Abstract
This work presents a colorimetric dye-based array for naked-eye detection of chicken meat spoilage. The array is obtained by fixing five acid–base indicators, m-cresol purple (1), o-cresol red (2), bromothymol blue (3), thymol blue (4), and chlorophenol red (5), and a sensing molecule specific for thiols, 5,5′-dithiobis(2-nitrodibenzoic acid), called Ellman’s reagent (6), on a cellulose-based support. The dyes, being permanently charged, are fixed on the support via ion-exchange. The entire degradation process of beast poultry meat, at ambient temperature and in a domestic fridge, is followed by the change of the color of the array, placed in the headspace over the meat samples. The device is set after selection of the most suitable starting form, which could be the acidic or the basic color of indicators, being the proper dye concentration and the dimension of the spots already established. Basing on sensors colors, we identified three levels of the degradation process of chicken meat, named SAFE, WARNING, and HAZARD. By instrumental analysis, we demonstrated that sensors response was correlated to volatile organic compounds (VOCs) composition in the headspace and, thus, to meat spoilage progress. We demonstrated that biogenic amines (BAs), commonly considered a critical spoilage marker, are indeed produced into the samples but never present in the headspace, even in traces, during the investigated time-lapse. The VOC evolution nevertheless allows one to assign the sample as WARNING and further HAZARD. Some indicators turned out to be more informative than others, and the best candidates for a future industrial application resulted in a bromothymol blue (3)-, chlorophenol red (5)-, and Ellman’s reagent (6)-based array.
Highlights
Meat spoilage is a very complex combination of processes, related to the activity of different bacteria, which, depending on external conditions, are responsible for the oxidation of glucose, lactic acid, and fatty acid and, eventually, the degradation of proteins.[1,2]Commonly, the methods employed to evaluate meat quality require instrumental or microbiological analyses and sensory evaluation
We limited our attention to chicken meat for its high perishability and large diffusion. With this in our mind, we present a dye-based colorimetric array selecting five different dyes that change their color in a pH range around neutrality.[12,13]
All reagents were of analytical reagent grade. m-Cresol purple (1), ocresol red (2), bromothymol blue (3), thymol blue (4), chlorophenol red (5), and Ellman’s reagent (6) were purchased by Carlo Erba or Sigma Aldrich
Summary
Meat spoilage is a very complex combination of processes, related to the activity of different bacteria, which, depending on external conditions, are responsible for the oxidation of glucose, lactic acid, and fatty acid and, eventually, the degradation of proteins.[1,2]. We limited our attention to chicken meat for its high perishability and large diffusion With this in our mind, we present a dye-based colorimetric array selecting five different dyes that change their color in a pH range around neutrality.[12,13] We want to stress that the pH interval of interest is more limited than expected if BAs were present, and it does not make any sense to explore a broad pH region, as done by other researchers.[14] we chose to develop the array directly on real samples, not on enriched amine samples[4] or samples left moldering for weeks[15] since, under these circumstances, a consumer definitively does not need any sensor to assess the stage of spoilage. A patent based on this idea has been deposited[17] and more recently the extension to WIPO PCT.[18]
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