FACTORS INFLUENCING THE QUALITY OF FOOD EXTRACTS FOR IN-VITRO AND IN-VIVO DIAGNOSIS

Food extracts for diagnostic purposes often lack sufficient activity a nd consistency. Biologically standardized food extracts are not availa ble on the market. Using extracts from plant-derived foods as examples , we investigated factors which may be important for the quality of su ch extracts. Divergent allergenic activities were found between strain s of apples, but not within varieties of celery tuber (celeriac), haze lnut, and peanut, respectively. Heating of the food remarkably reduced the activity of apple, hazelnut, and celeriac, but had little effect on peanut. By contrast, heating of semipurified protein extracts from celery tuber and apple for 30 min at 100 degrees C did not deplete the immunoreactivity of the major allergens, indicating that this is an i nappropriate test for identifying labile food allergens. Due to their high endogenous enzyme activities, apples and other fruits require spe cial extraction procedures applying either low temperature or enzyme i nhibitors. Variation of extraction conditions had little effect on the composition and activity of extracts from hazelnut. The storage stabi lity of skin test solutions from plant foods can be improved by avoidi ng phenol as an additive and by including 50% of glycerol. For model s tudies considering neoallergens, IgE was raised in mice against native and heated celery tuber, respectively. When extracts from nonthermall y and thermally processed celeriac were subjected to an RBL-cell media tor release assay with these sera, an inverse ranking was obtained wit h anti-heated celeriac IgE and anti-native celeriac IgE, respectively. These data indicated that new epitopes had been formed by the heating process. Since all parameters were tested in model experiments with e ither human or murine IgE, their relevance has to be proven in further clinical investigations. (C) Munksgaard 1998.