FISHERY BULLETIN: VOL. 71, NO. 1 



extraction stage was limited to 10 to 15 min 

 followed by centrifugation of the solids from 

 liquid. Under these conditions of extraction, 

 the residual lipid in the FPC is reduced to less 

 than 0.5%. Approximately 10 lb. from the last 

 stage centrifuged wet solids were used for dry- 

 ing experiments. 



To dry the wet solids, approximately 454 g 

 of wet solids were placed in an aluminum foil 

 dish and spread evenly to a depth of about 

 6.5 mm. Thermocouples were inserted into the 

 bed of solids for temperature recording. The 

 sample was then placed into a vacuum oven and 

 subjected to drying temperatures of (1) 40° to 

 50°C, (2) 60° to 70°C, (3) 90° to 100°C, (4) 

 110° to 120°C, or (5) 140° to 150°C for either 

 30 or 120 min. Residence time was from the 

 time the sample reached temperature. The sam- 

 ple, after drying, was milled in a Wiley milF 

 and passed through a 40-mesh screen. The 

 samples were then placed into polyethylene bags 

 for storage, and subsequent analysis. A control 

 was dried overnight at ambient temperature 

 and pressure. 



Methods of Analysis 



The following properties were determined: 



Salt soluble protein. — Two grams of FPC were 

 added to 50 ml of cold 5% NaCl (in 0.02 M 

 NaHCOa) and magnetically stirred for 3 hr 

 (Dubrow, 1971). The slurry was filtered 

 through Whatman *1 filter paper. The filtrate 

 was analyzed for nitrogen by Kjeldahl method 

 (Horwitz, 1965). Protein was calculated as 

 N X 6.25. 



Emulsion stability. — Two grams of FPC were 

 blended (Waring blender, Model *1083) in a 

 pint-size jar with 20 ml of 5% NaCl (in 0.02 M 

 NaHCOs) for 3 min at low speed. Twenty ml 

 of corn oil were added to the blender and the 

 entire mixture blended for 1.5 min at low speed. 

 Ten ml portions of the mix were then poured 



^ Reference to trade names does not imply endorse- 

 ment by the National Marine Fisheries Service, NOAA. 



into three graduated test tubes. The tubes were 

 placed in a water bath (at about 98°C) for 30 

 min and were then cooled in an ice water bath. 

 Since FPC is more lipophylic than hydrophylic, 

 measurements were taken of the volume of water 

 separated. If oil separated at the same time, 

 measurements were also taken of this phase. 

 Emulsion stability was calculated as the per- 

 centage of water (total) that separated from the 

 system. 



Residual isopropyl alcohol. — Residual IPA was 

 determined according to the method of Smith 

 and Brown (1969). 



Total volatiles. — Total volatiles were deter- 

 mined by placing a weighed sample in a 103°C 

 oven overnight; cooling in a dessicator and re- 

 weighing. 



RESULTS AND DISCUSSION 



Table 1 shows the results of drying temper- 

 ature and time upon the protein solubility of 

 the FPC solids. The wet solids, prior to drying, 

 had about 36.6% soluble protein. In compar- 

 ison, wet solids produced by extraction at 70° 

 to 80°C prior to drying contained only 3% sol- 

 uble protein. Drying overnight under ambient 

 conditions resulted in very little loss in solubility 

 (36.4% ) . Vacuum drying at 40° to 50°C showed 

 a 15-18% decrease in soluble protein over the 

 ambient dried sample. Variable and unexplain- 

 able results were obtained by drying at 60° to 

 70°C: the soluble nitrogen was less after 30 

 min drying than after 120 min. Increasing the 

 drying temperature to 90° to 100°C or to 110° 

 to 120 °C produced a further decrease in protein 

 solubility. Drying at 140° to 150°C resulted 

 in about a 65% decrease in solubility from the 

 starting wet solids. 



The emulsifying stability of the dried FPC's 

 produced under the various conditions of drying, 

 showed that ail treatments, except the FPC's 

 dried at 140° to 150°C formed stable oil: water 

 emulsions (Table 1). Separation of oil and 

 water occurred with the FPC's dried at 140° to 

 150°C. 



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