The water peak was suppressed
by irradiation of the water signal with a weak pre-saturation pulse.
Prior to Fourier transformation, the data was multiplied by a 0.3 Hz
line-broadening function. The 1H NMR spectra were manually
phased and baseline-corrected. Organic acids were identified from
spectra obtained from standard compounds and previous results
(Clausen et al., 2012). Peak area was determined by signal integration
and expressed relative to the internal standard, TMSP. Malic
acid was quantified by the doublet doublet (dd) signal at 2.4 ppm
and citric acid by the ½ dd signal at 2.6 ppm.