1,721,252 research outputs found
Yüksek hidrostatik basıncın palm stearin emülsiyonlarınındaki yağların kristalin yapıları üzerine etkisi.
No full textLipid crystal structures (polymorphs) are the determinant factors for sensorial, textural properties and the stability of the emulsions. Therefore, controlled crystallization gains importance during the production of foods such as margarine, confectionery, chocolate, etc. In literature, studies on the effect of high hydrostatic pressure (HHP) on lipid crystallization have contradictory results. To inspect the crystallization characteristics and response to the HHP treatment, palm stearinwater emulsions were prepared with two different emulsifiers (sodium caseinate and hydrogenated soy lecithin-xanthan gum mixture) and pressurized at 100 and 500 MPa, at 10, 20 and 40°C for 15 minutes. Particle size analysis, differential scanning calorimetry (DSC), transverse relaxation time (T2) and self-diffusion coefficient (SDC) determinations and small angle x-ray scattering (SAXS) were conducted to investigate the changes induced by HHP treatment. According to the results, HHP did not affect droplet size of sodium caseinate (SC) emulsions so it vi was observed that mean particle size was affected only by the types of emulsifiers and storage time. In addition, sodium caseinate has the capability to produce smaller particles than 80H_XG emulsion. HHP has no significant effect on the melting temperature of polymorphs; but pressure and storage time have significant effect on crystal polymorphs’ content in emulsions. HHP induced formation of more stable β crystals in both sodium caseinate and soy lecithin-xanthan gum mixture emulsions. In addition to this, HHP also induced solid wall formation in soy lecithin-xanthan gum mixture emulsions. Changes in α and β contents with respect to pressure and storage time were detected by T2 and SDC measurements. These findings suggested that the beginning of emulsions’ destabilization can be detected by NMR measurements. The pressure effect may easily be seen in the ab-initio structural model with SAXS measurements. The pressure application caused a structural change from spherical form to cylindrical form in sodium caseinate (SC) solution and SC emulsion droplets reached more compact spherical like aggregations. Ph.D. - Doctoral Progra
Yüksek hidrostatik basıncın soya protein izolatının fonksiyonel özellikleri üzerine etkisi
No full textSoy protein is a low-cost additive with high biological value, unique functional
properties, and beneficial effects on health, and it is widely used in the food industry
as an important ingredient. When the health and functional properties of soy protein
are considered altogether, there are several benefits for consuming and using it in
foods. High hydrostatic pressure (HHP) is a non-thermal novel processing
technology that has been generally used to destroys vegetative cells, microorganisms
and enzymes. Additionally, HHP treatment has an effect on protein structures,
resulting changes in the functional properties of proteins. The aim of the study was
to examine the effects of high hydrostatic pressure (HHP) treatment on functional
properties of soy protein isolate (SPI). The experiments were carried out at different
pressure parameters (300, 400 and 500 MPa) with a constant duration of 5 min at 25
oC and 40 oC. Also, the pH of the SPI samples was adjusted to pH 5 and pH 7 to
evaluate the pH effect with HHP treatment on the functional properties of SPI
prepared at 38% (w/v) concentration. Water holding capacity (WHC), solubility by
Lowry method, emulsion activity, and viscosity of untreated and HHP-treated soy
protein isolate were analyzed. Following that, characterization experiments
including Fourier transform infrared (FTIR) spectroscopy and Nuclear Magnetic
Resonance (NMR) relaxometry were performed to determine the changes in
secondary structure and hydration behavior of soy protein isolate (SPI), respectively.
