Use of Papain and Bromelain in the Production of Oyster

Pranisa Chuapoehuk and Nongnuch Raksakulthai

ABSTRACT MATERIALS AND METHODS

Minced oyster meat samples were hydrolyzed using papain The materials used were shucked cultured oyster, or bromelain at concentrations of 0, 0.1, 0.3, 0.5 and 0.7% (Crassostrea sp.) from Tambon Angsila, Amphur (w/w). Each sample was supplemented with 20% sodium Muang, Chonburi Province, Thailand; Papain enzyme chloride. It was found that 0.7% papain or 0.3% bromelain prepared by Kunkriangwong (1988) from papaya fruit yieldedthehighestsolublenitrogenin thehydrolysates. Oyster of Khagdam strain with protease activity of 30,000 prepared from 0.7% papain or 0.3% bromelain units per gram; and Bromelain enzyme (No. 083 BML) hydrolysates supplemented with 20% sodium chloride showed from Great Food Co., Bangkok, Thailand. no significant differences in proximate composition, pH, consistency,andsensoryevaluationscores.Chinese watercress Nine commercial samples were each stir-fried with these prepared oyster sauces received higher analyzed for protein, lipid, ash, moisture, carbohydrate acceptabilityscores than commercial oyster sauce (p <;0.05). and sodium chloride, using methods of AOAC (1980) The prepared sauces could be stored for 12 weeks at room and for total bacteria using the total plate count temperature in glass bottles with screw caps without mould method (ICMSF, 1987). To determine yeast and mould development. counts, potato dextrose agar supplemented with 10% was used (ICMSF, 1987). The samples were also INTRODUCTION tested for pH (Metrohm, 605) and consistency (Bostwich). Sensory scores were evaluated using a 9 In 1987, Thailand imported 93,522 kg of oyster sauce, point hedonic scale with score 1 for most unacceptable valued at 2.7 million baht, mainly from Japan and and 9 for most acceptable (Larmond, 1977). The sensory Hong Kong. In the same year, however, Thailand scores were given by 10 judges who were instructors exported 84,251 kg of oyster sauce, valued at ap- and students from the Department of Fishery Products, proximately 4 million baht. Countries that imported Kasetsart University and staff of the Fishery Products oyster sauce from Thailand in descending order of quantity Development Division, Department of Fisheries. were Saudi Arabia, Malaysia and the USA (Dept. of Customs, 1987). Optimal Concentration of Enzymes in Preparation of Hydrolyzates Several methods are employed to produce oyster sauce known as oyster oil in Thai. The most common are: Oyster meat samples were ground and mixed in screw- (1) dIluhon of concentrated sauces and supplementahon capped glass bottles with enzymes, papain or wIth colounng, odour and flavounng agents pnor to bromelain, at concentrations of 0, 0.1, 0.3, 0.5 and 0.7% packaging (2) hydrolysi~ of oyster meat with. hydro- by weight of the oyster meat. Each sample was thor- chlonc aCId and Improvmg the quahty by addmg soy oughly mixed with 20% sodium chloride by weight of sauce, sugar, monosodium glutamate, starch etc. ~Dept. oyster meat, and kept at 35 :t 1°C for 20 days. The of SCI:nce ServIces, 1976; JIttmun and Saehm, 198~). In samples were then boiled and filtered. The filtrates addItIOn, oyster powder IS used as a source of raw . were analyzed for total nitrogen (AOAC, 1980). Each matenal m sauce produchon as stated on the label. sample was replicated three times. The optimal ... . . concentration of enzyme to produce the highest total The obJechves of this study were 1) to determme optimal nitrogen was then determined. concentrations of the enzymes, papain or bromelain, in hydrolyzing oyster meat (2) to compare proximate . composition, pH, consistency, and sensory evaluation PreparatIon of Oyster Sauce scores of oyster sauces produced by the use of papain . and bromelain and commercial oyster sauces and (3) Oyster meat samples were ground and mIxed m- glass to determine whether the prepared sauces could be bottles wIth 0.7% papam or 0.3% bromelam. SodIUm stored for 12 weeks at room temperature. chloride was added at 20% by weight and thoroughly mixed. The bottles were kept closed at 35 :t 1°C for 20 days. The samples were then boiled for 2 minutes, filtered through Whatman No.4 paper and pH ad- justed to 4.5 - 5.0 with lactic acid. The filtrates were The authors are from the Department of Fishery Products. Faculty adjusted to give acceptable colour, odour and taste, by of Fisheries. Kasetsart University. Bangkok 10900, Thailand. mixing the liquid with the other ingredients recom-

196 ASEAN Food Journal Vol. 7, No.4, 1992 mended by the Department of Science Services (1976) Table 1. Proximate composition, consistency and pH and jittinun and Saelim (1985), as follows: of commercial oyster sauce'

