To determine the potential usage of modified hazelnut protein isolates as an encapsulation material

Plant proteins are used in foods due to their functional properties, but limitations such as low solubility, consistency and aroma restrict their application. In this study, it was aimed to improve the functional properties of hazelnut meal protein isolates obtained after cold pressing by high pressure (350-1400 bar) and pH (6-12) modifications. Techno-functional, physico-chemical and rheological analyzes were applied to the modified hazelnut protein isolate, and the optimum point was determined according to the results obtained and used as encapsulation material. The solubility, which was 5.3% in the control sample, reached the range of 10.64%-86.50% with modifications; especially pH increase significantly increased the solubility (p<0.05). Emulsion activity increased from 7.88 m²/g to 33.12 m²/g at pH 12, 875 bar conditions. In addition, emulsion stability index was determined as 48.17% at pH 11 and 500 bar conditions. Foaming capacity and stability reached 49.44% and 92.85% at pH 12 and 875 bar pressure conditions, respectively, indicating that proteins were significantly improved by high pressure and pH modification. The high-pressure (HP) treatment dominated the apparent viscosity properties at 875 bar conditions (Gʺ>Gʹ) and changes in the structural properties of proteins were observed. The highest amount of free -SH group was measured as 16.10 μmol/g at pH 9 and 1400 bar conditions, while the lowest value was determined as 4.72 μmol/g at pH 6 and 875 bar conditions. Zeta potential reached more negative values with increasing pH. Pressure and pH treatments caused significant changes in the secondary structures of the proteins. While regular structures such as α-helix and β-sheet were disrupted, the proportion of random coils increased with pressure and β-turn structures decreased. Surface hydrophobicity was highest at pH 9-1400 bar (559 units) and lowest at pH 7-500 bar (184 units). Moreover, pH increase caused a decrease in L* values of proteins and an increase in a* and b* values. The highest complex modulus was obtained at high pH and low pressure. HP treatment reduced the particle size and changed the morphology of hazelnut protein isolate (FPI). It was found that the conformational structure of proteins was disrupted by the interaction of increasing pH and pressure, which affected the epitope sites and reduced the allergenicity of FPI's. Furthermore, the combination of modified hazelnut protein isolate and maltodextrin (1:1) showed the highest protection effect in the microencapsulation of Lactobacillus acidophilus after drying at 130 °C with 81.55% viability and 66.80% under in vitro conditions.