Maataloustieteellinen A ikakauskirja
Voi 57: 163—165, 1985

Development of chemical composition of grain during growth and ripening

MAIJA-LIISA SALO
Department of Animal Husbandry, University of Helsinki,
SF-00710 HELSINKI. Finland

Abstract. The development of chemical composition of barley and oat grains was in-
vestigated in samples taken weekly from the beginning of kernel development to about two
weeks over the normal harvesting time.

The chemical composition of both grain species, but especially that of barley, was com-
plete when the colour of crops was turning from green to yellow: the starch content increased
from the initial zero level to its maximum, the sugar and crude fibre contents decreased to
the low level of ripe grains. Over-ripening decreased the starch content and kernel weight.

Introduction

Cereals are usually harvested at a stage of
full-ripeness, when the moisture content has
decreased, and the preparation of grain for
storage is thereby cheaper. The nutritive value
and yield is, however, complete before this.
Several authors have shown that deposition of
nutrients is completed when the moisture con-
tent of grain is 35—40 percent, i.e. at the stage
of yellow-ripeness. The over-ripeness, in turn,
decreases the volume weight, because respira-
tion requires energy. In a rainy season, also
the ear-sprouting wastes the energy depots
of grains (Gesslein 1959, Bengtsson, 1969,
1979, Madsen et al. 1972, Thomke 1972).

The purpose of the present study was to in-
vestigate the development of chemical com-
position during the growth and ripening of
grains and to what extent the green kernels due

to adeventious green shoots, or early autumn
frost diminish the nutritive value of the grain
crop.

Materials and methods

The study was performed at the Viikki Ex-
perimental Farm (60.2 °N) by taking weekly
samples from barley and oat crop from the
beginning of kernel growth to the time of
harvesting which in this rainy summer was
done only at the stage of over-ripeness. The
grains were cleaned from chaffts and awns,
and samples thereof were dried at room tem-
perature for measuring the 1000kernel weight,
in an oven at 103°C for determination of dry
matter, and in a vacuum oven at 50°C for
analysis. The ground samples were then
analyzed for determinants of Weende system.

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JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND



for sugars soluble in 80 percent ethanol (Salo
1965) and for starch (Salo and Salmi 1968).

Results and discussion

The analytical data show (Table 1) that the
chemical composition of grain is nearly com-
plete when the green colour of the grain crop
is turning to yellow. The most drastic change
occurs in the starch content, from nearly zero
to a 45 —55 % level. At the same time, the
sugar content falls to the low level of mature
grains, and the 100 kernel weight rises. The
changes in the protein content are small.

Because starch accounts for over 75 °7o of
the net energy value of low-fat grain species
(about 65 % in the high-fat oats), the starch
content best characterises the energetic value
of grains, as shown earlier (Salo 1978). The
content of cell wall substances (100 (starch
+ sugar + protein + fat + ash)) characterises
the same (Table 1). The nitrogen-free extracts
(NFE), the difference group of Weende system,
is a poor parameter of nutritive value, because
in addition to starch the NFE contain main

part of the cell wall substances of grains.
Crude fibre, the common criterion of feed
value, is fairly suitable for oats because of its
high and variable hull content, but poor for
barley, wheat and rye. Therefore it seems to
be more reasonable to analyze the grains for
starch than for crude fibre. Moreover, the
analytical method for starch is more exact.

This study was performed in a very rainy
summer (1981), and therefore harvesting was
done only about two weeks after the normal
threshing time. This delay impaired the
nutritive value of grains: the starch content
decreased and so did the weight of kernels.
The barley was even more damaged by rain
than was shown by the analytical data, since
the sprouted ears were not included in the
samples. The decrease of kernel weight and
volume weight of corn due to over-ripeness
has been reported by several authors (e.g.
Gesslein 1959, Bengtsson 1979, Larsson
1980). The cold and rainy summer caused on
the whole a diminished feed value of grains,
because the starch and protein contents were
below normal values.

Table 1. Kernel weight and chemical composition of grain during growth and ripening.

Sam- Colour Dry 1000 % of dry matter
j*'n ® °*. matter kernel cru(je crude crude ash N-free starch sugars cell walldate growing of weight .
lrlo , protein fat fibre extr. contents'1981 crop gram g v

%

Barley (variety Otra)
16. 7. green 28 5.2 11.3 1.9 13,9 4.9 68.0 3.2 13.6 65.1
23.7. green 29 16.1 10.0 2.7 10.7 3.7 72.9 37.3 7.0 39.3
30. 7. yellowish-green 39 26.4 10.2 3.0 7.2 3.2 76.4 53.5 2.9 27.2

