Total phenolic compounds in milk from different species. Design of an extraction technique for quantification using the Folin–Ciocalteu method

Milk protects the health of newborns because it contains essential compounds that perform metabolic activities. Despite these benefits, the study of phenolic compounds in milk has been poorly explored. The objective of this study was to develop and validate a technique for extracting total phenolic compounds (TPCs) from a milk matrix and then analyzing them using the Folin–Ciocalteu method. The extraction technique was applied to goat milk and involved the addition of methanol, acetonitrile, and Carrez I and II reagents, after which protein was separated from fat through centrifugation. Subsequently, the technique was applied to goat (69.03 ± 6.23 mg GAE/L), cow (49.00 ± 10.77 mg GAE/L), sheep (167.6 ± 58.77 mg GAE/L) and human milk (82.45 ± 12.3 mg GAE/L). The technique showed an acceptable linearity (R2 = 0.9998), limit of detection (6.03 mg GAE/L) and quantification (16.2 mg GAE/L), repeatability (RSD = 4%), reproducibility (RSD = 6.8%) and recovery (>85.41%); it is thus effective and can be used in the routine analysis of milk. TPCs obtained from each type of milk indicate a high variability among species and among members of the same species.