Microwave assisted extraction of garlic oil and garlic oleoresin

• Main Author: Nga, Nguyen Thi Anh
• Format: text
• Language: English
• Published: Animo Repository 2008
• Subjects: Garlic; Oleoresins; Extraction (Chemistry); Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/6966
• Institution: De La Salle University

The extraction of essential oil of garlic (Allium sativum L.) is an important research area because of its high potential in the pharmaceutical industry as well as in food technology. The use of microwave to extract the essential oil from garlic is an emerging technology. Microwave-assisted extraction (MAE) has many advantages, some of which are reduction in extraction time and amount of solvent used as well as higher efficiency compared to the traditional distillation process. This research involves the study of the production of oleoresin from Philippine garlic using microwave-assisted extraction with and without solvent. Best conditions were determined by varying the microwave power at 400W, 600W and 800W, temperature at 65oC, 70oC and 75oC; and irradiation time at 2 minutes and 5 minutes at the set temperatures. Both dried and fresh garlic were investigated using two solvents, namely, ethanol and ethyl acetate. Garlic oil was extracted using fresh garlic without solvent and under the microwave conditions such as temperature, time duration and power were varied at 90oC and 95oC, 30 minutes and 60 minutes and 400, 600 and 800watts, respectively. The best extraction conditions that gave the high yields as well as high peak area percentages of sulfur compounds were as follows: fresh garlic without solvent at 800W, 95oC and 30 minutes with yield 0.636%; dried garlic with ethanol as solvent at 800W, 70oC and 5minutes with yield 18.36%; the fresh garlic with ethanol solvent at 800W, 70oC and 2minutes with yield 48.09% and the fresh garlic with ethyl acetate solvent at 600W, 65oC and 5minutes with yield 18.95%. The physico-chemical properties of garlic oil and oleoresin, such as refractive index, specific gravity, acid value, ester value and pH at the best MAE conditions were determined. The extracted garlic oil gave a refractive index of 1.5745 and specific gravity of 1.074, both of which were in the range of the standards 1.559 – 1.579 and 1.040-1.090, respectively. This indicated the purity of this oil while the values from oleoresin of refractive index as 1.4375, 1.4630 and 1.4698; of specific gravity as 1.455, 1.313, and 1.297 for fresh garlic with ethyl acetate, ethanol solvent and dried garlic with ethanol solvent, respectively, were higher than the standards, which maybe due to the iv presence of resin in the oleoresin. The chemical properties with acid value as 13.061 and ester value as 71.823 obtained from garlic oil were high. This shows the free acid and fatty acid which exist in the extract product of garlic plant. The pH values of garlic oil and garlic oleoresin were between 5 and 6 confirming the acidity of the garlic oil and garlic oleoresin. The Kirby-Bauer method was used to test the antimicrobial activity of the extract for both the oil and the oleoresin at the best MAE conditions. Positive results were obtained from all 5 microorganisms tested for both. The garlic oil extract showed best effect of inhibition on the microorganisms up to a dilution of 1:16 (v/v) of garlic oil. The extract inhibited the gram positive bacteria Staphylococcus aureas and Bacillus subtilis as well as the fungi Candida albicans stronger than gram negative bacteria Escherichia coli and Pseudomonas aeruginosa.