Cryoconcentration of Flavonoid Extract for Enhanced Biophotovoltaics and pH Sensitive Thin Films A. Demirbas Agricultural and Biological Engineering, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL K. Groszman Department of Computational and Applied Mathematics, Rice University, Houston, TX M. Pazmi~ no-Hernandez Agricultural and Biological Engineering, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL D. C. Vanegas Food Engineering Department, Universidad del Valle, Cali Colombia B. Welt Agricultural and Biological Engineering, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL J. A. Hondred Mechanical Engineering Department, Iowa State University, Iowa City, IA N. T. Garland Mechanical Engineering Department, Iowa State University, Iowa City, IA J. C. Claussen Mechanical Engineering Department, Iowa State University, Iowa City, IA E. S. McLamore Agricultural and Biological Engineering, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL DOI 10.1002/btpr.2557 Published online October 4, 2017 in Wiley Online Library (wileyonlinelibrary.com) Flavonoids are important value added products for dye sensitized solar cells biosensors, functional foods, medicinal supplements, nanomaterial synthesis, and other applications. Bras- sica oleracea contains high levels of anthocyanins in leaf sap vacuoles, and there are many via- ble extraction techniques that vary in terms of simplicity, environmental impact, cost, and extract photochemical/electrochemical properties. The efficiency of value added biotechnolo- gies from flavonoid is a function of anthocyanin activity/concentration and molecule stability (i.e., ability to retain molecular resonance under a wide range of conditions). In this paper, we show that block cryoconcentration and partial thawing of anthocyanin from B. oleracea is a green, facile, and highly efficient technique that does not require any special equipment or pro- tocols for producing enhanced value added products. Cryoconcentration increased anthocya- nin activity and total phenol content approximately 10 times compared with common extraction techniques. Cryoconcentrated extract had enhanced electrochemical properties (higher oxida- tion potential), improved chroma, and higher UV absorbance than extract produced with other methods for a pH range of 2–12, with minimal effect on the diffusion coefficient of the extract. As a proof of concept for energy harvesting and sensor applications, dye sensitized solar cells and pH-sensitive thin films were prepared and tested. These devices were comparable with other recently published biotechnologies in terms of efficacy, but did not require expensive/ environmentally detrimental extraction or concentration methods. This low cost, biorenewable, and simple method can be used for development of a variety of value added products. VC 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:206–217, 2018 Keywords: anthocyanin, cryoconcentration, dye sensitized solar cell, pH sensitive thin film Introduction In plants, flavins are involved in photoprotection and photo- transduction, 1 nitrogen translocation, 2 and pollinator attraction. 3 Flavins include carotenoids (liposoluble) and anthocyanins Additional Supporting Information may be found in the online ver- sion of this article. Correspondence concerning this article should be addressed to E. S. McLamore at emclamor@ufl.edu 206 VC 2017 American Institute of Chemical Engineers