Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of Novel Functional Foods From Turkish Kabuli Type Chickpeas(Izmir Institute of Technology, 2015) Şahin, Damla Öykü; Yemenicioğlu, Ahmet; Yemenicioğlu, AhmetThe aim of this thesis is to obtain novel functional chickpea and chickpea products by incorporating bioactive green and black tea phenolics into Turkish Kabuli type chickpeas during controlled rehydration. The rehydration of chickpeas in green or black tea infusions and green tea extracts increased the total phenolic content and bioactive properties of chickpeas. Chickpeas rehydrated in green tea extract or green tea infusions for 2 hours showed almost 2.2 2.5 fold higher total phenolic content, flavonoid content and free radical scavenging based antioxidant capacity, and rehydrated in green tea extract, green tea or black tea infusions almost 2.2-2.6 fold higher antidiabetic activity than control chickpeas rehydrated in water. The increase of rehydration period from 2h to 10h could increase the total phenolic content and antioxidant activity of chickpeas, but the increased incubation period did not have any considerable positive effects on antidiabetic activity of chickpeas. No significant reductions were o served in total phenolic content, flavonoid content and antio idant activity of phenolic enriched chickpeas kept frozen at 18°C while some limited reductions were observed in phenolic content and antioxidant activity of phenolic enriched chickpeas dried and stored at +4°C for 3 months. The extraction and then characterization of the phenolic content, and antioxidant and antidiabetic activity of protein from phenolic enriched chickpeas clearly showed the binding of the incorporated phenolic compounds onto chickpea protein. Thus, it appeared that the protein extracted from phenolic enriched chickpeas could also be used as a functional food ingredient. This work clearly showed the possibility of obtaining functional chickpeas and chickpea protein by use of controlled rehydration in presence solutions containing green and black tea phenolics.Master Thesis Characterization of Antioxdant Activity and Protein Functionality in Some Legume Cultivars Grown in Turkey(Izmir Institute of Technology, 2008) Aydemir, Levent Yurdaer; Yemenicioğlu, AhmetTurkish chickpeas (4 cultivars) and lentils (6 cultivars) show similar total phenolic contents and free radical scavenging capacities in aqueous extracts ranging between 2869 and 4312 mg gallic acid equivalents/kg legume and 24.42 and 38.20 mmol Trolox equivalents/kg legume, respectively. However, the free radical scavenging capacity of lentil and chickpea protein extracts, range between 110 and 185 mmol Trolox/kg protein and 58 and 144 mmol Trolox/kg protein, respectively, clearly showed the higher free radical scavenging capacity of lentil proteins than chickpea proteins.Protein extracts of chickpeas and lentils showed considerable emulsifying and foaming capacities in almost at the same range, but emulsions and foams formed by chickpea proteins are more stable than those of lentil proteins. The lentil protein extracts are highly soluble and showed poor water absorption and gelling characteristics. In contrast, chickpea protein extracts showed moderate water absorption and gelling capacity.Chickpea protein extracts are also good oil absorbers with almost 1.5 to 2 fold better oil adsorption capacity than lentil protein extracts. Thus, chickpea proteins are suggested as soy and whey protein alternatives for functional proteins used in the food, drug and cosmetics industries. Considering functional properties of proteins for different cultivars, the outstanding Turkish chickpea cultivars are Gökçe and Cevdetbey, while the outstanding Turkish lentil cultivar is Alidayı. Variations in the functional properties of protein suggest the diversity of genes in chickpeas and lentils responsible for these properties. Thus, this study showed the possibility of improving functional properties of chickpeas and lentils by breeding programs.Master Thesis Control of Microbial and Enzymatic Changes in Intermediate Moisture Sun-Dried Figs by Mild Heating and Hydrogen Peroxide Disinfection(Izmir Institute of Technology, 2003) Demirbüker Kavak, Dilek; Yemenicioğlu, AhmetDuring cold storage, the enzyme pectin methylesterase (PME) caused softening and lossof desired gummy texture in rehydrated intermediate moisture (IM) sun-dried figs. Heat inactivation