An analysis of the influence of growth periods on physical appearance, and acemannan and elemental distribution of Aloe vera L. gel

Congo-red-acemannan (CR-acemannan) binding assay has been followed to compare the acemannan distribution in freeze-dried gel at two, three and four-year-old Aloe vera L To explore the seasonal influence gels are also analyzed at rainy and winter season from three-year-old plants. Detection of predominant functional groups and elemental analysis have been carried out by ATR-FTIR and SEM-EDS, respectively. SEM and L*a*b* color space analysis have been employed to explore the microstructure and appearance of freeze-dried gel, respectively. Acidity and electrical-conductivity have also been measured as the physical properties of gel. Electrical-conductivity was significantly high (p <= 0.05) at two-year-old plants and all of the gels are acidic in range (4.63 +/- 0.02 to 4.93 +/- 0.01). From H-1 NMR spectroscopy, no sign of retrogradation was noticed in dried gel. It has been observed that growth periods play the decisive factor influencing the acemannan and mineral concentration, and the color components of freeze-dried gel as well. Of the tested freeze-dried gels, the absorbance specific to CR-acemannan conjugate formation is maximum with three-year-old plants in summer, and minimum with two-year-old plants. Phenolic -OH, =CO, -CH3, -COO and C-O-C are the predominant functional groups present in gel. Collectively, sodium concentration was high in gel followed by magnesium, potassium and calcium. Among the considered minerals, the relative abundance is more with Mg, K and P at two-year-old Aloe. Sublimation at freeze-drying renders an unorganized dispersed structure to aloe gel by breaking down the compact parenchymatous cellular structure. Our experiments suggest that, the lightness of gel is high in winter, followed by summer, for a three-year-old plant. (C) 2013 Elsevier B.V. All rights reserved.