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    Oleogels of Some Plant Waxes: Characterization and Comparison with Sunflower Wax Oleogel
    (Wiley, 2021) Yılmaz, Emin; Keskin Uslu, Eda; Öz, Ceren
    This study aimed to develop the oleogels of teawax (TWO), rapeseed wax (RWO), orange peel wax(OWO), rose wax (RsWO), and beery wax (BWO), and tocompare their properties with sunflower wax oleogel(SWO). Since the literature lacks most of these newoleogels, the gained information would be valuable. Thewax oleogels were analyzed for their main physicochemi-cal, thermal, structural, rheological, and sensory properties.The minimum gelation concentrations (C*) ranged from1.0% (SWO) to 25% (RWO), with gelation times of0.3–205 min, respectively. While polarized light micros-copy images showed large crystal aggregates, X-ray dif-fraction patterns proved the presence ofβ ́ polymorphcrystals and some amorphous solids. Rheological analysesindicated that the samples had a weak-gel structure, andwere stable until around 30–70 C temperatures. Further,the oleogel samples showed a thixotropic rheologicalbehavior with force-related recovery at 10 C. Quantitativesensory descriptive analysis (QDA) proved that there weresome differences among the samples for sensory hardness,spreadability, liquefaction, rancid, waxy, and cooling attri-butes. Also, tea aroma in TWO, bitterness in OWO, androse aroma in RsWO were quite dominant. In conclusion,RWO and OWO seemed unsuitable for food applicationsdue to very high C* and bitterness, while RsWO and BWOcould be used in food formulations.
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    Potansiyel organojelatörlerle yeni oleojellerin geliştirilmesi ve karakterize edilmesi
    (Çanakkale Onsekiz Mart Üniversitesi, Lisansüstü Eğitim Enstitüsü, 2022) Keskin Uslu, Eda; Yılmaz, Emin
    Bu tez çalışmasında, daha önce oleojel üretiminde araştırılmamış veya kısmen araştırılmış bazı organojelatörlerle (kısmi hidrojene hayvansal yağ; çay, portakal kabuğu, dut, gül, kolza tohumu, balina, ve yün mumları; gliserol mono-oleat ve kolesterol; poligliserol stearat ve gliserol monostearat; laurik asit; γ-CD-MOF; bazı emülgatörler; kitosan, kitin, gam arabik, inülin, pektin, siklodekstrin karbonhidrat polimerleri; nohut, darı, arpa, jelatin, yumurta akı ve ipek fibroini proteinleri) yeni oleojeller ve emüljeller geliştirilmiştir. Ayrıca bilinen bazı organojelatörlerle kontrol örnekleri de üretilmiş ve karşılaştırma amaçlı olarak analiz edilmiştir. Emüljel üretiminde yağ fazı içinde sabitlenmiş hidrojel sistemi ile yapılandırma tekniği de bir yenilik olarak geliştirilmiştir. Ayrıca seçilen başarılı iki oleojel kullanılarak %50 yağ içeren, nişasta ve diğer karbonhidratları içermeyen düşük-yağlı mayonez ürünleri geliştirilmiştir. Geliştirilen yeni oleojellerin fiziko-kimyasal (MJK, kristal oluşum zamanı, yağ bağlama kapasitesi, KYİ, renk, FFA, PV gibi), termal (ergime ve kristallenme sıcaklık ve entalpileri), mikro-yapısal (polarize ışık mikroskobu), kristal morfolojisi (X-ışını kırınım deseni), stabilite (santrifüj testi), reolojik özellikler (gerinim, frekans, yapısal yenilenme ve sıcaklık rampa testleri) ve bazılarında duyusal analizler ve tüketici testleri gerçekleştirilmiştir. Literatür için birçoğu ilk ürün olmak üzere geliştirilen oleojellerin büyük çoğunluğunun dayanıklı, ergime ve akış özelliklerinin gıda ürünlerinde kullanıma oldukça uyumlu olduğu belirlenmiştir. Geliştirilen yeni oleojellerin doğrudan gıda (margarin ve sürülebilir yağlar), gıda ingrediyeni (fırıncılık, et, süt ürünleri, çikolata vb.), ve diğer (ilaç, kozmetik vb.) alanlarında uygulama araştırmaları önerilmiştir. Geliştirilen mayonezlerin yapısal ve duyusal özellikleriyle ticari muadilleriyle benzer özelliklerde olduğu anlaşılmıştır. Ayrıca kalori oranı oldukça düşük ve esansiyel yağ asitlerinin kaynağı olarak geliştirilmiştir.
