Berita Biologi, Volume 7, Nomor 6, Desember 2005 DEVELOPMENT OF PURE CULTURE STARTER FOR KECAP, AN INDONESIAN SOY SAUCE [Pengembangan Ragi Kecap Khas Indonesia Dengan Biakan Murni] i El. Joko Sulistyo 1 and Sayuki Nikkuni 2 'Research Center fot Biology, LIPIII. It. H. JuandaNo. 18 Bogot 16002, Indonesia 2 Food Science and Technology Division, JIRCAS, Ohwashi 1-1, Tsukuba, Ibaraki 305-8686, Japan ABSTRACT In order to prevent aflatoxin contamination during the production of kecap, an Indonesian soy sauce, a white-spored mutant K-IA strain induced from an aflatoxin-negative koji mold was applied to koji making process of kecap. While kecap koji making process took 9 days by conventional method without inoculum, the use of K-IA strain as a starter shortened the process to 3 days at room temperature. The koji prepared with this starter contained 2.3 x 10 7 cfu/g of Aspergillus sp. K-IA as the dominant species and some contaminants from the environment such as other species of Aspergillus (2.0 x 10'' cfu/g) and Mucorales (1.4 x 10 s cfu/ g). The mash prepared with kecap koji inoculated with this starter contained higher formol nitrogen (FN) and water-soluble nitrogen (WN) than those prepared with koji inoculated without any starter. These results demonstrated that the use of this starter did not only contribute to the prevention of aflatoxin contamination but also improved the conventional kecap fermentation process. Key words: Aspergillus, ragi kecap, soybean fermentation, non-aflatoxin. Untuk mencegah teijadinya kontaminasi aflatoksin selama pengolahan kecap di Indonesia, biakan mutan BAf berspora putih yang diinduksi dari kapang negatif aflatoksin, digunakan untuk membuat ragi kecap. Dibanding cara konvensional, penggunaan biakan K"1A dapat mempersingkat proses fermentasi koji dari 9 hari menjadi 3 hari pada suhu ruang. Hasil menunjukkan bahwa koji yang difermentasi menggunakan ragi mutan mengandung 2,3 x 10 7 cfu/g Aspergillus sp., dimana biakan K-IA ditemukan sebagai spesies yang dominan serta beberapa kontaminan berasal dari spesies lain Aspergillus (2,0 x 10'' cfu/g) dan Mucorales (1,4 x 10 5 cfu/ g). Sampel sari kecap yang difermentasi dengan koji hasil inokulasi ragi mutan, mengandung formol nitrogen (FN) dan nitrogen terlarut (WN) yang lebih tinggi dibanding sampel yang difermentasi menggunakan koji dari ragi konvensional. Hasil tersebut menunjukkan bahwa penggunaan ragi mutan tidak hanya bermanfaat dalam mencegah kontaminasi aflatoksin tetapi juga meningkatkan proses fermentation kecap konvensional. Kata kunci: Aspergillus, ragi kecap, fermentasi kedelai, bebas-aflatoksin. INTRODUCTION Kecap is a fermented soybean food known as Indonesian soy sauce. Whole soybeans, specially the varieties of black soybeans, are used as raw material for processing kecap. Kecap is prepared by spreading cooked soybeans on bamboo trays and leaving them for a period of time until molded soybeans (koji) are formed. Kecap manufacturers do not usually use any inoculum (tane-koji, ragi kecap) for koji preparation. During processing, molds grow on the cooked soybeans as the result of contamination from the environment such as the air and the previously used trays. Judoamidjojo (1986) reported that molds isolated from kecap koji were mostly from the genus of Aspergillus. It is known that agricultural food commodities such as peanut and maize are widely contaminated with aflatoxins, natural carcinogens, produced by fungi belong to Aspergillus section Flavi, in Indonesia (Dharmaputra, 1991). It was also reported that 15 out of 32 samples of Indonesian kecap contained aflatoxin Bj at concentrations of more than 5 ug/kg (Sadjonoefa/., 1992). Since the possibility of aflatoxin contamination cannot be ruled out in the traditional way of koji processing, thus, it is necessary to use a pure culture starter, ragi kecap from the standpoint of preventing aflatoxin contamination. In our previous study (Nikkuni et al., 2002), we induced white-spored mutants from koji molds by UV- irradiation and used them in kecap fermentation. We evaluated the possibility of distinguishing the mutant from aflatoxin-producing molds and revealed that white- spored mutant can be used as a starter for preparation 295