Citation: Magnaghi, L.R.; Zanoni, C.; Bancalari, E.; Hadj Saadoun, J.; Alberti, G.; Quadrelli, P.; Biesuz, R. pH-Sensitive Sensors at Work on Poultry Meat Degradation Detection: From the Laboratory to the Supermarket Shelf. AppliedChem 2022, 2, 128–141. https://doi.org/10.3390/ appliedchem2030009 Academic Editor: Jason Love Received: 19 May 2022 Accepted: 21 June 2022 Published: 24 June 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article pH-Sensitive Sensors at Work on Poultry Meat Degradation Detection: From the Laboratory to the Supermarket Shelf Lisa Rita Magnaghi 1,2, * , Camilla Zanoni 1 , Elena Bancalari 3 , Jasmine Hadj Saadoun 3 , Giancarla Alberti 1 , Paolo Quadrelli 1,2 and Raffaela Biesuz 1,2 1 Department of Chemistry, University of Pavia, Via Taramelli 12, 27100 Pavia, Italy; camilla.zanoni01@universitadipavia.it (C.Z.); giancarla.alberti@unipv.it (G.A.); paolo.quadrelli@unipv.it (P.Q.); rbiesuz@unipv.it (R.B.) 2 Unità di Ricerca di Pavia, Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Via G. Giusti 9, 50121 Florence, Italy 3 Department of Food and Drug, University of Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy; elena.bancalari@unipr.it (E.B.); jasmine.hadjsaadoun@unipr.it (J.H.S.) * Correspondence: lisarita.magnaghi@unipv.it Abstract: In the last twenty years, the number of publications presenting generalized pH-sensitive devices proposed for food freshness monitoring has been steadily growing, but to date, none of them have succeeded in exiting the laboratory and reaching the supermarket shelf. To reach this scope, we developed a large-scale applicable pH-sensitive sensor array to monitor perishable foods’ degradation. We ensured freshness monitoring in domestic conditions, using sales packages and during chilled storage, by simple naked-eye readout and multivariate imaging analysis, and we fully corroborated the device by (i) projection of unknown independent samples in the PCA model, (ii) TVB-N quantification and (iii) microbiological assay. The choice of commercial and cheap dye and polymeric support already employed in food packaging ensures the low-cost and scalability of the device and the promising results obtained make this device an eligible candidate for large-scale implementation. Keywords: pH-sensitive devices; chicken breast degradation; naked-eye reading; chemometrics; TVB-N; total viable count; industrial scale-up 1. Introduction Starting from the very beginning, in the last twenty years, the field of sensing de- vices has experienced a deep transformation with the widespread diffusion of differential sensing approaches inspired by mammalians’ olfaction and gustation [1,2]. Focusing on colorimetric sensors, the advent of digital color imaging (DIC) combined with multivariate data elaboration has further multiplied the opportunities and the possible strategies for the development of scalable devices for large-scale applications [2–5]. On one hand, DIC allows for the employment of low-cost and widespread image acquisition devices, such as mobile phones, cameras or scanners, eliminating the subjective error of naked-eye observation and summarizing the color information in three-dimensional coordinates [3,4]. On the other hand, these three-dimensional coordinates represent the eligible input dataset for multivariate algorithms that allow both qualitative and quantitative analyses, depending on the type of application [2,5]. The widespread diffusion of such approaches has brought about the rediscovery of “old” cross-reactive and chemo-responsive dyes whose colors are dependent upon their chemical environment: among all, the most prominent case is represented by pH indicators that used to be exploited only in classical acid–base titrations and which now play a fundamental role in manifold sensing devices both for solutions and vapor analysis [3,6–13]. As a matter of fact, pH is a key target parameter in a broad range of applications from AppliedChem 2022, 2, 128–141. https://doi.org/10.3390/appliedchem2030009 https://www.mdpi.com/journal/appliedchem