Protein quality and allergenicity assessment of chia seeds (Salvia hispanica): a molecular perspective on novel food safety.

Purpose: This study aimed to assess the protein quality and allergenic potential of chia seeds (Salvia hispanica), introduced in European market as a novel food (Regulation European Union 2015/2283) in 2019. Although chia is increasingly used as a plant-based ingredient, information regarding its protein profile and sequences is still limited. It follows that, without this essential knowledge, information of its allergenic potential is also lacking. Therefore, this work pose itself as a first building block, providing a detailed molecular characterisation of chia proteins and evaluating their allergenic potential and IgE cross-reactivity with other known allergens, such as sesame (Sesamum indicum).

Methods: Three chia flour samples-partial defatted flour as reference, standardised partial defatted flour, and protein concentrate-were analysed. Protein content was determined by Kjeldahl method. Protein quality was evaluated based on the amino acid profile and the estimation of amino acid score. Proteins were identified by SDS-PAGE through comparison with existing literature and then confirmed by in solution tryptic digestion coupled with high-resolution mass spectrometry analysis. Allergenicity was assessed by in silico sequence homology analysis with characterised sesame linear epitopes and in vitro immunoblotting using sera from sesame-allergic patients.

Results: The protein content ranged from 25% to 26% in the raw materials to 56% in the concentrate. Furthermore, SDS-PAGE profiles were comparable between samples, confirming the effectiveness of the extraction method applied. All samples showed balanced amino acid profiles and amino acid scores above one, meeting FAO/WHO requirements for adults and children. The main proteins identified in chia were 11S and 7S globulins, albumins and oleosins. The identified chia peptides were used to obtain a coverage of these with sesame protein sequences, confirming the attended homology. The potential cross-reactivity with sesame proteins, primarily retrieved from the literature, was then confirmed in vitro. IgE-binding was detected for major chia proteins, such as 11S and 7S globulin, and 2S albumin endorsing the attended cross-reactivity with sesame proteins.

Conclusion: This study provided insights on the effectiveness of the extraction method applied on chia protein quality, which is essential for their inclusion in balanced food formulations. The approach used for assessing allergenicity also highlighted that the level of molecular and immunological knowledge can differ among novel foods, making it challenging to define a general methodological framework for evaluating their allergenic potential and cross-reactivity risks. These results can be useful both as starting point for the inclusion of protein extracts from chia seeds as safe ingredient, while also highlighting the current lack of comprehensive molecular characterization-including incomplete sequence data and uncharacterized potential epitopes-which limits the full assessment of their allergenic risk.