studies indicated that the purified PME can be inactivated rapidly at 80 o and 90 oC. However, at or below 70 oC the enzyme showed activation by heating and inactivated very slowly. The in-situ activation of PME occurred much more extensively when sun-dried figs were rehydrated between 70o and 90 oC to produce IM figs with approximately 30 % moisture and this prevented the effective inactivation of enzyme even by rehydrations conducted at 80 o and 90 oC. The partial reduction of PME enzyme activity (almost 30 %) by rehydration of figs at 80 oC for 16 min may be used to delay undesirable textural changes in cold stored IM figs for 3 months. However, for longer storage periods hot reyhdration alone is not sufficient to prevent softening. No considerable yeast and mold growth was detected in IM figs cold stored 3-3.5 months.However, in some samples rehydrated in water at 80 oC, the total mesophilic aerobic counts and total yeast and mold counts showed a considerable increase when storage time exceeded 3-3.5 months. The rehydration of IM figs in 2.5 % H2O2 for 16 min at 80 oC reduced the total mesophilic aerobic microbial count of figs almost 90 %. Due to bleaching caused by H2O2, the brown fig color turned to a desirable and stable yellowlight brown as well. However, during cold storage the O2 gas released due to the decomposition of H2O2 by in situ fig catalase, accumulated within figs and caused some physical defects. Also, the residual level of H2O2 in the homogenates of disinfected figs was too much (300 ppm) and it seemed unlikely to eliminate this amount of H2O2 by physical or chemical means during processing. Pureeing IM figs eliminated residual H2O2 very rapidly. The application of rehydration first in 2.5 % H2O2 solution at 80 oC for 4 or 8 min and then in hot water at the same temperature for 12 or 8 min, respectively, also reduced the amount of residual H2O2 in IM figs considerably.Besides, these two-stage rehydration procedures eliminated the physical defects occurred in IM figs due to O2 gas release and gave firmer IM figs. To reduce the initial microbial load of IM figs, 4 and 8 min disinfections conducted in H2O2 solutions were less effective than 16 min disinfection in H2O2 solution. However, both 4 and 8 min disinfections effectively suppressed microbial load for at least 3.5 months and they may be used in the production of SO2 free light colored fig products.Master Thesis Characterization of Antioxidant Properties for Dried Organic Fruits in Turkish Market and Development of Novel Strategies To Increase Their Potential Health Benefits(İzmir Institute of Technology, 2013) Dervişoğlu, Gökhan; Yemenicioğlu, AhmetIn this thesis antioxidant parameters including trolox equivalent antioxidant capacity (TEAC) and total phenolics (TPC) and flavonoid (TFC) contents of major organic dried fruits (raisins, figs, prunes and apricots) produced in Turkey have been determined to understand the bioactive potential of these products. Moreover, a novel method based on controlled rehydration of specified dried fruits in phenolic extracts has been developed to boost the phenolic content and antioxidant activity of dried fruits with low bioactivity and potential health benefits. The TEAC, TPC and TFC of sun dried fruits varied between 35.7 and 74.1 μmol trolox/g (d.w.), 1762 and 4062 μg gallic acid/g (d.w.) and 830 and 2559 μg catechin/g (d.w.), respectively. The TEAC and TPC of prunes were 1.7 to 2.3 fold higher than those for apricots, raisins and figs which showed quite similar TEAC and TPC values. On the other hand, the TFC of prunes and figs were similar and 1.7 to 3 fold higher than those of raisins and apricots. The rehydration studies with raisins conducted in different concentrations (0.5% or 1% (w/w)) of green tea extract (GTE) and walnut shell extract (WSE) at room temperature until reaching of final moisture content of 38.73 % (w/w) showed the possibility of increasing TEAC, TPF and TPC of raisins 1.6-1.8 fold. Similar rehydration strategy applied to figs, prunes and apricots in 1% GTE to bring their moisture content to 39.83, 36.97 and 43.81 % respectively, caused 1.1-1.6 fold increase in TEAC, TPC and TFC of these dried fruits. This work clearly showed the considerably higher bioactive potential of organic dried prunes than organic dried raisins, figs and apricots. However, the application of controlled rehydration process developed in this work enables increasing