New packaging will make it easier to choose fresher fish based on ammonia sensor 11/07/2013 - 00:00 From the outside you can't see whether supermarket fish is still fresh. Once you remove the plastic foil it’s immediately obvious how fresh it is, but by then it has already reached your kitchen. PhD candidate Jenneke Heising is working on packaging with a built-in nose that tells your smartphone how fresh the fish is, before you buy it.Jenneke Heising’s research into three ways of measuring the freshness of packaged fish has been published in the Journal of Food Engineering. The three methods have one thing in common: they all involve measurements using a sensor in the packaging. As the fish decays, various substances are released into the air inside the packaging and they subsequently dissolve in water in the sensor. Heising has investigated the practicality of using sensors that measure acidity, conductivity or ammonia. The ammonia sensor does not appear to be very useful because the substance is only released once the fish is almost ‘off’. Acidity is unreliable because temperature appears to have too much influence on the readings. However, conductivity looks promising, Heising says.
