Burger on a wooden board
Out of 258 burger products, 13.6% were deemed "problematic"Getty

A molecular analysis of burger products has thrown up some surprising ingredients. Food analytics platform, Clear Labs, tested what constituted 258 different burger products and found rat and human DNA, as well as veggie burgers containing meat while others had pathogens.

About 13.6% of the products were "problematic" according to the researchers with 4.3% containing pathogenic DNA. Out of the 258 samples, three tested positive for rat DNA and one tested positive for human DNA. Of the vegetarian products, a larger 23.6% were described as problematic. Two of the veggie burgers contained beef traces and one black bean burger contained no sign of black beans.

All 258 tested products came from 79 brands and 22 retailers in Northern California. According to the report, the fast food industry had low levels of contamination but a number of fast food burgers had different nutritional values contrary to those stated by the companies.

A number of other substitutions were also detected. For example, pork DNA was found in one beef patty and one sample of ground beef; chicken DNA was found in one sample of fresh ground pork; one turkey burger and two beef burger products. Fourteen of the vegetarian burgers were missing ingredients altogether.

Pathogens were found in 4.3% of the samples. According to the authors of the report, one in six Americans will suffer food poisoning each year - out of which 3,000 cases will be fatal. The most common pathogen was yersinia pseudotuberculosis, which "can cause tuberculosis-like symptoms in animals and in humans".

Mahni Ghorashi, co-founder of Clear Labs said of the company: "Rather than having to run different tests to identify specific ingredients, pathogens, or contaminants, we can look blindly into samples, at scale, and monitor food supply chains like never before."

Clear Labs also previously released a report which found human DNA in hot dog products.