This project addresses the problem of ensuring the quality and safety of food products in the distribution chain, from the packaging line to the retail shelf. Many foods are packaged in sealed closures for various purposes: with modified-atmospheres to promote longevity, or to prevent product contamination (e.g. bacterial, moisture), or to protect consumers from tampering and intentional adulteration. However, after the package is sealed and leaves the production line, there is a lack of means to ensure that the environment inside a package is always correct, and the package integrity has been maintained when it reaches the consumer. The purpose of this project is to develop a "smart package" technology enabling a rapid non-destructive inspection of the environment inside packages, based on oxygen content, to ensure that the product quality and enclosure integrity is maintained and not violated. A goal is to enable monitoring of every package at any point throughout the food-supply chain, beginning with the QC at the point of packaging. With simple hand-held oxygen scanners, product could later be readily check anywhere in the distribution path. OBJECTIVES: The problem this project addresses is the safe and effective packaging and delivery of food and beverages. Packaging using modified-atmospheres with various oxygen concentrations (MAP), or vacuum, are common approaches used to preserve food quality and appearance. Our objective is to use oxygen-sensing as a tool for monitoring both package integrity and quality. In order to ensure that the oxygen concentration inside a package is always correct, and the package integrity is maintained after the package is closed and sealed, we plan to innovatively engineer an optically readable oxygen-sensing dye inside the package in the package material itself. We will develop a handheld instrument for interrogating the sensory material to nondestructively measure packages' O2 content with light. This technology will thereby enable 100 % QC of product and verification that a package's environment is properly maintained from the time of sealing out into the field to the point of sale. The ultimate objective is to enable practical fulfillment of the oxygen-sensing approach towards two categories of applications: 1. A means of verifying that a wide range of products requiring a particular MAP packaging and O2 level have the proper specified gas environment; 2. A means of verifying package integrity, both of seals and the containment materials, to ensure that there are no breaches, either accidental or maliciously. The latter utilization encompasses, in addition to MAP, those packages having an oxygen content different than ambient air - either the result of packaging under vacuum, or with pressure - or that can be made different via simple inert-gas purges. In both categories, a goal of enabling verification that a package's environment is properly maintained throughout the food-supply chain has targeted benefits that include: providing better means of quality control over packaged product, reducing risks, and promoting consumer safety. Summarily, our specific aims of Phase I, towards the ultimate goals are: 1. Demonstrate the feasibility of a practical and economical sensing technology that is capable of measuring sensor signal values associated with oxygen levels >2%. 2. Demonstrate the feasibility of acquiring oxygen measures rapidly using a small, portable, hand-held oxygen reading instrument. APPROACH: Our novel optical sensing technology puts a sensor in every package by incorporating oxygen-sensitive luminescent dye into polymers used directly in making packages. Our prime modality is to adapt flexible oxygen-barrier films, composites of multiple polymer layers, to include an oxygen-sensing layer. By melting the dye into raw polymer used to make the inner layers of films facing inside packages, the sensor dye will respond to the O2 in the package environment. The dye's luminescence is quenched by O2 in a concentration dependent manner. To derive oxygen values, an optical instrument measures the dye's luminescence, namely the degree of its quenching by O2 molecules diffusing in/out of the sensory polymer in equilibrium with the package contents. The interrogation process involves projecting light into the package to excite the dye in the sensor film. It emits light in a phosphorescent manner, producing signal that the instrument can read remotely. The O2 determination is based on measuring the lifetime, or decay aspect, of the dye's quenched phosphorescence. This measurement does not require contacting the package, invading, or destroying the product. By extracting lifetime-quenching information from the luminescent signal's decay, our approach gains significant advantage over absolute signal-intensity measures of O2. Potential errors impacting simple intensity-based measurements of returned light are avoided (e.g. errors from variations in dye concentration across a film, or differences in the distance between the package being sensed and the reading instrument). Circumventing such complications via our lifetime-based method has important ramifications enabling practical O2 reading: either on-line in a manufacturing plant with moving packages, or in the field with a portable instrument and the attendant variables of a hand-held reading. To accurately measure O2 at levels >2%, and read rapidly at distances inches from the package, our main challenge is dealing with small signals. Our Phase I tasks translate into increasing the size of our acquired optical signal. This will be addressed through two avenues worked in parallel. First, on the instrument side, we will focus on modifying it to deliver more excitation light to the sensor, thereby increasing the amount of emitted sensor-signal. Additionally, we will improve the instrument's light-collection optics to more efficiently acquire signal from the sensor. Second, on the sensor side, to measure at higher O2 levels we will explore the use of preferred dyes suffering less oxygen-quenching. Additionally, we will increase the concentration of sensor dye used in package polymers. Working the two avenues together, we will evaluate the performance of our improved system (instrumentation & sensors) using bench-test models simulating package conditions. New sensory films will be fabricated and characterized for oxygen-sensing capability to establish the O2 range and sensitivity achieved. Moreover, we will show through package tests that the technology can differentiate O2 changes in sealed packages and identify breaches in package integrity, i.e. package defects
