SOUTH African burger-and boerewors-lovers are getting more than they bargained for, according to research conducted by scientists at the University of Stellenbosch, which found processed meat products laced with undeclared ingredients ranging from water buffalo to soya.

Some of the hidden ingredients pose health risks to people with serious allergies, while others will offend people with strong religious or ethical convictions about the food they eat.

The label fraud is in direct contravention of the latest regulations to the Foodstuffs, Cosmetics and Disinfectants Act, which came into effect last year.

The research, published last month in the international peer review journal Food Control, assessed 139 processed meat products purchased from large and small retailers in four provinces. Using DNA analysis to test for 14 animal species, the scientists found widespread mis-labelling.

Raw sausages were the worst culprits, with pork found in half the sausages that did not declare it on the label, and chicken found in two-fifths of the sausages that did not list it as an ingredient.

They also found many products failed to declare soya and gluten, both of which are allergens that must be declared on food labels.

The scientists found pork and chicken were the most common undeclared ingredients, but identified water buffalo and donkey in some products too.

Study co-author Louwrens Hoffman, who holds the chair of meat science at the University of Stellenbosch, said some products were likely to have been accidentally contaminated during processing, while others had been deliberately adulterated. The study did not assess the percentage of undeclared ingredients in the products.

He declined to name brands, saying the research was not intended to "name and shame", and advised consumers to ask tougher questions of shop floor managers and restaurant staff.