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Ultrafiltration/Reverse Osmosis Concentration of Lobster Extract C University of Rhode Island DigitalCommons@URI Past Departments Faculty Publications College of Health Sciences 1999 Ultrafiltration/Reverse Osmosis Concentration of Lobster Extract C. N. Jayarajah University of Rhode Island C. M. Lee University of Rhode Island Follow this and additional works at: https://digitalcommons.uri.edu/chs_past_depts_facpubs Terms of Use All rights reserved under copyright. Citation/Publisher Attribution Jayarajah, C. N. and Lee, C. M. (1999), Ultrafiltration/Reverse Osmosis Concentration of Lobster Extract. Journal of Food Science, 64: 93-98. doi: 10.1111/j.1365-2621.1999.tb09868.x Available at: http://dx.doi.org/10.1111/j.1365-2621.1999.tb09868.x This Article is brought to you for free and open access by the College of Health Sciences at DigitalCommons@URI. It has been accepted for inclusion in Past Departments Faculty Publications by an authorized administrator of DigitalCommons@URI. For more information, please contact [email protected]. JOURNAL OF FOOD SCIENCE ENGINEERING/PROCESSING Ultrafiltration/Reverse Osmosis Concentration of Lobster Extract C. N. Jayarajah and C. M. Lee ABSTRACT town, CT) for 10 min to prepare supernatant and sediment for analyses of free amino ac- A membrane concentration system consisting of tubular polysulphone ultrafiltra- ids, nucleotides and organic acids. tion (UF) and polyamide reverse osmosis (RO) was evaluated for concentrating key water soluble flavor compounds from lobster extracts. Major flavor-giving Proximate analysis 9 compounds in the extract were glutamic acid, glycine, arginine, uridine 5 -mono- Proximate analysis was carried out accord- phosphate (UMP), succninic acid and glucose. Factors affecting performance of ing to AOAC (1975). The total protein nitro- the UF/RO systems, such as flow rate, feed solid level, temperature and pressure, gen content of the fractions was determined on permeate flux and solids rejection were measured. The optimum UF conditions by the micro-Kjeldhal method. The non-pro- 8 were 1.5% feed solid level, 15 L/min feed flow rate, 50 C feed temperature and 1 tein nitrogen content was determined after MPa log mean transmembrane pressure. The RO system retained all dissolved precipitating the protein with 10% trichloro- 8 flavor components and its ideal operating conditions were 40 C, 2.8 MPa log mean acetic acid. transmembrane pressure and a flow rate of 15 L/min. Key Words: UF/RO, membrane concentration, lobster extract, flavor HPLC analysis of free amino acids Free amino acids were analyzed by a Per- kin-Elmer HPLC Series 4 Solvent Delivery INTRODUCTION viable to separate protein from surimi waste System (Perkin-Elmer Corp, Norwalk, CT) KEY FLAVOR CONSTITUENTS IN SEAFOOD streams by a thin film tubular composite UF equipped with a cation exchange column (AA are reported to be primarily water soluble membrane (Mohr et al., 1989). The RO mem- 911, Interaction Chemicals, Mountain view, including low molecular weight free amino brane concentration is the most energy effi- CA) and a Rheodyne injector (Cadet, CA) acids, nucleotides, organic acids and sugars cient of those processes and it should be eco- with a 6 mL loop. Total protein nitrogen was (Hayashi et al., 1978, 1979, 1981; Konosu nomical to remove 2/3 of the water by RO determined on 6N HCl hydrolyzed samples. et al., 1978). A synthetic mixture may be and 1/3 by evaporation (Kessler, 1986). After evaporating to dryness, samples were formulated based on a flavor profile, but sen- Our major objectives were to evaluate the dissolved in 5 mL 0.1N HCl and filtered sory tests indicate that a formulated extract performance of a UF/RO tubular membrane through 0.22 µm cellulose nitrate filters (What- had mild and weaker “body” compared to a system for lobster flavor recovery on the ba- man, Clifton, NJ) prior to injection onto the boiled crab extract (Konosu and Yamaguchi, sis of permeate flux and solids rejection and HPLC column. Analysis was done in tripli- 1986). Thus, a full bodied flavor extract may to analyze flavor constituents in raw extracts. cate. For HPLC analysis, the mobile phase meet consumer demands if the flavor-giving consisted of two sodium citrate buffers of in- compounds come from crabmeat. Major MATERIALS & METHODS creasing pH (3.15 and 7.40) and was pumped production concerns are reliability of raw ma- at 0.5 mL/min. A step-wise gradient elution terial, recovery of volatile and nonvolatile Extraction procedure for feed was followed for 60 min. The HPLC grade components during extraction and potential solutions sodium citrate buffers (Pierce, Rockford, IL) loss of heat-labile flavor constituents during The extraction process (Fig. 1) involved were filtered through 0.45 µm Nylon-66 fil- concentration. thawing lobster bodies in water to facilitate ters (Ranin Instrument Co., Woburn, MA) Recovery