Final Examination for the Degree of PhD Food Science - XIAOYU LUO

Examining Committee
Dr. Keith Warriner, Chair
Dr. Loong-Tak Lim, Advisor
Dr. Alejandro Marngoni, Advisory Committee Member
Dr. Maria Corradini, Department Member
Dr. Christine Moresoli, University of Waterloo, External Examiner

TITLE: INVESTIGATIONS OF COLORIMETRIC INDICATOR SYSTEMS FOR THE DETECTION OF AMINES/TERPENES IN INTELLIGENT FOOD PACKAGING

ABSTRACT: Colorimetric indicators are versatile materials for intelligent packaging applications. The indicators can interact with the food matrices and/or the packaging environment and in turn reveal quality change or spoilage through detectable color responses. In this project, the fundamental aspects of colorimetric indicator systems applicable in intelligent packaging were investigated. The research covered the synthesis of indicator dyes, characterization of indicator’s color response upon the exposure to target analytes, development of scalable indicator fabrication methods, and evaluation of the performance in real food packaging conditions. Cinnamil- and quinoxaline-derivative dyes were successfully synthesized. They exhibited significant color responses upon the exposure to volatile amines  - fish spoilage volatiles. Quinoxaline-derivative indicators exhibited visually detectable color transition for the detection of fish spoilage at room temperature. Using free surface electrospinning as a manufacturing approach, curcumin-loaded electrospun nonwoven indicators were developed based on either polyvinylpyrrolidone or ethylcellulose/poly(ethylene oxide) carriers. When the curcumin-laden indicators were exposed to volatile amines, visually noticeable color change and fluorescence suppression were detected. In an attempt to scale up the production of the colorimetric indicator, in another study, the piezoelectric inkjet printing technique was investigated. Chemoresponsive indicator inks were formulated by manipulating their solution and rheological properties to optimize the printability in commercially available ink cartridges. The inkjet-printed indicators showed superior sensitivity for discriminating volatile amines at different concentration levels, and exhibited strong correlations with the volatile amine levels in package headspace of fresh fish fillets stored at refrigeration temperature over a 7 d storage period. To further explore the utility of the colorimetric indicator systems, a preliminary study was conducted for rapid detection of  monoterpenes in hemp essential oil through a colorimetric indicator assay. Myrcene and ocimene, which are the main monoterpene components in hemp essential oil, were responsible for the rapid color responses at 55°C. The colorimetric indicator developed here could be further improved for rapid quality assessment of other cannabis-based products. Overall, this research demonstrated the capability of various indicator dyes (curcumin, sulfonephthalein, cinnamil- and quinoxaline-derivatives) for food freshness monitoring, using volatile amine and fish as the model system. This research also demonstrated the feasibility of employing electrospinning and inkjet printing for large-scale production of the colorimetric indicators for food packaging and other applications.