A COMPARISON OF PROTEIN ASSAYS FOR THE DETERMINATION OF THE PROTEIN CONCENTRATION OF BEER

Seven protein assays have been compared for determination of the protein content of beer. Dialysis and ultrafiltration have been used to investigate possible interference and the protein content of the samples has been simultaneously monitored by sodium dodecyl sulphate-polyacrylamide gel electro-phoresis. The Fisons NA2000 Nitrogen/Protein Analyzer gave identical results to the standard Kjeldahl method but both measure nitrogen-containing compounds rather than protein. Colorimetric methods based upon the biuret reaction (including the Lowry and bicinchoninic acid protein assays) are particularly prone to interference from reducing substances and gave protein concentration values dependent upon the sample volume. The protein dye-binding assays (Coomassie Brilliant Blue and pyrogallol red-molybdate methods) were optimal for beer protein analysis displaying minimal inter ference and giving reproducible protein concentration values consistent with the protein content of the beers as indicated by electrophoresis.     

Inherent Variability in the Efficacy of the USDA Raw-Pack Process for Home-Canned Tomatoes

Studies of the USDA raw-pack process for home-canned tomatoes, using Bacillus licheniformis spores as the target organisms, revealed that water bath size and canning load did not affect heat penetxation rates in pint jars of tomatoes. However, because decreases in the water bath size and canning load shortened the come-up time and, as a result, lowered the maximum cold-spot temperature; the calculated process lethalities were lessened. Properly executed canning runs which varied in water bath size, amount of water in the bath, and load size produced calculated lethalities ranging between 1 and 7 log reduction.     

Constitution of Fireclays at High Temperatures: III, Deformation Characteristics

The hot-pressing characteristics of kaolin, fireclay, and plastic fireclay were determined between 1150° and 155O°C at 3000 to 10,000 psi under oxidizing conditions. Each clay could be pressed to near its true density at an optimum temperature. Insufficient temperature produced low bulk density; excessive temperature caused bloating. Synthetic glasses were prepared to represent the composition of the liquid phase estimated to be present at the optimum pressing temperature. Viscosities of the synthetic glasses were measured, and those of the optimum pressing temperature were estimated. The deformation characteristics are in reasonable accord with the Mackenzie and Shuttleworth hot-pressing equation for viscous flow.