PHENOLIC COMPOUNDS AND ANTIOXIDANT ACTIVITIES OF JAPANESE-GROWN OLIVE FRUIT DURING MATURATION AND QUALITY OF OLIVE OILS MARKETED IN JAPAN

MUDRIKAH, Dr. Ir. Supriyadi, M.Sc.

2018 | Tesis | MAGISTER ILMU DAN TEKNOLOGI PANGAN

Zaitun, tumbuhan khas Mediterania, telah ditanam di Jepang selama lebih dari satu abad dan mendorong negara ini untuk memproduksi minyak zaitun komersial. Meskipun demikian, Jepang mengimpor minyak zaitun terutama dari Spanyol dan Italia. Regulasi Uni Eropa Reg.432/2012 mensyaratkan setidaknya 250 mg kg-1 kandungan polifenol dalam minyak zaitun untuk mendapat klaim ‘perlindungan lemak darah dari stres oksidatif'. Oleh karena itu, penelitian ini bertujuan untuk menyelidiki senyawa fenolik dan aktivitas antioksidan buah zaitun Jepang selama pemasakan (Juli-November) dan untuk mengevaluasi kualitas extra virgin olive oil (EVOO) yang dipasarkan di Jepang. Metode esktraksi Quick, Easy, Cheap, Efficient, Ruge, and Safe (QuEChERS) dan ekstraksi cair-cair, masing-masing digunakan untuk mendapatkan fraksi fenolik dari buah zaitun dan minyak zaitun. Beberapa senyawa fenolik diidentifikasi dan dikuantifikasi menggunakan HPLC-PDA. Kandungan fenolik total (uji Folin-Ciocalteu's (FC)) dan aktivitas antioksidan (uji DPPH) juga ditentukan. Oleuropein sangat melimpah pada permulaan tahap pemasakan (Juli), kemudian menurun secara signifikan, bertepatan dengan naiknya produk degradasinya seperti 3,4-DHPEA-EA, hidroksitirosol, dan asam elenolat hingga September. Penurunan kandungan semua senyawa secara umum terjadi pada buah zaitun hitam yang matang. Buah zaitun mencapai kandungan total fenolik tertinggi (55,7 ± 2,0 g kgˉ1 GAE) pada bulan September, kemudian menurun hingga November. Aktivitas antioksidan buah zaitun Jepang yang tumbuh menunjukkan korelasi positif yang tinggi terhadap total konten fenolik (0,885, p <0,05, koefisien korelasi Pearson) dan mencapai nilai tertinggi (438,1 ± 42,5 mmol kgˉ1 TE) pada bulan September. EVOO komersial dari negara-negara Mediterania (Italia dan Spanyol) menunjukkan kandungan fenolik total maupun individual dan aktivitas antioksidan yang lebih tinggi dibandingkan dengan EVOO komersial Jepang. Di antara lima EVOO komersial yang dipasarkan di Jepang, hanya dua EVOO (dari Spanyol dan Italia) yang melampaui persyaratan minimum regulasi Uni Eropa Reg.432/2012 berdasarkan pada pengujian FC. Sementara itu, menurut uji HPLC, semua sampel memenuhi syarat.

Olive, a typical Mediterranean crop, has been grown in Japan for more than a century and encourages this country to produce commercial olive oil. Despite of that, Japan has been importing olive oil mainly from Spain and Italy. EU regulation Reg.432/2012 required at least 250 mg kg-1 of polyphenol contents in olive oil for ‘blood lipids protection from oxidative stress’ claim. Hence, this study aimed to investigate the phenolic compounds and antioxidant activity of Japanese-grown olive fruit during maturation (July-November) and to evaluate the quality of extra virgin olive oil (EVOO) marketed in Japan. Quick, Easy, Cheap, Efficient, Ruge, and Safe (QuEChERS) and liquid-liquid extraction method were used to obtain the phenolic fraction from olive fruit and olive oil, respectively. Several individual phenolic compounds were identified and quantified by HPLC-PDA. Total phenolic content (Folin-Ciocalteu’s (FC) assay) and antioxidant activities (DPPH assay) were also determined. Oleuropein was very abundant in the beginning of maturation stage (July), then decreased significantly, coincided with the rise of its degradation products such as 3,4-DHPEA-EA, hydroxytyrosol, and elenolic acid until September. General declining was observed for all compounds in fully mature olive (black) in November. Olive fruit reached the highest total phenolic content (55.7 ± 2.0 g kgˉ1 GAE) in September, then decreased until November. Antioxidant activity of Japanese-grown olive fruit showed high positive correlation to the total phenolic content (0.885, p<0.05, Pearson correlation coefficient) and reached highest value (438.1 ± 42.5 mmol kgˉ1 TE) in September. Generally commercial EVOOs from Mediterranean countries (Italy and Spain) showed higher level of total and individual phenol content and antioxidant activity compared to Japanese commercial EVOO. Among five commercials EVOOs marketed in Japan, only two EVOOs (from Spain and Italy) that surpassed the minimum requirement of EU regulation Reg.432/2012 based on FC assay. While, according to HPLC assay, all samples were qualified.

Kata Kunci : komponen fenolik, aktivitas antioksidan, buah zaitun dari Jepang, pematangan, minyak zaitun,