Fabrication and Characteristics of Microbial Time Temperature Indicators from Bio-Paste Using Screen Printing Method

Screen printing method was employed to produce microbial time temperature indicators (TTI). Bio-pastes containing lactic acid bacteria loaded Ca-alginate microparticles (LCAMs) and suitable for printing on polymer films have been produced. Through a spray-solidification method, polysaccharide gel microparticles allowed for the efficient encapsulation of the lactic acid bacteria, which chromatically induced a colour change in the pH indicator. As the alginate concentration of LCAMs increased, the size of the microparticles decreased. The average diameter of LCAMs ranged from (1.67 +/- 0.15) x 10(3) to (2.93 +/- 0.31) x 10(3) nm. For the evaluation of bio-pastes, the contact angles and lactic acid production properties were determined. Lower contact angles were obtained with decreasing pullulan concentration, indicating the increase in wettability for printing. The curve of lactic acid production by alginate immobilized cells was determined to take place as a zero-order reaction favourable to TTI colour change. Visibility of TTIs was greatly improved at microencapsulation sites. As the size of the LCAMs was decreased, the visibility was found to be improved. The Arrhenius activation energy (Ea) of CIFP009-based TTI was 117 kJ/mol. The results show that the developed manufacturing method would be used for an industrialized, simple and low-cost manufacturing method for microbial TTIs. Copyright (c) 2013 John Wiley & Sons, Ltd.