Yes, this is possible. Here are two options for sample preparation methods for pastry products:
1. Mill or homogenise sample materials. Weigh out a representative sample and extract with water (heated to 60˚C if necessary). Quantitatively transfer to a volumetric flask and dilute to the mark with distilled water. Mix, filter and use the appropriately diluted, clear solution for the assay.
Alternatively the sample can be treated with Carrez reagents after the extraction with water:
2. Mill or homogenise sample materials. Accurately weigh approx. 1 g of into a 100 mL volumetric flask, add approx. 40 mL of distilled water, mix and store at 60˚C for 15 min with occasional swirling. Add 2 mL of Carrez II solution and mix. Add 2 mL of Carrez I solution and mix. Add 4 mL of 100 mM NaOH solution and mix vigorously. Dilute to volume with distilled water and mix thoroughly. Filter an aliquot of the solution through Whatman No. 1 filter paper.
Discard the first few mL of filtrate. Use the clear filtrate (sample solution) in the assay. Alternatively centrifuge in a microfuge tube at 13000 x rpm and using the clear supernatant in the assay.
The procedures given here can be modified to suit the sample, e.g. the dilution effect of the lactose in the sample can be reduced by extracting the sample in a lower volume of water so that the final concentration of lactose is detectable by the kit. This would need to be assessed by the user.

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