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Vacuum packaging (VP) is used to reduce exposure of retail meat samples to ambient oxygen (O2) and preserve their quality. A simple sensor system produced from commercial components is described, which allows for non-destructive monitoring of the O2 concentration in VP raw meat samples. Disposable O2 sensor inserts were produced by spotting small aliquots of the cocktail of the Pt–benzoporphyrin dye and polystyrene in ethyl acetate onto pieces of a PVDF membrane and allowing them to air-dry. These sensor dots were placed on top of the beef cuts and vacuum-packed. A handheld reader, FirestinGO2, was used to read nondestructively the sensor phase shift signals (dphi°) and relate them to the O2 levels in packs (kPa or %). The system was validated under industrial settings at a meat processing plant to monitor O2 in VP meat over nine weeks of shelf life storage. The dphi° readings from individual batch-calibrated sensors were converted into the O2 concentration by applying the following calibration equation: O2 (%) = 0.034 * dphi°2 − 3.413 * dphi° + 85.02. In the VP meat samples, the O2 levels were seen to range between 0.12% and 0.27%, with the sensor dphi signals ranging from 44.03° to 56.02°. The DIY sensor system demonstrated ease of use on-site, fast measurement time, high sample throughput, low cost and flexibility.

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Aims:To develop an oxygen sensor-based method for testing total aerobic viable counts (TVC) in raw meat samples and cattle carcass swabs, which is rapid, simple, affordable, provides good sensitivity and analytical performance and allows on-site use. Methods and Results: The test uses the same sample preparation procedure as the established plate counting TVC method for meat samples and carcasses, ISO4833-1:2013. After this liquid samples are transferred into standard 25-ml vials with built-in phosphorescent O 2 sensors and incubated on a block heater with hourly readings of sensor signals with a handheld reader, to determine signal threshold time (TT, hours) for each sample. The method is demonstrated with the quantification of TVC in industrial cuts of raw beef meat (CFU per g) and carcass swabs (CFU per cm 2 ). Calibration curves were generated, which give the following analytical equations for calculating the TVC load in unknown samples from measured TT values: TVC [Log(CFU per cm 2 )] = 7.83-0.73*TT(h) and TVC [Log(CFU per g)] = 8.74-0.70*TT(h) for the carcass swabs and meat samples respectively. The new tests show good correlation with the ISO methods, with correlation coefficients 0.85 and 0.83 respectively. The testing requires no dilutions, covers the ranges 2-7 Log(CFU per g) for the meat samples and 1-7 Log(CFU per cm 2 ) for carcass swabs, and has time to result 1-10 h with faster detection of more contaminated samples. Conclusions: The sensor-based testing demonstrates simplicity, high speed, sample throughput and automation. It can provide a straightforward replacement for the conventional TVC tests, which are time consuming, laborious and have time to result of 48-72 h.