processes may involve evapo- removal of carapace and sand, followed by and degassed using helium before analysis. ration, freeze concentration or membrane sep- washing in a jet stream of water to discard Free amino acids were identified from reten- aration. Evaporation may destroy thermally unwanted entrails. The clean lobster bodies tion time using amino acid standards in 0.1N labile compounds and volatiles may escape were then ground at moderate speed using a HCl. The separated amino acids from the col- (Koseoglu et al. 1990). Freeze concentration meat grinder (Model A-120, Hobart Manu- umn were derivatized on a post-column reac- has been used to separate lobster flavor com- facturing Co., Troy, OH) with neither blade tion system which consisted of two Perkin- pounds without heat-induced flavor loss, but nor perforated plate, but with a screw installed. Elmer Series 10 reagent pumps for OPA and results in low yield (Jayarajah and Lee, 1987; Minced product was combined with an NaOCl solutions. The reaction was tempera- 1988). Membrane processes using thin film amount of water half the weight of the mince ture controlled at 528C. The isoindole deriva- tubular membranes with high solute retention and steam-cooked 20 min to extract water tives formed were detected by a LC-10 Per- have been commercially exploited in fruit juice soluble flavor components and inactivate kin-Elmer filter fluorescence detector with concentration (Pepper et al., 1989). Alvarez et spoilage causing enzymes and microorgan- excitation at 350 nm and emission at 418-700 al. (1997) evaluated process variables in con- isms. The cooked diluted mince was filtered nm. Data collection and calculation based on centrating apple juice by RO using a polya- through cheese cloth to produce a filtrate (the areas were performed with Chrom2 Software mide tubular membrane. It is commercially first extract). The retentate was pressed using on a Perkin-Elmer 3600 Data station connect- a Carver laboratory press (Carver Inc., Meno- ed to a Perkin-Elmer 660 printer. monee Falls, WS.) to a maximum pressure of 14 MPa to express mince juice. The com- HPLC analysis of nucleotides Authors Jayarajah and Lee are affiiated with the bined first extract and pressed juice was used The nucleotide analysis was carried out Dept. of Food Science & Nutrition, Univ. of Rhode Island, Kingston, RI 02881. Address inquiries to as feed stock for the UF/RO operation. Part following the method developed by McKeag Dr. C. M. Lee. of the extract was centrifuged at 2420g in a and Brown (1978) using a Perkin-Elmer Se- Sorvall refrigerated centrifuge (RC2-B, New- ries 3B liquid chromatograph fitted with a © 1999 Institute of Food Technologists Volume 64, No. 1, 1999—JOURNAL OF FOOD SCIENCE 93 UF/RO Concentration of Lobster Extract . Rheodyne injector which had a 6 µL loop. to use. Initially an isocratic elution with a low Woburn, MA) and injected onto the HPLC The system consisted of a strong anion ex- concentration mobile phase was carried out column in triplicate. The nucleotide standards change, Partisil 5 SAX RACII column (4.6 for 5 min followed by a 35 min linear gradient obtained from Sigma Chemicals (St Louis, mm 3 10 cm) (Whatman, Clifton, NJ). The (0–100%) elution and finally an isocratic elu- MO) were diluted to 0.10 mM with doubly- ion-exchange moiety was a quaternary nitro- tion with a high concentration buffer. Each deionized water. The standards were stored at gen which was Si-O-Si bonded to partisil. run lasted for 65 min including 15 min of 2208C. The eluted nucleotides were detected The column was protected by a guard column reequilibration. The separation of compounds at 254 nm and 0.10 AUFS sensitivity using a 3 8 (5 cm 4.6 mm) filled with pellicular C18 was conducted at 50 C and a flow rate of 2.0 variable length Perkin-Elmer LC-95 UV/Vis- packing material (Whatman). Doubly-deion- mL/min. The column was flushed with dou- ible Spectrophotometer, and identified from ized water was used to make all buffers. The bly-deionized water and stored in HPLC qual- retention times. Data collection and calcula- pH of low concentration aqueous buffer con- ity 100% methanol when not in use. Sample tion were done in the same setup used for sisting of 0.007M KH2PO4 and 0.007M KCl preparation was similar to that reported by amino acid analysis. was adjusted to 4.0 with dilute phosphoric Khym (1975). The protein was precipitated acid. The high concentration eluent was made by addition of 2 parts of trichloroacetic acid HPLC analysis of organic acids, sugars and alcohol with 0.25M KH2PO4 and 0.50M KCl and its (6% by weight) and centrifuged. After the pH pH was adjusted to 5.0 with dilute KOH. All of the supernatant was adjusted to neutral, the Analyses of organic acids, sugars and al- solvents were filtered through a 0.45 mm supernatant was filtered through 0.22 mm cohol followed the method of McCord et al.
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