In the first chapter of the thesis entitled ‘Potential Use of Superheated SteamTreatment In An Underutilized Fruit of Engkala (Litsea garciae) and Evaluation of Its Antioxidant Capacity’, an introduction on the study was given where the link between antioxidants, free radicals and degenerative diseases, which is the increasingly deterioration of the function or structure of the affected body tissues or organ over time, such as cancer, atherosclerosis, arthritis, gastritis, diabetes mellitus and neurodegenerative diseases were discussed. The onset of these diseases was confirmed by accumulation of free radicals that are produced from oxidation process as well as from toxic present in the environment. The damaging effects of the free radicals however can be stopped by the action of antioxidants supplied by plants when incorporated in a human diet. In the introduction, the role of polyphenols as antioxidants and their source especially from fruits were also discussed and engkala and avocado fruits, which belong in the same family were introduced as source of antioxidant in this study. Drying process of food was also discussed, emphasizing the use of freeze drying and superheated steam.In chapter 2, the characteristics of engkala fruit and its antioxidant capacity was evaluated. The physical properties, nutritional composition and minerals composition were discussed. This study showed that engkala fruit, just like avocado is a fleshy fruit where the pulp accounted for more than 50% of the fruit weight. Nutritional compositions of engkala showed that this fruit is high in moisture, protein, carbohydrate, K, Na, Fe, Zn and Ca. Polyphenol content of engkala was determined by measuring the total phenolic and total flavonoid content. Antioxidant activities of engkala extracts were determined by using DPPH assay and ORAC assay. In DPPH assay, the concentration of the extract inhibiting 50% of the DPPH radical activity was measured as an indicator of the antioxidant activity. In this study, the edible part of the fruit which is the pulp showed highest activity when dried with superheated-steam at the temperature of 170°C. In ORAC assay, the oxygen radical absorbing capacity of the fruit extract was measured. The pulp of engkala also showed the same pattern, where superheated-steam dried pulp at the temperature of 170°C gave the highest ORAC value. This study showed that superheated-steam drying gave higher polyphenol contents and antioxidant activities in engkala pulp, while freeze drying gave higher results in the seed part of the fruit. The polyphenol compound present in engkala extract was also studies by using HPLC, TG/DTA, GCMS and LC-MS system.In the third chapter, polyphenol content and antioxidant activities in avocado fruit was evaluated. The avocado pulp followed the same pattern as shown by engkala pulp, where the total phenolic, total flavonoid content as well as antioxidant activities in the pulp was significantly higher when dried with superheated-steam. The peel and seed on the other hand showed significantly higher results when freeze dried.In the fourth chapter, the antioxidant capacity of both engkala and avocado fruits were compared. The data showed that engkala pulp and seed showed higher antioxidant capacity compared to avocado. The peel on the other hand showed higher antioxidant capacity of avocado compared to engkala peel. Considering the edible part of the fruit, engkala was ranked higher than avocado where antioxidant capacity was in concern.The final chapters remark the conclusion of the whole study. It was concluded that both superheated-steam drying and freeze drying can offer their advantages in application of dried fruit production, where superheated-steam drying was preferred in drying the pulp of engkala and avocado, while freeze drying was the preferred method of drying for the seed and peel of engkala and avocado. The high potential of the by-products as given by the high antioxidant capacity especially when freeze dried suggested that they could be utilized and developed as natural antioxidants or food additives.九州工業大学博士学位論文 学位記番号:生工博甲第237号 学位授与年月日:平成27年3月25日1. Introduction and literature review|2. Engkala fruit: evaluation of its characteristics and antioxidant capacity|3. Evaluation of polyphenol content and antioxidant capacity in avocado fruit dried with superheated-steam|4. Fruits comparison and general discussion|5. Concluding remarks and suggestions for future research九州工業大学平成26年
