Molecular basis of the gelatinisation and swelling characteristics of waxy barley starches grown in the same location during the same season. II. Crystallinity and gelatinisation characteristics
2004
Qi, X. | Tester, R.F. | Snape, C.E. | Yuryev, V. | Wasserman, L.A. | Ansell, R.
Nine waxy barley samples (grown at the same site during the same season) were investigated to identify those molecular aspects of amylopectin structure and architecture which define the order and gelatinisation characteristics. Using 13C CP-MAS/NMR it was confirmed that the number of double helices within the starches were approximately constant although differences in crystallinity were identified by X-ray diffraction. These differences in terms of amount of crystalline order correlated well with gelatinisation temperatures. The onset (T(o)), peak (T(p)) and conclusion (T(c)) gelatinisation temperatures were 53.4, 59.2 and 68.1 degrees C on average with the associated enthalpy (deltaH) of 11.0 and 13.5 J g(-1) on a starch and amylopectin basis. Annealing of the starches below T(o) elevated T(o), T(p) and T(c) by + 11.9, +8.2 and +5.1 degrees C on average and sharpened the gelatinisation range (T(c) - T(o)). Acid hydrolysis after annealing increased T(o), T(p) and T(c) (especially T(c)) by +2.3, +17.4 and +34.7 degrees C on average. Annealing in the presence of alpha-amylase elevated similarly the gelatinisation parameters by +10.2, +7.1 and +2.8 degrees C for T(o), T(p) and T(c), respectively. Crystalline lamellae lengths were found to be 5.2 +/- 0.7 and 6.2 +/- 0.4 nm using high sensitivity differential scanning micro-calorimetry and differential scanning calorimetry, respectively.
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