Association of end-product adducts with increased IgE binding of roasted peanuts.

Recently, we have shown that roasted peanuts have a higher level of IgE binding (i.e., potentially more allergenic) than raw peanuts. We hypothesized that this increase in IgE binding of roasted peanuts is due to an increased levels of protein-bound end products or adducts such as advanced glycation end products (AGE), N-(carboxymethyl)lysine (CML), malondialdehyde (MDA), and 4-hydroxynonenal (HNE). To support our hypothesis, we produced polyclonal antibodies (IgG) to each of these adducts, determined their levels in raw and roasted peanuts, and examined their ability to bind to IgE from a pooled serum of patients with clinically important peanut allergy. Results showed that AGE, CML, MDA, and HNE adducts were all present in raw and roasted peanuts. Roasted peanuts exhibited a higher level of AGE and MDA adducts than raw peanuts. IgE was partially inhibited in a competitive ELISA by antibodies to AGE but not by antibodies to CML, MDA, or HNE. This indicates that IgE has an affinity for peanut AGE adducts. Roasted peanuts exhibited a higher level of IgE binding, which was correlated with a higher level of AGE adducts. We concluded that there is an association between AGE adducts and increased IgE binding (i.e., allergenicity) of roasted peanuts.

The effects of roasting on the allergenic properties of peanut proteins.

BACKGROUND: Because of the widespread use of peanut products, peanut allergenicity is a major health concern in the United States. The effect or effects of thermal processing (roasting) on the allergenic properties of peanut proteins have rarely been addressed. OBJECTIVE: We sought to assess the biochemical effects of roasting on the allergenic properties of peanut proteins. METHODS: Competitive inhibition ELISA was used to compare the IgE-binding properties of roasted and raw peanut extracts. A well-characterized in vitro model was used to test whether the Maillard reaction contributes to the allergenic properties of peanut proteins. The allergic properties were measured by using ELISA, digestion by gastric secretions, and stability of the proteins to heat and degradation. RESULTS: Here we report that roasted peanuts from two different sources bound IgE from patients with peanut allergy at approximately 90-fold higher levels than the raw peanuts from the same peanut cultivars. The purified major allergens Ara h 1 and Ara h 2 were subjected to the Maillard reaction in vitro and compared with corresponding unreacted samples for allergenic properties. Ara h 1 and Ara h 2 bound higher levels of IgE and were more resistant to heat and digestion by gastrointestinal enzymes once they had undergone the Maillard reaction. CONCLUSIONS: The data presented here indicate that thermal processing may play an important role in enhancing the allergenic properties of peanuts and that the protein modifications made by the Maillard reaction contribute to this effect.

Allergenicity of Maillard reaction products from peanut proteins.

It is known that peanut allergy is caused by peanut proteins. However, little is known about the impact of roasting on the allergenicity of peanuts. During roasting, proteins react with sugars to form Maillard reaction products, which could affect allergenicity. To determine if the Maillard reaction could convert a nonallergenic peanut protein into a potentially allergenic product, nonallergenic lectin was reacted with glucose or fructose at 50 degrees C for 28 days. Browning products from heat-treated peanuts were also examined. The products were analyzed in immunoblot and competitive assays, using a pooled serum (i.e., IgE antibodies) from patients with peanut anaphylaxis. Results showed that the products were recognized by IgE and had an inhibitory effect on IgE binding to a peanut allergen. Thus, the findings suggest that these Maillard reaction products are potentially allergenic and indicate the need to verify whether the Maillard reaction products formed in peanuts during roasting increase their allergenicity.

Low gastric hydrochloric acid secretion and mineral bioavailability.

Young infants and approximately 30% of the elderly have low secretion of hydrochloric acid by gastric parietal cells. It has been established that low hydrochloric acid secretion can lead to decreased absorption of ferric iron. Conflicting results have been obtained in clinical studies of the effects of intraluminal gastric pH values on calcium absorption. The results of an in vitro study suggest that the chemical form of the ingested calcium and the presence of protein may influence whether high intraluminal gastric pH values affect resultant calcium solubilities in the small intestine. The effects of low hydrochloric acid secretion on zinc absorption have not been ascertained. The results of an in vitro study indicate that high intraluminal gastric pH values would not affect resultant zinc solubilities in the small intestine following pancreatin digestion of soy protein isolate supplemented with calcium and/or zinc. Considering that the diets of many elderly contain primarily plant foods and that soy protein isolate formulas are commonly fed to infants, further research is especially needed to determine the effects of low hydrochloric acid secretion on mineral bioavailabilities from high fiber and phytate containing plant foods.

Effects of pH on mineral-phytate, protein-mineral-phytate, and mineral-fiber interactions. Possible consequences of atrophic gastritis on mineral bioavailability from high-fiber foods.

A common gastrointestinal tract problem afflicting the elderly is that of reduced hydrochloric acid secretion by the stomach mucosa. This results in raised stomach pH values and in reduced activity of the digestive enzyme pepsin, which is responsible for the hydrolysis of dietary proteins to polypeptides. The effects of these alterations of the stomach on the digestion of high-fiber foods and resultant mineral bioavailability have not been defined. This paper reviews the effects of pH on the mineral-phytate, protein-mineral-phytate, and mineral-fiber interactions that would be present in high-fiber foods. Possible consequences of raised stomach pH values on mineral bioavailability from high-fiber foods are discussed.

Effects of Ca(II) ions on Cu(II) ion-phytic acid interactions.

In vitro interactions among phytic acid (PA), Cu(II) ions, and Ca(II) ions were examined as functions of PA:Cu(II):Ca(II) molar ratios and pH. Ca(II) ions competed with Cu(II) ions for binding by the soluble phytate species for PA:Cu(II) molar ratios ranging from 10:1 to 1:6 and pH values in the 2.4-5.9 range. At pH values where precipitation occurred, Ca(II) ions potentiated Cu(II) ion binding by the precipitated phytate species for PA:Cu(II) molar ratios of 10:1 to 1:3. At lower PA:Cu(II) molar ratios, Ca(II) ions competed with Cu(II) ions for binding by the precipitated phytate species. Compositions of the precipitated copper-calcium phytates are reported.