Milk Proteins and Protein Analysis - Video Notes

Vocabulary flashcards covering key concepts from the lecture notes on milk proteins (casein and whey) and chemical analysis tests for proteins.

Casein

A major group of milk proteins; 3–4 —— are present in most species; high-quality, highly digestible protein important for growth of nursing young.

Whey proteins

All other milk proteins besides caseins; example in cow milk are beta-lactoglobulin and alpha-lactalbumin.

Beta-lactoglobulin

A principal whey protein in cow milk.

Alpha-lactalbumin

A principal whey protein in cow milk.

Immunoglobulin/ Serum Albumin

Antibodies found in milk; not synthesized by mammary epithelial cells; most derived from blood; limited local production by mammary tissue plasma cells provides local immunity.

Serum albumin

A blood protein found in milk; absorbed from blood; not synthesized by mammary epithelial cells.

Mammary epithelial cells

Cells in the mammary gland that synthesize caseins and whey proteins.

Plasma cells

Lymphocytes residing in mammary tissue that synthesize immunoglobulins for local immunity.

Local immunity

Immunity provided within the mammary gland via locally produced immunoglobulins.

Casein isolation

Laboratory procedure to extract and purify casein from milk using heat, acid precipitation, filtration, and solvent wash, then drying and weighing.

Yield percent

Percentage yield of casein: (weight of isolated casein / weight of milk sample) × 100.

Biuret test

Colorimetric test for peptide bonds; produces purple color when protein is present.

Ninhydrin test

Chemical test for amino acids with free amino groups; produces deep blue/purple color (Ruhemann's purple) for many amino acids; some amino acids (e.g., proline) may give negative.

Millon’s test

Test for tyrosine residues in proteins; produces red coloration when tyrosine is present.

Xanthroproteic test

Test for aromatic amino acids in proteins; yields yellow color that can turn orange with base.

Hopkin’s Cole test

Test for aromatic amino acids in proteins; produces a colored interface reaction (often violet) in positive samples.

Lead acetate test

Test for sulfhydryl groups (cysteine) in proteins; production of dark/black precipitate with heat.

Glycine

The simplest amino acid used as a substrate in these protein tests.

Proline

An amino acid with a cyclic structure; often yields negative results in some tests like Ninhydrin.

Cysteine

A sulfur-containing amino acid with a thiol group; detectable by the Lead Acetate test.