Chain Length-Dependent Reverse Micelle Extraction of Prolamins From Baijiu Jiuzao: Synergistic Effects of Ethanol, Ionic Strength, and Chaotropic Agent

This study investigated the chain length-dependent extraction efficiency of two cationic surfactants—dodecyltrimethylammonium bromide (C12, 12-carbon chain) and cetyltrimethylammonium bromide (C16, 16-carbon chain)—for reverse micelle extraction of prolamins from Baijiu Jiuzao (Chinese Baijiu distillers' grains). Although pH variations (4.0–9.0) had negligible effects, ethanol, ionic strength, and chaotropic agent demonstrated distinct chain length-dependent behaviors: ethanol increased C12's forward extraction efficiency by 10.6% (absolute) while enhancing C16's backward efficiency by 8.7%. Potassium chloride enhanced C16's forward efficiency by 4.7%, while potassium bromide significantly improved C12's backward efficiency by 15.9%. Guanidine hydrochloride consistently promoted C16 in both extraction phases. Dynamic light scattering demonstrated significant differences (p < 0.05) in reverse micelle sizes: C12 formed smaller empty reverse micelles (1.5 ± 0.2 nm) compared to C16 (2.5 ± 0.5 nm). During forward extraction, reverse micelles expanded significantly to 217.9 ± 6.3 nm (C12) and 311.2 ± 43.2 nm (C16). Backward extraction released prolamin particles of 449.0 ± 16.2 nm (C12) and 650.4 ± 29.7 nm (C16), confirming the size-exclusion-driven release mechanism. The more compact C12 reverse micelles correlated with lower total prolamin yield (26.6 ± 0.1% vs. 32.2 ± 0.1% for C16, p < 0.01) and substantially diminished bovine serum albumin recovery (5.2 ± 0.2% vs. 45.3 ± 2.5%, p < 0.01). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis corroborated these findings, further demonstrating that reverse micelle-extracted prolamins formed thermally stable dimers resistant to reductive cleavage. Combined with dynamic light scattering data (particle size range: 400–700 nm in the backward-extraction aqueous phase), these findings demonstrate that prolamin aggregates after reverse micelle extraction. These findings demonstrate that surfactant chain length as a key parameter for optimizing reverse micellar systems, where shorter-chain surfactants facilitate selective extraction, whereas longer chains enhance yields.