T2 distribution of boiled dry spaghetti measured by MRI and its internal structure observed by fluorescence microscopy

Abstract The T 2 distribution change of boiled dry spaghetti was evaluated by MRI T 2 maps and T 2 profiles, in which T 2 values were plotted against the distance from the surface. Morphological observations of its internal structure were conducted using fluorescence microscopy. The T 2 values monotonically decreased with the increase of the distance from the surface of boiled dry spaghetti, during the earliest stage after boiling. As the holding period increases from 10 to 120 min, the T 2 value decreases at the surface and increases at the spaghetti center. This is possibly owing to moisture redistribution in the boiled dry spaghetti during the holding period. Three slope-change points and four distinct slope regions were observed in the T 2 profile after a 120-min holding period, indicating that the T 2 gradient differed between the four regions after the moisture redistribution process. Differences in the degree of starch granule swelling and disintegration were observed using fluorescence microscopy. Appearance of the different slope regions in the T 2 profile is suggested to be related to regional differences in the degree of gelatinization in boiled dry spaghetti. One of the slope-change points in the T 2 profile was used to estimate the proportion of a less gelatinized region relative to the whole area of the cross-section. The total moisture content of the boiled spaghetti determined this proportion, regardless of the diameter of dry spaghetti before boiling. These findings indicate that monitoring changes in the T 2 profile of boiled dry spaghetti during the holding period is a useful method for evaluating differences in the internal microstructure and the degree of starch gelatinization, which affected the changes in the moisture distribution.