Application of the plastein reaction to mycoprotein: I. Plastein synthesis

The plastein reaction has been applied for the first time to mycoprotein fo llowing in situ digestion of crude material to solubilise protein and produ ce the required initial peptide mixture. Pepsin was found to be superior to the other proteinases tested (trypsin, chymotrypsin, papain, Streptomyces griseus proteinase) in the plastein synthesis step although in all cases yi elds of insoluble plastein were low (10-15%). Unusually, plastein yield was not much influenced by pH over the range 3.0-7.5, but percentage yield inc reased almost linearly over the peptide concentration range 11-43% (w/w) wh ile the absolute yield of plastein increased exponentially over this range. Incubation at different temperatures showed that the rate of plastein form ation was highest at 65 degreesC, reaching a maximum in 4-5 h but, although not reaching maximum yield for 24 h, a temperature of 37 degreesC gave app roximately 25% greater yield. In general terms, the results suggested that mycoprotein peptides represented a rather poor substrate for plastein synth esis and only opaque, viscous solutions were obtained rather than the more common thixotropic gel structures. (C) 2001 Elsevier Science Ltd. All right s reserved.