ABSTRAKKemunduran mutu ikan disebabkan oleh berbagai faktor, salah satunya adalah akibat aktivitas enzim katepsin. Aktivitas enzim katepsin dapat dihambat dengan inhibitor enzim. Inhibitor enzim dapat diperoleh dari jaringan daging ikan dengan cara memisahkan kompleks enzim-inhibitor dengan perlakuan pemanasan. Tujuan penelitian ini adalah mengekstrak dan mengaplikasikan inhibitor katepsin untuk menghambat kemunduran mutu ikan bandeng. Penelitian ini dilakukan dalam tiga tahap, yaitu (1) penentuan suhu optimum ekstraksi inhibitor katepsin, (2) penentuan daya hambat tertinggi berbagai konsentrasi inhibitor katepsin, dan (3) aplikasi inhibitor katepsin dalam menghambat kemunduran mutu ikan bandeng. Hasil penelitian menunjukkan bahwa inhibitor katepsin dapat diekstrak dengan baik menggunakan suhu 80 ⁰ C. Inhibitor katepsin yang diencerkan menggunakan bufer dengan perbandingan 1:1 memiliki aktivitas yang relatif sama dengan tanpa pengenceran. Proses kemunduran mutu pada ikan bandeng kontrol dalam penyimpanan suhu chilling terjadi selama 504 jam (21 hari) dengan interval waktu pengamatan 24 jam berturut-turut yaitu 0 jam (pre rigor), 96 jam (rigor mortis), 360 jam (post rigor), dan 504 jam (busuk). Proses kemunduran mutu ikan bandeng dengan perlakuan perendaman inhibitor katepsin terjadi selama 624 jam (26 hari) dengan proses sebagai berikut: 0 jam (pre rigor), 144 jam (rigor mortis), 408 jam (post rigor), dan 624 jam (busuk). Dengan demikian ikan bandeng yang direndam dengan inhibitor katepsin mencapai fase deteriorasi lebih lambat 5 hari.

Quality deterioration of fish is caused by various factors, one of them is due to the activity of cathepsin enzyme. Cathepsin enzyme activity can be inhibited by enzyme inhibitors. Inhibitors of the enzyme can be obtained from fish meat tissue by separating the enzyme-inhibitor complex with heat treatment. The purpose of this research was to extract and apply the cathepsin inhibitors to inhibit deterioration of fish quality. This research was conducted in three  steps: (1) the determination of the optimum extraction temperature for extraction of cathepsin inhibitors, (2) the determination of the most potent cathepsin inhibitors with various concentrations, and (3) the application of cathepsin inhibitors in inhibiting the deterioration of fish quality. The results showed that the cathepsin inhibitors was optimally extracted at 80°C. Cathepsin inhibitors diluted using buffer with a ratio of 1: 1 had the same relative activity without dilution. The process of quality deterioration of milkfish  control in chilling temperatures occured after 504 hours (21 days) storage with a 24-hour observation time interval. The complete process during observation was pre-rigor (0 hour ), rigor mortis (96 hours), post-rigor (360 hours), and deterioration (504 hours). The process of milkfish quality deterioration treated with soaking in  cathepsin inhibitors occured after 624 hours (26 days) storage with the detailed process as follows: 0 hour (pre-rigor), 144 hours (rigor mortis), 408 hours (post-rigor), and 624 hours (deterioration). Thus fish marinated with cathepsin inhibitors achieve slower deterioration phase 5 days. Keywords: cathepsin inhibitor, deterioration, pre-rigor, rigor mortis, post-rigor, quality deterioration.