ISI 32-1e Determination of Starch Size Distribution by Screening

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1. Scope	The method is applicable to starch		LT 1970 Rev. LT 7 Feb1999
2. Principle	Starch size distribution is determined by screening
3. Apparatus	3.1 Screening set of lit, one or more screens and bottom 3.2 Laboratory scale
4. Procedure	Weigh TARA of each screen and bottom
	Weigh 100 g starch sample and transfer to top screen.
	Shake stack of screens until fines through top screen is negligible.
	Remove top screen and shake until fines through next screen are negligible and so on until all screens are removed.
	Weigh TOTAL of each screen and bottom
5. Calculation	NETTO = TOTAL - TARA of each screen and bottom
	GRAND NETTO = Sum of individual NETTO
	Report with one decimal each starch fraction as percent of GRAND TOTAL and characterised by the trapping mesh width (opening) in micrometer.
	Example: 0 % > 250 µm 0.1% > 125 µm, (< 250 µm) 2.1% > 63 µm, (< 125 µm) 98.2 % < 63 µm		Mesh width in parenthesis may be omitted if it is obvious that fractions are not accumulated
6. Notes	Preferably use a 200 mm dim. vibrator sieve shaker and shake for 15 min. The following sizes belongs to an ISO main serie:		Screen Conversion Table
	DIN 4188	equivalent ASTM
	0.063 mm	230 mesh
	0.071 mm	200 mesh
	0.125 mm	120 mesh
	0.180 mm	80 mesh
	0.250 mm	60 mesh
	0.355 mm	45 mesh
7. Image			Sieve shaker