d20061027990

The Lowry protein assay method for protein concentration determination is one of the most venerable and widely-used protein assays. The Lowry protein estimation has been so widely used that it is a completely acceptable alternative to a rigorous absolute determination in almost all circumstances in which protein mixtures or crude extracts are involved.
So, from the graph we can see that when the protein is increased, the absorbance also increased. In this experiment, the eggs gred are not depend on the protein concentrations.

D20071029505...

In my opinion, egg grade or quality has nothing to do with nutritional value. Instead, the grade an egg receives has to do with the egg's shell quality and how the egg stands once it's cracked - two things that have more to do with food preparation than they have to do with food safety. Grades range from AA to C, though Grade C eggs are not available for consumer purchase.

Quality standards are as follows:

· Grade AA: Eggs of the highest quality have shells that are clean, unbroken and are shaped like a typical egg. The egg white is clear, firm, and springy, while the egg yolk is well-centered, free from defects and has a slightly defined outline.

Grade AA eggs are ideal for any use, but are particularly desirable for frying, poaching, and hard boiling.

· Grade A: Grade A eggs have shells that are very similar to higher graded eggs - they will be clean, unbroken and normally-shaped. The egg white will be clear and reasonably firm, though it won't stand as high as Grade AA egg whites. The yolk will be fairly well centered, free from defects, and it will have a fairly well-defined outline.

Grade A eggs are well suited for frying, poaching, and hard boiling, though they can be used for any purpose.

· Grade B: These lower grade eggs may have a shell that is clean or slightly stained. The shell will be unbroken, but may be weak or abnormally shaped. The egg white will be clear, though not springy, and the yolk may be slightly off center, enlarged and have minor (not serious) defects.

Grade B eggs are relatively flat when cracked compared to Grade AA and Grade A eggs. For this reason, Grade B eggs are best suited for scrambling, baking, or use as ingredients.

· Grade C: Grade C eggs will have clean to moderately stained shells. Shells will be unbroken, but may be abnormally shaped. The egg white will be flat and watery, and small blood clots or spots may be present. The yolk may be off center, enlarged and flattened and may show serious defects. The yolk outline will be plainly visible.

My opinion has been improved by my groups experiment last week.

D20071029506 Lowry assay

In my opinion, the eggs grade do not depend on protein contain. This is because, it depends on the albumen, spread, yolk, shell, and use. The classification determined by interior and exterior quality and designated by letters as AA, A and B. Grade AA eggs have thick, firm whites and high, round yolks. Their shells are clean and unbroken. Grade A eggs are like Grade AA, but their whites are reasonably firm. Grade A is usually sold in stores. Grade B eggs have thin whites and wider yolks. The shells are unbroken, but might show slight stains.

Egg Quality

	Grade AA	Grade A	Grade B
Break Out Appearance	Covers a small area.	Covers a moderate area.	Covers a wide area.
Albumen Appearance	White is thick and stands high; chalaza prominent.	White is reasonably thick, stands fairly high; chalaza prominent.	Small amount of thick white; chalaza small or absent. Appears weak and watery.
Yolk Appearance	Yolk is firm, round and high.	Yolk is firm and stands fairly high.	Yolk is somewhat flattened and enlarged.
Shell Appearance	Approximates usual shape; generally clean,* unbroken; ridges/rough spots that do not affect the shell strength are permitted.		Abnormal shape; some slight stained areas permitted; unbroken; pronounced ridges/thin spots permitted.
Usage	Ideal for any use, but are especially desirable for poaching, frying and cooking in shell.	Ideal for any use, but are especially desirable for poaching, frying and cooking in shell.	Good for scrambling, baking, and as an ingredient in other foods.

*An egg may be considered clean if it has only very small specks, stains or cage marks. Source: USDA

So, we can determine concentration of protein by using the Lowry Assay experiment. The higher the density of protein, so the absorbance also higher.

D20071029504...eggs...