This study showed that HHP treatment significantly (p<0.05) decreased WHC
compared to control, however there was no significant difference between WHC
results of pH 5 and pH 7 (p>0.05). Moreover, HHP treatment significantly enhanced
solubility of SPI at pH 7 compared to pH 5 and control, and also, at pH 5, the
solubility of HHP-treated SPI at ambient temperature was significantly higher than
that of SPI treated at 40 °C (p<0.05). Furthermore, although the emulsion activity
results revealed no significant difference (p>0.05) between HHP-treated SPI at pH 7
and untreated SPI, providing the appropriate pressure increased emulsion activity at
pH 5, but further increase in pressure resulted in reduced emulsion activity. Also,
viscosity of SPI significantly reduced due to HHP treatment at pH 5 and pH 7
compared to control (p<0.05). In addition, FTIR results showed that HHP treatment
caused remarkable changes in the secondary structure of SPI due to unfolding of
protein. Moreover, HHP treatment had no influence on SPI hydration behavior at pH
7 (p>0.05), but T2 values at pH 5 at 40 °C were significantly much higher than those
obtained for control and other treated SPI. In conclusion, the results of this study
showed that HHP application could be a valuable alternative to modify and improve
the functional properties of soy protein, which has an important role in novel product
development.Soya proteini, biyolojik değeri yüksek, benzersiz fonksiyonel özellikleri ve sağlığa
yararlı etkileri olan düşük maliyetli bir katkı maddesidir ve gıda endüstrisinde önemli
bir bileşen olarak yaygın olarak kullanılmaktadır. Soya proteininin sağlık ve
fonksiyonel özellikleri bir arada düşünüldüğünde, onu tüketmenin ve gıdalarda
kullanmanın çeşitli faydaları vardır. Termal olmayan yeni bir işleme teknolojisi olan
yüksek hidrostatik basınç (YHB), genellikle vejetatif hücreleri, enzimleri,
mikroorganizmaları yok etmek için kullanılmıştır. Ek olarak, YHB uygulamasının
protein yapıları üzerinde etkisi vardır ve bu da proteinlerin fonksiyonel
özelliklerinde değişikliklere neden olur. Bu çalışmanın amacı, yüksek hidrostatik
basıncın soya proteini izolatının fonksiyonel özellikleri üzerindeki etkilerini
araştırmaktır. Deneyler farklı basınç parametrelerinde (300, 400 ve 500 MPa) 25 oC
ve 40 oC'de 5 dakika sabit süre ile gerçekleştirilmiştir. Ayrıca, %38 konsantrasyonda
hazırlanan soya protein izolatının fonksiyonel özellikleri üzerindeki YHB ve pH
etkisini değerlendirmek için soya protein izolat numunelerinin pH'ı 5 ve 7'ye
ayarlanmıştır. Kontrol numunesi ve basınca maruz bırakılmış soya protein
izolatlarının su tutma kapasitesi, Lowry yöntemiyle çözünürlük, emülsifikasyon
aktivitesi ve viskozitesi analiz edilmiştir. Bunu takiben, soya proteini izolatının
ikincil yapısındaki değişiklikleri ve hidrasyon davranışındaki değişiklikleri
belirlemek için sırasıyla Fourier transform infrared (FTIR) spektroskopisi ve
Nükleer Manyetik Rezonans (NMR) Relaksometri ölçümünü içeren karakterizasyon
deneyleri yapılmıştır. Bu çalışma, YHB uygulamasının su tutma kapasitesini
kontrole kıyasla önemli ölçüde azalttığını (p<0.05) göstermiştir, ancak pH 5 ve pH
7'de su tutma kapasite sonuçları arasında önemli bir fark gözlemlenmemiştir
(p>0.05). Ek olarak, YHB işlemi, pH 5 ve kontrol ile karşılaştırıldığında pH 7'de
soya protein izolatının çözünürlüğünü önemli ölçüde arttırdığı ve ayrıca pH 5'te,
YHB ile muamele edilmiş SPI'nın oda sıcaklığındaki çözünürlüğü, 40 °C'de
muamele edilmiş SPI'den önemli ölçüde daha yüksek olduğu görülmüştür (p<0.05).
