HIDROLISIS ISOLAT PROTEIN BUNGKIL WIJEN (Sesamum indicum L.) SANGRAI DENGAN ENZIM BROMELIN DAN KARAKTERISASI SIFAT FUNGSIONALNYA

ERTHA MARTHA INTANI, Dr. Ir. Pudji Hastuti, M.S

2013 | Tesis | S2 Ilmu dan Teknologi Pangan

Pemanfaatan biji wijen putih sangrai sebagai sumber minyak akan menghasilkan limbah berupa bungkil wijen sangrai, yang kadar proteinnya dapat mencapai 50% tergantung metode ekstraksi minyaknya. Protein bungkil wijen sangrai dapat diisolasi dan dihidrolisis untuk meningkatkan sifat fungsionalnya. Peningkatan sifat fungsional protein dapat dilakukan dengan hidrolisis enzimatis. Salah satu enzim proteolitik yang dapat digunakan, yaitu enzim bromelin dengan spesifitas pemotongan yang luas pada empat residu asam amino. Tiap enzim memiliki suhu dan pH optimum tertentu dalam reaksi yang dikatalisisnya, namun belum diketahui kemungkinannya bila rasio enzim/substrat (E/S) besar atau kecil, dan waktu hidrolisis singkat atau lama. Penelitian ini bertujuan untuk mengetahui pengaruh konsentrasi enzim bromelin yang ditambahkan (rasio E/S) dan lama waktu hidrolisis terhadap derajat hidrolisis, berat molekul, dan karakteristik fungsional hidrolisat protein bungkil wijen sangrai. Biji wijen putih disangrai pada suhu 180oC selama 30 menit, kemudian diekstrak minyaknya dengan pengepresan dan pelarut n-hexane teknis. Protein bungkil wijen sangrai rendah lemak yang dihasilkan diisolasi dengan pelarutan protein pada pH 11 dan presipitasi pada pH 3,5. Isolat protein kemudian dihidrolisis dengan enzim bromelin pada pH 6 dan suhu 45oC dengan pengadukan konstan. Rasio E/S yang digunakan sebanyak 1% dan 5% (w/w) dan waktu hidrolisis selama 10, 20, 30, 60, dan 120 menit. Hidrolisat yang dihasilkan dianalisis derajat hidrolisis, berat molekul, kadar protein terlarut, indeks aktivitas dan stabilitas emulsi, serta kapasitas dan stabilitas pembentukan buih. Hasil penelitian menunjukkan bahwa peningkatan rasio E/S dari 1% (w/w) sampai 5% (w/w) meningkatkan derajat hidrolisis 1,85 kalinya; menurunkan berat molekul sebanyak 2-7 kDa dengan memunculkan satu tambahan pita protein baru dengan berat molekul 12-14 kDa; meningkatkan kadar protein terlarut 1,2 kalinya; tidak mempengaruhi indeks aktivitas emulsi dan indeks stabilitas emulsi walaupun adanya perlakuan hidrolisis dapat meningkatkan indeks stabilitas emulsi 1,4 kalinya; serta tidak mempengaruhi kapasitas dan stabilitas pembentukan buih walaupun adanya perlakuan hidrolisis dapat menurunkan stabilitas pembentukan buih sekitar 80-140%. Perpanjangan waktu hidrolisis dari 20 menit sampai 120 menit meningkatkan derajat hidrolisis 1,1 kalinya; tidak mempengaruhi berat molekul, kadar protein terlarut, indeks aktivitas emulsi, indeks stabilitas emulsi dan kapasitas pembentukan buih; serta menurunkan stabilitas pembentukan buih sekitar 25-40%.

Utilization of roasted white sesame seeds as a source of oil will produce roasted sesame cakes as by products, which has a high protein content as high as 50%, depends on oil extraction method. Roasted sesame cake protein can be isolated and hydrolyzed in order to improve functional properties. The improvement of functional properties of proteins can be performed by enzymatic hydrolysis. One of the proteolytic enzymes that can be used is bromelain with a wide hydrolysis specifity at four amino acid residues. Each enzyme has a specific optimum temperature and pH for its catalytic reaction, but it is not known if the likelihood of enzyme/substrate (E/S) ratio is large or small, and hydrolysis time is short or long. This study aimed to determine the effect of bromelain addition in various concentration (E/S ratio) and hydrolysis time on the degree of hydrolysis, molecular weight, and also functional characteristics of roasted sesame cake protein hydrolysates. White sesame seeds were roasted at 180oC for 30 minutes. The oil was removed by pressing and defatting using technical n-hexane. The protein of deffated flour of roasted sesame cakes were isolated by dissolving the protein at pH 11 and precipitation at pH 3.5. Protein isolates were hydrolyzed by bromelain at pH 6 and temperature 45°C with constant stirring. The E/S ratios were 1% and 5% (w/w) and the hydrolysis times were 10, 20, 30, 60, and 120 minutes. Hydrolyzate were analyzed for degree of hydrolysis, molecular weight, soluble protein content, emulsifying activity index, emulsifying stability index, and also capacity and stability of foam formation. The results showed that the increasing of E/S ratio from 1% (w/w) to 5% (w/w) increased degree of hydrolysis for 1.85 folds; decreased molecular weight 2-7 kDa by appearing one more protein band with molecular weight 12-14 kDa; increased soluble protein content for 1.2 folds; did not affect emulsifying activity and stability index although hydrolysis treatment could increase emulsifying stability index for 1.4 folds; and also did not affect foaming capacity and stability although hydrolysis treatment could decrease foaming stability approximately 80- 140%. The extension of hydrolysis time from 20 min to 120 min increased degree of hydrolysis for 1.1 folds; did not affect molecular weight, soluble protein content, emulsifying activity index, emulsifying stability index and foaming capacity; and also decreased foaming stability approximately 25-40%.

Kata Kunci : bungkil wijen, penyangraian, hidrolisis protein, enzim bromelin, sifat fungsional