Development and Characterization of a Flavoring Agent from Oyster Cooker Effluent D. S. Kim, † H. H. Baek, ‡ C. B. Ahn, § D. S. Byun, † K. J. Jung, † H. G. Lee, ⊥ K. R. Cadwallader, # and H. R. Kim* ,† Faculty of Food Science and Biotechnology, Pukyong National University, Pusan 608-737, Korea; Department of Food Engineering, Dankook University, Chunan 330-714, Korea; Department of Food Science and Nutrition, Yosu National University, Chunnam 550-749, Korea; Department of Food and Nutrition, Hanyang University, Seoul 133-791, Korea; and Department of Food Science and Technology, Mississippi State University, Mississippi Agricultural and Forestry Experiment Station, Box 9805, Mississippi State, Mississippi 39762 The general composition of concentrated oyster cooker effluent (OCE) was 80% moisture, 6.7% total nitrogen, 2.4% glycogen, and 8.5% ash. Optimum conditions for enzymatic hydrolysis of OCE were 50 °C, 2 h of reaction time, 0.1% amylase mixture (R-amylase plus glucoamylase), and 0.2% protease NP. Hydrolysis of OCE led to an increase in free amino acids, with taurine comprising ∼20% of the total. Inosine monophosphate was predominant (456 mg/100 g) among nucleotides and related compounds. Enzyme hydrolysis increased extractable nitrogen by ∼2-fold. Trimethylamine, tri- methylamine oxide, and total creatinine levels were not affected by enzyme treatment. Predominant aroma-active components of enzyme-hydrolyzed OCE included 2-acetyl-1-pyrroline and 3-(methyl- thio)propanal. Results of this study may help alleviate the wastewater disposal problem currently caused by OCE. Keywords: Aroma; enzymatic hydrolysis; flavor; gas chromatography-olfactometry; oyster; oyster byproduct; oyster cooker effluent INTRODUCTION The oyster industry is the largest commercial shellfish aquaculture industry in Korea, with an annual produc- tion in excess of 220000 metric tons. Eighty percent of the annual production is cooked and processed into canned oyster products. This process generates a large quantity of oyster cooker effluent (OCE) containing appreciable amounts of soluble components, such as peptides, amino acids, glycogen, and other organic compounds. About 40000 tons of OCE (6 °Brix) is generated per year in Korea. In most processing plants, OCE is discarded into waterways, causing pollution. OCE has potential as a feedstock for production of a value-added oyster flavoring; however, only a few seafood processors have realized the potential of con- verting this byproduct into a marketable flavoring agent. The potential for recovery of water-soluble organic components of discharge streams from shrimp process- ing plants has been demonstrated (Perkins and Meyers, 1997). The process for the recovery of organic materials from wastewater not only solves the pollution problem but also maximizes the use of food-processing wastes for ultimate human consumption. Wash water from clam processing plants has been converted into a potentially marketable natural clam flavoring agent (Reddy et al., 1989; Joh and Hood, 1979; Burnette et al., 1983) and a protein concentrate (Hang et al., 1980). Also, oyster shucking liquid waste, containing protein, nonproteinaceous nitrogen compounds, and other or- ganic materials, was concentrated and evaluated for human consumption as oyster soup (Shiau and Chai, 1990). However, the above studies focused on the utilization of oyster-processing byproducts by use of simple extraction and concentration steps only and did not consider the use of commercially available enzymes as processing aids to improve yields and the quality of final products. Enzymatic hydrolysis has been used to produce fla- vorants from seafood-processing byproducts (In, 1990; Kim et al., 1994a; Baek and Cadwallader, 1995, 1999). In general, proteolytic enzymes have been employed in these processes. In addition to proteases, use of am- ylases in the hydrolysis of OCE has potential because this material contains appreciable amounts of glycogen (Kim et al., 1996). A protease/amylase process has particular appeal because during thermal processing amino acids and peptides released by protease action can react with reducing sugars liberated by amylase action to generate cooked meat aroma. This technology has been used for the production of meat and savory flavors (Dziezak, 1986). The objectives of this study were to determine the chemical composition of OCE and to evaluate the use of enzymatic hydrolysis of OCE by combined protease/ amylase action to produce a hydrolysate suitable for further processing into a seafood flavoring agent. * Author to whom correspondence should be addressed (telephone 82-51-620-6338; fax 82-51-620-6330; e-mail hrkim@ pknu.ac.kr). † Pukyong National University. ‡ Dankook University. § Yosu National University. ⊥ Hanyang University. # Mississippi State University. 4839 J. Agric. Food Chem. 2000, 48, 4839-4843 10.1021/jf991096n CCC: $19.00 © 2000 American Chemical Society Published on Web 09/09/2000