DRYING CHARACTERISTRICS OF ALOE VERA AND ITS MATHEMATICAL MODELLING
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Date
2017
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Indira Gandhi Krishi Vishwavidhyalaya, Raipur
Abstract
Aloe vera (Aloe barbadensis Miller), is a short-stemmed juicy plant with green pointed and fleshy leaves entrapping a clear viscous gel. It can achieve a stature of 10-20 m with a girth up to 3 m. The annually produced flowers are orange in colour with the spikes reaching up to 90 cm tall. In India, the major areas under aloe vera cultivation are Alwar in Rajasthan, Satnapalli in Andhra Pradesh and Rajpipla in Gujarat. It is also found in the dry areas of states of Maharashtra and Tamil Nadu.
The annual consumption of aloe vera extract by the Indian pharmaceutical industries is 200 tonnes which is met from the wild sources from the states of Maharashtra and Tamil Nadu. Ayurvedic pharmacies are using only 1% of the total production from India. The use of aloe vera in the pharmaceutical industry is significant as far as the manufacturing of tropical ointments, gel preparation, tablets and capsules are concerned. The challenge of aloe vera drying is to maximize the retention of nutrients while minimizing the moisture content of product to a level where microbiological growth should not occur.
The physical characteristics of the aloe vera namely, length, width, thickness, apparent volume, leaf weight, gel weight and gel recovery were determined. The mean values of the length, width and thickness were found to be 551.18, 87.75 and 23.20 mm respectively, the average apparent volume and average weight of aloe vera leaf was found to be 291.88 cc and 344.18 g respectively. It was observed during the experiment that the aloe vera leaves having higher weight, had recorded better gel recovery.
The chemical properties of the dried aloe vera sample were determined namely, yield, pH, total carbohydrate, total starch, crude fat, crude fibre, total ash and protein. The rehydration characteristic of aloe vera gel was predicted from two parameters viz. rehydration ratio (RR) and water holding capacity (WHC). It was found that the sample dried at 70oC temperature exhibited better chemical and rehydration characteristics.
The fresh aloe vera samples were convectively dried at air temperature of 50, 60, 70 and 80oC and their drying behavior were investigated. The initial moisture content of the aloe vera samples was calculated to be 7042.85 per cent (db). After drying till constant weight was achieved, the moisture content was reduced to the range of 12.06 to 15.20% (db) for temperatures 80-50 oC. It was observed that, the moisture content of aloe vera samples decreased exponentially with drying time under all drying temperatures and for all experiments. The drying time required for higher temperature drying was less than that of low temperature drying. The coefficient of determination was more than 0.95 showing good correlation between the data collected.
The convective drying of aloe vera samples followed a typical trend. As the drying air temperature increased, the drying curves exhibited steeper slope indicating that the drying rate increased with increase in drying air temperature. The equilibrium moisture content of aloe vera sample at different temperatures used in the drying experiments was obtained using dynamic method. The influence of moisture content on effective moisture diffusivity and to estimate the activation energy for different drying air temperatures, further analysis of the falling rate drying period was carried out to estimate effective moisture diffusivity (Deff). It is observed that moisture diffusivity values increased with drying air temperature. The Deff increased with decrease in moisture content for all drying temperatures. The Deff started decreasing as the moisture content decreased further below at the end of drying.The activation energy and Arrhenius factor was found to be 19.83 kJ/mol and 1.98 x 10-07 respectively. It is implied from the figure that moisture diffusivity of aloe vera sample decreased linearly with increase in 1/T.
Description
DRYING CHARACTERISTRICS OF ALOE VERA AND ITS MATHEMATICAL MODELLING