Peanuts

Peanuts are legumes and thus related to soybeans, peas, beans, lenses, chick peas and lupine seeds. They all belong to the same botanical family, Leguminoseae/Fabaceae. Among those allergic to one legume it is not unusual to react to several legumes due to structural relations between proteins. Allergy to peanuts is sometimes accompanied with allergy to soy, pea, beans, lenses or lupine.

Peanuts are eaten roasted as snacks but serve also as raw material for the production of peanut flour and peanut oil. Peanut oil produced through evaporation has been shown to occasionally contain protein residues. It is not unlikely that such oil might pose a risk for the most sensitive peanut allergic individual. In cold pressed oil, the amount of residual proteins is so high that the opinion is that such oil is a potential risk for the peanut allergic consumer.

Peanuts can be used as garments in bakery goods, chocolate and ice cream. It is also common in pesto and in spice mixtures (Satay mein paste) for Asian dishes.
Peanut butter is composed of roasted and finely ground peanuts added with sugar, emulsifier, fat and salt.

Several allergenic proteins have been identified in the peanut to which allergic individual may react.

Labeling

The presence of peanut and products thereof in food products must always be declared, se further in LIVSFS 2004:27 Livsmedelsverkets föreskrifter om märkning och presentation av livsmedel [in Swedish]. (see link to the right). Peanut oil is not exempted from labeling.

Examples of methods of analysis

Sensitive commercial ELISA test kits are available for the analysis of peanut. The limit of quantification varies somewhat between the test kits and with the matrix being analyzed. In several assays the limit of quantification is 1 mg peanut /kg (ppm).

Peanut can be detected in food samples using rapid methods, based on test strips, which are soaked in an extract of the foodor ina swab sample extract. Such tests are only qualitative, i.e. the result is given either as peanut present (positive) or peanut is not present (not detected) in the food extract. Positive results need sometimes to be confirmed with quantitative methods. It is very important that qualitative test kits don’t give false negative results.

Peanuts can be identified with DNA methods. A positive result in a DNA analysis indicates the presence of peanuts in a sample.

Providers of test kit often have a validation protocol to be submitted with the test kit upon request. Laboratories using commercial assays must establish in house control of limit of detection and limit of quantification in actual matrices even if the test has been validated by the provider.

Allergic reactions / Doses

The lowest dose of peanut protein that elicitates an allergic reaction is not known. The concentrations of peanut proteins that have been detected in food products causing allergic reactions are listed below. Peanut proteins constitute about 30 percent of the peanut.

* Anaphylaxis means that the allergic individual suffers from blood pressure drop, respiratory comprise/cramps in the airways and a systemic shock reaction, called anaphylactic shock
** Fatal anaphylaxis means that the shock develops to unconsciousness and death