Volatile Compound Profiling and Quality Assessment of Sweet Fermented High-Amylose Rice: A Comparative GC-MS Analysis with Traditional Glutinous Rice Fermentation

High-amylose Lueang Patew Chumphon (LPC) rice, a Thai geographical indication variety, represents an underutilized resource for functional food development. This study investigated sweet fermented LPC rice (SFLPC) compared to conventional sweet fermented glutinous rice (SFGR) through comprehensive microbial, chemical, and nutritional characterization. Starter cakes contained Aspergillus sp., Rhizopus stolonifer, and Pediococcus pentosaceus (>99% similarity by ITS/16S rRNA sequencing and MALDI Biotyper). Both varieties demonstrated comparable fermentation with pH reductions to ~3.5 and lactic acid production (~6 g/L). GC-MS analysis with mass spectral library matching and Linear Retention Index (LRI) comparison tentatively annotated twelve volatile compounds. Absolute peak area analysis revealed distinct variety-specific profiles: SFGR was characterized by significantly higher ethyl palmitate (75.89 ± 19.30 vs. 16.80 ± 7.21 × 106, p = 0.008) and isobutyl alcohol (33.09 ± 3.56 vs. 23.53 ± 1.71 × 106, p = 0.014), exclusive ethyl dodecanoate (44.87 ± 20.60 × 106), and exclusive 2,4-di-tert-butylphenol, while SFLPC showed exclusive ethyl acetate formation. Isoamyl alcohol was the dominant volatile in both varieties, with comparable absolute peak areas (273.91 ± 22.65 vs. 267.54 ± 28.78 × 106, ns). SFLPC demonstrated superior mineral retention (2.1-fold phosphorus, 1.9-fold potassium and magnesium) and enhanced antioxidant capacity (IC50: 3.30 vs. 5.20 μg/mL, representing 36% improvement). Degree of gelatinization analysis validated comparable starch gelatinization (32.5–40.1%) despite different cooking methods, confirming volatile differences arose from rice variety rather than processing. These findings demonstrate high-amylose LPC rice as a promising fermented food substrate offering enhanced nutritional properties and volatile compound profiles through traditional fermentation.