Evaluation of low field (5.40-MHz) proton magnetic resonance measurements of D-w and T-2 as methods of nondestructive quality evaluation of apples

A 5.40-MHz NMR system was used for measuring the self-diffusion coefficient of water (D-w) and the spin-spin relaxation constant (T-2) in apple (Malus xdomestica Borkk) tissue. The pulsed field gradient spin echo (PFGSE) tech nique was used to measure D-w, and the Carr-Purcell-Meiboom-Gill (CPMG) tec hnique was used to measure T-2. T-2 and D-w values were compared for apples with differing amounts of soluble solids concentration (SSC) and with and without internal defects, such as bruising, watercore, and internal brownin g,'Granny Smith','Golden Delicious', and 'Delicious' apples were tested, In 'Golden Delicious', D-w highly correlated with apple tissue SSC (P < 0.002 , r(2) = 0.68), This indicates that D-w could potentially be used for sorti ng 'Golden Delicious" apples based on SSC, but the coefficient of determina tion needs to be improved before it would be commercially viable. There wer e no measurable differences in D-w among healthy apple tissue and tissue af fected by either watercore or internal browning, T-2 values showed no relat ionship between healthy apple tissue and bruised tissue in 'Golden Deliciou s' and 'Granny Smith'. However, in 'Delicious' tissue, T-2 values were stat istically different between healthy and bruised tissue (P < 0.02), Further comparisons in 'Delicious' between watercore and healthy apple tissue showe d no differences. But, there were statistical differences found between T-2 in healthy apple tissue and tissue with internal browning (P < 0.01), Thes e results indicate that T-2 could potentially be used for separating 'Delic ious' apples with internal browning or with bruising from healthy apples. T itratable acids and pH were correlated for 'Golden Delicious' (P < 0.08), T his correlation is significant because one may be able to noninvasively mea sure pH in 'Golden Delicious' apples using NMR, which could then be correla ted to titratable acids.