RESULTS AND DISCUSSION:
Graph 1 Calibration curve for Standard Gallic acid A standard curve of gallic acid was constructed to determine the amount of total phenolic contents in the black grams. The equation for the gallic acid was expressed as y= 0.002x (R2=0.973). The results of the study were expressed as gallic acid equivalent (GAE) in μg/ g of dry weight.
Single factor experiments
Effect of solvent type on extraction of phenolic compounds Selection of extraction solvents is very important as it has important role in the determination of the amount and the type of phenolic compounds that will be extracted. Aqueous alcohols particularly acetone, ethanol and methanol are usually preferred for the extraction of the phenolic compounds from
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Study indicates that ethanol at an optimal concentration of 25% (v/v) is more effective than water for the extraction of polyphenols which reached the maximum of 69.75 mg of GAE/ g of dry black gram powder The use of lower concentrations of alcohol has the added advantage that the proteins are not likely to be denatured and possibly their physico-chemical and functional properties are not impaired and indicated that the protein content of the extract is not decreased by the extraction at low concentrations of alcohol. There will be drop in total phenolic content with 100% ethanol9.
Effect of extraction temperature on extraction of phenolic compounds
The extraction of phenolic compounds was checked in the temperatures ranging from 300C to 600C. At 30°C, there was increase in polyphenol extraction. At higher temperature, the extraction of polyphenols was not effective; this may be due the decomposition of phenolic compounds or may be due to the breakdown of phenolic content which are present in the sample network. Also increase in the temperature leads to loss of solvent which will increase the cost of the extraction process15.
Effect of Time on extraction of
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Dev 2.11 R-Squared 0.9654
Mean 58.46 Adeq Precision 14.255
C.V. % 3.61
Co-efficient of determination (R2) for the model is 0.964, it indicates 96.54% of variability and the result of chance is 3.46%. Co-efficient of Variation (C.V) is found to be 3.61%, the reliability of the experiment is based on the lower value of C.V. An adequate precision value of 14.255 which was greater than 4, it indicates an adequate signal, and hence this model can be used to navigate the design space.
Table 5 Data obtained from ANOVA ( Ethanol)
Factor Coefficient Estimate df Standard Error 95% CI Low 95% CI High VIF
Intercept 59.68 1 1.22 56.55 62.81
A-Temperature -6.84 1 0.75 -8.76 -4.92 1.00
B-pH 2.20 1 0.75 0.28 4.12 1.00
C-Stirrer Speed -0.39 1 0.75 -2.31 1.53 1.00
AB 3.77 1 1.05 1.06 6.48 1.00
AC 0.22 1 1.05 -2.49 2.93 1.00
BC 0.46 1 1.05 -3.18 2.25 1.00
A2 3.44 1 1.10 0.61 6.26 1.01
B2 -5.01 1 1.10 -7.84 -2.19 1.01
C2 -0.71 1 1.10 -3.53 2.12 1.01
Final equation in terms of actual