We don’t know yet how the horse DNA recently found in cheap
burgers supplied by several supermarkets in the UK got there, whether by
accident or deliberately but debasing or adulterating food by using something cheaper
to bulk it out it is an ancient tradition. The incentive is great. A trader or
producer who does this and gets away with it makes a profit. Recent high
profile cases that were prosecuted include the case where melamine was discovered in milk in China in 2007. At least in the
horse DNA case there is not a food safety concern as horse is deemed edible while melamine is definitely not.
The first steps to safeguard food quality in Europe were
taken several centuries ago. The first example is considered to be the 1516 German
purity law for beer, the Reinheitsgebot, which
stated that beer could only have 3 ingredients, water, barley and hops ( they
didn’t know about yeast). The problem had been the use of some questionable
preservatives, including a few poisons rather than hops in beer. The law also
regulated demand for wheat and rye by limiting their use to bread rather than
UK food standards began to be laid out in 1875 in the Sale
of Food and Drugs Act of 1875.. For a frightening list of the contaminants put
in bread, tea, coffee and beer just prior to this Act see the Royal Society for
Chemistry’s article “The fight against food adulteration”. Your daily loaf could be contaminated with chalk, alum (poisonous!)
potatoes, calcium sulphate, clay, and even sawdust. Giving evidence to the
House of Commons in 1856 Dr Hassall one of the doctors pushing for change
listed some coffee adulterants: “roasted peas,
coffee grounds, parsnip, and madder root” Report of the Select
Committee Of The House Of Commons On The Adulteration Of Food.. He was keen
to see legislation as thousands of his analyses published in the Lancet, showed food adulteration was
very common and the substances used sometimes positively dangerous to the
public’s health. In the US laws were enacted about meat quality in the late
1800s and early 1900s.
Adulteration or contamination of meat with other meat
products can be a difficult substitution to spot in foods where the meat is cut
up or ground. The protein and fat composition of the meat give clues, and
immunological testing can differentiate individual proteins from different
animals. DNA testing using PCR methods has been around more than 10 years and
seems to be the best method yet.
PCR relies on identifying specific DNA sequences in a
target species or group of species and using these to create DNA primers that can bind to the species
DNA in a test situation and replicate the DNA for further analysis. Recent research
has focussed on finding primers that can identify a wide range of species
because the DNA sequence they bind to is the same across many species. One such
set was published in the last month by scientists at University of Oviedo, in
primers for species authentication of animal foodstuff in a single polymerase
chain reaction). They claim their test is cheap, quick and
efficient and that it can identify foods of animal origin from many groups of animals including fish. It also works on DNA that has been
degraded to some extent e.g. by cooking.
The amusing thing about the (alleged) horsemeat scandal is
that horse is actually quite a healthy meat, with a low fat content compared to
other red meats.
For the latest research on authenticating meat- see the CABI database Nutrition and Food Sciences database.