Bioactivity Potential of Hazelnut-Based Product Fermented with Different Cultures of Lactic Acid Bacteria

Plant-based food products have been developed from diverse plant sources as new food choices. Fermentation of plant matrices with lactic acid bacteria (LAB) has been shown to improve quality and bioactivity of the resulting product while proteolysis by the LAB in the plant-based matrix remains to be elucidated. In this study, a hazelnut-based matrix prepared for a plant-based product was fermented with four different starter cultures of LAB, and their effects on proteolysis, bioactivity and allergenicity were investigated. Sucrose supplementation of the hazelnut matrix stimulated fermentation and time to reach to the target pH of 4.5 was shortened. CH-1 was the fastest acidifying culture reducing pH to the target value after 5 h. While the cultures RSF-736 and CHN-11 required 18 h for fermentation, R-707 was co-cultured with CH-1 to reach the target pH within the same time. Bacterial counts were in the range of 5-8 log cfu/g without a significant change after 15 days of storage in the hazelnut-based products. Level of proteolysis as measured by changes in soluble protein and total free amino acid contents differed among the cultures. Reductions in the amounts of hazelnut proteins were also confirmed by SDS-PAGE analysis, especially in the products prepared with cultures R-707+CH-1 and RSF-736. Allergenicity of the hazelnut matrix, determined by a hazelnut-specific ELISA test, significantly decreased after fermentation with all the cultures. Fermentation also enhanced total phenolic content and antioxidant activity of the hazelnut matrix with CHN-11 demonstrating the highest values after storage. On the other hand, fermentation did not significantly alter α-amylase inhibitory activity compared to the activity of 10.2% in the unfermented control. In addition, fermentation resulted in no change or a slight reduction in ACE inhibitory activity compared to the activity of 46.9% in the unfermented control depending on the culture. These findings demonstrate that LAB species can degrade hazelnut matrix leading to a reduction in allergenicity and enhancement of antioxidant activity.