Chemical Profiles and Physicochemical Properties of Southern Thai Curry Paste Influenced by Heat Treatment and In Vitro Digestion

Southern Thai curry paste is a distinctive traditional product made from diverse herbal ingredients, and both processing and digestion can cause notable physical, chemical, and biological changes in its composition. The effects of pasteurization (PP), sterilization (SP), and gastrointestinal digestion on the physical qualities, chemical composition, α -glucosidase inhibitory activity (both maltase and sucrase), and osteoprotective activity of sour curry paste (SP) and roasted curry paste (RP) were evaluated in this study. The physical and chemical analyses revealed that the total color difference ( ΔE* ) values were observed within the range of 1.75–11.87, the Browning Index values were measured between 131.36 and 320.79, and the pH values ranged from 4.15 to 4.83. The contents of phenolic compounds were found to range from 0.09 to 1.55 mg GAE/g, while flavonoid compounds ranged from 30 to 90 mg QE/g. In contrast, no significant differences were detected in the moisture content (Mc) and water activity ( a w ) values. The most abundant volatile compound identified in RP was 3,5-Methanocyclopentapyrazole, 3,3a,4,5,6,6a-hexahydro-3a,4,4-trimethyl. In vitro simulated digestion was performed, and changes in α -glucosidase inhibitory activity (both maltase and sucrase) as well as osteoprotective activity were observed. The levels of osteocalcin (OC), osteoprotegerin (OPG), receptor activator of nuclear factor kappa ligand (RANKL), and the RANKL/OPG ratio were examined on days 7 and 14 of the experiment. Southern Thai curry paste demonstrates strong potential as both a traditional food and a health-promoting product, with active components that remain stable after processing and simulated digestion, supporting its roles in blood glucose regulation and osteoporosis prevention.