6. 8. yellowish 49 32.7 10.9 2.5 6.6 3.1 76.9 53.9 2.5 27.1
13.8. yellow 62 37.1 11.8 2.3 5.8 3.0 77.1 55.0 2.6 25.3
20. 8. grayish-yellow 54 30.0 12.2 2.3 6.3 2.9 76.3 53.0 1.9 27.7
27.8. grayish-yellow 68 29.8 11.7 2.3 6.1 2.9 77.0 53.4 2.6 27.1
Oats (variety Sisu)
23. 7. green 34 9.5 7.7 1.5 29.8 3.4 57.6 2.8 7.3 77.3
30.7. green 39 17.0 8.1 5.5 21.9 3.8 60.7 20.0 5.8 56.8

6. 8. green 47 25.5 8.5 6.7 16.3 3.3 65.2 37.9 2.9 40.7
13.8. light green 53 33.0 8.5 6.5 13.3 3.2 68.5 42.8 1.5 37.5
20.8. light yellow 57 36.5 8.3 6.2 12.5 3.4 69.6 44.1 1.1 36.9
27.8. light yellow 62 37.0 9.2 6.1 11.7 3.0 70.0 44.6 0.8 36.3
3.9. light yellow 66 32.5 10.1 6.0 12.1 3.2 68.6 45.4 0.9 34.4
10.9. light yellow 77 31.0 10.5 5.8 12.9 3.1 67.7 42.6 1.4 36.6

100 (starch + sugars + protein + fat + ash)

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A preliminary study was performed the
previous year, but samples were taken less
frequently and regularly. That summer was,
in turn, warm and favourable, ripening of
crops was rapid and the nutritive value of
grains good. The chemical composition of
grains was, however, even that year complete
far before the normal harvesting time. The
samples taken from spring wheat indicated
that like oats wheat grain developed to com-
plete nutritive value somewhat faster than
barley.

References

Bengtsson, A. 1969. Fodersädens grundkvalitet och
växtodlingätgärderna. Akt. frän Lantbr.högsk. 132:
I—3l.
1979. Avkastning och kvalitet i olika mognadstadier.

Sveriges lantbr.univ. Konsulentavdeln. rapporter all-
mänt 18: 2: I—7.1 —7.

Gesslein, S. 1959. Sträsädens mognadsförlopp och skör-
demetoderna. Växtodling 13, 164 p. Uppsala.

Larsson, S. 1980. Hösträg. Försök med kvävegödsling
och skördetider. Sveriges lantbr.univ. Inst, för växtod-
ling. Rapport 86.

Madsen, A., Bengtsson, A., Kivi, E. & Mikkelsen, K.
1972. Hosttidspunktets inflydelse pä byggens foder-
vaerdi. 395. beretning fra forsogslaboratoriet. Koben-
havn. 128 p.

Salo, M.-L. 1965. Determination of carbohydrate frac-

SELOSTUS

Jyvän kemiallisen koostumuksen kehitys
viljan kasvun ja tuleentumisen aikana

Maija-Liisa Salo
Helsingin yliopisto, Kotieläinlieteen laitos,
00710 Helsinki

Ohran ja kauran jyvän kemiallisen koostumuksen muo-
toutumista seurattiin näytteistä, joita otettiin viikottain
jyvän kehityksen alusta viljan puintiin, mikä sateiden
vuoksi siirtyi pari viikkoa normaalia puintiaikaa myöhem-
mäksi.

Jyvien kemiallinen koostumus oli lopullinen jo kelta-

In conclusion, the nutritive value of grains
is complete when the crop still looks very
under-ripe. If the grains are preserved for feed
as silage, the crop can be harvested at the
stage of yellow-ripeness or a little before that.
The high moisture content, 40—45 %, is an
advantage in the silage preservation of crushed
grains. If, however, drying or some other more
common preservation technique is applied, it
is reasonable to let the crop dry up, but not
over-ripen.

tions in animal foods and faeces. Acta Agr. Fenn. 105:
I—lo 2.

1978. Relationships between physical and chemical
characteristics and calculated metabolizable energy
values in barley and oats with highly variable volume
weight. J. Scient. Agric. Soc. Finl. 50: 276—284.
& Salmi, M. 1968, Determination of starch by the

amyloglucosidase method. J. Scient. Agric. Soc. Finl.
40: 38—45.

Thomke, S. 1972. On the influence of different stages of
ripeness on the productive value of barley fed to
chickens, laying hens, rats and mice. Acta Agric. Scand.
22: 107—120.

Ms received April 10, 1985

tuleentumisen alussa, ohran vähän kauraa varhaisemmin.
Tärkkelyspitoisuus oli silloin noussut maksimiarvoonsa
ja sokeri- ja kuitupitoisuus laskenut kypsän viljan tasol-
le. Valkuaispitoisuus muuttui kasvu- ja tuleentumiskau-
tena vain vähän. Ylituleentuminen alensi jyvien tärkke-
lyspitoisuutta ja 1000 jyvän painoa.

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