Lupin, a legume, has an average protein content of just over 30 per cent, compared with 44 to 48 per cent in soybeans.
The ingredient has increasingly been recognised for its nutritional and food processing qualities, and consumption has become much more widespread since the introduction of lupin flour as an ingredient in wheat flour in the 1990s.
It is also increasingly being used in food formulations to replace soy flour in speciality bakery and pasta products.
But allergic reactions to lupin have also been well documented. The European Food Safety Authority (EFSA) says that IgE-binding proteins of lupin flour extracts have been identified and show in vitro cross-reactivities with peanut and other legumes, although the most clinically relevant cross-reactions are with peanut proteins.
This means that lupin flour could pose a risk to consumers with food allergies, notable peanuts. Researchers in the UK have cautioned that people with peanut allergy - about 1 per cent of the UK population - should avoid any products containing it until they have another allergy test.
A team at the Royal Free Hospital, London, who published their findings in a recent edition of The Lancet, (2005; 365: 1360), highlighted the case of a 25-year-old woman who, in August 2004, had an allergic reaction after eating a restaurant meal of chicken, French-fried potato, and onion rings.
Anaphylaxis - a life-threatening allergic reaction - was diagnosed. According to the UK researchers, the consumer knew she had a severe allergy to peanuts, but not to lupin, later identified in the onion ring batter she had consumed.
EFSA says there is no definite indication that technological treatments alter the allergenic potential of lupin, although reduction in allergenicity has been reported after autoclaving lupin seeds at 138°C for 30 minutes. The frequency of allergic reactions to lupin in the general population is unknown.
The authority says that most, though not all, allergic reactions have been reported in peanut allergic individuals. The possibility of under-reporting of allergy cases cannot be excluded, as until recently lupin was a hidden ingredient in various bakery and meat products.
One controlled study in peanut allergic patients suggests a clinically relevant cross-reactivity rate of about 30 per cent, but higher (68 per cent) rates have been reported. Clinical reactions range from mild local reactions to systemic anaphylaxis.
Ingested doses of lupin flour reported to have triggered clinical reactions range from 265 to 1000 mg, but the lowest dose triggering reactions has not been established.