NUTR*3210 (Weeks 1-6)

What does RDA mean?

Answer explanation

Recommended Dietary Allowance: the needs of ~97% of population are met

Provide the formula for percent moisture.

Answer explanation

Percent moisture = ([wet weight - dry weight]/wet weight) x 100%

...where dry weight is the sum of weights of all nutrients except water!

True or False? Typically, with crude fat (ether extract) there is an overestimation.

• True

• False

Answer explanation

Crude fat is overestimated because the process in which it is obtained from (ether extraction) uses an organic solvent. Chlorophyll, resins, waxes in plants, and other substances that are not nutrients are soluble in organic solvents, thus overestimating crude fat.

True or False? Typically, with crude protein (Kjeldahl analysis) there is an underestimation.

• True

• False

Answer explanation

Crude protein is slightly overestimated because other sources of nitrogen such as nitrates, nitrites, urea, and nucleic acids are not considered (due to the assumption that all nitrogen is from protein) and therefore these non-protein sources would be part of the crude protein calculation - thus over-estimating crude protein content!

Provide the formula for percent crude fat.

Answer explanation

Provide the formula for percent crude fibre.

Answer explanation

Provide the formula for percent Nitrogen free extract (NFE).

Answer explanation

The NFE estimates starch & sugar content, but cannot distinguish between the two.

The NFE accumulates ALL of the ERRORs that exist for the other components of proximate food analysis.

Provide the formula for ASH (mineral content).

Answer explanation

Potential sources of error / limitations:

• Volatile minerals may be lost when burning the residue

• No information about individual minerals

Provide the formula for percent crude protein.

Answer explanation

Potential sources of error / limitations:

Assumes all proteins have 16% nitrogen when the true range is 13-19% (e.g., peanuts = 18% N therefore conversion factor = 5.5)

Doesn't take into account other sources of nitrogen such as nitrates, nitrites, urea, nucleic acids, etc.

Provide the formula for percent dry matter.

Answer explanation

Percent dry matter = 100% - percent moisture

For review:

Percent moisture = ([wet weight - dry weight]/wet weight) x 100%

...where dry weight is the sum of weights of all nutrients except water