Life could depend on the variety of spice! At least if you're a food-poisoning microbe planning to grow on a good-old burger. Spanish researchers have discovered that adding pepper and tomato to burgers could boost their shelf-life by more than a fortnight, without artificial additives, keeping bugs like salmonella and listeria at bay and saving on spoiled food. The findings could also give the humble burger a much-needed health boost.
According to Pedro Roncales of the University of Zaragoza in Spain and colleagues writing in the February issue of the Journal of the Science of Food and Agriculture adding either sweet or hot ground pepper to a burger slows the natural oxidation of proteins and fats that turn meat rancid as well as inhibiting the growth of poisonous bacteria.
The researchers produced eight batches of beef burgers, containing different amounts of cayenne pepper, red sweet pepper and lycopene-rich tomato products. Lycopene-rich tomato strains are being developed mainly in Israel in order to improve their antioxidant ability. The burgers were stored in a refrigerator at 2 Celsius and the team tested them for microbial activity every four days by smell, discolouration, pH and bacterial head count.
They found they could extend the shelf-life of beef burgers from an average four days to about sixteen with a dash of pepper - the hotter the better. Tomatoes had a similar but not quite as strong an effect on stretching burger life from eight to twelve days. Tomatoes also added plenty of cancer-protective lycopene - the tomato's natural red colourant - to the fast-food favourite. "It is not fully understood why tomato products aren't as potent," says Roncales, "but peppers contain more antioxidant molecules such as carotenoid and phenolic compounds."
Cooks, of course, have known since ancient times that culinary herbs and spices could help preserve many different foods. Modern researchers had assumed that the presence of antioxidants was the main benefit (aside from improving flavour) of adding such spices. However, Roncales and his colleagues have now cooked up another reason to spice up burgers and meat because of the antibacterial effects of spices.
The chemicals in peppers that make them spicy hot are known as capsaicinoids. It is these hot molecules that Roncales and his colleagues suggest help protect meat from spoilage but not from the colonising bacteria, such as listeria and salmonella that otherwise grow even in the chilly atmosphere of a fridge. This, they think is down to the presence of other as yet unidentified compounds, because both hot and cool peppers have such similar effects on inhibiting bacteria.
The team is now investigating the chemical ingredients of peppers, such as carotenoids (vitamin A compounds), tocopherols (vitamin E compounds), and ascorbic acid (vitamin C) to see whether it is these components that have the desired antibacterial effect. "We are also studying various herbs, such as rosemary, oregano and others, and white and black pepper," he told us.
"Peppers and tomatoes are already popular food additives in many parts of the world because they enhance the flavour of food," says Roncales, "Our results have shown that they may also be used as an effective alternative to synthetic antioxidants to prolong the shelf life of meat and meat products." He adds that he is confident the use of natural antioxidant and antimicrobial herbs and spices will be of increasing interest to food companies. "It will take only a short time for them to start including this in their commercial advertising and promotions," he adds.