SSSP software to detect spoiled food

Oct 28 2009

Let's start with an example: You have just picked up a pack of cold-smoked salmon from the supermarket chill cabinet to serve for your family lunch on Sunday. On its way from the factory to the lunch table, the salmon product has been exposed to varying temperatures. Now, how can you be sure the product is still good to eat when you take it out of the refrigerator to make sandwiches?

This is a complicated question, and the answer depends on how long and at what temperature the salmon product has been stored, its product characteristics including how strongly it was smoked and how many lactic acid bacteria it contains! But what our brains cannot easily grasp, a computer and a piece of free software from DTU Aqua can.

The software helps producers of seafood, including fresh and lightly preserved products such as cold-smoked salmon, to ensure that their products are suitable for consumption right up until the sell-by date and to prevent unacceptable growth of human pathogenic bacteria.

The Seafood Spoilage and Safety Predictor (SSSP) software can read specific temperature measurements and this can be used to evaluate the effect of the temperature variation products are actually exposed to in chill chains e.g. from processing to the supermarket chill cabinet. In fact, this information makes it possible to identify ways of improving shelf-life and food safety.

International software in 15 languages
Version 3.1 of the Seafood Spoilage and Safety Predictor (SSSP) software, as the new programme from DTU Aqua is called, was released in August 2009 and is available for download free of charge (http://sssp.dtuaqua.dk). SSSP is available in 15 different languages to improve its usefulness for a seafood sector that often operates globally. In fact, seafood raw material and final products are frequently transported long distances and across borders. At the same time, the software is an example of effective dissemination of research results, says Paw Dalgaard, a Senior Scientist at DTU Aqua. So far, the software has been downloaded by more than 4,000 companies, food inspectors, organisations and consultants from 105 countries around the world.

"We had completed extensive laboratory studies, developed mathematical models to predict shelf-life and safety of seafood and published our findings in all the right places. However, industry and the food authorities often don't have the time to seek information in that form. We therefore decided to do something else - to develop a piece of user-friendly software which provides easy access to all the information. The difficult bits, i.e. the mathematical models, have been kept out of sight, and the predictions are easy to obtain and ready to use", explains Paw Dalgaard, who developed the SSSP software together with, among others, Brian Cowan from DTU Aqua.

Predicts whether the number of bacteria in seafood will grow
SSSP v. 3.1 includes an extensive model to predict if the human pathogenic bacterium Listeria monocytogenes can grow in seafood products. This model has made the program popular in many parts of the world, reckons Paw Dalgaard, DTU Aqua.

"Listeria monocytogenes is a serious problem because high concentrations of the bacterium can cause listeriosis in people, a potentially fatal bacterial disease. Listeria can be present in lightly preserved seafood, meat, salad and some dairy products. This is due, among other things, to the fact that it can be difficult to remove the bacterium completely from processing equipment, despite careful cleaning and disinfection," explains the senior scientist.
Low concentrations of Listeria monocytogenes in ready-to-eat food are not problematic with respect to food safety, but it is essential to prevent growth of the bacterium to high concentration and this is where predictions and software becomes most helpful.

Also works for meat products
The SSSP software has been developed for seafood products, but growth of Listeria monocytogene can also be predicted in other types of food.

"We get quite a few enquiries from people wanting to use the program for various ready-to-eat foods. As part of a large-scale international study undertaken in collaboration with scientists from Australia, Denmark, France and the Netherlands, we have therefore tested our Listeria monocytogenes growth model by comparing data from almost a thousand trials involving meat, seafood, poultry and dairy products. The results, which were presented at a conference in Washington DC in September, confirmed that our model holds - also outside our own laboratory - and that it is reliable for both seafood and meat products. This is very interesting."

New important bacterium
In addition to a model for Listeria monocytogenes, the most recent version of SSSP also contains models for histamine formation in seafood.

"Several research projects conducted during the past ten years have shown that histamine can be formed in some marine fish products even though they have been kept refrigerated and chill stored as prescribed. This histamine formation at low temperature most likely contribute to the unacceptably high incidence of histamine fish poisoning in many countries, including Denmark," says Paw Dalgaard, adding:

"In our laboratory, we have identified a bacterium able to form very high concentrations of histamine in refrigerated marine fish products. The bacterium was not previously identified and we named it Morganella psychotolerans. With the new software it is possible to predict, e.g., how much salt you needed to add to cold-smoked tuna to ensure that the bacterium does not form histamine within the shelf-life of the product."

http://www.aqua.dtu.dk/English.aspx