Protein Quality Flashcards
Which factors are a requirement in determining protein quality?
Digestibility and availability
What factors can affect protein quality?
Amino acid profile
Content and balance of essential and nonessential amino acids
Content of limiting amino acids
Protein digestibility
Bioavailability
What are limiting amino acids?
Essential amino acids that interrupt protein synthesis because there is not enough of them and required in large amounts
Lysine and methionine
Who discovered the concept of limiting amino acids?
Carl Sprengel and Justus con Liebeg
What is leibegs barrel?
A concept used to present the relative supply of nutrients by using different length staves to represent the limiting factors
How is digestibility and bioavailability different?
Digestibility is described as a fraction of protein ingested and absorbed by an animal that is not excreted
Bioavailability is how well the body can utilize the nutrients after digestion
How can you asses digestibility of protein?
Fecal assay: measures amount of aa absorbed to the amount of aa recovered in feces, main method because of simplicity and sample size
Ileal assay: records collected digested feed sample from cannulated or slaughtered animal and compares to the original feed, more accurate test because fermentation has not taken place
What is biological value?
The measure of how much absorbed protein becomes incorporated with the proteins already inside the body
BV = (N intake - N output (fecal N + urinary N))/(N intake - N fecal) x 100
What is Net protein utilization?
Determines the ratio of amino acids converted to proteins to the ratio supplied in the diet
1 = 100% utilization
NPU = (body N content with test protein - body N content with protein free diet)/(N intake) x 100
What is protein efficiency ratio?
Measures the body weight gain per unit of protein consumed
2.5 or higher is ideal
PER = body weight gain/protein consumed x 100
What is amino acid score?
The analysis of amino acid profiles using a high pressure liquid chromatography
AAS = (mg of aa per g of test protein)/(mg of aa per g of reference protein)
