Phd Degree / Doktora

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Innovative Food Applications of Novel Multifunctional Active Edible Gel Fillings and Coatings
(01. Izmir Institute of Technology, 2022) Barış Kavur, Pelin; Yemenicioğlu, Ahmet
This 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.
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, Ahmet
The 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.
Polysaccharide Based Packaging Film for Fresh Cut Produce
(Izmir Institute of Technology, 2017) Şamlı, Merve; Harsa, Hayriye Şebnem; Büyükkileci, Ali Oğuz
In this thesis, agro industrial wastes such as bracts and leaves of artichoke were used to develop biodegradable packaging materials for fresh-cut artichokes. As flim forming materials; cellulose, hemicellulose, lignin and wax fractions were extracted by using mild alkaline treatment applied to artichoke wastes. Carboxy methyl cellulose was chemically synthesized from extracted cellulose fiber. A mechanical process (Masuko Supermasscolloider, at-100 um grind size via 5 times feeding) with minimum environmental impact was selected to obtain cellulose micro fibrils with micro sized dimensions (50-200 um in length and 10-30 um in width).These fractions used as polysaccharide sources in film forming solutions. Different combinations of these polysaccharide based film materials were optimized using General Factorial Design and four film combinations were selected among the films produced.elected films were MFC and CMC based having good elasticity (16 % strain), tensile strength and low gas permeability properties (150mlO2/m2.day).Different concentrations of additives such as wax, stearic acid, chitosan were used with the glycerol addition of plasticizer. SEM analyses of selected films showed films showed films having smooth surface and dense structure by looking their cross sectional area. Thermal analyses proved sealabilitiy of films obtained by extracted fractions from artichoke at 200-250 oC temperature intervals. But, presence of MFC in films hindered the heat sealing ability. Therefore, MFC and CMC based films successfully showed optimal properties when they were combined with glycerol, stearic acid and wax.

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