antioxidant potential and phenolic contents of figs, raisins and apricots to the level of prunes.Master Thesis Production of Commercially Suitable Pectin Methylesterase and Polyphenol Oxidase From Agro-Industrial Wastes(Izmir Institute of Technology, 2004) Şimşek, Şebnem; Yemenicioğlu, AhmetIn this study, some simple and effective extraction and/or partial purification procedures were developed to obtain pectin methylesterase (PME) and polyphenol oxidase (PPO) enzymes from orange peels and mushroom stems, respectively. Also, some characteristics of enzymes were investigated and their stable preparations were obtained in liquid or lyophilized forms. Valencia orange peels contain considerable PME activity (300-350 mL NaOH/min/100 g) that is quite stable during season for at least 5 months. The enzyme was ionically bound to cell walls and can not be extracted by homogenization with water. However, the addition of suitable amounts of NaCl (10 g /100 g extraction mixture) to pellet, obtained by homogenization of peels several times with water, and 30 min mixing (at 200 rpm) may be effectively used to extract the enzyme. The PME in orange peels contains almost the same amount of heat stable and heat labile fractions and the enzyme can not be activated by mild heating. A slight activation (almost 20 %) may be achieved by adding 1 mM CaCl2 to enzyme extracts. However, at higher concentrations the addition of CaCl2 was inhibitory. The PME activity in extracts, stabilized by use of 0.1 % Na-benzoate and 0.1 % K-sorbate, is stable almost 5 months at + 4 oC (maintains > 90 % of its activity). Thus, the commercial preparations of enzyme may be obtained in liquid form. The extracted PME was successfully used to prepare edible films from citrus pectin For the extraction of PPO, on the other hand, mushroom stems were first processed to acetone powder. The acetone powders were then extracted with Na-phosphate buffer and partially purified with ammonium sulfate (90 % saturation) or acetone precipitation (2-fold). Following dialysis, the recoveries and purification folds obtained from the partial purification of monophenolase activity of PPO from the same acetone powder were 74-86 % and 3.4-4.3 and 55-67 % and 5.4-6.2 for ammonium sulfate and acetone precipitations, respectively. Thus, it appears that the ammonium sulfate precipitation gives a higher yield but lower purity. The monophenolase activity of partially purified PPO is heat labile and showed inactivation above 45 oC. The enzyme exhibited a pH optimum between pH 6.0 and 8.0. The pH stability of enzyme was maximal at pH 7.0 and 8.0. However, at pH 4.0 the enzyme lost most of its activity after 24 h incubation. The optimum temperature of enzyme was found as 40 C. The monophenolase activity of PPO enzyme showed no stability in acetone powders at + 4 oC. However, it showed good stability at -18 oC for two months with retention of 60-70 % of its activity. The PPO partially purified with ammonium sulfate precipitation and dialysis, and lyophilized by using dextran or saccharose as supporting materials also retained its monophenolase and diphenolase activities for three months at -18 oC. The effect of lyophilization with dextran on temperature stability of enzyme was insignificant. However, lyophilization with dextran reduced the pH stability of monophenolase activity at 4.0 moderately. In addition to its monophenolase activity on tyrosine and diphenolase activity on L-DOPA, PPO lyophilized with dextran can also use phloridzin as substrate. Thus, it appears that the enzyme may be used in different food applications including the production of antioxidants and colorants, modification of proteins, fermentation of cocoa and black tea, etc.Master Thesis Characterization and Modification of Antioxidant Proteins From Plat Materials(Izmir Institute of Technology, 2005) Arcan, İskender; Yemenicioğlu, AhmetIn this study, the radical scavenging and iron chelating capacity of proteins from heat treated (20 min at 90 oC) or thermally processed (20 min at 121 oC) chick-peas andkidney-beans were compared. Lyophilized crude protein extracts from chick-peas contained more protein (1.5-3 fold) and showed higher free radical scavenging (up to 2.3 fold) and iron binding capacity (up to 3 fold) than lyophilized crude protein extracts form kidney-beans. The thermal processing of chick-peas did not cause a significant change in the radical scavenging