Glass Transition and Rheological Properties of Aloe Vera (Aloe Barbadensis, L.) Dried by Different Methods

Abstract

Aloe vera (Aloe barbadensis L.) is a plant from the lily family that possesses therapeutic and antioxidant properties. Extracts or gels from aloe vera leaves are widely used in skin care products, and lately, as health supplement. Substandard products arising from poor processing methods are a problem for the aloe market. Aloe vera possesses bioactive properties that may be lost when subjected to processing procedures that involve heat or shearing action. The suitability of emerging techniques such as Refractance Window (RW) method for drying heat sensitive herbal products such as aloe vera was investigated and comparisons made with freeze and spray drying. The dried materials were examined for changes in glass transition temperature and rheological behavior after reconstitution. Addition of corn maltodextrin contributed to shifts in glass-liquid transition of aloe powder. Variously dried aloe powder had different viscosities after reconstitution. Both the RW and freeze-dried aloe vera had a light cream color compared to the whiter (higher lightness value) spray dried powder. During 7 weeks of storage at 35°C, yellowness and redness of both RW and freeze-dried aloe increased slightly and in proportion to the overall hue was from 4 to 6.