Solid-state 13C NMR investigation of molecular ordering in the cellulose of apple cell walls.
1994
Newman R.H. | Ha M.A. | Melton L.D.
A resolution-enhanced (13)C nuclear magnetic resonance(NMR) spectrum of cell wall material isolated from Braeburn apples has revealed a pair of signals assigned to cellulose chains exposed on crystal surfaces, providing evidence for a high degree of molecular ordering on those surfaces. Proton spin relaxation editing revealed no detectable amorphous cellulose and provided an estimate of about 23 chains in a typical crystallite. Cellulose in apple cell walls was found to be distinctive, with triclinic I alpha and monoclinic I beta crystalline forms present in similar proportions. Hence, its composition is intermediate between the family of bacterial and Valonia celluloses, rich in the triclinic crystalline form, and the family of cotton and ramie celluloses, in which the monoclinic form is dominant. Implications for apple crispness are discussed.
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