PART VU.K.Standard method for determining matter other than basic cereals of unimpaired quality
1.For common wheat, durum wheat and barley, an average sample of 250 g shall be passed through two sieves, one with slotted perforations of 3,5 mm and the other with slotted perforations of 1,0 mm, for half a minute each.U.K.
In order to ensure constant sifting, it is advisable to use a mechanical sieve, for example a vibrating table with fitted sieves.
The matter retained by the sieve with slotted perforations of 3,5 mm and that passing through the sieve with slotted perforations of 1,0 mm must be weighed together and regarded as extraneous matter. Where the matter retained by the sieve with slotted perforations of 3,5 mm includes parts in the ‘other cereals’ group or particularly large grains of the basic cereal, those parts or grains shall be returned to the sifted sample. During sifting, in the sieve with slotted perforations of 1,0 mm, a close check must be made for live pests.
From the sifted sample, a sample of 50 to 100 g shall be taken using a separator. This partial sample must be weighed.
The partial sample should then be spread out on a table with tweezers or a horn spatula and broken grains, other cereals, sprouted grains, grains damaged by pests, grains damaged by frost, grains in which the germ is discoloured, mottled grains, extraneous seeds, ergots, damaged grains, decayed grains, husks and live pests and dead insects must be extracted.
Where the partial sample includes grains still in the husk, they shall be husked by hand, the husks obtained being considered as pieces of husks. Stones, sand and fragments of straw shall be considered extraneous matter.
The partial sample shall be passed for half a minute through a sieve with a mesh size of 2,0 mm for common wheat, 1,9 mm for durum wheat and 2,2 mm for barley. Matter which passes through this sieve shall be considered as shrivelled grains. Grains damaged by frost and unripe green grains shall belong to the ‘shrivelled grains’ group.
2.An average sample of 500 g in the case of maize and 250 g for sorghum, is shaken for half a minute in a sieve which has slotted perforations of 1,0 mm. Check for the presence of live pests and dead insects.U.K.
Using tweezers or a horn spatula, extract from the matter retained by the sieve with slotted perforations of 1,0 mm stones, sand, fragments of straw and other extraneous matter.
Add the extraneous matter thus extracted to the matter which has passed through the sieve with slotted perforations of 1,0 mm and weigh them together.
Using a separator, prepare a partial sample of 100 to 200 g in the case of maize or 25 to 50 g for sorghum from the sample passed through the sieve. Weigh this partial sample. Spread it out in a thin layer on a table. Using tweezers or a horn spatula, extract the pieces of other cereals, grains damaged by pests, grains damaged by frost, sprouted grains, extraneous seeds, damaged grains, husks, live pests and dead insects.
Next, pass this partial sample through a sieve with a 4,5 mm round mesh for maize and 1,8 mm round mesh for sorghum. The matter which passes through this sieve shall be considered as broken grains.
3.Groups of matter other than basic cereals of unimpaired quality, determined according to the methods referred to in 1 and 2 must be weighed very carefully to the nearest 0,01 g and distributed according to percentage over the average sample. The particulars entered in the analysis report shall be to the nearest 0,1 %. Check for live pests.U.K.
As a general rule, two analyses must be made for each sample. They must not differ by more than 10 % in respect of the total of the above mentioned matter.
4.The apparatus to be used for the operations referred to in 1, 2 and 3 is as follows:U.K.
sample separator, for example a conical or grooved apparatus;
precision or assay balance;
sieves with slotted perforations of 1,0 mm, 1,8 mm, 1,9 mm, 2,0 mm, 2,2 mm and 3,5 mm and sieves with a 1,8 mm and 4,5 mm round mesh. The sieves may be fitted to a vibrating table.