Development of Polyaniline as a Sensor for Food Quality and Spoilage Detection

Abstract

This thesis describes the research that has been completed for the application of polyaniline as a food quality indicator.

It has been reported by WRAP (Waste and Resources Action Programme) that in the UK alone, a third of all purchased food items are thrown away regardless of the quality or condition. It has also been reported by DEFRA (Department for Environment Food and Rural Affairs) that the food manufacturing and processing industry is one of the UK’s largest producers of land filled waste.

At present, the available technology for food freshness determination is largely based on use-by dates which are often recognised as unreliable - or qualitative time temperature indicators (TTIs); which can be costly and do not give an actual measurement of bacterial activity. It is anticipated that the technology produced from this research will give a viable and low cost solution to help minimize preventable food waste from consumers - as well as improving food industry process efficiency, especially in the field of food supply chain management.

The sensors being developed employ a conducting polymer film as a sensor which reacts with volatiles evolving from selected food products (salmon and herring). As food biochemically degrades, the concentrations and volumes of these gases change, and this has been studied by analytical techniques such as gas chromatography and SIFT-MS. Food spoilage has also been followed by the growth and identification of specific spoilage bacteria. The sensor exhibits a number of quantifiable physical changes when exposed to differing volatile mixtures produced by the food stuffs. These physical properties include colour and conductivity changes which are distinctive and easily measurable.

Correlations have been shown between increases in microbial activity and the change in conductivity of the films. These sensors will be able to inform consumers more reliably when the food is safe to consume as well as providing the food industry with more information on traceability and stock conditions of fresh meat and fish. In the context of the catering industry, these sensors will also aid in the decreasing the number of reported cases of food poisoning by observing - in real-time - the condition and safety of food.