DUBROW: FISH PROTEIN CONCENTRATE 



60r 



50- 



40- 



30- 



20- 



400 



500 



600 



700 



WAVE LENGTH mii 



Figure 1. — Reflectance spectra of FPC's steam desolven- 

 tized, as either dry solids or alcohol wet solids, at 2 to 3 

 psi for or 10 min. 



protein solubility as compared to the nonsteamed 

 sample. 



The emulsifying capacity and stability of the 

 treated solids was affected in a manner similar 

 to that for protein solubility. Both the non- 

 steamed and the 0-min treated samples of FPC's 

 emulsified in oil and water systems. On the 

 other hand, the solids steamed for 5 and 10 min 

 showed a decrease in emulsion stability. 



Steam desolventization of the dry solids re- 

 duced the residual IPA with each increment 

 of exposure time. The initial residual content 

 was 55,000' ppm, and after 10 min the level was 

 found to be 367 ppm. The total volatiles of the 

 treated solids ranged from 6.4% (0 min) to 

 4.9% (10 min). 



The color of the FPC's after steaming showed 

 only a slight darkening. The color changed from 

 a grayish tan to a slight yellowish tan with re- 

 spect to time of exposure. Hunter L, a, and b 



values are presented in Table 3. Figure 1 illus- 

 trates the reflectance spectra for the 0-min and 

 10-min FPC's and shows that the 10-min steamed 

 dry solid sample was similar in its reflectance 

 to the 0-min steamed wet solid sample; whereas 

 the 0-min steamed dry solid was much lighter. 



CONCLUSIONS 



Two critical steps in the preparation of FPC 

 by low temperature extraction with IPA are the 

 drying and the desolventizing. Both stages in- 

 volve heating: either dry or moist heat, or both. 

 The results of this study showed that drying 

 alcohol wet FPC solids at ambient conditions 

 resulted in negligible loss in soluble protein and 

 emulsifying capacity. Hot air drying of the wet 

 solids, under vacuum, at temperatures ranging 

 from 40° to 50°C to 110° to 120°C for 30 or 120 

 min resulted in a temperature dependent de- 

 crease in protein solubility. The dry FPC's, 

 however, still retained emulsifying capacity. 

 Under these drying conditions, the residual IPA 

 was reduced to 2 to 3%. Higher drying tem- 

 peratures of 140° to 150°C resulted in further 

 loss of protein solubility and a complete loss in 

 emulsifying capacity. 



Removal of residual IPA, to a level of less 

 than 250 ppm, by steam desolventization, was 

 faster for wet solids than for dry solids. This 

 procedure, however, brought about a 70% loss 

 in protein solubility, a complete loss in emulsion 

 stability, and a significant darkening of the 

 product as compared to steam dry solids. 



A similar loss in functionality, but at a slower 

 rate and with less darkening of the FPC's, re- 

 sulted from steaming dry solids. 



Low temperature extraction coupled with low 

 temperature drying produced FPC with greater 

 functional properties than that produced by high 

 temperature drying. To retain this function- 

 ality, methods other than steaming appear to be 

 necessary. 



ACKNOWLEDGMENT 



The author wishes to extend his deepest ap- 

 preciation to Thomas BroAvn for his valuable as- 

 sistance in the course of this work. 



103 



