A DIT researcher is trying to zap bugs that could be lurking in fruit juices or smoothies, writes Claire O'Connell
Consumers these days want it all - nutritious and safe food in a drink that tastes great and has a long shelf-life. These demands are prompting researchers in Dublin to gauge whether treatments such as ozone and ultrasound can destroy rare but potentially harmful bugs in fruit juice while retaining the drink's important vitamins and flavours.
Traditionally the food industry has used heat-based treatments like pasteurisation to destroy microbes and improve food safety, states Dr PJ Cullen, a lecturer at the school of food science and environmental health at Dublin Institute of Technology (DIT).
"The problem is that as you heat something you lose the sensory and nutritional characteristics, and consumer demand means that is no longer acceptable."
Many outlets now sell packaged, unpasteurised fruit juices, and while the risks are low, there are concerns that if disease-causing microbes like E coli enter the processing chain and are not treated, they could survive in the product, according to Dr Cullen.
"The idea is that if we can come up with a novel, non-thermal way of (treating) juice that doesn't remove the characteristics, it will produce something that will hopefully be safe from food-borne diseases and it will extend the shelf-life."
A DIT group led by Dr Cullen, Dr Paula Bourke and Dr Jesus Frias is now teaming up with Dr Colm O'Donnell in University College Dublin to see whether subjecting juices and smoothies to ozone or ultrasound can zap the bugs while retaining taste and nutritional content.
Ozone is unstable, so when you bubble it through the juice it can disrupt the membranes of microbes it comes into contact with causing them to burst. Then the ozone should break down into oxygen, explains Dr Cullen. "The benefit of this system is that (ozone) is so unstable that it would disappear."
The Food and Drug Administration in the US has drawn up guidelines on using ozone and the Dublin researchers plan to validate them with their experiments. Ozone is already used to disinfect water, especially in Europe, but fruit juices and thicker smoothies are more complex because they contain organic matter that can shadow and protect micro-organisms, explains Dr Cullen. "We want to try and overcome that problem by controlling the bubbles and how they disperse in the liquid."
The three-year project, which is funded by the Department of Agriculture and Food, will also subject juices and smoothies to power ultrasound, which acts like a depth-charge, explains Dr Cullen. "It creates little bubbles which grow in the liquid and they get larger and larger, then there's a critical point at which they can no longer absorb any energy and they implode violently. That sends out a shock wave into the liquid," he says.
It remains to be seen whether the new measures can control microbes in the juice without also damaging important nutrients like vitamins. "We don't really know what's going to happen, we are hoping we will get a beneficial effect," says Dr Cullen.
"The technology is currently being used in other areas and we want to see what happens in this particular system. If it doesn't work, we would recommend to industry that you shouldn't do this."
However if all goes well, Dr Cullen estimates that consumers could benefit from better-tasting, safe and nutritious juices within around five years.