Hydrolysate 60g SampleTotalN Protein Fat Moisture Ash Carbohydrate NaCl Consis pH glKg %% % % % %tency 2 0g (cm/min) Sugar 7g Glucose 109 1 1.5 0.9 0.8 76.8 8.5 13.4 7.5 1.1 5.1 Sodium succinate 19 2 2.6 1.6 1.3 73.5 6.6 18.1 7.8 1.3 5.1 Succinic acid 0.3g Monosodium glutamate 2.7g 3 4.4 2.7 0.4 69.0 8.7 19.5 6.9 0.8 5.2 Modified corn starch 5g 4 4.7 2.9 1.0 62.5 12.5 15.1 12.3 1.3 5.1 Water 20g 5 4.8 3.0 0.9 60.5 10.5 25.5 10.4 1.4 5.0

This mixture was thoroughly mixed and boiled for 2 6 4.9 3.1 1.9 76.6 6.4 13.7 4.5 0.7 5.6 minutes to produce the prepared oyster sauces. 7 6.8 4.3 0.4 57.9 13.0 24.8 12.2 0.9 5.7 The prepared oyster sauces were ana lysed and evalu- 8 7.1 4.4 0.7 82.1 6.3 8.8 4.5 1.2 5.5 ated in the same way as the commercial oyster sauces. To compare acceptability, the prepared oyster sauces 9 7.4 4.6 1.0 82.3 6.2 6.8 4.5 1.2 5.4 and the most acceptable commercial oyster sauce sam- ples were used as a in stir-fried Chinese lValues are averages of three determinations. watercress. The stir-fried watercress samples were evaluated by 10 panelists. At the present time there is no official standard for oyster sauce. These analyses of protein content in Storage Life of Prepared Oyster Sauces commercial oyster sauce (Table 1) could be used as a basis for requiring a 3% protein content in prepared The prepared oyster sauces were stored at room oyster sauce, since the average protein content is 3.07% temperature (about 30°C) in 50mL glass bottles with screw caps for 12 weeks. The sauces were checked every The pH of commercial oyster sauces (Table 1) ranged 2 days for mould development. from 5.0 to 5.7, which agreed with the 5-6 range set by TISI (1983) for . The consistency values RESULTS AND DISCUSSION ranged from 0.7-1.4 em per minute. Consistency of the sauce should be related to the amount of starch or Commercial Oyster Sauces othercarbohydrateadded,howevertheregressionanalysis of the carbohydrate content and consistency shows no The proximate composition of commercial oyster sauce correlation (r'=0.008). samples (Table 1) varied greatly. The average protein content was 3.1 %. It has been reported that protein Table 2 shows significant differences (P <;: 0.05) in nitrogen as well as peptide and amino acid nitrogen sensory evaluation scores of commercial oyster sauces. are essential to the flavour of some common food such as soy sauce (Kirimura, Shimizu, Kimizuka, Ninomiya and Katsuya, 1969) and fish sauce Table 2. Sensory evaluation scores] of commercial (Raksakulthai, Lee and Haard, 1986). The specification oyster sauce for flavouring sauce issued by the Thai Industrial Standards Institute (TISI, 1970) required the total ni- Sample Sensory evaluation score trogen content to be not less than 30 g/L and amino Colour Odour Flavour Total acid nitrogen to be not less than 20 g/L. The standard for local fish sauce (TISI, 1983) requires total nitrogen 1 6.8a 4.8a 5.4bc 17.0 contents in first and second grade fish sauce to be not 2 4.1c 4.9a 5.9abc 14.9 less than 20 and 15 g/L, respectively and amino acid 3 4.8a 6.2a 6.9a 19.9 nitrogen not less than 10 and 7.5 g/L, respectively. The 4 7.0a 5.9a 5.2c 18.1 standard for soy sauce (TISI, 1987) requires protein 5 4.9bc 2.3b 3.2d 10.4 content (N x 6.25) in the extra grade and first grade 6 3.7c 4.8a 4.6c 13.1 white soy sauce to be not less than 5.5 and 4.5% by 7 5.9ab 4.7a 5.5abc 16.1 weight, respectively, in extra and first grade salty black 8 7.1a 5.6a 6.7ab 19.4 soy sauce to be not less than 8.5 and 7.5, respectively. 9 6.1ab 5.4a 5.9abc 17.4 In black soy sauce the protein content must be not less 1 than 2.0% and in sweet soy sauce the protein content Values followed by the same letter in the same column must be not less than 1.5%. are not significantly different (p..; 0.05).

