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
Bioactive compounds are secondary metabolites of plants that having pharmacological or toxicological effects in man and animals Bernhoft, 2010. This part of work determined the
amount of several bioactive compounds i.e. total phenolic compounds, chlorogenic acid, caffeine, and anthocyanin in CGR extracts. From the phytochemical screening, the phenolic compound and
chlorogenic acid content were assayed qualitatively in CGR. Caffeine and anthocyanin also were determined in this work because of the relationship of those bioactive compounds and antioxidant
activity.
1. Total Phenolic Compounds TPC
The TPC content in the CGR extract obtained with different time of MAE was shown in Figure 9. The results showed that sample B 3 minutes, B 4 minutes and A 4 minutes had
higher amount of phenolic compounds 751.15 mg GAE100 g; 662.40 mg GAE100 g; and 582.07 mg GAE100g, respectively than the others.
Furthermore, different times of MAE also generated different amount of phenolic compounds in the extracts. Generally, 3 minutes of MAE generated higher amount of phenolic
compounds 255-751 mg GAE100 g than the other times. MAE could generate higher amount of phenolic compounds in the extract than the control treatment 123
– 280 mg GAE100 g. The amount of phenolic compounds in MAE of CGR extracts were approximately five-fold lower than
those in coffee beans 1200-2400 mg GAE100 g in aqueous extractions Upadhyay, 2011. 10
11 12
13 14
15 16
17 18
19 20
A B
C D
E F
G H
I J
E x
tra ct
io n Yie
ld
CGR Extracts
3 min 4 min
5 min Control
19
However, the amount of phenolic compounds in CGR extract using hexane as solvent 1300 mg GAE100 g was higher than those extracted with water Ramalakshmi et al., 2009. In this study,
the extraction of CGR using water as solvent also had lower of phenolic compounds 300 mg GAE100 g than those extracted with hexane resulted in Ramalakshmi study. This could be
explained by the fact that phenolic compounds are generally more soluble in organic solvents less polar than water Kim et al., 2002. Alcohols, particularly methanol and ethanol were also more
efficient than water in extracting phenolics from different natural sources such as citrus peel, black tea, barley and medicinal plants Rehman, 2006.
a
The amount of phenolic compounds expressed as gallic acid equivalent GAE The values with different letters a-af in each column show a significant difference
p0.05 Figure 9 Total phenolic compounds of coffee ground residue extracts
2. Chlorogenic Acid Compounds CGA
