Prediction of postharvest dry matter, soluble solids content, firmness and acidity in apples (cv. Elshof) using NMR and NIR spectroscopy: a comparative study

Dry matter (DM), soluble solids content (SSC), firmness and acidity by proton nuclear magnetic resonance (NMR) T2 relaxometry and near infrared (NIR) spectroscopy were investigated on a total of 390 apples (cv. Elshof). The fruit came from four different pre- or postharvest treatments and covered a large range of DM (11.4–20.0 %) and SSC values (10.5–18.3 °Brix). NIR was superior in predicting DM (R2 = 0.82) and SSC (R2 = 0.80), compared to NMR (R2 = 0.50 and R2 = 0.58). However, NMR relaxometry was able to detect multiple water populations assigned to different water pools in the apples and variation in the water distribution between different pre- and postharvest treatments. Differences in the mobility of the vacuole water (population T24) were consistent with changes in fruit firmness. In conclusion, even though NIR is superior in predicting DM and SSC, NMR provides useful information about the intrinsic water state and its distribution in the fruit.