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Development of Sensor Systems for Food Quality Monitoring
(01. Izmir Institute of Technology, 2022) Büyüktaş, Duygu; Farris, Stefano; Korel, Figen
The main objective of this thesis is to fabricate electrochemical sensors for the detection of 2,4-diaminotoluene (2,4 TDA), 2,6-diaminotoluene (2,6 TDA), and 4,4´-methylene diphenyl diamine (MDA), possibly carcinogenic primary aromatic amines (PAAs) that poses a serious health risk because they can transfer from multilayer food packages including adhesives based on aromatic polyurethane (PU) systems, to the food. The thesis is based on the following three chapters: (1) Development of a nano-modified glassy carbon electrode for the determination of 2,6-diaminotoluene (2) A screen-printed electrode modified with gold nanoparticles/cellulose nanocrystals for electrochemical detection of 4,4´-methylene diphenyl diamine (3) Development of a nano-modified screen-printed electrode for the determination of 2,4-diaminotoluene. In this work, full electrochemical characterization of the nano-modified electrodes was carried out, and the electrochemical properties were described. Migration tests were also conducted to modified sensors in order to investigate their potential application in real food systems. The results of this work clearly showed that modified electrochemical sensors allow reliable quantification of the most important primary aromatic amines migrating from packaging materials to food and can be used as an alternative to the commonly used conventional analytical techniques for the detection of these toxic compounds.
Feasibility of Eugenol Encapsulated Poly (lactic Acid) (pla) Films Via Electrospinning as a Novel Delivery System for Volatile Compounds in Food Packaging Systems
(Izmir Institute of Technology, 2017) Arserim Uçar, Dilhun Keriman; Korel, Figen; Korel, Figen; Yam, Kit L.
Food safety and quality are important issues in food industry. The aim of this research was to evaluate the feasibility of delivering eugenol via poly(lactic) acid (PLA) emulsion fibers-grafted PLA films with bacterial cellulose into the package headspace. For this purpose, first, bacterial cellulose crystals as a natural carrier for eugenol were produced. The influence of hydrolysis temperature, time, and acid to cellulose ratio, acid concentration and type with the addition of the neutralization step on the structure, and the properties of bacterial cellulose crystals were studied. Nanocrystals, which had high thermal stability and high crystallinity bacterial cellulose, were produced. Bacterial cellulose stabilized oil-in-water Pickering emulsions were produced as carriers for eugenol. The emulsion formulations consisting of cellulose fibers and crystals, eugenol, and surfactants were characterized for food packaging applications. PLA films were produced with obtained eugenol emulsions and poly(lactic) acid which were obtained via the electrospinning method. The produced films revealed a significant antibacterial effect on L. innocua, and E. coli inoculated tomato stem scars as real food model. The fabricated films also had significant antifungal activity on B.cinerea inoculated table grapes. Developed novel biodegradable-PLA cellulose composite films had a great potential for delivering bioactive volatile compounds for intelligent food packaging applications. The findings of this research supports the technical feasibility of delivering eugenol for antimicrobial active packaging applications via electrospun fibers.
Detection of Staphylococcus Aureus Using Quqntitative Real-Time Polymerase Chain Reaction and Loop-Mediated Isothermal Amplification Methods in Turkish White Cheese
(Izmir Institute of Technology, 2013) Kadiroğlu, Pınar; Korel, Figen
The aim of this study was to utilize the quantitative real-time polymerase chain reaction (qPCR) method for direct quantitative detection of S. aureus in Turkish white cheese samples and identification of the isolated colonies using phenotypic and molecular methods. The TaqMan and LNA probe-based qPCR analyses were compared by targeting the nuc gene of S. aureus cells to improve the performance of qPCR analyses to quantify low levels of S. aureus cells. TaqMan probe-based assay was found to be more sensitive than LNA probe based assay in S. aureus pure culture and artificially contaminated white cheese sample studies. For direct bacterial DNA extraction from cheese samples, four different methods were compared. The detection range of S. aureus quantification was improved down to 13.2 CFU/g with the combined DNA extraction method of using trypsin and the food DNA extraction kit in artificially contaminated cheese samples. In the naturally contaminated cheese samples, the bacterial numbers calculated by the qPCR method were higher than the plate counts which can be related to detection of live and dead cells together. Loop-mediated isothermal amplification (LAMP) method was found to have some weak points in giving consistent results with lower efficiency value for detection of S. aureus. In the identification part of the study, 207 pure cultures were obtained. Among the 24 phenotypically and genotypically characterized isolates, 3 isolates were found to be S. aureus according to the sequence analyses of the 16S ribosomal DNA genomic region.

Phd Degree / Doktora

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