Food Tests Flashcards

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Make sure you understand the information on each card. If something's unclear, click the link to the revision notes at the bottom of the page for more details.

2️⃣ Test yourself:

Look at the question or prompt on each card and try to remember the answer before flipping it over.
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Note: We may include questions that have multiple correct answers. It's useful to remember specific examples to understand these concepts better.

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What do food tests check for?

They check for starch, reducing sugars, protein, and lipids in foods.

Mash the food with distilled water. Filter to remove lumps, and use the liquid.

Iodine solution. It changes from orange-brown to blue-black if starch is present.

Add Benedict’s solution to about 5 cm³ of the sample and heat in a 75 °C water bath for 5 minutes. A colour change from blue shows sugar is present.

Blue = none. Green = a little. Yellow or orange = more. Brick-red = lots.

Add Biuret reagent to the sample. It turns from blue to lilac or purple if protein is present; if not, it stays blue.

Add a few drops of Sudan III and shake gently. A red oil layer forms on top if lipid is present; if not, no separate red layer appears.

Filtering can remove the fat. The test may then miss lipids that are there.

It heats the sample safely and evenly to about 75 °C without a flame.

Use the same volumes, the same temperature, and the same time for each test.