food tests Flashcards

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1
Q

What nutrients do we test

A

1- Carbohydrates : Reducing sugar , starch

2- Protien

3- fats/lipids

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2
Q

Define reagent

A

A reagent - a chemical that is used to detect the presence of another chemical or substance.

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3
Q

define qualitative

A

produces a change that is judged by the experimenter, rather than an exact number/measurement.

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4
Q

what is used to test for starch and describe the colour change

A

Iodine and it turns from orange/brown to blue/black

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5
Q

what is used to test for reducing sugars and describe the colour change

A

Benedict solution and it turns from blue to brick red

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6
Q

what is used to test for protien and describe the colour change

A

Biuret and it turns from blue to purple/violet

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7
Q

what is used to test for fats/lipids and describe the colour change

A

ethanol and it goes from clear to emulsion : cloudy white, milky

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8
Q

Explain how we can test for each of the following substance: Protein

A

We test for protein using a biuret solution..First you’re going to mash the food sample using a pestle and a mortar. Next you are going to put that into a filter paper and rinse it with water.Then you are going to collect the filtrate and you are going to put a few drops of biuret solution onto it and shake well. If protein is present in that food sample then the colour will turn to purple/violet. If protein is not present in that food sample then it will remain blue.

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9
Q

Explain how we can test for each of the following substance: Reducing sugar

A

We test for reducing sugars using benedict’s solution.First you’re going to mash the food sample using a pestle and a mortar. Next you are going to put that into a filter paper and rinse it with water.Then you are going to collect the filtrate and you are going to put a few drops of benedict’s solution onto it and shake well. Then you are going to place it into a bath of water for 5 mins and heat. The colour will remain blue if reducing sugar is present and will turn brick red if it is not present.

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10
Q

Explain how we can test for each of the following substance: starch

A

We test for starch using iodine solution. You place a few drops of iodine solution on the food sample directly,shake well and observe the colour change. If the colour is orange/brown, then starch is not present in that food sample. And if the colour changes to blue/black, then starch is present in that food sample.

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11
Q

Explain how we can test for each of the following substance: fats/lipids

A

We test for fats/lipids using ethanol..First you’re going to mash the food sample using a pestle and a mortar. Next you are going to put that into a filter paper and rinse it with water.Then you are going to collect the filtrate and you are going to put a few drops of ethanol onto it. Then you’ll shake it and add water. If fats is not present it will be clear ( no emulsion formed), if fats are present then emulsion will form and it will turn cloudy,milky and bubbles will be formed.

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