Phd Degree / Doktora
Permanent URI for this collectionhttps://hdl.handle.net/11147/2869
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Doctoral Thesis Production of Pectin From Wastes and Low-Grade Products of Sun-Dried Fig Processing: Optimization of Pectin Extraction and Characterization of Its Major Properties(01. Izmir Institute of Technology, 2023) Çavdaroğlu, Elif; Yemenicioğlu, AhmetThis thesis aimed extraction and characterization of pectin from processing wastes as stalks and low-grade fruits of sun-dried figs as an alternative pectin source. The extraction performed with three techniques (hot acidic, ultrasonic, enzymatic extraction) was optimized for key parameters. The hot acidic extraction, the most feasible method, yielded 11.7% crude fig stalk pectin (CSP) and 9.4% crude low-grade fig pectin (CFP) at optimal extraction conditions. The CSP had higher galacturonic acid content (GA: 34.2%) and degree of esterification (DE: 45%) than CFP (GA: 32.2% and DE: 36.7%). Purification of CSP gave pectin (PSP) with the highest GA (63%) and DE (65.9%). Despite differences in sugar compositions (D-glucose, L-rhamnose, D-galactose and L-arabinose), fig and citrus pectins displayed similar molecular weights and FT-IR profiles. The fig pectins were characterized for their gelation, antioxidant activity, water/oil absorption, emulsification/foaming capacities and stabilities, and viscosity. The properties of edible fig pectin films obtained with or without CaCl2 crosslinking were also investigated. PSP films showed greater mechanical strength (15.6-19.1 MPa), but lower water vapor permeability (6.28-12.85 g.mm/m2.day.kPa) than other films. The crosslinked CFP film exhibited the lowest solubility (32.8%) and degree of swelling. The emulsion films of CFP with eugenol (EUG) characterized and applied as a coating on whole melons effectively inhibited Listeria innocua (-2.2 log reduction) within 1 weeks at 10 °C. Fig pectins exhibited comparable or superior functional properties than commercial pectins, thus, utilization of low-quality figs and fig stalks into pectin could provide huge economic benefits to Turkish dried-fruit industry.Doctoral Thesis Innovative Food Applications of Novel Multifunctional Active Edible Gel Fillings and Coatings(01. Izmir Institute of Technology, 2022) Barış Kavur, Pelin; Yemenicioğlu, AhmetThis thesis organized as two chapters aimed to develop and test multifunctional novel gel filling and coating. In Chapter 1, the thesis focuses on developing antimicrobial and antibrowning gelatin based gel filling to produce safe caramel apples. For this purpose, water holding capacity and mechanical stability of gelatin (GEL) gels were improved by the incorporation of soy proteins (SP) and inulin (IN), respectively. The water activity (aw) of gels was also reduced to < 0.9 by the addition of sucrose (SUC). The apples were cored and the void cores were filled with GEL-SP-IN-SUC blend gel solution containing synergetic antimicrobials, nisin and lysozyme, and antibrowning agent ascorbic acid (each at 1% in gel). Candy sticks were then placed into gel-filled void cores, and apples were kept at 4oC for 20 h for gelation of filling before caramel dipcoating. The caramel apples with antimicrobial GEL-SP-IN-SUC filling showed 2.4 – 2.9 D lower Listeria count than traditional caramel apples during 7-day cold storage. The active blend gel-filling also prevented discoloration of apple core. In Chapter 2, the thesis focuses on controlling postharvest sprouting and microbial risks associated with shallot bulbs by active chitosan based coating loaded with eugenol (EUG). The sustained release of EUG was achieved by applying ultrasonic homogenization (US) to prepare a composite of chitosan (CHI) with chickpea proteins (CP) (CHI:CP ratio of films = 2). The CHI-CPEUG coating successfully reduced the sprouting and inhibited the inoculated E. coli and L. innocua in shallot bulbs by 2.3 log and 1.7 log, respectively.Doctoral Thesis Investigation of Compensatory Effect of Copper Mineral and Iron-Protein Complexes on Iron Deficiency Anemia in Human Enterocyte Cell Culture Model(Izmir Institute of Technology, 2021) Hoşer, Ezgi; Güleç, Şükrü; Yemenicioğlu, AhmetIron deficiency is the most encountered worldwide nutritional disease, affecting women, babies, and children. When dietary iron absorption is insufficient to fulfill physiological demands, nutritional iron insufficiency arises. Legumes are a low-cost source of protein that are also beneficial for human health. From a nutritional standpoint, the iron-chelating ability of legume proteins is of importance since they may have high iron mineral stability against in vitro digestion because they are bound to proteins. Legume proteins extracts are commonly utilized as functional components; however, their functionality must be proved in a cell culture system by assessing their physiological activity. Furthermore, during iron deprivation disturbances in copper homeostasis have been observed repeatedly in the literature. And this pointed out that copper might have a compensatory effect on anemia caused by iron deficiency dependant cellular signaling mechanisms. Within this context, the main objectives of this Ph.D. thesis were (i) to develop highly