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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Modeling Drying Kinetics Of Grape Seeds And Skins From Turkish Cultivars

Gezer, Pervin Gizem 01 July 2011 (has links) (PDF)
Grape pomace is a valuable waste product and various end-products have been obtained after treatments. Recently, these have been commercialized due to their health-promoting effects. Drying is a crucial part of these treatments. This study aimed to analyze the drying kinetics of grape pomace parts, which are seeds and skins. Two grape types were used in this study, namely Emir and Bogazkere varieties of Vitis Vinifera species. Seeds and skins of each variety were dried in a tray dryer at an air velocity of 1 m/s with four different air temperatures / 40, 50, 55 and 60&deg / C. The drying curves showed that the drying r ate increased with the air temperature. Six different drying models were selected from the literature and the best fitted model was determined by application of appropriate statistical methods. It was found that for Bogazkere seeds / Modified Two Term Model, for Bogazkere and Emir skins / Modified Page Model and for Emir skins / Logarithmic Model gave the best fit. The effective moisture diffusivities of each type were found for each temperature and were determined by two different approaches, experimental and estimation. The values and variation of Deff / L2 with temperature were calculated and were found to be increasing with temperature and that the Deff / L2 values were larger for grape skins than grape seeds. Arrhenius type equation was used in order to explain the temperature dependency of Deff / L2.
82

Effects Of Edible Chitosan Coating On Quality Parameters Of Pomegranate (punica Granatum) Arils

Can Cetin, Ayca 01 February 2012 (has links) (PDF)
The effects of edible chitosan coating on quality factors of pomegranate (Punica granatum) arils were investigated in the present research. For that purpose, pomegranate arils were treated with 0% (control) and 1% chitosan (extracted from shrimp shells and deacetylated (.75%)) solutions and stored at 4
83

Production Of Chips And Crisp From Jerusalem Artichoke

Baltacioglu, Cem 01 February 2012 (has links) (PDF)
Jerusalem artichoke has been cultivated in various regions without any special breeding technique. On the other hand, in food industry it does not have a wide usage area. Hence, in food industry its use as a potato substitute in some products is believed to be increasing its economical value. As a first attempt chips and crisps produced from Jerusalem artichoke was analyzed for texture, sensory, color, oil and moisture content. Jerusalem artichoke chips were fried in a bench top deep fat fryer for 120s, 180s and 240s at 160&deg / C, 170&deg / C, 180&deg / C and 190&deg / C. When microwave oven was used samples were cooked for 60s, 75s, 90s, 105s, 120s, 135s and 150s at 600 Watt and 900 Watt. Rheological properties of Jerusalem artichoke puree were investigated and Xanthan gum (2%wb) and sodium metabisulphite (1%wb) added for the desired puree consistence and color. After the production of puree Jerusalem artichoke flour was produced and water added to this flour then dough obtained again. Rheological behaviour of the original puree and these prepared from the containing 1- 4.5 and 1 - 5.0 part water were quite similar. In the light of the experimental results obtained as frying temperature and treatment time increased, moisture content and lightness of the Jerusalem artichoke products have decreased but a*and b* values, hardness, fracture and oil content increased. The best results for frying of Jerusalem artichoke seem to be 180&deg / C with about 240s treatment time for the chips and the same temperature for 180s for the crisps. As microwave power level and duration of treatment increased, moisture content and lightness of the microwave cooked Jerusalem artichoke products have decreased, but a* and b* values increased. Hardness and fracturability values of the products first increased with time and then decreased. When microwave oven was used, the best results were obtained for about 105s treatment time at 600W for the Jerusalem artichoke chips and about 60s processing time at 900W for the crisp. Since treatment time for cooking was significantly reduced when microwave cooking was used, this method could be recommended as an alternative to conventional deep fat frying, as oil is not used as well.
84

Effect Of Nanoencapsulation Of Purified Polyphenolic Powder On Encapsulation Efficiency, Storage And Baking Stability

Luca, Alexandru 01 July 2012 (has links) (PDF)
The primary objective of this study was to obtain nano-emulsion containing polyphenolic compounds extracted from sour cherry pomace and to investigate the effect of degritting of polyphenolic concentrates on the encapsulation efficiency and particle size distribution of capsules and emulsions. It was also aimed to study storage and baking stability of the capsules. Extracted polyphenolic concentrate was degritted at 10,000 rpm for 2 min. Purification reduced Sauter mean diameter (D[32]) of concentrated extract from 5.76 &mu / m to 0.41 &mu / m. Unpurified and purified concentrates were freeze dried for 48 h to obtain extracted phenolic powder (EPP) and purified extracted phenolic powder (PEPP), respectively. Powders were entrapped in two types of coating materials which contain 10% maltodextrin (MD) or 8% MD-2% gum arabic (GA). Samples were prepared by ultrasonication (160 W, 50% pulse) for 20 min. Emulsions containing EPP had D[32] of 1.65 and 1.61 &mu / m when they were entrapped in 10% MD and 8% MD-2% GA coating material solutions, respectively. It was possible to obtain nano-emulsions when purification step was performed. Emulsions prepared with PEPP and coated with 10% MD and 8% MD-2% GA had D[32] of 0.396 and 0.334 &mu / m, respectively. Encapsulation efficiency of the capsules increased significantly from 86.07-88.45% to 98.01-98.29% by means of degritting (p&le / 0.001). Loss of total phenolic content during storage at 43% and 85% relative humidities was smaller for encapsulated powders when compared to powders not entrapped in coating material. In addition, encapsulation significantly increased retention of phenolic compounds from 15.1-22.2% to 30.4-30.7% during baking (p&le / 0.05).
85

