Hop extract microcapsules prepared by complex coacervation for aroma enhancement in heat-not-burn cigarettes

Heat-not-burn (HNB) tobacco products often suffer from limited aroma richness because flavor formation and release are constrained by their relatively low heating temperatures. In this study, hop extract microcapsules were developed as a thermally protected aroma-delivery system for HNB tobacco products. Citra hop (Humulus lupulus L.) extract was prepared by supercritical CO₂ extraction and encapsulated using gelatin/chitosan complex coacervation. SAFE–GC–MS identified 82 volatile compounds in the hop extract, mainly monoterpenes, sesquiterpenes and esters. The resulting microcapsules showed an encapsulation efficiency of 59.91%, a production yield of 89.6%, a total hop extract retention of 85.8%, a total core loading of 47.88%, and a mean particle size of 6.54 μm. FTIR supported the incorporation of hop extract into the gelatin/chitosan wall matrix, while TG/DTG analysis showed improved thermal stability, with the initial decomposition temperature increasing by approximately 50°C compared with free hop extract. Py–GC–MS at 300°C identified 120 thermal-release or transformation products, including terpenes, alcohols, aldehydes, ketones, esters, acids and heterocyclic compounds. When applied to tobacco flakes, the 3% microcapsule group achieved the highest expert sensory score (80.60 ± 0.36), which was significantly higher than the control, 1% and 5% groups (p < 0.05), with higher scores for aroma, smoke volume, aftertaste and uniformity. These results indicate that hop extract microcapsules are a feasible aroma-enhancement strategy for HNB tobacco products. Further device-relevant real-time release kinetics, toxicological evaluation, residual crosslinker analysis and long-term stability studies are still required before practical application.