bioavailable, edible protein-iron complex hydrolysates from legumes that can be used as an additive in food products and investigate their functional properties against iron deficiency anemia. Also, (ii) investigating the compensatory effects of copper mineral on iron deficiency anemia and, (iii) its main application for functional food development were other driving forces for the experiments. It was revealed that protein (peptide)-iron complexes derived from lentil (10:1 ratio) and soybean (20:1 and 40:1 ratios) significantly influenced the iron-dependent gene regulation in enterocyte cells compared to the anemic group. Moreover, intracellular gene regulation was mainly affected by copper treatment in the basolateral side of enterocyte cells during IDA, indicating that blood copper level might have the ability to control the enterocyte iron metabolism at molecular and genetic levels during iron deficiency anemia.Doctoral Thesis Exploring Lysozyme-Nisin Antimicrobial Synergy at Different Conditions for Novel Food Applications(Izmir Institute of Technology, 2019) Sözbilen, Gözde Seval; Yemenicioğlu, AhmetThe main objective of this thesis is to explore lysozyme-nisin antimicrobial synergy in combination with refrigeration, mild heating or edible packaging for novel food applications. The thesis is based on the following four chapters: (1) Characterization of biochemical properties of lysozyme at different conditions; (2) Lysozyme-nisin synergy in combination with mild heating against Listeria innocua: test of findings in inoculated raw-milk (3) Lysozyme-nisin synergy in combination with chitosan coating against Listeria innocua: test of findings on coated inoculated sprouting seeds; (4) Lysozyme-nisin synergy in combination with refrigeration against lactic acid bacteria (LAB): test of findings in boza, a traditional fermented beverage. The results of this thesis clearly showed that the use of lysozyme-nisin synergy in combination with mild heating at 50 ºC or in combination with edible chitosan coating could be employed to reduce risk of listeriosis from raw-milk and sprouted seeds, respectively. It is also clearly demonstrated that the lysozyme-nisin synergy in combination with refrigeration could be used to delay acidic spoilage of boza without reducing LAB below 106 CFU/mL. This thesis clearly showed the high potential of using lysozyme-nisin synergy against pathogenic or spoilage bacteria as an effective hurdle.Doctoral Thesis Development of Novel Antimicrobial, Antioxidant and Bioactive Edible Gels Intended for Food Preservation and Promotion of Human Health(Izmir Institute of Technology, 2017) Boyacı, Derya; Yemenicioğlu, AhmetThe aim of this thesis was the development of edible gelatin (GEL) based composite gels with antimicrobial, antioxidant, and bioactive properties. For this purpose, composite gels of gelatin with rice starch (RS), candelilla wax (CW) and soy protein isolate (SPI) were incorporated with lysozyme (LYS) and green tea extract (GTE). LYS and GTE release profiles of GEL and its composites were tested in aqueous media and cold-smoked salmon selected as a model food. GEL, GEL/RS and GEL/CW gels did not show considerably different LYS and GTE release profiles in aqueous media, but their release profiles in the model food system were different. GEL/SPI gels bound LYS and prevented its release from the gels, but they released GTE. GEL showed the most rapid LYS delivery onto smoked salmon, while GEL/RS and GEL/CW caused sustained LYS delivery profiles. The total LYS delivered from GEL and GEL/RS gels onto smoked salmon were similar while GEL/CW gels caused almost 30% lower LYS delivery onto food samples. On the other hand, GEL/CW gels caused the highest amounts of GTE delivery onto model food. In broth media at 4°C, all LYS containing gels (with or without GTE) showed antimicrobial activity with a minimum 1.5 decimal reduction in L. innocua that was used as a target bacterium. In smoked salmon samples, the LYS containing gels inhibited the growth of L. innocua, but they did not cause a significant reduction in its counts. Antioxidant capacity, antihypertensive and antidiabetic activity, and cytotoxicity tests against human colon carcinoma cells (Caco-2) conducted with released GTE proved the bioactive potential of developed gels. The gels were also tested for their water binding capacity, and physical (textural properties) and morphological (SEM images) properties. This work clearly showed the possibility of using active gels as multifunctional delivery tools (as coating material, pad or pre-cast film) to prevent microbial and oxidative changes in food and to enhance their bioactive properties.Doctoral Thesis Production of High Quality Functional Proteins From Legumes and Plant Based Agroindustrial Wastes and Byproducts(Izmir Institute of Technology, 2014) Aydemir, Levent Yurdaer; Yemenicioğlu, AhmetIn this thesis, technological and bioactive properties of protein concentrates and isolates form Turkish lentil and chickpea cultivars and hazelnut meal has been characterized. This study aimed to increase industrially suitable alternatives to soy and animal origin proteins. The functional properties (solubility, gelation, water and oil absorption, emulsion and foaming capacity and stability) of