Analytical quantification of primary and secondary lipid oxidation:

• Thiobarbituric Acid (TBA) test measures secondary oxidation products, specifically malonaldehyde, which reacts with TBA to form a pink chromogen ($532\text{ nm}$).
• Peroxide Value (PV) measures primary oxidation products (hydroperoxides) iodometrically and serves as the most standard indicator of the initial rate of lipid autoxidation.
• Iodine value measures total fatty acid unsaturation.
• Acid value measures free fatty acids produced by lipolytic hydrolysis, not autoxidation.

Distinction between non-enzymatic browning and lipid oxidation markers:

• Furosine is the definitive acid-hydrolysis marker derived from Amadori products (lactulosyl-lysine) used to monitor early Maillard reactions in pasteurized and UHT milk.
• Lactulosyl lysine is the primary Amadori product formed in milk during heat processing.
• Hydroxymethylfurfural (HMF) is an intermediate heterocyclic marker used extensively to measure intermediate Maillard reaction intensity.
• Octa-2,4-dienal is a volatile unsaturated aldehyde produced by the autoxidation and cleavage of polyunsaturated fatty acids (linoleic/linolenic acid); it is an oxidized lipid off-flavor marker, NOT a Maillard reaction marker.

Biochemical basis of colostrum thermal coagulation:
(A), (B), (D) Electrolytes and fat play secondary roles in destabilization.
(C) First-milking bovine colostrum contains exceptionally high levels of total protein ($14\text{ to }18\%$, compared to ~3.3% in mature milk), driven primarily by huge concentrations of heat-labile whey proteins, especially Immunoglobulins ($IgG_1$, representing up to $80\%$ of colostral whey protein). Immunoglobulins denature and unfold readily at temperatures above $60\text{--}65^\circ\text{C}$, exposing hydrophobic residues that cross-link into a rigid thermal coagulum. This extreme protein load causes colostrum to curdle instantaneously upon heating.