1. A tamper-proof barcoded quality indicator operative to provide a machine-readable indication of exceedance of at least one time and temperature threshold following actuation thereof, said indicator comprising: a first barcode including at least one first colorable area, said first barcode being machine-readable before exceedance of said at least one time and temperature threshold; at least a second barcode including at least one second colorable area, said second barcode not being machine-readable before exceedance of said at least one time and temperature threshold; a coloring agent located at a first location on said indicator; a coloring agent pathway operative, following actuation of said quality indicator, to allow said coloring agent to move, at a rate which is at least partially a function of time, from said first location to said first and second colorable areas simultaneously for simultaneous coloring thereof upon exceedance of said time and temperature threshold, thereby causing said first barcode to become unreadable and at the same time causing said second barcode to become machine-readable; and a tamper-proof actuator element operative to actuate said quality indicator upon removal thereof from said quality indicator.