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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 Alteration of proteins upon high-pressure processing treatment(Elsevier, 2025) Yildiz, Gulcin; Yıldız, GökçenHigh-pressure processing (HPP) is an innovative nonthermal technology used in the food industry to enhance food safety, extend shelf life, and preserve sensory and nutritional qualities. This chapter explores the alterations in protein structure and functionality resulting from HPP. Proteins are sensitive to high pressure, which can lead to changes in their conformation, aggregation, and engagement with other food components. The extent and nature of these alterations depend on various factors, including pressure levels, treatment duration, pH, the specific protein's type and structure, and presence of other food components. The chapter investigates the effects of HPP on protein denaturation, unfolding, and aggregation, as well as the resultant impacts on protein solubility, emulsifying abilities, foaming characteristics, gelation, rheological features, and water/oil holding ability. Additionally, it examines how HPP affects the enzymatic activity of proteins, with implications for food safety and nutrition. The findings demonstrate that HPP can be tailored to achieve desired modifications in protein properties, offering potential applications in developing novel food products and enhancing the quality of existing ones. The chapter contributes to a more detailed exploration of the molecular dynamics influencing protein alteration during HPP, paving the way for future research and applications in food research and technology. © 2025 Elsevier Inc. All rights reserved.Öğe Comparison of chemical, physical, and ultrasound treatments on the shelf life of fresh-cut quince fruit (Cydonia oblonga Mill.)(Wiley, 2020) Yildiz, Gulcin; İzli, Gökçen; Aadil, Rana MuhammadThe study was conducted to examine the effect of chemical treatment (ascorbic acid and calcium chloride), physical treatment (water bath at 65 degrees C), and ultrasound (US) in ultrasonic bath for the prevention of enzymatic browning of fresh-cut quince slices during 14 days of storage. The treated quince slices were analyzed in terms of color, polyphenol oxidase, and pectin methyl esterase activity, bioactive compounds, sensory, and microbial analysis. The results showed that US treatment inhibited (p < .05) the growth of bacteria, mold, and yeast in fresh-cut quince slices during 4 degrees C storage. The US-treated slices showed a significant (p < .05) improvements in bioactive compounds as well as improved physical properties as compared to all other treatments. Similarly, US-treated samples showed the best color values with the lowest value of enzyme activities showing less enzymatic browning. Moreover, the findings showed that the lowest score for decay and off-odor were obtained for the quinces treated with US. Practical applications A significant improvement in the quality of US-treated fresh-cut quinces with the comparison of other chemical and physical treatments was achieved. This study will contribute a novel method to develop US-treated fresh-cut fruit and vegetables with an enhanced product quality and extended shelf life. In overall, processing of fresh-cut quince fruit with a US treatment might be applied to get a high-quality and browning-free product.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 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 Influence of microwave and microwave-convective drying on the drying kinetics and quality characteristics of pomelo(Wiley, 2019) Yildiz, Gulcin; İzli, GökçenThe present study investigated the effects of microwave (90 and 160 W) and combined microwave-convective (90 W-55 degrees C, 90 W-65 degrees C, 90 W-75 degrees C, 160 W-55 degrees C, 160 W-65 degrees C and 160 W-75 degrees C) drying techniques on the drying kinetics, color parameters (L*, a*, b*, C, alpha degrees and Delta e), total phenolic content (TPC), and antioxidant capacity (ATC) of pomelo samples. The drying data were fitted to 10 typically used thin-layer drying models to select a suitable model for drying of pomelo. Comparing the statistical parameters of applied models, the Diffusion Approach, Midilli et al., and Page models were found to be the best-fitting models in describing drying kinetics of the pomelo samples. It was observed that the drying temperature and/or microwave power changed significantly the all color parameters, TPC, and ATC. The combined microwave-convective drying resulted in shorter drying times with higher drying rates and high-quality dried pomelo samples. Practical applications A significant improvement in the quality retention of combined microwave-convective drying of pomelo slices was achieved. This piece of work will provide a novel method to produce microwave-convective-dried pomelo fruits with a significantly improved product quality. A practical implication is that drying of pomelo slices with an optimum condition by combined microwave-convective process can be used to get a high-quality product with a higher ATC, TPC, and color.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.Öğe Power ultrasound and its applications in food processing(Nova Science Publishers, Inc., 2023) Yildiz, Gulcin; Yıldız, GökçenThis book includes seven chapters about power ultrasound and its applications in food processing. Chapter One describes the application of ultrasound technology in refining vegetable oils. Chapter Two provides data related to the effect of ultrasound pre-treatment in drying food. Chapter Three presents the effect of sonication treatment on the quality properties of apple-carrot juice. Chapter Four summarizes the ultrasound-assisted extraction of pectin from tropical fruit by-products. Chapter Five discusses the value-added ultrasound technology assuring the safety of seafood. Chapter Six details the comparison of antioxidants and ultrasound treatment on the color, enzymatic browning and bioactive compounds of fresh-cut radishes. Chapter Seven highlights the comparative analysis of ultrasonic probe and water bath systems on the functional properties of whey protein isolate. © 2023 by Nova Science Publishers, Inc. All rights reserved.