Effect of enzymatic hydrolysis combined with processing on allergenicity of food allergens

Food allergies are worldwide public health problems. Enzymatic hydrolysis has mild conditions, and high efficiency and stability, meaning it is widely used to reduce the allergenicity of food allergens. However, using only enzymatic hydrolysis allows allergens to retain some allergenicity, thereby limiting its application; combining enzymatic hydrolysis with processing represents a potentially effective solution to solve this issue. Here, the effects of three combinations of enzymatic hydrolysis and processing on food allergen allergenicity were reviewed: pre-processing before hydrolysis, hydrolysis under processing, and hydrolysis before processing. The mechanisms, advantages, and limitations of each combination were discussed. Combing pre-processing and enzymatic hydrolysis more effectively reducing allergenicity than a single treatment. However, each combination affects allergenicity through different mechanisms: (1) most pre-processing procedures (heating, ultrasound, high hydrostatic pressure, pulsed electric field, and pulsed ultraviolet light) disrupted conformational epitopes and increased enzyme accessibility by altering protein spatial structures; (2) cold plasma and fermentation reduced allergenicity mainly by hydrolyzing epitopes, yet combined with enzymatic hydrolysis further reduced allergenicity owing to the differences in hydrolysis sites; (3) glycation and polyphenols binding reduce allergenicity by masking linear epitopes, whereas enzymatic hydrolysis eliminates unmasked epitopes. Hydrolysis under processing improves hydrolysis efficiency; however, only limited research exists on the enzymatic changes that occur during processing. Hydrolysis before processing (especially fermentation) produces proteins with hypoallergenic, good sensory, and functional properties. The allergen allergenicity may increase, decrease, or remain unchanged depending on the processing method, conditions, enzyme type, and allergen source.