Effects Of Gluten Protein Fractions To Dough Properties And End-products Quality In Bread Wheat

Wheat quality improvement is one of important breeding objective in China. Understanding the function of gluten protein fractions will be useful for quality improvement. In the present study, an HPLC protocol used for wheat protein separation was established. Two experiments were used to investigate the relationship between the quantification of gluten protein fractions and quality properties. In Experimentâ… , 19 Chinese leading winter wheat cultivars with high quality and 2 Auatralian cultivars were sown in Shijiazhuang, Anyang, Zhengzhou. and Jinan in 2002-2003 and 2003-2004 cropping seasons. In Experimentâ…¡, 9 Chinese leading cultivars from Chinese spring sown regions, 20 lines from CIMMYT, and 4 Australian cultivars were sown in three locations, viz., Yongning in Ningxia autonomous region, Wuwei in Gansu province, and Linhe in Inner mongolia autonomous region, in 2003 and 2004. All samples from Experimentâ… and Experimentâ…¡were used to analyze the grain-related quality properties, such as flour protein content(FPC), Zeleny sedimentation volume or SDS sedimentation volume(ZSV or SSV), farinograph and extensograph parameters(water absorption, WA; development time, DT; stability, ST; maximum resistense, Rmax-; extensibility, Ext; extension area, EA), and to quantify the amount of gluten protein fractions in flour. Pan bread and Chinese white salted noodle(CWSN) qualities in Experimentâ… were evaluated, and northern-style Chinese steamed bread(CSB) quality was evaluated in Experimentâ…¡. The main results obtained in this study are presented below.1. The RP-HPLC and SE-HPLC methods were established for separating and quantifying the storage protein fractions, which were effective to evaluate and predict wheat quality.2. Chinese high quality winter wheat is characterized with better kernel properties, higher flour yield, medium to high FPC, and stronger gluten strength. However, fair or inferior gluten quality and poor extensibility was observed, thus fair pan bread and noodle quality. Dough quality properties, pan bread and CWSN quality, and the quantity of gluten protein fractions were significantly affected by genotype, environment and genotype-environment interaction. The variation of protein fraction in quantity resulted in the variation of dough quality properties and pan bread quality, howerer, which had weak effects on noodle quality. The quantity of glutenin and its fractions was mainly determined by genotype, while that of gluten proteins and total gliadin were largely affected by environment. Correlation analysis showed that the amount of gliadin are highly and positively correlated with FPC(r=0.80). The quantity of gluten proteins are significantly and positively correlated with dough strength(except for Ext), and the quantity of LMW-GS can explain 83.3% of the total variation in dough maximum resistance. The quantity of x-HMW is highly correlated with dough properties compared with than y-HMW. The ratios of gliadin to glutenin fractions significantly and negatively correlated with dough strength(r=-0.55-0.89, P<0.001 or 0.01), with pan bread score(r=-0.74, P>0.001), which can explain 55.0% of the total variation in pan bread score. The quantity of gliadin and the ratio of HMW-GS to LMW-GS together can explain 61.4% of the total variation in dough extensibility, which is correlated with dough extensibility with r of 0.73(P<0.001) and r of-0.60(P<0.01), respectively. Decreasing the ratio of HMW-GS to LMW-GS can improve dough extensibility for strong gluten strength wheats. Selecting the high quality glutenin subunits, increasing the quantity of glutenin, and decreasing the ratio of gliadin to glutenin could improve gluten quality and pan bread making quality.3. Medium to weak gluten strength was observed for spring-sown wheats. The quantiy of gluten protein fractions, grain-related quality properties, and steamed bread quality were significantly affected by genotype and environment. The association between the quantity of protein fractions and dough properties, and CSB quality largely depended upon the status of 1B/1R translocation. Higher correlation coefficients were observed in non-tranlocation lines in Comparison with tranlocation lines. In non-translocation lines, the quantity of glutenin fractions are significantly and positively correlated with dough strength(r=0.81-0.94, P<0.001), and with stress relaxation(SR) and CSB score(r=0.56-0.62, P>0.01). The ratio of gliadin to glutenin significantly and negatively correlated with dough strength(r=-0.77-0.93, P<0.001), with CSB score(r=-0.73-0.79, P<0.001) acounting for 53.3%-62.4% of the total variation in CSB score. The ratio of HMW-GS to LMW-GS significanlty and positively correlated with dough strength(r=0.67-0.72, P<0.05), and CSB score(r=0.46, P<0.05); the ratio of x-HMW to y-HMW significantly and positively correlated with dough strength(r=0.44-0.62, P<0.05). Requirments for CSB were similar to pan bread in terms of medium flour protein content, and increasing the expression of glutenin and decreasing the ratio of gliadin to glutenin would be the key to improving gluten strength for spring wheats and CSB making quality. It is possible to develop 1B/1R cultivars with acceptable processing quality through careful selection of HMW-GS and LMW-GS, and increading the quantity of glutenin.This study clearly showed the quality performance of Chinese wheats. Aim at different wheat products, modification of the composition in quantity of gluten protein will be crucial for further improvement of wheat quality in China.