Moisture sorption isotherms, thermodynamic properties and sorption properties of walnut flavor microcapsules

Abstract

Flavorings are encapsulated through spray drying to ensure protection throughout their shelf life. However, the stability of microencapsulated flavorings largely depends on the choice of wall material. This work evaluates three wall material systems of walnut flavor: microcapsules of mesquite gum (MMG), whey protein concentrate (MWPC) and a 1:1 (w:w) mixture of both (MMG-WPC), onto their moisture sorption isotherms, fitting to GAB model, thermodynamic and sorption properties at different temperatures (25, 35 and 40°C). The MMG displayed greater monolayer moisture adsorption capacity (M0: 4.69-5.52 kg H2O/100 kg dried solid (d.s.)) and adsorbent-adsorbate interaction due to its greater hygroscopicity, but less tendency to agglomeration trend than MWPC and MMG-WPC. The MMG exhibited the lowest differential enthalpy and entropy values, promoting an advantageous dehydration process and ensuring greater stability, which was attributed to the enhancement of water molecular order. Additionally, MMG displayed the largest sorption surface area, facilitating the moisture sorption process. Therefore, all three microcapsules’ systems were able to stabilize the walnut flavor, however, their slight differences in their moisture sorption capacity led to different stabilization mechanisms that affected their shelf life.