capacity of their lyophilized crude protein extracts, but improved the iron chelating capacity of these proteins almost 80 %. However, the thermal processing reduced both the radical scavenging and iron binding capacity of crude lyophilized proteins form kidney beans by 20-40 % and 60 %, respectively.Partial purification by ammonium sulfate precipitation or DEAE-cellulose chromatography increased the antioxidant capacity of thermally processed chick-pea proteins. The DEAE cellulose chromatography also showed the presence of 5 and 3 antioxidant protein fractions in heat treated and thermally processed chick-peas, respectively. Hot acidic hydrolysis at 80 oC for 30 min in presence of 1.5 M HCl increases the specific antioxidant activity of protein extracts, but causes the formation of undesired Maillard reaction products. Hot extraction at 85 oC for 30 min at pH 2.5 extracts the antioxidant proteins selectively, whereas 85 oC for 30 min at pH 9.5 extracts both antioxidant proteins and other proteins.Master Thesis Production of Functional Packaging Materials by Use of Biopreservatives(Izmir Institute of Technology, 2005) Mecitoğlu Güçbilmez, Çiğdem; Yemenicioğlu, AhmetIn this study, partially purified lyophilized lysozyme (LSZ) and lactoperoxidase (LPS) from chicken egg white and bovine whey were incorporated into zein and alginate films, respectively. The LSZ showed very low affinity to zein films. Thus, when zein films incorporated with 63-455 .g/cm2 (187-1318 U/ cm2) LSZ was exposed to release tests in distilled water, the enzyme released rapidly from the films with release rates of 9 to 29 U/cm2/min. The ethanol used in film making caused significant activation of the LSZ. Therefore, the released LSZ activity from zein films was mostly 130-300 % higher than the activity incorporated into films. On the other hand, the LPS incorporated into alginate films showed a very high affinity to these films and immobilized.The incorporation of 0.53 or 1.06 mg/cm2 proteins such as crude thermally processed chick-pea proteins (TP-CP) and sericine in combination with LSZ and LPS into zein or alginate films increased the antioxidant activity of edible films significantly.In zein films, the incorporation of antioxidant proteins reduced the total activity of LSZ released from the films between 50 % and 75 %, but increased the immobilized enzyme activity 3.5-15 fold. On the other hand, incorporation of antioxidant proteins into alginate films enhanced LPS activity slightly to moderately. The results of this study clearly showed the good potential of edible films and natural biopreservatives in active packaging.Master Thesis Development of Ph-Controlled Triggering Mechanisms for Controlled Release of Lysozyme(Izmir Institute of Technology, 2011) Boyacı, Derya; Yemenicioğlu, AhmetIn this study, zein and whey protein (WP) based films and their blends and composites have been prepared to obtain pH-controlled triggering mechanisms for controlled release of lysozyme. The total amount of lysozyme released from standard zein films was not considerably affected from changes in pH between 7.3 and 5.3 since this hydrophobic biopolymer lacked charged ionisable groups to bind lysozyme ionically. In contrast, incorporation of lentil protein isolate (LPI) into zein created a composite structure and caused binding of positively charged lysozyme (pI>9.0) on negatively charged groups of LPI (pI: 4.5-6) within the film matrix in release medium with pH between 5.3 and 7.3. The amount of bound lysozyme in zein-LPI composites increased linearly as LPI concentration increased between 1,5 and 4,5 mg/cm2 at pH 7.3. The release of bound enzyme could be triggered by reducing pH of release medium from 7.3 to 4.3, down below pI of LPI. On the other hand, films of WP (pI≈5.2) bind considerable amount of lysozyme due to their inherent net negative charges close to neutrality. The release of bind lysozyme could be trigged as pH of release medium reduced from 6.0 to 3.0, down below the pI of WP. The preparation of WP-oleic acid blend and WP-bees wax composites increased the film porosity and amounts of released lysozyme from films at pH 4.5 and 5.0, by 2-4 and 1.2-1.5 folds, respectively. The zein and WP based films containing 0.7 to 1.4 mg/cm2 lysozyme showed good antimicrobial activity against Listeria innocua. This work showed the potential of creating pH-controlled release systems during antimicrobial packaging of food.