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Describe a laboratory or field method to determine any two of the following: (a) The percentage of sugar in a sample of grass - Leaving Cert Agricultural Science - Question 4 - 2008
Question 4
Describe a laboratory or field method to determine any two of the following: (a) The percentage of sugar in a sample of grass. (b) The influence of any one named e... show full transcript
Worked Solution & Example Answer:Describe a laboratory or field method to determine any two of the following: (a) The percentage of sugar in a sample of grass - Leaving Cert Agricultural Science - Question 4 - 2008
Step 1
The percentage of sugar in a sample of grass.
Answer
To determine the percentage of sugar in a sample of grass, follow these steps:
- Sample Preparation: Chop the grass into small pieces and place them in a plastic bag to remove air. This prevents oxidation of the sample.
- Freezing: Place the bag in a freezer until the grass is fully frozen.
- Squeezing Sap: After freezing, squeeze the grass to extract the sap into a container; this sap contains the dissolved sugars.
- Refractometry: Place a drop of the sap into a refractometer to measure the refractive index, which will correlate to the sugar concentration.
- Calculation: Read the value on the refractometer scale and calculate the percentage of sugar, possibly repeating the process or averaging multiple samples for accuracy.
Step 2
The butterfat content of milk.
Answer
To find the butterfat content in milk, the following method should be used:
- Milk Sampling: Take a sample of milk either from the beginning of the milk production or from a specific quantity of milk (e.g., one pint).
- Temperature Adjustment: Bring the sample to approximately 20 °C to ensure proper consistency for analysis.
- Adding Acid: Slowly add concentrated sulfuric acid to the milk sample. This helps to break down the proteins and allows the butterfat to separate.
- Adding Ingredients: Next, add butyrometer, which will facilitate the measurement of the fat content. Gently invert the mixture to ensure even distribution.
- Centrifugation: Transfer the mixture to a centrifuge and spin it to separate the layers.
- Final Measurement: After centrifugation, measure the butterfat percentage from the resultant graduations in the butyrometer. The typical result should fall between 3-5%.