Analyses On Factors Affecting Wheat Flour Whiteness

The experiments were carried out on the experiment field of Crop Cultivation and Physiology Key Laboratory of Jiangsu Province, Yangzhou University from 2002 to 2004. The effects of genotypes, ecological factors and storage time on wheat flour whiteness were studied, the changes of PPO activity, pentosan and carofenoid contents in grains of different wheat varieties during grain filling period were analyzed, the relationship of flour whiteness to key quality traits was discussed, and the effects of cultivating measure on flour whiteness were also analyzed. The main results were as follows. 1. Effects of genotypes, ecological factors and storage time on flour whitenessFlour whiteness was significantly different among wheat varieties, which might indicate that flour whiteness was mainly determined by genotype. Whiteness of red wheat flour was 5-6% higher than that of white wheat in 2003 and 2004. Flour whiteness changed along with ecological condition and production year. Flour whiteness could increase with the elongation of storage time after being milled, which might be divided to 3 types: type 1, flour whiteness became stable after increasing; type 2, flour whiteness declined after increasing; type 3, flour whiteness kept increasing. Flour whiteness got maximum value at different storage time for different varieties. The order of flour whiteness in wheat varieties for different end uses was weak-gluten wheat > medium-gluten wheat>strong-gluten wheat.2. Relationship between flour whiteness and quality traitsFlour whiteness was significantly negatively correlated with protein content among genotypes, and the correlation among different treatments in same genotype was negative, but not significant. Dry and wet gluten contents negatively correlated with flour whiteness, too. Flour whiteness was less than 72, when wet gluten content was higher than 35% and dry gluten content was higher than 12%. Flour yield was negatively correlated with flour whiteness. Flour whiteness had negative correlation with ash content in flour and grains. The lower the ash content in flour was, the higher the flour whiteness was. There was a quadratic relationship between flour whiteness and grain weight. Test weight was positively correlated with flour whiteness. The relationship of flour whiteness (y) to protein content(x₁), amylose content(x₂), wet-gluten content(x3),loafvolume(x4), ashcontent(x5), flour yield(x₆) could be expressed as: Y=42. 922-2. 738X,+0. 887X2+0. 402X^+0. 353X4-11. 053X5-0. 071X6, R2=0. 8233. Effects of PPO activity, carofenoid and pentosan on flour whitenessPPO was mainly in the outer part of wheat kernels. PPO activity in flour and grain; negatively related with flour whiteness. With the development of grains, PPO activity rose at first, then declined gradually before the 21st day after anthesis (DAA). After the 21st DAA, PPO activity rose quickly, and reached the maximum at maturity. The distribution of pentosan in grains was the same as PPO. Pentosan content in grains was high on the 14th DAA, then began to drop, it reached the minimum on the 28th DAA, but it gradully rose again after that. Pentosan content had negative correlation with whiteness. The contents of chlorophyll and carotinoid showed an inverted "V" type change, which reached the maximum on the 14th DAA and the minimum at maturity. The maximum and minimun values could affect flour whiteness, and the deeper the grain color was, the greater the difference between them was.4. Effects of cultivation measures on flour whitenessThe results showed that sowing date, plant density, N fertilizer and P fertilizer couldaffect flour whiteness. With the increasing of plant density or the delay of sowing date, flour whiteness showed an inverted "V" type change. Under the same application time, with the increase of N fertilizer application amount in a certain extent, flour whiteness of Yangmai 13 and Yangmai 15 all declined, but the difference in Yangmai 13 was not significant. With the same N fertilizer application amount, the earlier the application time was, th...