Malt

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Chen et al. / J Zhejiang Univ SCIENCE B 2006 7(1):79-84

79

Journal of Zhejiang University SCIENCE B
ISSN 1673-1581
http://www.zju.edu.cn/jzus
E-mail: jzus@zju.edu.cn

Relationship between malt qualities and β-amylase activity
and protein content as affected by timing of
nitrogen fertilizer application*
CHEN Jin-xin (陈锦新), DAI Fei (戴 飞), WEI Kang (韦 康), ZHANG Guo-ping (张国平)†‡ (Department of Agronomy, Zhejiang University, Hangzhou 310029, China) †

E-mail: zhanggp@zju.edu.cn

Received Aug. 25, 2005; revision accepted Oct. 5, 2005

Abstract: The effects of different timing of N fertilizer application at the same rate on grain β-amylase activity, protein concentration, weight and malt quality of barley were studied. Grain β-amylase activity and protein concentration were significantly higher in treatments where all top-dressed N fertilizer was applied at booting stage only or equally applied at two-leaf stage and booting stage than in the treatment where all top-dressed N fertilizer was applied at two-leaf age stage only. On the other hand, grain weight and malt extract decreased with increased N application at booting stage. There were obvious differences between barley varieties and experimental years in the grain and malt quality response to the timing of N fertilizer application. It was found that grain protein concentration was significantly and positively correlated with β-amylase activity, but significantly and negatively correlated with malt extract and Kolbach index. The effect of grain protein concentration on malt quality was predominant over the effect of grain β-amylase activity.

Key words: Barley, Nitrogen fertilizer, β-amylase, Malt quality doi:10.1631/jzus.2006.B0079
Document code: A

INTRODUCTION
Barley β-amylase is synthesized during grain
development and stored in mature grains. It plays an
important role in determining good malting quality
(Ziegler, 1999; Evans et al., 2003). Georg-Kraemer et
al.(2001) found that β-amylase activity was a better
predictor of diastatic power (DP) than α-amylases in
barley grains, and increased markedly during germination. High level of DP was required in brewing processes and was an important characteristic for
estimating the quality of malt for beer production
(Evans et al., 1995). Grain protein content is a key


Corresponding author
Project supported by the National Natural Science Foundation of China (No. 30270779) and the Special Research Foundation for Doctor Discipline of Chinese Universities (No. 20020335028)
*

CLC number: S512.3+1

“gateway” characteristic for malting quality. Excessively high protein level is commonly associated with lower soluble substance content and malt extract
quality, resulting in unacceptable malt quality. Grain
weight was also reported to be related to malt extract
(Erkkila et al., 1998; Swanston and Molina-Cano,
2001), so that, these characteristics are closely correlated with malt quality. Several studies showed that β-amylase activity,
grain protein content and weight were influenced to
large extent by environmental factors, although they
are mainly controlled by genetic factors (Bathgate,
1987; Smith, 1990). High quality of malting barley is
reflected by optimal protein content (9.5%~11.5%),
higher β-amylase activity and grain weight. Grain
protein content is greatly affected by N availability in
soil, and closely related to the rate and timing of N
fertilizer application (Birch et al., 1997; Eagles et al.,

80

Chen et al. / J Zhejiang Univ SCIENCE B 2006 7(1):79-84

1995).
It is often difficult to keep protein content below
the upper limit to ensure the malt quality. In southern
China, it is a regular practice to top-dress N fertilizer
at booting stage in order to realize yield potential.
This results in malters and brewers complaining about
unstable malt quality and low extract yield from
grains grown in this area. However, high N fertilization rate or ratio of N...
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