School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
J Agric Food Chem. 2012 Feb 1;60(4):1075-83. doi: 10.1021/jf204168f. Epub 2012 Jan 19.
Increased molecular mobility and structural changes resulting from water plasticization of glassy solids may lead to loss of the entrapped compounds from encapsulant systems. In the present study, the stability of water-soluble vitamins, vitamin B(1) (vB(1), thiamin hydrochloride) and vitamin C (vC, ascorbic acid), in freeze-dried lactose and trehalose at various water activities was studied. Water sorption of lactose-vB(1), lactose-vC, trehalose-vB(1), and trehalose-vC systems was determined gravimetrically. Glass transition and crystallization of anhydrous and plasticized sugar-vitamin systems were determined using thermal analysis. Critical water activity was calculated using water sorption and glass transition data. The retention of the vitamins was measured spectrophotometrically. The results showed that the amorphous structure protected the entrapped vitamins at low a(w). Crystallization of lactose accelerated vitamin degradation, whereas trehalose retained much higher amounts of the vitamins. Glass transition and critical water activity of solids and crystallization of component sugars should be considered in the stabilization of sensitive components.
由于玻璃态固体的水增塑作用导致分子迁移率增加和结构变化，可能会导致包封系统中被包封化合物的损失。在本研究中，研究了水不溶性维生素，维生素 B(1)（vB(1)，盐酸硫胺素）和维生素 C（vC，抗坏血酸）在不同水活度的冷冻干燥乳糖和海藻糖中的稳定性。通过重量法测定了乳糖-vB(1)、乳糖-vC、海藻糖-vB(1)和海藻糖-vC 体系的水分吸附。使用热分析测定了无水和增塑糖-维生素体系的玻璃化转变和结晶。使用水分吸附和玻璃化转变数据计算临界水活度。通过分光光度法测量了维生素的保留率。结果表明，在低 a(w)时，无定形结构保护了包封的维生素。乳糖的结晶加速了维生素的降解，而海藻糖则保留了更多的维生素。在稳定敏感成分时，应考虑固体的玻璃化转变和临界水活度以及成分糖的结晶。
