Microbiological, physiochemical, and immunological analysis of a commercial cashew nut-based yogurt

Authors: Mattison, Chris; ARYANA, KAYANUSH - Louisiana State University; CLERMONT, KRISTEN - Oak Ridge Institute For Science And Education (ORISE); PRESTENBURG, ERIC - Oak Ridge Institute For Science And Education (ORISE); Lloyd, Steven; Grimm, Casey; WASSEMAN, RICHARD - Allergy Partners Of North Texas Research

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2020
Publication Date: 11/4/2020
Citation: Mattison, C.P., Aryana, K.J., Clermont, K., Prestenburg, E., Lloyd, S.W., Grimm, C.C., Wasseman, R.L. 2020. Microbiological, Physiochemical, and Immunological Analysis of a Commercial Cashew Nut-Based Yogurt. International Journal of Molecular Sciences. https://doi.org/10.3390/ijms21218267.
DOI: https://doi.org/10.3390/ijms21218267

Interpretive Summary: Cashew nut allergy often results in severe reactions, and cashew nut allergens are stable to several types of processing. There are three cashew allergens (Ana o 1, Ana o 2, and Ana o 3) that often cause reaction. Ana o 3 is an immuno-dominant cashew allergen that is strongly correlating with systemic allergic reactions. Fermented foods are thought to have several health benefits and are regularly consumed around the world. Fermentation of peanuts and tree nuts could be a useful processing method to reduce the potency of nut allergens and potentially create value-added, hypo-allergenic, and therapeutic foods. A commercial yogurt made from cashew nuts (Cashewgurt) was evaluated for microbiological, physiochemical, and immunological properties to characterize the effects of lactic acid bacterial (LAB) fermentation on cashew nut allergens. The Cashewgurt contained LAB numbers high enough to be beneficial to consumers. Evaluation of soluble protein extracted from Cashewgurt using several assays indicated a clear reduction in intact Ana o 1 and 2 content but Ana o 3 was relatively unaffected by the fermentation process. The presence of intact Ana o 3 in the final Cashewgurt product is a surprising result and suggests this type of fermented nut food may also have application as a potentially oral immunotherapy substance. Continued evaluation of commercial and laboratory peanut and tree nut fermentation conditions including bacterial strain selection, media content, and fermentation times could result in cashew nut-based yogurt with rationally engineered allergen content.

Technical Abstract: Cashew nut allergy often results in severe reactions, and cashew nut allergens are stable to several types of processing. Fermented foods are thought to have several health benefits and are regularly consumed around the world. Fermentation of peanuts and tree nuts could be a useful processing method to reduce the potency of nut allergens and potentially create value-added, hypo-allergenic, and therapeutic foods. A commercial yogurt made from cashew nuts (Cashewgurt) was evaluated for microbiological, physiochemical, and immunological properties to characterize the effects of lactic acid bacterial (LAB) fermentation on cashew nut allergens. Average counts for lactobacilli, bifidobacteria and Streptococcus thermophilus in the Cashewgurt were 7.73, 4.40, and 7.42 log10 CFU/mL, respectively, indicating that the lactobacilli and S. thermophilus counts were high enough to be beneficial. The Cashewgurt had a pH of 4.46, titratable acidity of 0.53% lactic acid, and viscosity of 13640 cP, with the pH and viscosity being comparable to commercially available cow milk yogurts. The L* a* b* C* h* color values of the Cashewgurt indicated that it was off white in color. SDS-PAGE analysis of soluble protein extracted from Cashewgurt indicated a clear reduction in intact Ana o 1 and 2 content compared to untreated cashew nut extract. Further, immunoblot and ELISA of soluble Cashewgurt protein with polyclonal rabbit anti-cashew and cashew allergic IgE indicated overall reduced allergen binding. Despite this, over two-thirds of the Ana o 2 allergen sequence as well as three peptide fragments of Ana o 1 were observed by LC-MS/MS analysis of trypsinized soluble yogurt protein, indicating that several linear sequences of each allergen remain. In contrast, SDS-PAGE, mass spectrometric analysis of gel bands, immunoblot with polyclonal anti-cashew sera, and ELISA with a monoclonal anti-Ana o 3 antibody all revealed that Ana o 3 was relatively unaffected by the fermentation process. In conclusion, Ana o 1 and Ana o 2 are sensitive to degradation while Ana o 3 survives fermentation during yogurt production. The presence of intact Ana o 3 in the final Cashewgurt product is a surprising result and suggests this type of fermented nut food may also have application as a potentially oral immunotherapy substance. Continued evaluation of commercial and laboratory peanut and tree nut fermentation conditions including bacterial strain selection, media content, and fermentation times could result in cashew nut-based yogurt with rationally engineered allergen content.