Analytical test kits for ensuring milk-free food production

Which test for what?

• The Sandwich ELISA RIDASCREEN^®FAST Milk (Art. No. R4652) is suitable for testing foods of unknown composition, which may contain both casein and β-lactoglobulin (BLG) in unknown proportions. The test contains antibodies against both, BLG and casein. In a sample with natural protein ratios, it detects approx. 50 % casein and approx. 50 % BLG, i.e. it will reliably detect traces of both proteins. The result measured in the ELISA is a composite value from the reaction of both antibodies. If the unknown sample contains only casein, only the anti-casein antibody will provide a response. The same applies to the anti-BLG-antibody. The composite result is expressed in mg/kg (ppm) of milk protein. However, this value does not have to correspond to the natural proportions of milk. The test can detect up to 0.7 ppm (mg/kg) milk protein, which corresponds to a theoretical conversion of 21.9 ppm milk. The skimmed milk powder NIST SRM 1549A with a protein content of 26.5 % is used as the calibrator.

• The Sandwich ELISA RIDASCREEN^®FAST Casein (Art. No. R4612) is suitable for testing foods that may contain predominantly casein or caseinates. If the casein content of the sample is known, it can be converted to milk protein. If it is a food to which cow’s milk has been added or which contains contaminants from cow’s milk, the casein content is 2.6 %. Whey products, which consist mainly of BLG, also contain traces of casein and can therefore be used for the test. The test detects the amount of casein contamination present in the whey sample. The level of contamination in relation to the BLG is not known. Therefore, the measured casein content of a whey sample cannot be converted to the milk concentration. However, a positive casein result indicates milk contamination of the food. The presence of milk protein must be indicated on the label.

• The Sandwich ELISA RIDASCREEN^®FAST β-Lactoglobulin (Art. No. R4912) is suitable for testing foods that may contain predominantly whey protein. The amount of BLG indicates a relation to the amount of whey present in the food and thus in any case the presence of milk protein. The food must be labelled. Caseins and caseinates cannot be produced BLG-free during manufacture. An existing contamination can be detected in the test. The level of contamination in relation to casein is not known. Therefore, the measured BLG of a casein sample cannot be converted to the milk concentration.

• The competitive ELISA RIDASCREEN^® β-Lactoglobulin (Art. No. R4901) is suitable for the testing of hydrolyzed dairy products, especially for hypoallergenic baby food, as the competitive format is able to detect smallest protein fragments (one epitope) in highly hydrolyzed dairy products.

• The qualitative rapid tests (LFDs) of bioavid Lateral Flow Milk (Art. No. BL623-15) and Lateral Flow Casein incl. Hook Line (Art. No. BLH714-15) enable a quick and simple, but only qualitative detection (yes/no answer) of milk or casein, respectively. They can be used as a qualitative control in the context of allergen management according to HACCP (Hazard Analysis and Critical Control Points). Surfaces can be examined for milk contamination during food production in order to detect and prevent cross-contamination. The effectiveness of the cleaning of equipment and plant can be checked and the screening of food for milk/casein contamination can be examined. The casein test also includes a hook line, which would reveal a hook effect in the case of highly positive samples.

Conversions according to the food composition

• Conversion of casein into milk:
  The result of the RIDASCREEN®FAST Casein test (Art. No. R4612) is given in mg/kg casein and can be converted into milk or milk protein, if the sample contains casein. If samples contain cow’s milk the casein content is 80 % of the milk protein, which in turn accounts for 3.2 % of the milk. Example: 10 mg/kg (ppm) casein were measured; 12.5 ppm milk protein were calculated (10 ppm casein x 100 % / 80 %) and 390.6 ppm milk (12.5 ppm milk protein x 100 % / 3.2 %).

• Conversion of β-Lactoglobulin (BLG) into milk:
  The result of the RIDASCREEN®FAST β-Lactoglobulin test (Art. No. R4912) is expressed in mg/kg BLG and can be converted into milk or milk protein, if the sample contains whey or BLG. If samples contain cow’s milk, the BLG content is 10 % of milk protein, which in turn accounts for 3.2 % of the milk. Example: 1 mg/kg (ppm) BLG was measured; 10 ppm milk protein was calculated (BLG 1 ppm x 100 % / 10 %) and 312.5 ppm milk (10 ppm milk protein x 100 % / 3.2 %).

• Conversion of milk protein into milk:
  The result of the RIDASCREEN®FAST Milk test (Art. No. R4652) is expressed in mg/kg of milk protein and can be converted into milk. The conversion factor of milk protein into milk is 31.25. If the measured milk protein value is multiplied by the factor of 31.25, the result is obtained in mg/kg (ppm) of milk. Example: 1 mg/kg (ppm) milk protein x 100 % / 3.2 % = 31.25 ppm milk.

• Conversion of milk powder into milk:
  Milk powder equates to about 10 % of milk because milk contains about 90 % of water. If the value is measured in milk powder and multiplied with the factor of 10, the result is expressed in milk.
  Example: 1 ppm milk powder x 100 % / 10 % = 10 ppm milk.