Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, 1428 Ciudad de Buenos Aires, Argentina.
Carbohydr Res. 2010 Jan 26;345(2):303-8. doi: 10.1016/j.carres.2009.10.014. Epub 2009 Nov 5.
It has been suggested that the crystallization of a sugar hydrate can provide additional desiccation by removing water from the amorphous phase, thereby increasing the glass transition temperature (T(g)). However, present experiments demonstrated that in single sugar systems, if relative humidity is enough for sugar crystallization, the amorphous phase will have a short life. In the conditions of the present experiments, more than 75% of amorphous phase crystallized in less than one month. The good performance of sugars that form hydrated crystals (trehalose and raffinose) as bioprotectants in dehydrated systems is related to the high amount of water needed to form crystals, but not to the decreased water content or increased T(g) of the amorphous phase. The latter effect is only temporary, and presumably shorter than the expected shelf life of pharmaceuticals or food ingredients, and is related to thermodynamic reasons: if there is enough water for the crystal to form, it will readily form.
有人认为，糖水合物的结晶可以通过从无定形相除去水来提供额外的干燥作用，从而提高玻璃化转变温度（Tg）。然而，目前的实验表明，在单糖体系中，如果相对湿度足以使糖结晶，那么无定形相的寿命将很短。在本实验条件下，不到一个月就有超过 75%的无定形相结晶。在脱水系统中形成水合晶体（海藻糖和棉子糖）的糖作为生物保护剂的良好性能与形成晶体所需的大量水有关，而与无定形相的含水量降低或 Tg 升高无关。后一种影响只是暂时的，预计短于药品或食品成分的预期货架期，这与热力学原因有关：如果有足够的水形成晶体，它就会很容易形成。