In my opinion, the grade of an egg not determines the protein content in it. This is because determination of grade in egg is comes from other aspects. Classification determined by interior and exterior quality and designated by letter AA, A and B. In the grading process, eggs are examined for both interior and exterior quality and are sorted according to weight or size. Grade quality and size are not related to one another. In descending order of quality, grades are AA, A and B. There is no difference in nutritive value between the different grades.

Below are the qualities of egg:

	Grade AA	Grade A	Grade B
Break Out Appearance	Covers a small area.	Covers a moderate area.	Covers a wide area.
Albumen Appearance	White is thick and stands high; chalaza prominent.	White is reasonably thick, stands fairly high; chalaza prominent.	Small amount of thick white; chalaza small or absent. Appears weak and watery.
Yolk Appearance	Yolk is firm, round and high.	Yolk is firm and stands fairly high.	Yolk is somewhat flattened and enlarged.
Shell Appearance	Approximates usual shape; generally clean,* unbroken; ridges/rough spots that do not affect the shell strength are permitted.		Abnormal shape; some slight stained areas permitted; unbroken; pronounced ridges/thin spots permitted.
Usage	Ideal for any use, but are especially desirable for poaching, frying and cooking in shell.	Ideal for any use, but are especially desirable for poaching, frying and cooking in shell.	Good for scrambling, baking, and as an ingredient in other foods.

*An egg may be considered clean if it has only very small specks, stains or cage marks. Source: USDA

Egg composed of shell, air cell, shell membranes yolk, vitelline membrane, albumin and chalazae.

The total concentration of protein for example egg can be determine by doing Lowry Assay experiment. The principle behind the Lowry method of determining protein concentrations lies in the reactivity of the peptide nitrogen[s] with the copper [II] ions under alkaline conditions and the subsequent reduction of the Folin-Ciocalteay phosphomolybdicphosphotungstic acid to heteropolymolybdenum blue by the copper-catalyzed oxidation of aromatic acids. The Lowry method is sensitive to pH changes and therefore the pH of assay solution should be maintained at 10 - 10.5.

The result that we get from the Lowry assay is that when the density of protein is higher, the absorbance is higher. The concentration of protein can be determine from the graph that we sketched.

D20071029484 Lowry assay

In my opinion, the grade of eggs does not depend on the protein contain but it depends on the albumen, spread, yolk, shell, and use. There is no difference in nutritive value between the different grades. Classification determined by interior and exterior quality and designated by letters as AA, A and B. Grade AA eggs have thick, firm whites and high, round yolks. Their shells are clean and unbroken. Grade A eggs are like Grade AA, but their whites are reasonably firm. Grade A are usually sold in stores. Grade B eggs have thin whites and wider yolks. The shells are unbroken, but might show slight stains.

Egg Quality

	Grade AA	Grade A	Grade B
Break Out Appearance	Covers a small area.	Covers a moderate area.	Covers a wide area.
Albumen Appearance	White is thick and stands high; chalaza prominent.	White is reasonably thick, stands fairly high; chalaza prominent.	Small amount of thick white; chalaza small or absent. Appears weak and watery.
Yolk Appearance	Yolk is firm, round and high.	Yolk is firm and stands fairly high.	Yolk is somewhat flattened and enlarged.
Shell Appearance	Approximates usual shape; generally clean,* unbroken; ridges/rough spots that do not affect the shell strength are permitted.		Abnormal shape; some slight stained areas permitted; unbroken; pronounced ridges/thin spots permitted.
Usage	Ideal for any use, but are especially desirable for poaching, frying and cooking in shell.	Ideal for any use, but are especially desirable for poaching, frying and cooking in shell.	Good for scrambling, baking, and as an ingredient in other foods.

*An egg may be considered clean if it has only very small specks, stains or cage marks. Source: USDA

We can determine concentration of protein by using the Lowry Assay. If the density of Lowry is higher, the absorbance also higher. Its means, protein concentration also higher when the absorbance higher.