These are just three of the papers released at the Society for General Microbiology's four-day meeting at the University of Edinburgh in Scotland, which ends on 6 September.

Extending the shelf life of cooked ham

In today's sessions Roisin Lagan from the College of Agriculture, Food and Rural Enterprise in Cookstown, Northern Ireland presents research that could be used to extend the shelf life of cooked ham to 39 days.

Currently cooked ham holds a 55 per cent share of the UK cooked meat market. In a bid to maintain and expand this market processors are looking at new technologies to extend shelf life and open up new European markets for pork products.

Traditional cooked ham has a maximum shelf life of about 21 to 28 days, a countdown that begins from the time the meat is processed.

Lagan and his team found that treating cooked and sliced ham with a protective culture of Lactobacillus sakei, a common lactic acid producing bacterium, extended the shelf life by up to an additional 11 days.

"Many dairy products such as cheeses and yoghurts and some fermented meat products already use lactic acid producing bacteria to protect and preserve their products, and we know these are acceptable to consumers in terms of taste," said Lagan.

The scientists tested commercially cured and Lactobacillus treated meat on an untrained panel of consumers. The Lactobacillus treated meat was rated as tastier, with a better texture and overall more acceptability than the same conventionally treated ham.

Chemical studies showed that the bacteria treated ham was drier and slightly more acidic than the conventionally preserved version of the meat.

The food scientists then looked at the shelf life of the new product and found that the lactic acid bacteria culture helped to prevent other types of bacteria from growing on the treated ham, protecting it from possible contamination by food poisoning bacteria or ones which would taint it by destroying its flavour and texture.

The discovery means that the scientists have found a reliable and cost effective way of developing a tasty ham product with a maximum shelf life of 39 days when stored at 4 C said Lagan.

"This in turn will allow processors to have longer production runs leading to less wastage, thus reducing the environmental impact of storing and processing food waste," he stated. " The increased shelf life will allow UK companies to compete more effectively on a global scale. Consumers will be assured a reliable, safe cooked ham product."

Tracking Yersinia enterocolitica

In another presentation Brenda Murphy of the Veterinary Food Safety Laboratory, Cork County Council and Centre for Food Safety at the University College Dublin gave details of an ongoing two-year study to track how the human disease causing bacteria, Yersinia enterocolitica, enters the food chain in Ireland.

The study on the pathogen, a leading source of gastrointestinal diseases, could help processors and regulators cut down on its prevalence at the farm, rather than having it end up on a fork.

Scientists will monitor pig carcasses and pig meat in slaughterhouses, butchers' premises and retail outlets.

The scientists will examine 1,800 pig tissue samples from three slaughterhouses and 200 pork meat samples from 50 retailers.

So far, of 516 samples studied, 2 per cent have already been found with non-disease causing Yersinia enterocolitica, and 3 per cent have been found to contain the bacteria with disease causing genes.

Some of the contaminated samples were also shown to contain antibiotic resistant strains of the bacteria, representing an emerging pathogen which is a potential public health risk, Murphy said.

Public health officials do not yet know quite how significant or not the problem is, she added.

"Consumers and the food industry will benefit from improved biosecurity measures based on our scientific findings," she stated. "This will lead in turn to better monitoring and reduction in the risk of dissemination of the pathogen."

Once the team has identified the full extent of the problem in pigs they plan to include screening other food animals such as cattle to work out where else the organism might occur.

Cutting salt does not increase pathogen risk

In a third paper today researchers at the University of Limerick in Ireland said their study indicated that cutting the salt content of processed foods has no impact on the risk of food contamination.

The study should provide some degree of confidence to food manufacturers globally, who are under regulatory and consumer pressure to reduce salt levels in their products in response to the health concerns.

However, because salt also acts as a preservative. An industry move to slash sodium levels could be expected to increase the risk of food spoilage by bacteria.

"In general we discovered that the growth of different sorts of typical food spoilage bacteria was unaffected by the various salt levels we tested, which means that low salt foods are just as safe as conventionally processed ones" said Edel Durack, who presented the results of the study.

The team checked safety levels of low salt foods by studying the behaviour of different strains of food spoilage bacteria inoculated into model systems.

All the bacteria studied were capable of growing in the highest concentration -- 3 per cent -- of salt used, they said. Even at this level of salt none of the bacteria experienced any difficulty in surviving for 24 hours.

However, the researchers found differences between the salt tolerances of all the bacteria tested. Their results confirmed that some bacteria strains actually exhibited greater resistance to the high salt environment.

This is in line with previous findings that have shown salt to have a stimulating effect on some types of bacteria.

"At the moment our results are helping processors reduce salt levels in frozen ready to eat meals," stated Durack. "Generally these meals carry a large percentage of the recommended daily allowance of salt. This type of food is becoming increasingly popular and is in high demand due to its convenience and time restrictions placed on consumers due to modern day lifestyles."

He says the study can be used to aid the development of a new range of low salt foods that will help people to reduce levels in their diet, reducing their risk of cardiovascular diseases linked to excess sodium, without compromising product safety.

In the UK, Ireland and the USA, over 80 per cent of salt intake comes from processed food, with 20 per cent of salt intake coming from meat and meat products, and about 35 per cent from cereal and cereal products.

In processed meat products, salt helps activate proteins to increase water-binding activity, improves the binding and textural properties of proteins, and helps with the formation of stable batters with fat.

Other presentations at the meeting included one on food- and water- borne pathogens, entitled "Food, fluids, fingers, faeces and flies". A workshop on the molecular detection of food and water pathogens is scheduled for tomorrow.

The Society for General Microbiology is the largest microbiology society in Europe, and has over 5,500 members worldwide.