Abstract:

There are many reports about factors affecting noodle-making quality. However, few of them consider the characteristics of starch chemical structure (especially, the structure of amylopectin) and how they determine the physical properties, such as flour viscosity traits. So this study was carried out to investigate the relationships between starch chemical structure, flour viscosity traits and noodle quality. And it will facilitate the selection of noodle-specific wheat varieties.
Twenty wheat cultivars from Shandong province were grown in the farm of Shandong Agricultural University with same field managements in the year of 2001 and 2002. Seeds harvested in the two years were respectively stored for 3 months, and milled with a Junior-3100 experimental mill (Brabender company, Germany). Wheat starch was extracted, digested completely withα-amylase(EC 3.2.1.1, Sigma) and analyzed by High Performance Liquid Chromatograms (HLPC) with a Sugar-PAKTW carbohydrate analysis column (Waters). Flour viscosity traits were analyzed by 3-D RVA (3-D rapid viscosity apparatus, Newport Scientific company, Australia).
The results (Table 3) indicated that there were differences in digested product amount between cultivars. The amounts of oligosaccharides with a degree of polymerisation (DP)≥4 were significantly positively correlated with noodle quality scores. The correlation coefficients of DP≥4 oligosaccharides contents with noodle appearance and with elasticity were both higher. These indicate that the quality of noodles can be improved by DP≥4 oligosaccharides.
DP≥4 oligosaccharides has at least one branching point. The greater amounts of DP≥4 oligosaccharides, the more branches the starch has. So it is concluded that noodle made from the wheat with starch of more branch points tends to have good quality.
On the other hand, considering the fact that the starch with closer branches is digested more difficultly with α-amylase, a greater amount of digested DP≥4 oligosaccharides indicates that the given starch has not closer branches. So it can be deduced that wheat for high quality noodle probably contains the starch with loose branches.
At the same time, some flour viscosity traits were highly positively correlated with DP≥4 oligosaccharides contents, such as Peak Viscosity and Break down.
It is concluded, from the positive correlation between the amounts of DP≥4 oligosaccharides and noodle quality score, that wheat for high quality noodle contains the starch with more and looser branches.

Key words: Wheat, Starch, Structure, Viscosity, Noodle