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  1. Toh, J.J., Khoo, H.E., Azrina, A.
    MyJurnal
    This study aimed to compare the antioxidant content and antioxidant capacity of pulp and peel of two varieties of pomelo fruit (Tambun White and Tambun Pink). Antioxidants including total phenolic content, total flavonoid content and ascorbic acid content were determined using Folin-Ciocalteu reagent assay, aluminium chloride colorimetric assay and AOAC method, respectively. Antioxidant capacity of pomelo pulp and peel was measured using ferric reducing antioxidant potential and trolox equivalent antioxidant capacity assays. The peels of both pomelo fruits had higher antioxidant content and capacity than their pulps. Moreover, the white variety of pomelo had higher antioxidant content and capacity compared to the pink counterpart. Trolox equivalent antioxidant capacity of the samples was positively high correlated with total phenolic content (r = 0.978) and total flavonoid content (r = 0.959), except for ascorbic acid. Therefore, pomelo peel from white variety possessed higher antioxidant properties and it is potentially rich sources of natural antioxidants.
  2. Tan, K.P., Khoo, H.E., Azrina, A.
    MyJurnal
    This study aimed to determine and compare antioxidant components and antioxidant capacity in different parts (skin, pulp, mace and seed) of nutmeg. Freeze dried samples were extracted using 80% methanol, while Folin-Ciocalteu assay was employed to determine total phenolic content, aluminium chloride assay was applied to determine total flavonoid content and ascorbic acid was assessed by titrimetric method. Antioxidant activities were evaluated by ferric reducing antioxidant power and trolox equivalent antioxidant capacity (TEAC) assays. Results revealed that nutmeg seed contained the highest TPC followed by mace, skin and pulp. Similar observation was also found for TFC. The highest ascorbic acid content was found in nutmeg mace, while the lowest was in its pulp. For antioxidant activity, nutmeg seed possessed the highest FRAP and TEAC values, while nutmeg pulp had the lowest as compared to other parts. Phenolic compounds in nutmeg samples have exhibited strong correlation with antioxidant capacity. Therefore, nutmeg is a potential functional food with high antioxidants, especially nutmeg seed. Phenolic compounds in nutmeg samples have exhibited strong correlation with antioxidant capacity. Therefore, nutmeg is a potential functional food with high antioxidants, especially nutmeg seed.
  3. Azimah, R., Azrina, A., Khoo, H.E.
    MyJurnal
    The aim of this study was to determine hydrolytic stability [acid value (AV)] and oxidative stability [peroxide value (PV) and conjugated dienes (CD)] of selected blended oils during potato frying. The blended oils were prepared by blending palm oil with corn oil (POCO), sesame oil (POSO) and rice bran oil (PORBO). Blended vegetable oils were prepared in a ratio of 1 to 1 (v/v) and tested for 0, 10 and 20 times after frying potato. AV and PV were determined by titration method, while CD was determined using the spectrophotometric method. Increasing frequency of oil frying contributed to increased level of AV in all blended oils. PVs were increased in all samples, with most noticeable increment observed in POSO, followed by PORBO and POCO. CD levels of the blended oils were also increased after 20 times of potato frying compared with the unused oil and after 10 times of frying. POCO was the most stable oil in terms of hydrolytic and oxidative stabilities. It is most suitable for deep-fat frying of potato chips and industrial application.
  4. Khoo, H.E., Chong, E.L., Sia, C.M., Chang, S.K., Yim, H.S.
    Malays J Nutr, 2014;20(1):101-111.
    MyJurnal
    Introduction: Hygrocybe conica (HC), a wild mushroom commonly consumed by the indigenous people (Orang Asli) in Peninsular Malaysia, was assessed for its antioxidant content. Methods: The HC mushroom was extracted using distilled water and the crude extract partitioned using different solvents and open column chromatography to evaluate its potential antioxidant properties. The mushroom extract was partitioned using liquid-liquid extraction into the hexane (Fl), chloroform (F2), butanol (F3) and formic acid (F4) fractions. Based on solvent polarity, the water extract of the mushroom was fractionated into non-polar (FI), semi-polar (Fii), and polar fractions (Fiii) using open column chromato­ graphy. Antioxidant capacities were determined using DPPH, ABTS, and ferric reducing antioxidant power (FRAP) assays while Folin-Ciocalteu reagent assay was used to determine total phenolic content (TPC). Results: The HC extract had the highest TPC and DPPH scavenging capacity compared to its extract fractions. TE values (ABTS assay) of F2 and F4 were not significantly higher than the HC extract. Among the extract fractions of different polarities, Fiii had the highest antioxidant capacities (DPPH and FRAP) compared to FI and Fii while FRAP values of these fractions were not significantly lower than the FRAP value of HC extract. The HC extract had significantly lower antioxidant capacity than antioxidant standards (ascorbic acid and BHA). Tannie acid as the main bioactive component in HC mushroom was detected using HPLC method. The presence of phenolics in HC extract was also confirmed using TLC. Conclusion: Due to the presence of potent phenolic components, the mycelia of HC could be consumed for potential antioxidative benefits.
  5. Woo, P.F., Yim, H.S., Khoo, H.E., Sia, C.M., Ang, Y.K.
    MyJurnal
    This study investigated the effects of different percentages of ethanol (0 - 100%), extraction times (1 - 5 h) and temperatures (25 - 60°C) on total phenolic content (TPC) and antioxidant activity (AA) of sapodilla pulp and peel. TPC was determined by Folin-Ciocalteu reagent method, while AA was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, 2,2-azino-bis-(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assay, ferric reducing antioxidant power (FRAP) assay and β-carotene bleaching (BCB) assay. Based on the optimal extraction conditions used, sapodilla pulp extract had TPC of 3.89 mg GAE/g, 63.20% of DPPH scavenging activity, 4.30% of ABTS scavenging activity, 19.17% of BCB activity, and FRAP value of 15.24 mg TE/g; while its peel extract had TPC of 9.23 mg GAE/g, 92.95% of DPPH scavenging activity, 5.36% of ABTS scavenging activity, 8.14% of BCB activity, and 27.85 mg TE/g (FRAP value). Using the optimal extraction conditions for sapodilla pulp (40% ethanol as extraction solvent that extracted at 60°C for 4 h) and sapodilla peel (80% ethanol and 2 h extraction time at 40°C), highest antioxidants can be extracted from the pulp and peel.
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