The firm said the adulterant varies depending on region of the world with examples in India including water, calcium or urea while in Europe it is mostly different milk species.
“Commonly, cow milk is the cheapest milk, therefore the most common adulterant. Goat is a more expensive milk but in cases we want to have a pure sheep milk, then goat can be the adulterant.
It depends on the prerequisites set by the EU for a cheese to attain Protected Designation of Origin (PDO).
“It is a common trait of countries producing goat and sheep milk, such as Spain, France, Italy, Greece, Turkey, Portugal, etc. Especially in the EU, a PDO product has a certain added-value which is virtually undone by having different species' milk in your cheese.”
Detection and quantification
ProGnosis Biotech has tests for milk adulteration and ELISA kits to quantify adulteration.
Bio-Shield Cow is an ELISA test for detection of cow milk in sheep or goat milk and Bio-Shield Goat is an ELISA test to detect goat milk in sheep milk.
Bio-Shield Goat has a 0-50% calibration range while Bio-Shield Cow ELISA has a 0-40% calibration range and the coefficient variation (CV) in both cases is less than 6.5%.
The limit of detection (LOD) for Bio-Shield Cow is 0.03% cow milk in sheep or goat milk and Limit of Quantitation(LOQ) is 0.15% and in Bio-Shield Goat LOD is 0.06% goat milk in sheep milk and 0.20% LOQ.
All conjugates and reagents come in ready to use form and both tests take 85 minutes.
The firm also has an ELISA test to detect composition of cow milk in mature cheese.
Bioshield Cow Cheese ELISA traces cow immunoglobulin in the final product with a LOD of 0.04% and LOQ of 0.15% but effectiveness depends on thermal treatment of milk.
It works for Feta but not Halloumi which is processed twice and the second time at 120 degrees for more than 30 minutes.
ProGnosis Biotech said there are constant attempts to adulterate more expensive milk with cheaper products.
“There are different prices depending on the country, but in every case, cow is the cheapest milk €0.30-€0.40 cents per litre, goat is €0.55-€0.65 cents per litre and sheep is €0.90-€1.05 cents per litre.
“In the EU, for example, France, Spain, Italy, Greece, Bulgaria and Portugal produce all three products.''
Immunoglobulins and milk allergy
Many cheeses such as Roquefort are 100% of one specific milk.
“The Rapid Cow and Rapid Goat sensitivity is 0.1% and it is five minutes long. If there is any immunoglobulin it will be caught by the stick. Regular pasteurization is not a problem for ProGnosis Biotech rapid tests for adulteration, since it preserves a high percentage of immunoglobulins in milk,” said the firm.
“In comparison to ELISA, PCR can act only as a qualitative method in these kind of samples, as there is no actual way to confirm a balance among the presence of cow DNA and the actual % of cow milk in the original raw material.
“With a very low LOD at 0.1% for Rapid Tests and 0.15% for ELISA kits, immunoassays are a much better way to trace and quantify adulteration than PCR.
“Trace with a stick which samples are adulterated and put adulterated samples onto ELISA and find out the percentage of adulteration. The need is precision and accuracy; you want to have precise reports to pay farmers in a relevant way and easy to use procedures not to commit mistakes.”
ProGnosis Biotech said bovine milk allergy is also important in Western markets.
“The increase in testing is driven also by caution for allergens and it is imperative to point-out that cow milk is a known allergen. Almost 15% of infants and youngsters are allergic to cow milk, while about 75% of allergic reactions among children are due to egg, peanut, cows‘ milk, fish and various nuts, which renders the total absence of cow milk very important.
“For the industry it makes sense to perform tests in the raw materials to avoid testing with PCR in the final product, when no correction actions can be implemented as the product is already on the shelves. This will enforce the industry's goal of attaining and preserving PDO for its products.”