78 MARINE PRODUCTS OF COMMERCE 



superior and without actual data of their important properties. Such claims usually 

 arise from enthusiasm and should be regarded with skepticism unless actual 

 physical data are presented in reproducible units. Furthermore, no phycocolloid 

 can be said to be generally superior to another. Superiority must be stated in 

 specific terms. Japanese agar is not superior to Irish moss gel as a stabilizer for 

 chocolate milk; Irish moss gel (in its present forms) will never replace agar 

 as a bacteriological culture medium. 



Hypnea Agar— A New Type. Hijpnea musciformis, which is common along the 

 Atlantic coasts of North, Central, and South America, was first studied as a 

 source of agar in 1942 (Humm). Preliminary results were variable and puzzling 

 until it was realized that all solutes have a profound effect upon the physical 

 properties of the Hypnea extractive. Several publications (DeLoach et al., 1946; 

 Himim and Williams, 1948) and a patent (Humm, 1948) discuss these phe- 

 nomena in some detail. 



There is no fundamental diflFerence between the reaction of Hypnea gel to 

 solutes and that of Irish moss gel (discussed on page 59), ordinary agar, and 

 other phycocolloids obtained from red algae. In the case of Hypnea, however, the 

 efiFect of solutes on physical properties is greatly magnified, with the result that 

 these properties can be controlled over a remarkably wide range in respect to gel 

 strength, temperature of gelation and melting, viscosity, and other characteristics. 

 The efiFect of solutes on Gelidium and Gracilaria agar is so slight that detection 

 is almost impossible, while Irish moss gel is intermediate in reaction. 



The influence of various electiolytes is apparently in the order of the lyotropic 

 series, with the cations exerting more influence than the anions. Non-electrolytes, 

 such as sugars and alcohols, both simple and complex, are also very active as gel 

 conditioners although studies of their relative eflFects have not yet been published. 

 In equimolar concentrations there is evidence, subject to re-examination, that 

 the alcohols are effective in the following (decreasing) order: methyl and ethyl 

 alcohol, propylene glycol, ethyl and methyl "Cellosolve," ethylene glycol, di- 

 ethylene glycol, and glycerin. The efiFect is apparently a result of the relative 

 hydration of the alcohol in the presence of a solution of Hypnea extractive. 



Hypnea musciformis is known to occur in commercial abundance in three areas: 

 the vicinity of Beaufort, N. C, Tampa Bay, Florida, and along the coast of Brazil 

 between Recife and Aracaju. In North Carolina, where commercial quantities 

 were harvested in 1945 and 1946, the species is abundant usually from May 

 through July; in the Tampa Bay area the greatest annual development occurs from 

 December through February. In both localities plants that break loose, drift, and 

 accumulate in certain areas constitute the stage of potential commercial value. 

 There is considerable annual variation of abundance. In Brazil attached plants 

 occur in quantity between the reef and the beach and apparently are not seasonal, 

 although collecting and drying would probably be limited to the dry season, 

 October through March. 



Since the colloid obtained from Hypnea is soluble in cold water, drying of the 

 seaweed must occur without excessive rain. Once dry, Hypnea can be washed 

 briefly in fresh water without loss of its gelose. Carefully washed Hypnea, from 

 which all but traces of salts have been removed, can be extracted in pure water 

 at room temperature with the formation of a clear, viscous sol. If the concentration 

 of solutes (other than the Hypnea colloid) is low enough, gelation does not occur, 



