Novel coating containing colourants from the red pitaya
Natural colourimetric indicators are environmentally friendly and safe alternatives to those based on synthetic materials. However, low stability usually limits the use of many natural colourants in commercial settings, especially at high temperatures. A new study demonstrates the application of betalains extracted from the peel of red pitaya (Hylocereus costaricensis) as natural colorants in diagnostic packaging materials. Extracted betalain pigment (BP) and dye (BD) were applied to BP-based screen-printing ink (BPi) and BD-based film (BDf), respectively. The color transitions of BPi and BDf were observed at high temperatures as a function of time.
Promising bio-based materials
BPi could be screen printed with good appearance properties. BD could be applied homogeneously to a methylcellulose thin film. Both BPi and BDf exhibited a color change from the initial pink to orange and yellow, respectively, depending on temperature and storage time. At 180 ̊C, a complete change in colour was observed for both BPi and BDf. Therefore, BPi and BDf are promising bio-based materials for the development of time-temperature dependent materials.
The study has been published in Progress in Organic Coatings, Volume 178, May 2023.