Thermal Properties of Aloe Vera Powder and Rheology of Reconstituted Gels

Aloe vera (Aloe barbadensis L.) is a plant from the lily family that possesses therapeutic and antioxidant properties. Extracts from aloe vera leaves are widely used in skin care products, and recently in health drinks and supplements. Substandard aloe products arising from poor processing methods or adulteration with other compounds is a major problem for the aloe industry. Functional properties of aloe vera may be affected by processing procedures that involve heat or shearing action. In this study, aloe vera extract was dried using spray drying (SD), freeze drying (FD), and Refractance Window (RW) drying methods to investigate the effect of those methods on glass transition temperature (Tg), total carbohydrates, reducing groups, particle size distribution, and viscosity of solutions formed after reconstitution with deionized water. The Tg of SD aloe was in the range of 65°C ±3.2°C compared to 70°C to 78°C for the latter two drying methods. Addition of corn maltodextrin contributed to shifts in Tg of aloe powder. Solutions prepared from spray-dried aloe had the lowest viscosity, while freeze-dried and RW-dried counterparts had higher and nearly equal consistency. The activation energy for network formation of solutions reconstituted from SD powder was 23.9 ±0.1 kJ mol-1, which was slightly lower than the 24.6 ±0.3 and 24.7 ±0.4 kJ mol-1 obtained with FD and RW drying, respectively.