Power plant system reliability analysis : applications to insurance risk selection and pricing

Trayhorn, Benjamin January 2012 (has links)
Within the Speciality Engineering Insurance Field the use of engineering opinion is the main component in risk analysis for underwriting decision making. The use of risk analysis tools to quantify the risk associated with perils such as mechanical breakdown is limited. A reliability model for the risk analysis of mechanical breakdown risk for the power generation sector, PowerRAT, has been developed and its performance evaluated against historic claim data. It has proven to closely forecast actual losses over a portfolio of power plants, and differentiate between power plant type; conventional steam, simple and combined cycle gas turbine plants. Differentiation based on the factors of equipment type and policy terms has been demonstrated. A review of existing survey report methodology has shown highly variable quality of reports with significant missing information on which to make underwriting decisions. A best practice survey report contents has been proposed in order to provide a consistent level of information for comparison with other risks. The development cycle of PowerRAT has led to a proposed framework for the development of future risk assessment tools for insurance. This is built on four main areas: risk identification, data analysis, calculation methodology and insurance factors.
86

Rheological Characterization Of Tahin/pekmez (sesame Paste/concentrated Grape Juice) Blends

Arslan, Elif 01 January 2004 (has links) (PDF)
The aim of this study was to determine the rheological properties of tahin/pekmez blends at different tahin concentrations (20-32%) and temperatures (35-65 &deg / C) by using a concentric cylinder rotational viscometer. Samples were sheared with seven different rotational speeds at an increasing order. The shear rates (0.75-63.9 s-1) were calculated by the Power-law Approximation method. Tahin/pekmez blends were found to exhibit non-Newtonian, shear thinning behavior at all temperatures and tahin concentrations. The experimental data of apparent viscosity versus shear rate were successfully described by the Power-law model. The model parameters / flow behavior index, n varied in the range of 0.7-0.85, whereas the values for the consistency coefficient, K, were in the range of 282-2547 mPa.sn. Apparent viscosity and consistency coefficient of blends increased with increasing tahin concentration and decreasing temperature. Temperature dependency of K was described by an Arrhenius-type equation. Activation energies (Ea) of the blends appeared in the range of 13376-28592 J/mol as the tahin concentration was increased from 20% to 32%. The effect of temperature on n was found to be significant but did not follow any descriptive trend. The relationship between K and tahin concentration was explained by exponential and power functions while tahin concentration had no significant effect on flow behavior index. Power function was found to be superior in explaining the variation of Ea with tahin concentration. A mathematical model was formulated to determine the combined effect of temperature, tahin concentration and shear rate on apparent viscosity.
87

Design Of A New Equipment For Sesame Seed Dehulling

Gungor, Ugras 01 January 2004 (has links) (PDF)
In this study, new methods and processing equipments for sesame dehulling were investigated. First, water absorption of sesame seed was studied at 20, 30, and 40&deg / C. The data could be modeled using Peleg equation where it was found that the constant k1 was inversely related to temperature but the effect of temperature on k2 was negligible. In the second phase of the work a lab scale continuous screw conveyor as dehuller and two equipments, (1) fluidized bed dryer and (2) hull separator to function as agitator, dryer and separator, for hull separation were designed. Fluidized bed unit was unsuccessful as it caused rapid drying of seeds before hulls can be removed. Using designed dehuller and hull separator, seeds at 30.5, 50.4 and 70.7 % db moisture contents were processed at dehuller speeds of 420, 840, and 1150 rpm. It was found that the percentage of dehulled seeds was linearly dependent on moisture content, optimal speed of designed dehuller was 840 rpm, and results for the efficiency of dehulling the seeds were significantly the same at 420 and 1150 rpm. Repeated passes of seeds through dehuller not only increased the efficiency of dehulling but also the percentage of damaged seeds. A dehulling efficiency of about 92.5 % was attained after four passes. The possibility of soaking seeds in an enzyme solution before dehulling was also investigated. By this means, after soaking in 0.2 % (v/v) Peelzyme-I solution for 15 min, a dehulling efficiency of 95 % was achieved.
88

