the metabolic and structural changes in strawberries during 14 days of storage. Ultrasound applications demonstrated potential in preserving freshness, enhancing nutrient retention, inhibiting microbial growth, and minimizing enzymatic browning in fresh produce. Treated strawberry samples were stored at 4 degrees C, with analyses conducted on days 1, 3, 7, and 14 to assess antioxidant capacity (DPPH, FRAP, ORAC), total phenolic content, total flavonoid content, ascorbic acid content, enzyme activities (polyphenol oxidase [PPO] and pectin methyl esterase [PME]), texture, color, microbial load, and sensory attributes. Ultrasound treatment significantly (p < 0.05) inhibited microbial growth (bacteria, mold, and yeast), improved bioactive compound retention, reduced enzymatic activities, and minimized browning compared to other treatments. Ultrasound-treated samples also maintained superior color parameters, exhibited lower decay rates, and had better sensory scores, particularly regarding off-odor. By extending shelf life, reducing enzymatic degradation, and preserving nutritional and sensory qualities, this study highlights ultrasound as a promising scalable, non-thermal approach for the postharvest preservation of strawberries and fresh-cut produce, aligning with the demand for clean-label, minimally processed foods.
