Effect of Different Thermal Processing and Addition of Oil on the Physical, Chemical, Anti-Inflammation, Antioxidant and Anti-Diabetic Properties of Garlic Extract

Chew, Jia Ni (2021) Effect of Different Thermal Processing and Addition of Oil on the Physical, Chemical, Anti-Inflammation, Antioxidant and Anti-Diabetic Properties of Garlic Extract. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Garlic (Allium sativum L.) is a type of plant that has been proved to bring health benefits to consumers due to its diverse bioactive compounds. This study investigates the effect of different thermal processing and addition of oil on the physical (pH, colour) and chemical (TPC, TFC), antioxidant, anti-inflammation, and anti-diabetic properties of garlic extract. Initially, garlic was treated using conventional oven and microwave separately with the additional and without oil, followed by methanol extraction. The pH and colour change of garlic after heating were determined. The antioxidant (FRAP, DPPH), anti-inflammation (albumin denaturation inhibition), and anti-diabetic (alpha-amylase inhibition) properties were determined using the methanolic extract of garlic. The pH of garlic was found significantly (p<0.05) affected with the thermal processing while there is no significant of colour change after different heating processes. Result indicated that long heating time and addition of oil produced garlic with high phenolic and flavonoid contents. Besides, the antioxidant property of garlic was found significant impacted after thermal processing. The anti-inflammation property of garlic was found significantly increased when the oil was added, and heat treatment applied especially the 4 minutes oven-treated garlic exhibited the highest anti-inflammation activity (40.7±3.47% inhibition). In terms of anti-diabetic property, there is no significant difference between raw garlic and conventional-treated garlic while the microwave-treated garlic showed significantly higher activity than raw garlic except 60s microwave-treated garlic (1.59±0.0505% inhibition). These results suggested that garlic heated in microwave with oil had the highest antioxidant and anti-diabetic activity while garlic heated in conventional oven with oil had the highest anti-inflammation activity. On this basis, the cooking method, and the application of oil onto the garlic should be taken into account so that the specific health benefits can be preserved and improved. Lastly, there were 63 responders involved in survey. Based on their responses, it found that most of them had sufficient knowledge regarding to health benefit of garlic and preserving cooking method meanwhile they had limited knowledge regarding the benefit of oil during cooking.