Recovery Of Strawberry Aroma Compounds By Pervaporation

Isci, Asli 01 July 2004 (has links) (PDF)
Pervaporation is a selective membrane technique in which a liquid feed mixture is separated by means of partial vaporization through a non-porous perm-selective membrane. This method can be used for the recovery of heat sensitive aroma compounds to avoid them from thermal damage in beverage industries. The main objective of this study was to determine the effects of feed temperature (30, 40, 50&deg / C), composition (different model solutions, strawberry essence), concentration (50, 100, 150 ppm) and permeate pressure (4, 8 mbar) on the recovery of aroma compounds of strawberry by pervaporation in terms of mass flux and selectivity. In addition, it was aimed to optimize the extraction conditions (extraction time, temperature, agitation speed, strawberry matrix) of Solid-phase microextraction (SPME), which is used for the analysis of strawberry aroma compounds. Optimum results for SPME were obtained at 40&deg / C, 700 rpm for 30 min and no matrix effect was observed. Pervaporation experiments were performed using a hydrophobic membrane, PERVAP 1070 (PDMS). As the feed temperature increased, the mass flux and selectivity increased and the total mass flux followed an Arrhenius type relation. Decreasing downstream pressure increased both total flux and selectivity, while increase in feed concentration led to higher organic fluxes but lower selectivities. In general, PERVAP 1070 showed a higher selectivity towards Methyl butyrate (MTB) than Ethyl butyrate (ETB) and MTB flux was affected negatively by the presence of ETB in the feed solution. Pervaporation experiments were also performed with a strawberry essence and strawberry model solution. The selectivities of MTB and ETB were negatively affected by the presence of other aroma compounds.
89

Effects Of Different Batter Formulations On Quality Of Deep-fat Fried Chicken Nuggets

Dogan, Seyhan Firdevs 01 July 2004 (has links) (PDF)
The main objective of this study was to evaluate the effects of different flour and protein types on quality of deep-fat fried chicken nuggets. Additionally, the rheological properties of batters were studied and the batter viscosity was correlated with fried product quality. In the first part of the study, the effects of soy and rice flour (5%) addition to the batter formulation on product quality were studied. Coating pick-up of batters, and moisture content, oil content, texture, color, volume, porosity, and cooking yield of nuggets were determined for 3, 6, 9 and 12 minutes of frying times at 180&ordm / C. In the second part of the study, the effects of protein types (soy protein isolate, whey protein isolate and egg albumen) at different concentrations (1 and 3%) on quality attributes were studied. A batter formulation with no flour or protein addition was used as control. In both parts of the study, flow behavior of batters prepared using different flour and protein types were determined. Soy flour and soy protein isolate (SPI) provided the highest apparent viscosity. Batter viscosity was found to be correlated with coating pick-up. All batters were found to show thixotropic behavior. The batters were modeled as power-law fluid and all of them turned out to be shear-thinning except egg albumen added batter, which was shear-thickening. As a result of the study, among the flour and protein types used, 3% whey protein isolate (WPI) was found to be the most effective ingredient on improving quality parameters of deep-fat fried chicken nuggets. 3% WPI added batters provided the hardest and crunchiest product with the darkest color. It also reduced the oil content of fried nuggets significantly. However, low cooking yield values were observed for batters with 3% WPI. On the other hand, soy flour containing batters provided high cooking yield. Therefore, if high cooking yield with low oil content is desired, soy flour can be advised to be used in batter formulations for chicken nuggets.
90

Effects Of Different Batter Formulations On Quality Of Deep-fat Fried Carrot Slices

Akdeniz, Neslihan 01 August 2004 (has links) (PDF)
The main objective of the study was to evaluate the effects of starch and gum types on product quality of deep-fat fried carrot slices. It was also aimed to evaluate the applicability of image processing for determination of oil uptake. In the first part of the study, carrot slices were dipped into batters containing three different concentrations of dextrin or pre-gelatinized tapioca starch and fried for 2, 3, and 4 minutes at 170&plusmn / 2 oC. Coating pick-up of batter formulations and moisture content, oil content, frying yield, bulk density, porosity, texture and color of fried slices were evaluated. In the second part of the study, the effects of different gum types (HPMC, xanthan gum, guar gum, guar-xanthan gum combination) on quality attributes were studied. No starch or gum added coating formulation was used as the control. Finally, images of carrot and batter sections of the fried samples were obtained using digital camera and area fractions of oil droplets were determined using image processing. Acceptable product quality was obtained at higher concentrations of pre-gelatinized tapioca starch. On the other hand, increasing dextrin concentrations had an adverse affect on the product quality. As a result of the study, guar-xanthan gum combination has been found as the most effective additive on the batter performance. This additive provided the highest moisture content, lowest oil content, highest volume and lightest color to the product after frying. The porous and crunchy structure obtained using this combination was at the acceptable level for deep-fat fried products. Determination of area fraction of oil droplets on carrot and batter surfaces of fried samples using image processing was correlated with the oil content of fried product at initial stages of frying. The correlation coefficient between moisture content and frying yield was found as 0.90. A correlation was also determined between oil content and moisture content (r= -0.88).

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