Ek olarak, emülsiyon aktivitesi sonuçları, pH 7'de YHB ile muamele edilmiş SPI ile
işlem görmemiş SPI arasında önemli bir fark (p>0.05) ortaya koymamasına rağmen,
uygun basıncın sağlanması pH 5'te emülsiyon aktivitesini arttırmıştır, ancak basınçta
daha fazla artış, emülsiyon aktivitesinin azalmasına neden olmuştur. Ayrıca,
kontrole kıyasla pH 5 ve pH 7'de YHB işlemine bağlı olarak SPI'nın viskozitesi
önemli ölçüde azalmıştır (p<0.05). Ek olarak, FTIR sonuçları, YHB uygulamasının,
SPI'nın ikincil yapısında proteinin açılmasından kaynaklanan dikkate değer
değişikliklere neden olduğunu göstermiştir. Ayrıca, YHB işleminin pH 7'de SPI’nın
hidrasyon davranışı üzerinde hiçbir etkisinin olmadığı (p>0.05), fakat 40 °C'de pH
5'teki T2 değerleri, kontrol ve diğer işlenmiş SPI için elde edilenlerden önemli ölçüde
daha yüksek olduğu NMR ölçümü sonuçlarında görülmüştür. Sonuç olarak, bu
çalışmanın sonuçları, yeni ürün geliştirmede önemli bir role sahip olan soya
proteininin fonksiyonel özelliklerini değiştirmek ve geliştirmek için YHB
uygulamasının değerli bir alternatif olabileceğini göstermiştir.M.S. - Master of Scienc
Isıl olmayan işlemlerle balık jelatinin jelleşme özelliklerinin geliştirilmesi.
No full textGelatin is mostly obtained from skin, bone or connective tissues of bovine or porcine land animals. Gelatin is commonly used in confectionery products as the main gelling agent and as a hydrocolloid and stabilizer in liquid food systems. Due to religious preferences, helal gelatin has started to be very common in Middle Eastern countries and bovine gelatin is mainly utilized for that purpose. Gelatin could also be obtained from fish which is very abundant in nature however it has weak gelation ability. There are different studies in the literature that explored the gelation ability of fish gelatin by adding additional substances as CaCl2 or other hydrocolloids. In this research, it is hypothesized that fish gelatin could be modified by using processing techniques as High Hydrostatic Pressure (HHP) and ultrasonication (US). HHP was applied at 400 MPa, at two different temperatures (10o C and 30o C) by keeping process time constant at 15 minutes. Ultrasonication experiments were conducted at 24 kHz at two different amplitudes (100% and 60%) for 5 and 10 minutes. In order to compare the gelation abilities of the fish gelatin, bovine gelatin is used as a commercial gelatin type. The results showed that HHP treatment on fish and bovine gelatin could stabilize gelatin network by organizing the structure and reduce free volume. Furthermore, US treatment could destroy gelatin network, change gelation mechanism and decrease the degree of aggregation. NMR spectroscopy vi measurements were useful to monitor change in protein structures and intramolecular forces between protein and water molecules. Gelation properties and hydration of gelatins were identified by using T1 and T2 values. When the T2 results of fish and bovine gelatin were compared, it concluded that the free water of fish gelatin was higher than bovine. Moreover, gelation capability of the bovine gelatin was higher than fish gelatin. In order to estimate the change in the amino acid structure of the gelatin after HHP and US treatments, FTIR measurements were used. FTIR results indicated that the secondary structure of the amino acids was rearranged after treatments.Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Food Engineering
Enhancing the Quality Parameters and extending the shelf life of pomegranate juice by High Hydrostatic Pressure (HHP) processing against thermal treatment
No full textE. coli o157:h7 ve s. Aureus'un havuç suyunda yüksek hidrostatik basınca bağlı inaktivasyon kinetiği ve hücresel hacim değişikliği analizi.
