concentrations of allergen may, at some low but finite probability, elicit harm in highly sensitive individuals.
Food allergens often occur as components of processed foods, and many allergic reactions occur following exposure to such allergens (Bock et al., 2001). Therefore, it is important to understand how the nature or composition of the food (i.e., the food matrix) affects the elicitation of a reaction.
Very little information exists on matrix effects for the majority of allergens. It has been reported that fat content can modify the reactions in a peanut DBPCFC (Grimshaw et al., 2003). Three of four subjects challenged with peanut flour in a matrix containing 31.5% fat reacted at a higher than expected dose, and had reactions that were more severe than expected, based on previous exposures to a standard recipe containing 22.9% fat. Upon rechallenge with the 22.9% recipe, their reactions returned to expected levels with respect to dose and severity. The cumulative dose of peanut protein required to elicit reactions was 12 to 31 times higher when using the higher fat recipe. The authors suggested that the peanut allergens in the higher fat recipe were not readily available to react with IgE on mast cells in the mouth. This was based on the observation that radioallergosorbent test (RAST) inhibition assays and enzyme linked immonosorbent assay (ELISA) detection tests showed that peanut allergens in the higher fat mixture were less available in vitro. In addition, these three patients all had histories of an initial oral challenge response. The lack of an oral early warning with a high-fat food may have caused these patients to consume more allergen prior to the onset of other symptoms. By the time digestion of the fat took place in the stomach and intestine, the total dose consumed was higher, resulting in a more severe reaction.
Grimshaw et al. (2003) further reported that the slopes of RAST-inhibition curves did not change for peanut allergens in high-fat versus low-fat mixtures, indicating that there was no change in antibody-binding properties. Thus, it appears that the antigenic properties of the peanut flour were not altered by the higher fat matrix, and that the changes in apparent threshold may have resulted from a combination of physiological and behavioral factors.
Kato et al. (2001) also observed a matrix effect with the major egg allergen ovomucoid. The ability of ovomucoid to bind IgE was reduced in a model pasta composed of durum wheat and egg white. This decrease was attributed to changes in antigenicity associated with formation of disulfide bonds between the ovomucoid and wheat gliadins.
2. Processing Effects Numerous studies have described alterations in allergens as a result of processing or cooking. Various types of processing (e.g., heating, milling, fermentation) may alter the antigenic properties of allergens because these processes can affect the three-dimensional structure of proteins and thus the IgE binding epitopes. The type and extent of structural alterations may vary depending on the processing method. This is especially true for
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