Öğe Quality retention in pumpkin powder dried by combined microwave-convective drying(Springer, 2022) İzli, Gökçen; Yildiz, Gulcin; Berk, Senel EcemThree distinct drying methods, microwave drying (MWD), convective drying (CVD) and microwave-convective drying (MWCVD) with a grinding process were applied to obtain pumpkin powder. The effects of CVD (60, 70 & 80 °C), MWD (100 & 200 W) and MWCVD (100 W-60 °C, 100 W-70 °C, 100 W-80 °C, 200 W-60 °C, 200 W-70 °C, and 200 W-80 °C) applications on the physicochemical properties (water activity, bulk, tapped & particle densities, porosity, flowability, cohesiveness, swelling capacity, water holding capacity and water solubility index), color values (L*, a*, b*, C, αo and Δe), bioactive compounds (5-Hydroxymethyl-2-furfural (HMF), total phenolic content (TPC) and antioxidant capacity (DPPH and ABTS)) of the eleven pumpkin fruit powders were compared. The MWCVD, namely pumpkin powders dried at 200 W–80 °C resulted in shorter drying times with high‐quality dried pumpkin powders. The bulk, tapped and particle densities of pumpkin powders at 200 W-80 °C by MWCVD were 0.56, 0.66 and 1.74 g/cm3, respectively. These values are indicators of the good porosity (61.82%) of pumpkin powders. In addition, the highest TPC (1277.08 mg GA/100 g dw) and ABTS (126.99 ± 3.31 µmol Trolox/g dw) was observed for microwave-convective dried pumpkin powders at 200 W-80 °C. On the other hand, the lowest HMF level (10.12 ± 1.78 mg/kg dw) was found for the pumpkin poowders dried by MWCVD at 200 W-80 °C. In overall, dried pumpkin powders by a MWCVD method can be employed to acquire a high-quality food material along with an enhanced physicochemical properties, color and bioactive components.Öğe Quantum and Tempus Theories of Functional Food Science(CRC Press, 2025) Yildiz, Gulcin; Yıldız, GökçenThe field of Functional Food Science has witnessed significant advancements in recent years, driven by the need to understand and enhance the health benefits of foods beyond basic nutrition. This chapter introduces two groundbreaking theoretical frameworks—Quantum Theory and Tempus Theory—that offer innovative approaches to optimizing functional foods at both molecular and temporal levels. Quantum Theory, rooted in the principles of quantum mechanics, explores the behavior of bioactive compounds at the atomic and subatomic scales. It provides insights into molecular interactions within functional foods, enabling researchers to manipulate and optimize the stability, solubility, and bioavailability of nutrients. By leveraging concepts such as wave-particle duality, quantum tunneling, and quantum entanglement, this theory facilitates the design of novel food formulations that enhance health outcomes through targeted nutrient delivery and improved metabolic processes. Tempus Theory, in contrast, focuses on the temporal dynamics of nutrient metabolism and physiological responses, emphasizing the importance of aligning dietary practices with the body’s natural biological rhythms. This theory highlights the role of circadian rhythms and other temporal cues in influencing nutrient absorption, metabolism, and overall metabolic efficiency. By studying the effects of meal timing, seasonal variations, and individual chronotypes, Tempus Theory provides a framework for chrononutrition—tailoring dietary recommendations to optimize health based on the time of day or individual biological rhythms. The integration of Quantum and Tempus Theories offers a synergistic approach in Functional Food Science, merging molecular precision with temporal adaptation. This comprehensive framework has the potential to revolutionize personalized nutrition, paving the way for new strategies that enhance health and prevent disease through diet. By combining the microscopic insights of Quantum Theory with the macroscopic considerations of Tempus Theory, researchers and nutritionists can unlock new possibilities for developing functional foods that are both scientifically advanced and aligned with the body’s natural processes. This chapter explores these innovative perspectives, providing a foundation for future research and development in the rapidly evolving field of Functional Food Science. © 2026 selection and editorial matter, Mohammad Ashrafuzzaman & Jack A. Tuszynski; individual chapters, the contributors.Öğe The effect of ultrasound pretreatment on quality attributes of freeze-dried quince slices: Physical properties and bioactive compounds(Wiley, 2019) Yildiz, Gulcin; İzli, GökçenThe study was conducted to examine the effect of ultrasound (US) pretreatment on physical and chemical/nutritional attributes of freeze-dried quince slices. The quince fruits were washed, hand-peeled and cut with a dimension of 1 cm (L) x 0.2 (W) cm x 1 cm (H). The quince samples were treated in an ultrasonic bath in three different times which were 10, 20, and 30 min. Untreated and ultrasonically pretreated quince samples were dried in a freeze dryer. Freeze-dried samples were analyzed in terms of physical properties such as shrinkage, rehydration, color, water activity, and hardness and bioactive compounds including total phenols, ascorbic acid, and antioxidant capacity. A significant difference was observed among untreated and ultrasonically pretreated quince samples. The freeze-dried quince slices treated with a US (especially 20 min-treatment) showed a higher preservation of bioactive compounds in addition to improved physical properties compared to the untreated quince samples. In overall, US pretreatment is a promising process as demonstrated in current research by its capability to better retain freeze-dried quince quality in terms of physical and chemical properties. Practical Applications The freeze drying of quince fruit with the aid of US pretreatment was investigated. A significant development in the quality preservation of freeze-dried of quince slices with an US-pretreatment was accomplished. This research will contribute a useful technique to produce freeze-dried quinces with a significantly enhanced product quality. Drying of quince samples with a freeze drying in addition to US-pretreatment might be applied to get a high-quality fruit with an improved bioactive compounds and physical property.
