Research Of Starch Granule Distribution Of Waxy Wheat And Its Response To N₂

In recent years, waxy wheat which contained very low amylose became the most important material to research the wheat starch amplifying. In1995, Japan first breed the waxy wheat and the udon noodle made from this waxy wheat flour behaved better quality property. Research reported that amylose content was negatively correlated to flour quality. Low amylose content behaved superior pasting property:it is easy to pasting and the degradation resistance was improved. Waxy wheat performed better quality because of the differences of starch content and granule distribution from non-waxy wheat. Wheat with certain granule distribution had its own physiochemical properties and became the key additive to flour modification. Previous study reported the distribution of wheat starch granule was affected by both gene and environment. As a common regulating factor, N2can affect the starch granule distribution. In present research, we selected several wheat cultivars which behaved different waxy property, and set4levels of N2at farmland. Then we analyzed the starch formation, granule distribution and pasting property of waxy wheat combined the inner experiment. The main aspects of this research were displayed below:1. Analyzed the differences of several wheat cultivars on starch formation and pasting property. There were seven cultivars were selected in this experiment, and they were three waxy wheat and their own waxy and non-waxy parents respectively. We analyzed the differences of starch content and starch granule distribution of different cultivars, and researched the special starch characteristics and quality properties of waxy wheat starch. In according to the research results, the amylose content of waxy wheat was extremely low (<1.3%), while its amylopectin content was higher than non-waxy wheat. Waxy wheat amylopectin starting to form at DAA9to DAA14and reached to the peak value at DAA14, whatever, the non-waxy wheat reached to the peak value at DAA29. It indicated that waxy wheat had the higher amylopectin synthesis ability. The starch granule distribution of different waxy wheat was different:at the latter stage of filling, waxy wheat biosynthesized much more medium and small granules. It indicated that the amylose was the main material to expand starch granules while the amylopectin was the necessary meterial of starch granules. Because of the low amylose content, the viscosities of waxy wheat were lower than non-waxy wheat. In experiment, waxy wheat behaved low peak time, trough viscosity and setback, and high break down. It indicated that waxy wheat starch was easy to gelatinize, but the viscosity was not stable.2. The dynamical formation of wheat with different waxy property under different N2level. In this research, we selected two cultivars with different waxy property:they are NM1and YM158respectively. In the same time, we set4levels of N2and to explore the special characteristics of biosynthesis, constituent, granule distribution and quality property of waxy wheat. We found that the amylose content of NM1was much lower than YM158, and consistently, the GBSS activity of NM1was very low. It maybe indicate that the GBSS was the key enzyme for the biosynthesis of amylose. The difference of starch granule size distribution of NM1and YM158was obvious:NM1had bigger proportion of B-, C-type granules compared to YM158, and the mean granule diameter of YM158was bigger than NM1generally. Because of the difference of amyloes content, there were significant difference of pasting property between the two type starch, and waxy wheat preferred better aging-resistant property. Under different N2level, starch property was different. It is best for improving starch content that a suitable higher level of N2.3. Make sure the differences of starch with different wheat flour and different granule distribution on starch content and pasting property. Abstracting starch from Ningmai1(NM1, waxy wheat) and Yangmai158(YM158, non-waxy wheat) respectively, and separating A-type and B-type starch granules from each cultivar subsequently. Through experiment, we found that NM1starch contained low amylose content and hence behaved higher peak and breakdown viscosity and lower setback viscosity than YM158. And there were significant differences of the granule distribution between A-, B-type granules of YM158and NM1. YM158contain bigger volume percent of A-type granules while NM1contain bigger volume percent of B-type granules. In both NM1and YM158starch, the A-type granules behaved higher viscosities value than the B-type granules. After measuring the starch composition and content of A-, B-type granules of each cultivar, we found that higher amylose content corresponding to lower viscosity in NM1(amylose content of starch:2.33-5.35), but in YM158(amylose content of starch:28.37-32.37), the higher amylose content corresponding to higher viscosity. We guessed that the correlation of pasting properties and amyloes content is not certain, and it related to the cultivar and different content range of amylose. Based on it, we blended starch from different cultivars and their A-, B-type starch granules, and then to search for an optimum blend ratio in which the quality of flour-made food will be best improved and hope to construct a balance between quality properties and nutrition function of wheat-made food.