Ascorbic acid degradation in amorphous solid dispersions was compared to its degradation in the crystalline state. Physical blends and lyophiles of ascorbic acid and polymers (pectins and polyvinylpyrrolidone [PVP]) were prepared initially at 50:50 (w/w), with further studies using the polymer that best inhibited ascorbic acid crystallization in the lyophiles in 14 vitamin : PVP ratios. Samples were stored in controlled environments (25 to 60 °C, 0% to 23% RH) for 1 mo and analyzed periodically to track the physical appearance, change in moisture content, physical state (powder x-ray diffraction and polarized light microscopy), and vitamin loss (high performance liquid chromatography) over time. The glass transition temperatures of select samples were determined using differential scanning calorimetry, and moisture sorption profiles were generated. Ascorbic acid in the amorphous form, even in the glassy amorphous state, was more labile than in the crystalline form in some formulations at the highest storage temperature. Lyophiles stored at 25 and 40 °C and those in which ascorbic acid had crystallized at 60 °C (≥70% ascorbic acid : PVP) had no significant difference in vitamin loss (P > 0.05) relative to physical blend controls, and the length of storage had little effect. At 60 °C, amorphous ascorbic acid lyophiles (≤60% ascorbic acid : PVP) lost significantly more vitamin (P < 0.05) relative to physical blend controls after 1 wk, and vitamin loss significantly increased over time. In these lyophiles, vitamin degradation also significantly increased (P < 0.05) at lower proportions of ascorbic acid, a scenario likely encountered in foods wherein vitamins are naturally present or added at low concentrations and production practices may promote amorphization of the vitamin. PRACTICAL APPLICATION Vitamin C is one of the most unstable vitamins in foods. This study documents that amorphous ascorbic acid is less stable than crystalline ascorbic acid in some environments (for example, higher temperatures within 1 wk), especially when the vitamin is present at low concentrations in a product. These findings increase the understanding of how material science properties influence the stability of vitamin C.

中文翻译：

---

L-抗坏血酸在无定形固态下的降解

将无定形固体分散体中的抗坏血酸降解与其在结晶状态下的降解进行比较。最初以 50:50 (w/w) 制备抗坏血酸和聚合物（果胶和聚乙烯吡咯烷酮 [PVP]）的物理混合物和冻干剂，进一步研究使用在 14 种维生素中最能抑制冻干剂中抗坏血酸结晶的聚合物：PVP比率。样品在受控环境（25 至 60 °C，0% 至 23% RH）中储存 1 个月，并定期分析以跟踪物理外观、水分含量变化、物理状态（粉末 X 射线衍射和偏光显微镜）和维生素损失（高效液相色谱法）随着时间的推移。使用差示扫描量热法测定选定样品的玻璃化转变温度，并生成水分吸附曲线。在最高储存温度下，在某些配方中，无定形形式的抗坏血酸，即使是玻璃状无定形状态，也比结晶形式更不稳定。在 25 和 40 °C 下储存的冻干菌和在 60 °C 下已结晶的抗坏血酸（≥70% 抗坏血酸：PVP）与物理混合对照相比，维生素损失没有显着差异（P > 0.05），长度存储影响不大。在 60 °C 时，无定形抗坏血酸冻干剂（≤60% 抗坏血酸：PVP）在 1 周后相对于物理混合对照物损失了更多的维生素（P < 0.05），并且随着时间的推移维生素损失显着增加。在这些冻干菌中，维生素降解在抗坏血酸比例较低的情况下也显着增加（P < 0.05），食品中可能遇到的一种情况，其中维生素天然存在或以低浓度添加，生产实践可能会促进维生素的无定形化。实际应用 维生素C是食物中最不稳定的维生素之一。该研究表明，在某些环境中（例如，1 周内的较高温度），无定形抗坏血酸的稳定性不如结晶抗坏血酸，尤其是当产品中维生素含量较低时。这些发现加深了对材料科学特性如何影响维生素 C 稳定性的理解。该研究表明，在某些环境中（例如，1 周内的较高温度），无定形抗坏血酸的稳定性不如结晶抗坏血酸，尤其是当产品中维生素含量较低时。这些发现加深了对材料科学特性如何影响维生素 C 稳定性的理解。该研究表明，在某些环境中（例如，1 周内的较高温度），无定形抗坏血酸的稳定性不如结晶抗坏血酸，尤其是当产品中维生素含量较低时。这些发现加深了对材料科学特性如何影响维生素 C 稳定性的理解。