On the molecular structure of the amylopectin fraction isolated from "high-amylose" ae maize starches.
The amylopectin fractions from starch of a series of amylose-extender (ae) maize samples (HYLON(®) V, VII and VIII starches) were isolated and analysed for their molecular composition and structure. The fractions from all samples contained both a high and a low molecular weight fraction (HMF and LMF), of which LMF increased with the amylose content of the starch and appeared to have substantially more of long chains than HMF. A normal amylose-containing maize starch (NMS), which served as a reference sample, contained very little LMF, which suggested that LMF was the inherent result of the effect of the loss of starch branching enzyme IIb activity in the ae mutants. Clusters were isolated from the amylopectin fractions using Bacillus amyloliquefaciens α-amylase, which effectively hydrolyses long internal chain segments between clusters. During the hydrolysis process, clearly more of small dextrins were released from the ae starches in comparison to NMS. It appeared that some of these small dextrins did not precipitate in methanol together with the majority of the clusters. Nevertheless, isolated clusters from the HYLON starch samples were smaller than in NMS and the clusters possessed a lower density of branches with longer chains. The composition of small, branched building blocks was also clearly different: HYLON starch samples possessed much more of single-branched blocks and less multiple-branched blocks than NMS.
Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
Ghazal
G
Peymanpour
Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
Massimo
M
Marcone
Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
Sanaa
S
Ragaee
Department of Molecular and Cellular Biology, Summerlee Science Complex, University of Guelph, Guelph, ON N1G 2W1, Canada.
Ian
I
Tetlow
Ingredion Incorporated, 10 Finderne Avenue, Bridgewater, NJ 08807, USA.
Christopher C
CC
Lane
Department of Food Science and Nutrition, University of Minnesota, St Paul, MN 55108, USA.
Koushik
K
Seetharaman
Department of Food Science and Nutrition, University of Minnesota, St Paul, MN 55108, USA. Electronic address: eric.bertoft@abo.fi.
Eric
E
Bertoft
D000687:Amylopectin / Q000737:chemistry* / Q000302:isolation & purification*; D000688:Amylose / Q000737:chemistry*; D000069977:Bacillus amyloliquefaciens / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry; D015394:Molecular Structure; D003313:Zea mays / Q000737:chemistry*; D000516:alpha-Amylases / Q000737:chemistry
D001426:Bacterial Proteins; D000688:Amylose; D000687:Amylopectin; D000516:alpha-Amylases
Amylopectin clusters; Amylose extender starch mutant; Building blocks