The metabolome following intake of onion by-products is evaluated. Thirty-two rats were fed a diet containing an onion by-product or one of the two derived onion by-product fractions: an ethanol extract and the residue. A 24 hour urine sample was analyzed using (1)H NMR spectroscopy in order to investigate the effects of onion intake on the rat metabolism. Application of interval extended canonical variates analysis (ECVA) proved to be able to distinguish between the metabolomic profiles from rats consuming normal feed and rats fed with an onion diet. Two dietary biomarkers for onion intake were identified as dimethyl sulfone and 3-hydroxyphenylacetic acid. The same two dietary biomarkers were subsequently revealed by interval partial least squares regression (PLS) to be perfect quantitative markers for onion intake. The best PLS calibration model yielded a root mean square error of cross-validation (RMSECV) of 0.97% (w/w) with only 1 latent variable and a squared correlation coefficient of 0.94. This indicates that urine from rats on the by-product diet, the extract diet, and the residue diet all contain the same dietary biomarkers and it is concluded that dimethyl sulfone and 3-hydroxyphenylacetic acid are dietary biomarkers for onion intake. Being able to detect specific dietary biomarkers is highly beneficial in the control of nutritionally enhanced functional foods.

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Summary• Polyphosphate (polyP) is presumably central to phosphate (P) metabolism of arbuscular mycorrhizal (AM) fungi, but its synthesis, location and chain lengths are poorly characterized. Here, we applied noninvasive and nondestructive nuclear magnetic resonance (NMR) spectroscopy to obtain novel information on AM fungal polyP.• In vivo 31 P NMR spectroscopy was used to characterize polyP and other P pools in external hyphae and in mycorrhizal roots of associations between Glomus intraradices and cucumber ( Cucumis sativus ).• A time-course study of P-starved external hyphae supplied with additional P showed that polyP appeared more rapidly than vacuolar inorganic P. These P metabolites also appeared in the roots, but later. PolyP considerably exceeded amounts of vacuolar inorganic P, where it was located in acidic, presumably vacuolar compartments, and had a short average chain length.• The rapid synthesis of polyP might be important for the maintenance of effective hyphal P uptake. Our data support the hypothesis that polyP is the major P species translocated in the tubular vacuolar network, the presence of which was previously demonstrated in AM fungi.

The objective of this study was to develop a calibration model between time-domain low-field nuclear magnetic resonance (LF-NMR) measurements and dry matter (DM) content in single potatoes. An extensive sampling procedure was used to collect 210 potatoes from eight cultivars with a wide range in DM content, ranging from 16 to 28%. The exponential NMR relaxation curves were resolved into four mono-exponential components using a number of solution diagnostics. Partial least-squares (PLS) regression between NMR parameters (relaxation time constants T(2,1-4) and magnitudes M(0,1-4)) and DM content resulted in a model with low error (RMSECV, 0.71; RMSEP, 0.60) and high correlation (r(CV), 0.97; r(test), 0.98) between predicted and actual DM content. Correlation between DM content and each of the proton populations revealed that M(0,1) (T(2,1), 3.6 ms; SD, 0.3 ms; r, 0.95) and M(0,4) (T(2,4), 508 ms; SD, 53 ms; r, -0.90) were the major contributors to the PLS regression model.

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