ASEAN Food Journal Vol. 7, No.4, 1992 197 Six samples were not significantly different in colour Table 3. Proximate composition, consistency and pH (5.9 - 7.1), but the remaining three samples received of prepared oyster sauce' unacceptably lower scores (3.7 - 4.9). Eight samples showed nonsignificantly different scores (4.8 - 6.2) for Enzyme Protein Fat Moisture Ash CHO NaCl Consis pH odeuy but were significantly different from the % % % % % % teney . . . Icm/minl sarnp Ie receIvIng an 0 d our score 0 f 2..3 Flye samp Ies were not significantly different in flavour scores (5.5 Papain - 6.9) but were significantly different to samples re- 0.7% 4.9 0.2 63.8 14.2 16.9 14.6 0.8 5.0 ceiving scores of 5.4 or lower. Bromelam. 0.3% 5.1 0.8 65.1 13.7 16.9 13.5 0.8 5.0 Commercial oyster sauce samples receiving high sen- . 1 sory evaluation scores were brown in colour, smooth Values are average of duplicate determination of three in texture, not too thick and had a sme]] of boiled replicates. oyster, while samples receiving low scores were lighter in colour, had a salty taste and very mild odour. found in the samples treated with papain, leaving less q Prepare d 0 ys ter Sauces fat in the li uid Part. Protein values of Pre pared Oyster sauces were higher than those of commercial sauces. Figure 1 shows the effect of concentration of papain However, the pH and consistency of prepared and or brornelain, on total nitrogen in oyster hydrolyzates. commercial sauces were similar. Papain at 0.7% and bromelain at 0.3% by weight of oyster meat yielded the highest total nitrogen contents. The colour, odour and flavour of the two prepared From 100g of oyster meat, papain and bromelain sauces were not significantly different. The total sensory yielded 50 and 60mL of hydrolyzate, respectively. evaluation scores of the prepared sauces were higher than those of the commercial sauces.

7.0 Table 4 shows the overall preference scores of stir-fried Chinese watercress with prepared and commercial Legend 0 papain sauces. The average preference score of the sauce 6.0 6 bromelain prepared from papain was higher but not statistically different from that of the sauce prepared from 5.0 bromelain. The preference scores of the prepared ::? sauces were, nevertheless, higher (p ,;;0.05) than those :9 4.0 of the commercial sauces. ~ '"" ~ 3.0 Table 4. Sensory evaluation scores of prepared and (tj commercial oyster sauces and acceptability ~ scores of stir-fried Chinese watercress with 2.0 different oyster sauces.

1.0 Sensory scores Acceptability Colour Odour Flavour scores

Prepared sauce 7.1a 6.5a 6.5a 7.7a 0.1 0.2 0.3 0.4 0.5 0.6 0.7 using papain 0.7% Cone. of enzyme (%) Prepared sauce 6.7a 5.3a 6.4a 7.4a . . using bromelain FIg. 1 Effect of enzyme concentratIOns on the total 03%0 nitrogen content of oyster hydrolyzate. Values' plotted are averages of three determinations. . Best commerCiaI 6.7a 6.2a 6.9a 5.9b oyster sauce

The proximate composition, consistency, pH, and sen- Values are averages of 11 panelists; values in the same sory evaluation scores of prepared oyster sauces are c~lumn followed by the same letter are not significantly presented in Table 3. The protein, moisture, ash, car- d1fferent (p ,;; 0.05) bohydrate and sodium chloride content of sauces prepared from papain or bromelain were not significantly dif- There was no development of mould in the prepared ferent but the fat content of the sauce prepared with sauces kept at room temperature in glass bottles with papain was much lower than in the sauce prepared with screw caps for 12 weeks, indicating that the sauces can bromelain(Table3). This is perhaps due to more residue be stored under such conditions for at least 12 weeks.

198 ASEAN Food Journal Vol. 7, f\lo. 4, 1992 ACKNOWLEDGEMENT Kunkriangwong, J. Use of papaya milk and papain to improve qualityofbeeffrom old cow. (In Thai). Grateful acknowledgement is due to the National Kasetsart University, 1988. M.5 Thesis. Research Council of Thailand for providing the nec- essary financial assistance. Larmond, E. Laboratory methods for sensory evaluation of food. Research Branch, Dept. of RFERENCES Agriculture, Canada. Publication 1937. 1977.

AOAC. Official Methods of Analysis 13th ed. Wash- Raksakulthai, N., Lee Y.Z. and Haard N.F. Effect of ington D.C.: Association of Official Analytical enzyme supplements on the production of fish Chemists, 1980. sauce from male capelin (Mallotus vi1losus). Can. Inst. Food Sci. Techno!. J. 19: 28-33; 1986. Department of Science Services. Oyster sauces. Ministry of Science and Technology. 102-105 (In Thai). 1976. Thai Industrial Standards Institute (TIS!). Specifications for flavouring sauce. Bangkok: Ministry of In- Department of Customs. Foreign Trade Statistics of dustry, 1970. (In Thai). Thailand. Bangkok. 1987. TIS!. Standard for local fish sauce. Bangkok: Ministry ICMSF. Microorganisms in food. 1: The significance of Industry, 1983. (In Thai). and methods of enumeration. 2nd ed. Toronto: University of Toronto, 1987. TIS!. Standard for soy sauce. Bangkok: Ministry of Industry, 1987. (In Thai). Jittinun, S. and Saelim, J. Development of mollusc sauce products. Dept. of Food Science and Technology, Chulalongkorn University. (In Thai). 1985.

Kirimura, L Shimizu A., Kimizuka K., Ninomiya T. and Katsuya N. Contribution of peptides and amino acids to the taste of foodstuffs. J. Agric. Food Chern. 17: 689-695; 1969.

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