Novel Hazelnut Protein Isolate-Polysaccharide Conjugates for Microencapsulation of Lactobacillus Acidophilus: Effects on Microstructure, Digestion Resistance, and Storage Stability

Abstract

This study investigated the potential of hazelnut protein isolate (HPI) in conjugation with sodium alginate (SA) or gum arabic (GA) as novel wall materials for the microencapsulation of Lactobacillus acidophilus via spray drying. The effects of different inlet air temperatures (130 degrees C and 160 degrees C) and pump rates (10 and 15 mL/min) on the survival, morphological characteristics, and storage stability of the probiotics were evaluated. All microencapsulated formulations maintained high viability (> 7.0 log CFU/g) after drying, successfully exceeding the therapeutic threshold. SEM observations showed that GA-HPI matrices formed smoother and more spherical microcapsules, and SA-HPI matrices exhibited a more rugose and compact structure. Encapsulation significantly improved the resistance of L. acidophilus against simulated gastric fluid (pH 3.0), with GA-HPI-1 exhibiting the highest gastric survival ratio (66.07%). Conversely, SA-HPI formulations, particularly SA-HPI-3 (160 degrees C, 10 mL/min), showed superior performance during a 60-day storage period. The enhanced stability of the SA-HP-3 formulation is hypothesized to be linked to the potential formation of a dense, glassy matrix, as suggested by the high outlet temperature (82 degrees C) and the resulting low water activity. At an aw of 0.185, molecular mobility is expected to be significantly restricted, which likely contributed to the immobilization of the probiotic cells and the prevention of metabolic degradation. Kinetic modeling using linear regression showed that the GA-HPI conjugates maintained viability well for the first 15 days, but a breakdown occurred after the 30th day. These findings demonstrate that hazelnut protein-polysaccharide conjugates are effective plant-based carriers for probiotics, with the SA-HPI system offering exceptional long-term stability for functional food applications.