Effects of the Varietal Diversity and the Thermal Treatment on the Protein Profile of Peanuts and Hazelnuts

Elisabetta De Angelis,Linda Monaci,Simona Lucia Bavaro,Rosa Pilolli

doi:10.1155/2018/7635957

Abstract

Several buffer compositions were compared for their efficiency in protein extraction from both raw and roasted peanut and hazelnut samples, the final goal being to understand the modification of protein solubility upon roasting and maximize the extraction yield. Denaturant conditions provided by urea-TBS buffer resulted in satisfactory extraction yields for both peanut and hazelnut samples, before and after the thermal treatment. In addition, different varieties of peanuts and hazelnuts were characterized to highlight the extent of variability in the protein profile accounted by the varietal factor and eventual differential resistance among cultivars to protein modification induced by the thermal processing. The protein profile was characterized by gel electrophoresis, and specific bands were analyzed by micro-HPLC-MS/MS coupled to software-based protein identification. No significant difference was observed for the investigated hazelnut cultivars, namely, Campana, Romana, and Georgia, whereas interesting features were presented for the peanut varieties Virginia, Zambia, and China. In particular, Zambia variety lacked two bands of approximately 36 and 24 kDa that were visible in Virginia and China varieties, which could suggest a lower allergenic potential of this particular variety which deserves to be further investigated before drawing final conclusions.

Highlights

Nuts represent a popular food in the common diet and are considered among the healthiest snack, thanks to the wide range of essential nutrients
In the optimization of a reliable method for protein extraction, the main limitations for protein solubility are the structural and/or chemical modi cations induced by thermal processing
The values of protein recovery were 41%, 36%, 27%, and 19% for urea-TBS, Tris·Cl, ammonium bicarbonate, and Phosphate buffer saline (PBS), respectively. is trend was in agreement with that reported by Chassagne et al, which optimized the extraction procedure of raw and processed peanut proteins from di erent varieties, using two sequential steps based on 50 mM Tris·Cl, 150 mM NaCl, pH 7.4, and ethanol/water 20 : 80 (v/v) bu ers [25]. ey showed that the total protein content of the di erent peanut varieties was comparable, but their extraction e ciency was variable

Summary

Introduction

Nuts represent a popular food in the common diet and are considered among the healthiest snack, thanks to the wide range of essential nutrients. Due to the high content of allergenic proteins therein contained, tree nuts and peanuts are responsible for approximately 80% of anaphylactic reactions and account for over 50% of child fatalities related to food allergies in industrialized countries [2, 3]. Peanut allergy a ects mostly the population of North America, United Kingdom, and Australia. It has been estimated that approximately 2% of children and 0.5–1% of US population is a ected by peanut allergy, while in the United Kingdom, a birth cohort study from the Isle of Wight estimated the prevalence of peanut allergy at 1.3% [6, 7]. Despite the increasing knowledge about the molecular and immunological properties of peanut and hazelnut allergens, the understanding of the processes and factors causing the severity of allergic reactions is still limited [9]

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Conclusion