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Savory Peptides Present in Moromi Obtained from Soy Sauce Fermentation of Yellow Soybean 1
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Hanifah Nuryani Lioe , AntonApriyantono ,Dedi Fardiaz , Budiatman Satiawihardja , Jennifer M. Ames , and Elizabeth L. Inns 1
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Department of Food Technology and Human Nutrition, Faculty of Agricultrual Technology, Bogor Agricultural University, P.O. Box 220, Bogor 16002, Indonesia School of Food Biosciences, The University of Reading, Whiteknights, Reading RG6 6AP, United Kingdom 2
The presence of savory peptides in moromi has been investigated. Moromi was prepared by fermenting yellow soybean using Aspergillus oryzae as the starter at the first step (mold fermentation) and 20 % brine solution at the next step (brine fermentation). The moromi was then ultrafiltered stepwise using membranes with M W cut-offs of 10,000, 3,000, and 500 Da, respectively. The fraction with MW < 500 Da was chromatographed using Sephadex G-25 SF to yield four fractions, 1-4. Analysis of soluble peptides, NaCl content, α-amino nitrogen, amino acid composition, peptide profile using CE coupled with DAD, taste profile and free glutamic acid content, were performed for each fraction. Fraction 2 contained a relatively high total glutamic acid content, but a relatively low free glutamic acid content and had the highest umami taste. This fraction also had more peptides containing non-aromatic amino acids than the other fractions. The peptides present infraction2 may play a role, at least in part, in its intense umami taste.
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© 2004 American Chemical Society
In Challenges in Taste Chemistry and Biology; Hofmann, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2003.
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Introduction It is known that many peptides have taste, i.e., bitter, sweet, sour, salty and umami. These peptides were isolated from cheese (11, 12), beef broth (31), hydrolyzed soy protein (17), miso (27), soy sauce (16), fish protein hydrolysate (20), as well as synthesized in the laboratory (21, 32). Savory peptides had interested scientists attention since Yamasaki and Maekawa reported the isolation of a "delicious" peptide from beef broth in 1978. The peptide was an octapeptide having the primary structure Lys-Gly-Asp-GluGlu-Ser-Leu-Ala. Later, this peptide was called as the "beefy meaty peptide" (BMP) and the synthesized one had a meaty (31), umami, savory (28) taste. Now, BMP is called STEP (savory taste-enhancing peptide), i.e. a peptide that is able to enhance savory taste (26). Soy sauce is one of the fermented soybean products (13) which is rich in flavor due to either volatile (2, 24) or non-volatile compounds (3, 4, 17, 22). Apriyantono et al. (4) investigated sensory and peptide characteristics of soy sauce and its fractions obtained by ultrafiltration. They reported that peptides with molecular weight of less than 500 Da may play a role, at least in part, in increasing the intensity of the umami taste. It is very likely that some peptides having an umami taste are present in soy sauce, but they have not been identified yet. Therefore, attempts have been made to obtain the fractions containing peptides that are responsible for the umami taste, by further fractionation of moromi fraction with molecular weight of less than 500 Da. These fractions were then characterized chemically and sensorially and their peptides profiles were determined.
Materials and Methods Materials Materials for moromi preparation, i.e., yellow soybean and salt were obtained from a local market in Bogor (Indonesia). Dry culture of Aspergillus sojae was obtained from Konno Moyashi Co. (Kobe/Osaka, Japan). Moromi Preparation Yellow soybean was boiled in water (1:3 w/v) for one hour, cooled and drained. Cooked soybean was inoculated with 0.5 % (w/w) Aspergillus sojae
In Challenges in Taste Chemistry and Biology; Hofmann, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2003.
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182 starter. Inoculated soybean was incubated at room temperature for three days to obtain koji. Koji was soaked in 20 % brine solution (1:3 w/v) and then incubated at room temperature for eight weeks. The resulting fermentated product was called moromi. The moromi was homogenized, put in cheesecloth and then pressed by hand. The suspension obtained was centrifuged at 14 000 rpm for 10 minutes at 4 °C. Once centrifiigationfinished,the fat layer at the top was discarded, moromi liquid was then collected. Such preparation was done in three replicates. Ultrafiltration Process Moromi liquid was submitted to ultrafiltration cell at temperature 2-4 °C under 2-3 bar N pressure using 50 mL stirred cell ultrafiltration unit (Amicon, Inc., Beverly, MA). Stepwise ultrafiltration was carried out using a 0.45 μιη porosity membrane followed by Y M 10 (molecular weight cut-off/MWCO 10 000 Da), Y M 3 (MWCO 3 000 Da) and YC 05 (MWCO 500 Da) membranes (Amicon, Inc., Beverly, MA) . The fraction with molecular weight of less than 500 Da (Fraction MW
