Meat packaging is at the heart of two new trends in the US. A Massachusetts company is developing food labels that change colour to signal the freshness of packaged meat, while several retailers are refusing to sell meat packaged with carbon monoxide.

Food Quality Sensor International developed several techniques to detect toxins, including wrap that detects chemical changes caused by bacteria, and its new labels – which take their stimulus from the food’s chemical structure – add one cent in packaging costs for each dollar of meat sold. The company may also apply its technology to milk.

Meanwhile, chains including Publix, Wegmans and Super Fresh will not sell meat processed with carbon monoxide to retain its red colour, following adverse consumer reaction.

The Food and Drug Administration says the low amount used poses no health risk, and there is no evidence that it is being used to induce consumers to buy meat that is not fresh, adding freshness should be determined by dates, odours and bulging packages.

Nevertheless, one congressman is threatening legislation banning the practice, and consumer groups are calling for mandatory labelling of such packages, sold regularly by Hormel and Cargill. The meat industry opposes mandatory labelling, and says packaging at the plant means less handling and increased food safety.