Glassy state physical stability versus vitamin B₂ chemical stability in saccharide-modulated, freeze-dried corn...

This study examined saccharide effects on physical stability and vitamin B₂ retention in corn starch matrices with restricted glassy state mobility. Vitamin B₂ was selected for its susceptibility to light and moisture. Matrices containing glucose, sucrose, raffinose, or stachyose were gelatinized and freeze-dried. Water sorption isotherms and glass transition temperature (T_g)-water relationships were modeled using Guggenheim-Anderson-de Boer (GAB) model and Gordon-Taylor equation, respectively. Among the saccharide-containing matrices, T_g increased with saccharide molecular size, whereas the monolayer moisture content generally decreased from glucose to stachyose. Combined GAB and Gordon-Taylor analysis showed that raffinose- and stachyose-containing matrices remained glassy state over a wider water activity range at 25 °C than glucose- and sucrose-containing matrices, consistent with microscopy and X-ray diffraction results. Vitamin B₂ stability under humid and light stress did not strictly follow T_g trends, indicating that T_g predicts moisture-induced physical changes but not vitamin B₂ stability alone.