Proteomics in food authenticity and food safety
What new can we learn about peanut allergens by proteomics?
Resistance to digestion by digestive proteases represents a critical property of many food allergens. However, peanuts, as a lipid-rich food, represent a challenge for downstream analyses of the digestome. This is particularly reflected in the methodological difficulties in analyzing proteins and peptides in the presence of lipids. Furthermore, different thermal treatments of peanuts affect protein extraction and digestion. Roasting of peanuts seems to enhance the extraction of proteins during intestinal digestion toa notable extent. Thermal processing of peanuts impaired the gastrointestinal digestion of the peanut proteins, especially in the case of roasted samples.Post-translational modifications (PTMs) are covalent changes occurring on amino acid side chains of proteins, and yet neglected structural and functional aspect of protein architecture. Weconducted a comprehensive bottom-up proteomic study to investigate the impact of peanut roasting on readily soluble allergens and their PTM profiles. Besides inducing protein aggregation and denaturation, roasting may facilitate change in their PTM pattern and relative profiling.We have shown that Ara h 1 is the most modified major allergen in both samples in terms of modification versatility and extent. The most frequent PTM was oxidation of methionine especially in roasted samples. PTMs uniquely found in roasted samples were, hydroxylation (Trp), formylation (Arg/Lys), and oxidation or hydroxylation (Asn).Proteomic PTM profiling was confirmed by immunoblotting with a series of PTM-specific antibodies. Great variety of proteoforms of peanut allergens is readily available for interaction with the immune system.