Australian Food Scientists Develop Dairy Spoilage Organism Test
Scientists at Food Science Australia (FSA) have developed a new and faster test for detecting the presence of cold-loving microbes, called psychrotrophs. The test, named Psychro-Fast, offers the dairy industry a new tool for improving storage life for pasteurized milk. When milk spoils before its use-by date, even when it has been carefully stored and handled, it is usually because of the presence of these psychrotrophs, says FSA dairy researcher Dr. Heather Craven. "In health terms these bacteria are pretty harmless, but they do pose a problem if they get into the milk because then whole batches can go off," she explains.
"Even if you keep the milk chilled, they can multiply from a few per milliliter to over a million in the space of just six days." Many traditional microbiological tests used by dairy plants are slow and insensitive, or else pick up the wrong organisms. But the Food Science Australia test, developed by scientists there over several years, is simple, super-sensitive and indicates the presence of typical spoilage organisms the next day.
Milk is mixed with a selective agent to screen out unimportant microbes and an indicator, then incubated at 30° C. If psychrotrophs are present, their numbers will rapidly climb to millions per milliliter - and the indicator turns the milk sample pink. The test can be easily adjusted to count numbers of spoilage organisms.
The test will help assure milk plants that their milk will exceed its declared shelf-life, so long as it is kept at 4° C or less. Victorian Quality Manager for Dairy Farmers, Mr. Trevor McManus, says the Psychro-Fast test has enabled dairy farmers to tune up hygiene at each point in the production line, and has become a key performance indicator for production teams.
Dr. Craven says the test can be used to monitor the whole dairy production line from pasteurizer to carton, in order to pinpoint the source of any spoilage problem. And apart from fresh milk, the test can also be used to improve the quality and shelf life of other dairy products such as butter, cream and cottage cheese.
Food Science Australia is Australia's largest food research organization, and is a joint venture between CSIRO and the Australian Food Industry Science Centre (AFISC).
This research was supported by the Dairy R&D Corporation and the Victorian Department of Natural Resources and Environment.
For more information contact Dr. Heather Craven, Food Science Australia. Tel: 61 03 9742 0112; Lloyd Higginbotham, Tel: 61 03 9742 0341.