Observation of the location and form of anthocyanin in purple potato using time-resolved fluorescence

Abstract

Abstract Anthocyanins are water soluble phenolic compounds present in fruit and vegetables which are responsible for the bright red, blue and purple colours of these food products. They are also responsible for the characteristic autumn leaf colouration in some trees. These are versatile compounds, as well as having application in the food industry, they have also found usage to sensitise titanium dioxide in research related to dye sensitised solar cells. This has prompted investigation into their photophysical properties in order to elucidate their charge transfer mediation behaviour. Recently anthocyanins are becoming of high interest both from a health point of view and because of their potential usage as food colouring agents. However, anthocyanins are very unstable compounds and their stability can be affected by several factors such as temperature, pH, oxygen and light. Here we show the effect of the microwave process (which is a promising method for anthocyanin extraction) on the location and form of anthocyanin in Purple Majesty potato (novel variety of purple potato rich in anthocyanins, the major one of which is petanin), when compared with the raw potato using time-resolved fluorescence techniques, both on extracted anthocyanin and in-situ on potato slices using fluorescence lifetime imaging. Industrial relevance Anthocyanins can be extracted from plant based food and have potential application in Food Industry because of their anti-microbial and anti-oxidant properties. This group of compounds also present strong (principally) red and purple colourations in plant matter, which make them interesting to use as food colorants by the Food Industry. However, anthocyanins can have different structures (forms) which are dependent of the environmental conditions (mainly pH/complexation/concentration) which can affect their properties. Considering that these compounds can be extracted from plants it is important to easily observe their location in the cell and to elucidate their properties. Because of this requirement we show, in this paper, that it is possible to use time-resolved fluorescence, using microscopy and time-resolved emission spectra, which we believe add novelty to obtain pertinent information from extracted (unpurified) anthocyanin and in-situ within the potato tuber cells. This shows the potential of these techniques in elucidating data in this study and with future application in food industry.