Foam volume freeze-dried

Foam Volume. The determination of foamability was carried out using the procedure of Hermansson et al. (9.) with modifications. A 1 g sample of the freeze-dried protein fraction was homogenized with 90 ml of citrate-phosphate buffer in a Sorvall Omnimixer at 3000 rpm. The resultant foam and liquid were transferred to a 250 ml graduated cylinder and the mixer cup washed with 10 ml of buffer. The cup was drained for 2 min and the cylinder allowed to stand for 30 min at which time the foam volume was measured. The influence of pH and ionic strength on foam volume was established using the buffer systems previously described. 

NMR. Quantitative liquid-state carbon-13 nuclear magnetic resonance ( 3c NMR) spectra were recorded for humic and fulvic acid from Como Creek foam and for stream and foam fulvic- and humic- acid samples from the Suwannee River at the U.S. Geological Survey, laboratory in Arvada, CO. C NMR could not be performed on other humic substances due to insufficient sample or instrument availability. The acquisition parameters used were as follows C NMR spectra were recorded on a Varian XL-300 NMR spectrometer at 75 MHz. Each sample (200 mg of freeze-dried material) was dissolved in deuterated water and deuterated sodium hydroxide was added to ensure solution a total solution volume of approximately 6 to 7 mL. Spectra were recorded using a 30,000 Hz spectral window, a 45 pulse width, a 0.199 second acquisition time, and a pulse delay of 10 seconds for quantitative spectra. The number of transients was 10,000, and line broadening was 50 Hz. 

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