Citation
Anzian, Aliaa
(2018)
Effects of drying methods on chemical composition, antioxidant and antibacterial activities of torch ginger (Etlingera elatior Jack) flower extracts and essential oil.
Masters thesis, Universiti Putra Malaysia.
Abstract
Torch ginger (Etlingera elatior Jack) flower is a well-known spice for local delicacies
and natural remedies that has been reported to possess significant antioxidant and
antibacterial activities. However, the maturity stages, drying conditions and extraction
methods are still questionable in preserving bioactive compounds of torch ginger
flower. Therefore, the aims of this study were to profile the bioactive compounds in
different maturity stages (tight bud and full bloom) of torch ginger flowers using Gas
Chromatography-Mass spectrometry (GC-MS). Then, the effect of drying methods;
freeze, oven and sun drying on extraction yield and antioxidant activities of selected
maturity stage of torch ginger flowers were studied. Torch ginger flower’s essential oil
extracted using subcritical carbon dioxide (SubC-CO2) were evaluated for antioxidant
and antibacterial activities against selected foodborne pathogens, namely Bacillus
cereus ATCC10876, Escherichia coli ATCC11229, Klebsiella pneumoniae
ATCC13773, Listeria monocytogenes ATCC19111, Salmonella Typhimurium
ATCC13311, and Staphylococcus aureus ATCC29213. Maturity stage had significant
effect on percentage area of bioactive compounds concentrations (caryophyllene and 1-
dodecanol) in torch ginger flower extract. Oven drying was identified as optimum
extraction yield of 37.8±2.48% with high level of scavenging activity of 62.4±1.24%
and IC50 value of 9.68 mg/mL, ferric reducing assay power of 2340.7±65.53 mg
Fe2+/100 g, total phenols content of 331.6±2.85 mg GAE/100 g and total flavonoids of
465.8±2.08 mg QE/100 g. The antioxidant activities of torch ginger flower’s essential
oil through DPPH assay (90.0±0.25%), FRAP assay= 8876.5±36.35, ABTS scavenging
activity= 81.8±2.10%, TPC= 1590.2±3.74 mg GAE/100 g and TFC= 1686.2±17.34 mg
QE/100 g. Minimal Inhibitory Concentration (MIC)= 1.56 mg/mL and Minimal
Bactericidal Concentration (MBC)= 3.13 mg/mL of torch ginger flower’s essential oil
were able to inhibit the growth of B. cereus and K. pneumoniae. This study clearly indicated that torch ginger flower could be potentially used as natural antioxidant and
antibacterial agent in the food and pharmaceutical fields.
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