17
The values with different letters a-h in each column show a significant differencep0.05 Figure 6 Total lignin of dried-coffee ground residue
B. Extraction of CGR
The dried-CGR samples were extracted by MAE method using water as the solvent under the MAE conditions of 800 W and times 3, 4 and 5 minutes. The CGR extract was shown in
Figure 7.
Figure 7 CGR extracts obtained for A three minutes of MAE extraction and B non-microwave extraction
Water was chosen as the solvent because of the higher dielectric constants of water which made it had higher diffusivity into matrix Jain et al., 2009, additionally, water is considered safe
for application in food. A 800 W of microwave power were used based on earlier studies Upadhyay, 2011. This research used household microwave to extract the CGR. The household
microwave could not control the temperature of extraction. Times of extraction became a crucial factor to control the risk of bioactive compounds degradation and to get the maximum yield of
extracts.
The graph showing the relationship between time of extraction to the CGR extract yield produced was shown in Figure 8. The shorter time, the greater extraction yield of CGR was
obtained. Although the increasing of the extraction time could increase the quantity of analytesyield extracted into the solvent, the shorter time could maintain the temperature below the
fg h
de c
ef b
cd g
a ef
50 100
150 200
250 300
350 400
450 500
A B
C D
E F
G H
I J
L ig
nin m
g g
Dried-Coffee Ground Residue
A B
18
solvent boiling temperature Mandal et al., 2007. The over exposure of the higher temperature may lead to thermal degradation of constituents which sensitive to high temperature. MAE of
polyphenols and caffeine was found to increase up to 3 min and later decreased with the increase of time Pan et al., 2003.
MAE for 3 minutes resulted in higher yield than longer times of extraction 4 and 5 minutes. Earlier studies have reported that 5 minutes was the best time of MAE temperature
50
o
C that yield gave higher chlorogenic acid in coffee bean ground Upadhyay, 2011. The different results occurred because this work used household microwave with uncontrolled
temperature of extraction while Upadhyay used close-vessel microwave. In this study, the temperature of water and CGR mixtures measured after 3, 4, and 5 minutes extraction were 75
o
C, 90
o
C, and 105
o
C, respectively. Therefore, the high temperature of extraction was thought to increase the risk of bioactive compounds degradation. As compared to the control treatment, MAE
had higher extraction yield. Tremendous pressure from microwave energy could leach out the constituents from matrix faster Mandal et al., 2007.
Figure 8 Extraction yield of CGR extract with various time of extraction
C. BIOACTIVE COMPOUNDS IN COFFEE GROUND RESIDUE CGR