No full textThe main objective of this study was to determine the pressure induced inactivation mechanism of pressure-resistant Escherichia coli O157:H7 933 and Staphylococcus aureus 485 in a low acid food. Firstly, inactivation curves of pathogens were obtained at 200 to 400 MPa at 40ºC in peptone water and carrot juice. First-order and Weibull models were fitted and Weibull model described the inactivation curves of both pathogens more accurately than first-order model, revealing that food systems could exhibit either protective or sensitizing effect on microorganisms. Carrot juice had a protective effect on E. coli O157:H7 whereas it had a sensitizing effect on S. aureus, due to the naturally occurring constituents or phytoalexins in carrot roots that could have a toxic effect. Secondly, scanning electron microscopy (SEM) and fluorescent microscopy images of studied pathogens were taken. Developed software was used to analyze SEM images to calculate the change in the view area and volume of cells. Membrane integrity of pressurized cells was also examined using fluorescent microscopy images. The increase in average values of the view area and volume of both pathogens was significant for the highest pressure levels studied. The increase in volume and the view area could be explained by the modification of membrane properties, i.e., disruption or increase in permeability, lack of membrane integrity, denaturation of membrane-bound proteins and pressure-induced phase transition of membrane lipid bilayer. The change in volume and the view area of microorganisms added another dimension to the understanding of inactivation mechanisms of microbial cells by HHP.Ph.D. - Doctoral Progra
Effect of high hydrotatic pressure (hhp) on the surface hydrophobicity of milk proteins.
No full textYüksek hidroststatik basınö uygulaması ile Mezgit (Gadus merlangus euxinus) ve hamsinin (Engraulis encrasicolus) muhafazasının ve raf ömrünün uzatılması.
No full textHigh Hydrostatic Pressure (HHP) application, alone or in combination with refrigeration, ambient or moderate heating temperatures; inactivates pathogenic and spoilage microorganisms and conserves the product „„freshness‟‟ with fewer changes when compared to conventional food preservation processes. During handling and frozen storage, quality deterioration of seafood brings the risk of contamination, quality loss and a potential threat to food safety and human health. In this respect, the aim of this study was to determine the effect of HHP on quality factors and shelf life of anchovy (Engraulis encrasicolus) and haddock (Gadus merlangus euxinus) under different pressure, temperature and time combinations. Due to their high perishability and easy availability in Turkey, anchovy (Engraulis encrasicolus) and haddock (Gadus merlangus euxinus) samples were chosen and pressurized with HHP at 200, 300 and 400 MPa, at 5, 10 and 15 °C for 5 and 15 min. According to the results of physical and chemical analysis which were performed to HHP treated fish samples; such as color (L*, a*, b* and ΔE), trimethylamine nitrogen (TMA-N), and 2-thiobarbituric acid (TBA); best HHP combinations were selected for shelf life analysis as 200 MPa, 5 °C for 5 min for anchovy; both 200 MPa, 5 °C for 5 min and 400 MPa, 15°C for 5 min for haddock. In order to determine the effect of HHP on the shelf life, untreated and HHP treated samples were stored at refrigeration temperature (4 °C) for 15 days. Every each day, sensory, color (L*, a*, b* and ΔE), pH, trimethylamine-nitrogen (TMA-N), thiobarbituric acid (TBA), total volatile basic-nitrogen (TVB-N) and total plate count (TPC) analysis including statistical analysis (ANOVA) were monitored for untreated and treated samples during 15 days at refrigeration temperature (4 °C). Considering the rejection limits for consumption, effect of HHP to shelf life was evaluated. When all conclusions were combined, the shelf life extension was determined averagely as 9 days for pressurized anchovies (200 MPa 5 °C for 5 min) when stored at 4 °C. Also for haddock, shelf life was extended to 13 days and 15 days when samples pressurized with 200 MPa at 5 °C for 5 min and 400 MPa at 15 °C for 5 min, respectively; since all control samples of anchovy and haddock became unacceptable within 3 days.M.S. - Master of Scienc
Determining Effects of Cooling Rate on Crystallization Behavior of Palm Kernel Stearin (PKS) by Nuclear Magnetic Resonance (NMR)”
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