Determination of seafood spoilage by digital colorimetry of indicator test systems

A simple and affordable colorimetric procedure for determination of the seafood spoilage (e.g., shrimp, squid, catfish and herring) using a smartphone and chemometric analysis is considered. The proposed colorimetric sensor consists of 12 zones, i.e., disks of cellulose paper 4 mm in diameter impregnated with acid-base indicators with a color change in the pH range of 3 – 8.8. Spoiling of the seafood is accompanied with a release of volatile biogenic amines that change the color of the indicator zones. A device and a method for measuring the colorimetric parameters of a test system using a smartphone as a recording device equipped with a specialized RGBer product are described. Processing of the data array (the sum of the R, G, and B channel values for each indicator, or the R, G, and B values for individual indicators) was performed using the XLSTAT software. Patterns of the degradation of food products identified in the study made it possible to propose a method for assessing the quality of seafood in real time. The optimal time regime of heat treatment of the sample was determined, which is necessary for the isolation of biogenic amines and the formation of an analytical signal. The parameters for identification of the seafood spoilage are the values of the main component F1 (or the position of the images on the canonical function projection graph) after evaluating the colorimetric data using the principal component method. The results obtained with a colorimetric sensor match the data for determination of the total microbial number of the analyzed products. The considered method for assessing spoilage of the seafood is distinguished by the simplicity of hardware design, the availability of the materials and software resources used, the rapidity of the procedure, and the mobility of the means for recording the analytical signal.