Lee, Angelina Mei Ling (2016) Effect of different drying techniques on nutritional and phytochemical composition, antioxidant and acetylcholinesterase inhibition properties of edible red seaweed, Kappahycus alvarezii. Masters thesis, Universiti Malaysia Sabah.
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Abstract
Post-harvest process is an important factor that one must take into consideration in order to ensure that good seaweeds are produced and best quality of seaweeds is maintained as to command high value in the market. However, this post-harvest processing affects the quality such as content and activity of bioactive compounds in the seaweeds. The aim of the present study was to investigate the effect of different drying techniques on phytochemical content, antioxidant and acetylcholinesterase inhibition activity as well as nutritional composition of Kappaphycus alvarezii; crocodile and tambalang giant morphotypes. The cleaned seaweeds were divided into seven portions and was dried using seven drying conditions; (1) oven-drying at 40 ºC, (2) oven-drying at 80 ºC, (3) sun-drying, (4) hang-drying, (5) sauna-drying, (6) shade-drying and (7) freeze-drying. First, determination of total phenolic, flavonoid, anthocyanin and carotenoid contents were done spectrophotometrically. Oven-drying at 40 ºC extract of crocodile morphotype contained highest value of total phenolic (53.33 mg GAE/100 g), while the oven-drying at 40 ºC extract of tambalang giant morphotype contained highest values of total flavonoid (34.50 mg CE/100 g), total anthocyanin (1.47 mg C-3-GE/ g) and total carotenoid (0.26 mg BC/ g). Sauna-drying extract of tambalang giant morphotype contained lowest values of total phenolic (20.33 mg GAE/100 g) and total carotenoid (0.02 mg BC/ g), while the sauna-drying extract of crocodile morphotype contained lowest values of total flavonoid (9.83 mg CE/100 g) and total anthocyanin (0.53 mg C-3-GE/ g). Evaluation of antioxidant activity was conducted using DPPH free radical scavenging assay, ferric reducing power (FRAP) and radical scavenging ABTS assays. Oven-drying at 80 ºC extract of crocodile morphotype displayed highest scavenging activity (93.29 %), while the oven-drying at 40 ºC extract of crocodile morphotype displayed strongest reducing ability (7.81 mM Fe2+/ g) and antioxidant capacity (0.54 mg AEAC/ g). Acetylcholinesterase is an enzyme known to breakdown the neurotransmitter acetylcholine which leads to Alzheimer’s disease. Acetylcholinesterase inhibition assay was done and the result showed that oven-drying at 40 ºC extracts of both morphotypes displayed highest acetylcholinesterase inhibition activity with the values of 45.03 % (crocodile morphotype) and 24.89 % (tambalang giant morphotype), when tested at 100 mg/ml concentration. However, there was no acetylcholinesterase inhibition activity detected in sauna-drying and freeze-drying extracts in both morphotypes. Based on correlation analysis, all dried samples showed positive correlation between phytochemical content and antioxidant, positive correlation between phytochemical content and acetylcholinesterase inhibition effect and positive correlation between antioxidant and acetylcholinesterase inhibition effect. Proximate analysis test showed that freeze-drying samples of both morphotypes contained lowest amount of ash content, while the others show no significant differences. Shade-drying samples of both morphotypes contained lowest amount of moisture content, while the others show no significant differences. Freeze-drying samples (crocodile and tambalang giant morphotypes) contained highest percentage of crude lipid (1.26 % and 1.21 %), crude fiber (8.28 % and 8.42 %) and crude protein (14.10 % and 14.69 %), while the oven-drying 80 ºC samples (crocodile and tambalang giant morphotype) contained highest percentage of carbohydrate (55.14 % and 54.24 %). Lowest percentage of crude lipid, crude fiber and crude protein were found in sun-drying and sauna-drying samples of both morphotypes, while carbohydrate in the oven-drying at 40 ºC sample of both morphotypes. Analysis for major and trace mineral elements showed that the oven-drying at 40 ºC samples of both morphotypes contained highest value of Na, Ca, Mg and Mn, while the shade-drying samples of both morphotypes contained highest value of K, Fe and Zn. Lower mineral elements was tested in sun-drying and sauna-drying samples of both morphotypes. Based on the drying techniques studied, oven-drying at 40 ºC is the best drying technique used to retain the phytochemical content, antioxidant and acetylcholinesterase inhibition activity and some mineral compounds in seaweeds, while freeze-drying is the best drying technique used to retain the nutritional content in seaweeds. As a conclusion, post-harvest process such as drying could greatly influence the occurrence of phytochemical content, antioxidant and acetylcholinesterase inhibition activity as well as nutrient content in the dried seaweeds.
| Item Type: | Thesis (Masters) |
|---|---|
| Keyword: | Post-harvest process, Seaweeds, Phytochemical, Kappahycus alvarezii |
| Subjects: | Q Science > QK Botany > QK1-989 Botany > QK710-899 Plant physiology |
| Department: | INSTITUTE > Institute for Tropical Biology and Conservation |
| Depositing User: | DG MASNIAH AHMAD - |
| Date Deposited: | 04 Jul 2024 14:09 |
| Last Modified: | 04 Jul 2024 14:09 |
| URI: | https://eprints.ums.edu.my/id/eprint/39026 |
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