Optimal temp found for tackling E.coli, preserving taste in cured sausages

Exposing cured sausages to mild heat treatment for a 24-hour period is effective in both combating E.coli and maintaining product quality, according to new research from Norway.

The three-year project, led by the Nofima institute, examined a range of methods in tackling foodborne pathogens in processed sausages and assessed not just their efficacy but also their implementabilty within the meat industry.

The research found high pressure processing to be effective but that high investment costs were probably the greatest barrier to entry. The team also examined how storage temperatures can affect bacteria proliferation.

Optimum temperature

They concluded that use of mild heat treatment methods were both effective and practical - with the crux being the combination of duration and temperature. The relationship between the two depends largely on the extent of the temperature increase and the duration of the heat treatment. The higher the temperature and the longer the duration, the better the effect – but this can also affect the taste and other sensory properties, said the scientists.

Tests demonstrated that heat treatment at around 43C for 24 hours had “a good effect with minimal sensory alterations”, said researcher Even Heir.

“Our aim was to find a regime that was effective in killing 99.999 per cent of E. coli - a 5 log CFU reduction - without affecting the quality, texture, and taste too much,” Nofima Mat senior research scientist Lars Axelsson said.

He added that while investigations centred on E.coli, all bacteria would probably be affected to varying degrees, with species such as Salmonella “most likely to respond in the same way.”

Industry implementation

But the group acknowledged incorporation of the method into industrial processes had yet to be developed and would almost certainly need the involvement of companies.

Heir said it should be up to individual producers to test out the documented methods on their own products to find the balance between temperature, duration and sensory properties.

“The standard process for sausage making in the industry already involves maturation in climate or smoking chambers,” said Axelsson. “These can probably be set to an extra step, but if this is logistically possible is not known at the moment.”

However, he added that mild heat treatments for sausages are already used extensively in North America.

Storage

In a separate development, the research also found that storage of sausages at various temperatures and periods will slowly diminish E.coli counts. Storage at room temperature for one month gave approximately a 2 log CFU reduction, whereas 4C showed a rate of decrease of less than 1 log CFU.

Axelsson estimated the research could help meat processors in evaluating the benefits of implementing either a heat treatment regime or introducing a longer holding time of the products at room temperature.

“They now know that these are steps that can be used to increase the safety, without diminishing the quality,” he added. “There may be a cost, though – in terms of changing the logistics, investing in a new climate chamber, longer holding times, etc.”

He said this had to be balanced against the potential risk which he said was “very small”.

Source: Nofima institute