globulin proteins from chickpeas are comparable or superior than those of soy proteins and most animal proteins (fish and bovine gelatin, egg white and whey proteins) with the exception of gelation capacity of bovine gelatin. The chickpea proteins got extremely high water (4.9-7.9 g/g) and oil (10.9-14.6 g/g) absorption capacity. The lentil globulins showed high protein solubility (0.56-0.69 g/g) and oil absorption capacities (6.9-10.4 g/g), but missed water absorption and gelation properties. The lentil proteins showed 2-3 fold higher antioxidant capacity than the chickpea proteins, and antioxidant lentil protein fractions could be separated or concentrated by isoelectric precipitation, ion exchange chromatography and ultrafiltration. The hazelnut meal globulins showed satisfactory oil absorption (7.4-9.4 g/g) and good foaming (7.1 to 18.9 ml foam with 10 mg/ml), but poor water absorption, gelation and emulsion properties. The hazelnut proteins also form water soluble yellowish to brownish and reddish colored transparent edible films with 10-12.5 % (w/w) solutions. However, the most outstanding properties of hazelnut meal proteins is their high bioactivity including free radical scavenging (158-461 μmol Trolox/g), iron chelation (60.7-126.7 μmol EDTA/g) and angiotensin-converting enzyme inhibition (IC50: 0.57-1.0 mg/mL) capacities. Thus, a functional beverage, hazelnut milk enriched with trypsin and pepsin hydrolyzed hazelnut globulins, was developed as an example functional food product. This work showed the good potential of selected Turkish plant resources as animal and soy protein alternatives.Doctoral Thesis Development of Functional Composite Edible Packaging Materials for Controlled Release of Bioactive Substances(Izmir Institute of Technology, 2013) Arcan, İskender; Yemenicioğlu, AhmetThe aim of this study was to control the release of bioactive agents by modification of hydrophobicity and morphology of zein films using composite and blend film making methods. The bioactive agents incorporated into zein based films were lysozyme and phenolic compounds. The incorporation of beeswax, carnauba or candelilla wax into films gave composite films containing amorphous wax particles, while the incorporation of oleic, lauric or linoleic acid into films caused formation of blend films containing many spherical zein capsules within their matrix. The release profiles of phenolic compounds from zein films were successfully altered by the development of composite and blend films. The composites and blends can show 2.5 to 17 fold lower lysozyme release rates than the controls. The lysozyme release rates of composites reduced as the melting point of waxes increased. The chain length and the concentration of fatty acid used in blend films could also have affected the release rates of lysozyme. The phenolic antioxidants, catechin, gallic acid, p-hydroxy benzoic acid and ferulic acid are effective plasticizers of zein films. These phenolic compounds eliminate the classical brittleness problem of zein films and increase their flexibility considerably (up to 196%). Furthermore, catechin contributed to controlled release properties of films by reducing the film porosity. The phenolic compounds also provided antioxidant activity to films (up to 86 μmol Trolox/cm2). The blends and composites of zein films containing phenolic compounds or lysozyme and phenolic compounds showed antimicrobial activity on critical food pathogenic bacteria or indicator microorganisms including Escherchia coli O157:H7, Listeria monocytogenes, Listeria innocua and Campylobacter jejuni. This work showed the possibility of obtaining advanced edible films having flexibility, antimicrobial and antioxidant activity and controlled release properties.Doctoral Thesis Development of Novel Bio-Based Methods for Inhibition of Plant Pathogens(Izmir Institute of Technology, 2013) Alkan, Derya; Yemenicioğlu, AhmetIn this thesis, to develop a post-harvest bio-based preservation method for spoilage of fresh fruits and vegetables, antimicrobial packaging commonly applied for inhibition of human pathogenic bacteria was adapted for inhibition of plant pathogenic bacteria including Pseudomonas syringae, Erwinia amylovora, Xanthomonas vesicatoria and Erwinia carotovora. The zein based films were developed by incorporation of pure phenolic acids such as gallic acid (GA), cinnamic acid (CA), vanillic acid (VA); essential oils such as carvacrol (CAR), thymol (THY), eugenol (EUG) and citral (CIT) and phenolic extracts obtained from clove, artichoke, oregano and walnut shells into film forming solutions. The films containing phenolic acids between 1 and 4 mg/cm2 were effective on all bacteria. Essential oils at concentrations between 2 and 4 mg/cm2 and clove extract at concentrations between 4 and 8 mg/cm2 were found effective against pathogens except P. syringae. The HPLC analysis showed that the clove extracts owe its inhibitory activity to high concentration of GA which is a potent antimicrobial. The incorporation of natural compounds and extracts into films caused significant changes in morphologies and mechanical properties of films. This thesis showed the good potential of antimicrobial films against plant pathogens for the first time in the literature.