  • Küçük Resim
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    Preparation and characterization of glycerol monostearate and polyglycerol stearate oleogels with selected amphiphiles
    (Elsevier Ltd, 2021) Keskin Uslu, Eda; Yılmaz, Emin
    This study aimed to prepare and compare sunflower oil oleogels with glycerol monostearate (GMS) and polyglycerol stearate (PGS) organogelators. Also, GMS oleogels with Pluronic F68 (F68) and Span 80 (SP80) amphiphiles, and PGS oleogels with Pluronic F68 and Tween 60 (TW60) amphiphiles were prepared to evaluate the effects of amphiphiles on oleogel properties. Minimum gelation concentration, gelation time, oil binding capacity, instrumental color, thermal properties, microscopy, X-ray diffraction patterns, and rheological properties were measured. Results indicated that the addition of the amphiphiles reduced minimum gelation concentration, increased crystals size, enhanced gelation time, changed color values, and reduced melting temperatures. Further, amphiphile addition yielded more stable but softer textures. All samples were thermo-reversible and stable during storage. New data for food-grade PGS oleogels were provided for the literature. PGS oleogels were found as good as GMS oleogels in most properties. Future studies with the prepared oleogels for various applications, including food products are envisioned.
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    Preparation and characterization of oleogels and emulgels with glycerol monooleate–cholesterol mixtures
    (Springer, 2021) Keskin Uslu, Eda; Yılmaz, Emin
    This study aimed to prepare and characterize oleogels and emulgels with glycerol monooleate (GMO): cholesterol gelator system. Oleogels, including 5 and 10% of each gelator were prepared. Emulgels with the same organogelator mixture concentrations, and 10 and 20% water phase were also prepared successfully. The gelation time decreased as the added gelator mixture and water concentrations increased. All samples had signifcant oil binding capacity and creamish-white colors. The oleogels melted just below body temperature, while emulgels melted around body temperature as determined by diferential scanning calorimetry. The samples’ crystalline networks were observed with the X-ray difraction analysis and displayed β and β′ polymorphic type crystals. Rheological measurements revealed that as gelator mixture concentration increased, gel strength enhanced, but in the emulgels, the gel strength decreased signifcantly as added water content increased. All oleogels and emulgels showed time-dependent thixotropic recovery ability. Temperature ramp tests indicated that the oleogels were stable up to 28 °C, but the emulgels kept their gelled consistency up to 70 °C. Overall, the common properties of these new oleogel and emulgels were provided. Future studies for some applications are foreseen.
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    Preparation and characterization of oleogels with tallow and partially hydrolyzed tallow as organogelators
    (CSIC Consejo Superior de Investigaciones Cientificas, 2021) Keskin Uslu, Eda; Yılmaz, Emin
    The aim of this study was to evaluate the organogelation potential of tallow fat (TF) and partially hydrolyzed tallow fat (HTF) against saturated monoglyceride (MG) and a saturated monoglyceride + diglyceride mixture (MDG) as the organogelators. TF itself created oleogel at a 30% addition level, while HTF, MG and MDG oleogels were prepared at 10% addition levels. Fatty acid composition data showed that the oleogel of HTF (HTFO) was quite similar to those of MG and MDG oleogels. Solid fat content, free fatty acidity and peroxide values were found to be in acceptable ranges for HTFO. Thermal properties, crystal morphology and X-ray diffraction patterns were also evaluated. Rheological analyses indicated that all oleogels had higher storage modulus (G') than loss modulus (G''). The time-sweep test showed that after applying higher shear rates, the gels re-formed at rest. Further, all oleogels maintained their gelled consistency until around 54 °C. The results suggest that HTF could be a cheap, efficient, fast melting, safe and readily available organogelator.
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    Sunflower Oil-Beeswax Oleogels Are Promising Frying Medium for Potato Strips
    (Wiley, 2021) Aydeniz Güneser, Buket; Yılmaz, Emin; Keskin Uslu, Eda
    Sunflower oil-beeswax oleogels at 3% (BWO-3) and 8% (BWO-8) organogelator concentration are prepared to evaluate oleogels as frying medium for potato strip frying against commercial sunflower oil (SO). Rheological and thermal analyses of oleogels prove that the samples are fully solid (20 +/- 3 degrees C) and totally liquid (180 degrees C), and thermoreversible. Fresh and used (after frying) fat analyses show that free fatty acidity (FFA), peroxide value (PV) and total polar materials (TPM) are enhanced in all samples at the 7th h, but the relative enhancement levels are lower in oleogel samples. Potato strips fried in oleogels absorb significantly less oil (11.97% and 12.07%) than the control sample (15.20%). Potatoes fried in oleogels are also more bright and yellower than the control sample. Textural profile of the fried potatoes indicates that the samples fried in oleogels are harder, springier, and gummier than that of the control sample. Sensory analysis shows that oleogel fried potatoes get higher sensory scores. Also, overall acceptability of potatoes fried in BWO-8 sample is the highest (8.50) among all. The prepared oleogels are found quite promising frying medium in this study. Further studies with other types of oleogels in extended period frying of various foods are suggested. Practical applications: The development of innovative frying techniques to produce healthier products with lower fat and calorie values are still a remarkable research area. Oleogelation is an emerging strategy used for solid-like oil designing and based on the formation of 3D networks by the addition of organogelators. Oleogelation is accepted as a healthy strategy to structure liquid oils into solid consistency, and oleogels have great edible applications in processed foods, and can be used as a frying medium. This work can guide the use of sunflower oil-beeswax oleogels as a frying medium and allow the development of more healthy fried snacks.