To compare maize and potato starch and investigate the effect of freezing starch gels

Make a smooth suspension of 18g of maize starch and 300 ml water (this is 6%).  Heat to 95°C stirring all the time.  Note any changes in viscosity and translucency.  Label two plastic  cups and fill the gelatinised starch paste about 1 cm from the top.

Repeat above procedure using potato starch.

Put one sample of maize gel and one of potato gel aside, to be placed in a freezer.  These will be thawed out and examined next week.

The other two plastic cups are to be left in the room and examined next day. 

Determine the gel strength as follows:

• Push a knitting needle into the gel while it is still in the cup
• Tip the gel out and record its height again
• From the two results calculate the percentage sag for each gel

%         sag      =          (height in the cup – height on plate) x 100

                                                         height in the cup

Naturally, a low % sag indicates a strong gel.