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

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 (Tg)-water relationships were modeled using Guggenheim-Anderson-de Boer (GAB) model and Gordon-Taylor equation, respectively. Among the saccharide-containing matrices, Tg 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 Tg trends, indicating that Tg predicts moisture-induced physical changes but not vitamin B2 stability alone.