Thermal Processing of Peanut Grains Impairs Their Mimicked Gastrointestinal Digestion While Downstream Defatting Treatments Affect Digestomic Profiles

Abstract

Resistance to digestion by digestive proteases represents a critical property of many food allergens. Recently, a harmonized INFOGEST protocol was proposed for solid food digestion. The protocol proposes digestion conditions suitable for all kinds of solid and liquid foods. 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. Therefore, the removal of the lipids seems to be a prerequisite for the downstream analysis of digestomes of lipid-rich foods. Here, we aimed to compare the digestomes of raw and thermally treated (boiled and roasted) peanuts, resulting from the INFOGEST digestion protocol for solid food, upon defatting the digests in two different manners. The most reproducible results of peanut digests were obtained in downstream analyses on TCA/acetone defatting. Unfortunately, defatting, even with an optimized TCA/acetone procedure, leads to the loss of proteins and peptides. The results of our study reveal that different thermal treatments of peanuts affect protein extraction and gastric/gastrointestinal digestion. Roasting of peanuts seems to enhance the extraction of proteins during intestinal digestion to a notable extent. The increased intestinal digestion is a consequence of the delayed extraction of thermally treated peanut proteins, which are poorly soluble in acidic gastric digestion juice but are easily extracted when the pH of the media is raised as in the subsequent intestinal phase of the digestion. Thermal processing of peanuts impaired the gastrointestinal digestion of the peanut proteins, especially in the case of roasted samples.

Effect of Sample Preparation on the Detection and Quantification of Selected Nuts Allergenic Proteins by LC-MS/MS

“…PVPP and SDS buffer methods debited similar protein profiles; even though the proteins from the PVPP method seemed to be more abundant ( Figure 2 ). In contrast, it could be shown in the study of Prodic et al [ 45 ] that TCA/acetone precipitation of milled peanut grains could results in many proteins in the low molecular weight range depending on the prior treatment executed (e.g. gastric treatments).…”

INFOGEST Digestion Assay of Raw and Roasted Hazelnuts and Its Impact on Allergens and Their IgE Binding Activity

“…Food allergen resistance to digestion is an essential factor that contributes to allergenicity; we aimed to examine the outcome of in vitro gastric digestion of hazelnut based on INFOGEST protocol [ 15 ], and whether the roasting process affects gastric digestion pattern and resistance of the main hazelnut allergen, Cor a 9. These tasks were not easy to complete, since in vitro gastric digestion of hazelnut as a whole food is challenging for analyses due to the presence of lipids, sugars, phenols, and other biomolecules, especially after thermal treatment such as dry roasting [ 17 ]. IgE reactivity of the non-defatted hazelnut digesta was compared by 1D and 2D immunoblotting and ELISA, using either individual or pooled sera from hazelnut allergic patients.…”

“…Studying the efficiency of protein extraction during in vitro gastric food digestion that has been thermally treated requires proper control of the digestion process, e.g., complete in vitro simulating digestion mixtures but without digestive enzymes [ 17 ]. Extraction during digestion represents a key element in liberating proteins from a fat-rich texture, e.g., from tree nuts.…”

“…INFOGEST protocol strongly recommends following consecutive digestion phases (oral, gastric, intestinal phase) without any defatting prior to digestion, to avoid neglecting the impact of allergen-protecting lipids and the food matrix in general. Our previous studies have developed and improved this approach [ 16 , 17 ]. In addition, it is critical to analyze the IgE binding potency of gastric digestion products of raw and roasted hazelnuts, because it has been shown that gastric digesta of raw and roasted peanuts differ in digestion fragments and allergenicity, which are central to duodenal sensitization processes [ 16 , 17 , 18 ].…”

“…Our previous studies have developed and improved this approach [ 16 , 17 ]. In addition, it is critical to analyze the IgE binding potency of gastric digestion products of raw and roasted hazelnuts, because it has been shown that gastric digesta of raw and roasted peanuts differ in digestion fragments and allergenicity, which are central to duodenal sensitization processes [ 16 , 17 , 18 ]. Thus, this study aimed to characterize the structural and allergenic properties of the hazelnut allergens and their gastric digestion, using fragments from raw and roasted hazelnuts, focusing on Cor a 9, which was isolated and purified from the raw and roasted hazelnut extracts.…”