Can anyone provide me with a good way to dissolve the starch when doing OSTT?
I am running into problems to dissolve it since it gets kind of a jelly consistency after heating up the solution and without heat, I don´t get it to dissolve. Thank you very much. Best regards Marcela
I have no idea what OSTT could be, but below I describe an established method for the preparation of molecular starch solutions with minimal degradation. The advantage is that a solution in water is obtained, which can be diluted at will with DMSO or NaOH. This affords flexibility when doing e.g. SEC-MALLS. It is a down-scaled and simplified version of the method by W. Banks and C.T. Greenwood, Starch/Staerke 19 (1967) 394-398:
Starch (30 mg dry matter) is weighed into a screw-cap tube (10 ml) with inert rubber septum, suspended in water (300 microliter), and DMSO (2.7 ml) is added with agitation. The suspension is rotated for 24 h to swell the starch. n-Butanol (6 ml) is added to precipitate the swollen starch, which is recovered by centrifugation (3000 rpm, 30 min). The pellet is washed twice with n-butanol and suspended wet in boiling water (6 ml) under a stream of nitrogen (see below) in order to reduce molecular degradation. The closed tube is placed in a bath at 100 C and 2 needles are inserted through the septum, for the in- and outlet of nitrogen, respectively, in order to reduce water evaporation. Typically 30-60 min hold time on the bath is sufficient to complete the dissolution of the pellet and the evaporation of n-butanol. After cooling, water is added to compensate for evaporation losses. An aliquot (1 ml) is mixed with DMSO (4 ml) to obtain a (nominal) 0.1 % starch solution in 80 % DMSO which is filtered on 0.45 micrometer Nylon for SEC.
Our experience with this method is mainly with potato starch.
It is oral starch tolerance test. You use to measure starch degradation into glucose in the guts.
it's difficult to dissolve native starch in a concentration above 5% without any jelly formed. but the modified starch can
If your test is relevant to starch digestion in the gut, my previous suggestion for molecular starch dissolution is totally irrelevant. There are standard protocols for this, whereby starch is analysed in vitro for rapidly and slowly digested starch, and resistant starch (RDS, SDS, and RS). From the result an in vitro glycemic index (GI) is calculated.
Two useful papers that I know, giving detailed protocols:
(1) H.N. Englyst, S.M. Kingman, J.H. Cummings. Classification and measurement of nutritionally important starch fractions. Eur. J. Clin. Nutr. 46 (1992) S33-50.
(2) K. Englyst, H. Englyst. Detecting nutritional starch fractions. in: A.C. Eliasson (ed.), Starch in food. Structure, function and applications, pp. 541-559, Woodhead Publishing, Cambridge (2004).
Essential is that the starch sample is tested 'as eaten', which means that sample weight and preparation depends on starch food type (biscuit, bread, pasta, potatoes, sauces).
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