UBC Theses and Dissertations
The utilization of heat coagulated beer wort protein (trub) Yeow, Tony
Trub obtained from the brewing process was extracted using isopropanol as solvent to yield a bitter hop resin fraction and an insoluble protein complex. The protein was subjected to an amino acid analysis; lysine was the limiting amino acid in trub protein, followed by isoleucine. Its essential amino acid index was approximately equivalent to that of barley protein. Functionally, it was found that trub protein had poor solubility, particularly at acid pH values, but that its water-holding capacity was good. Quantitative evaluation of the trub resin was carried out by lead conductometry, the lead conductance value of 68% being used as a guide to potential brewing value. The extracted resin was also examined qualitatively for its bittering potential by TLC. Although many resin components were separated by means of TLC, difficulties with identification yielded inconclusive results in this area. Finally, the bittering capacity of the trub resin was organoleptically compared to fresh hops in prepared beers. Trub resin was capable of bittering beer but imparted a harsher character to beer than fresh hops. Moreover, the resin tended to inhibit the formation of a stable yeast head during the ale fermentation. Finally, the actual resin extraction procedure was empirically examined to determine the combined effect of agitation and solvent-ratio on the yield of resin and protein. Protein yield was unaffected by these 2 factors, but resin yield was found to be most efficient when employing maximum agitation and using the minimum amount of solvent. Using more solvent did not significantly increase resin yield and tended to depress the effect of agitation.
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