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Human and animal milk contain a rich variety of milk proteins that meet the needs of their newborns. In total, 1263 skim milk proteins and 1754 MFGM proteins were identified in human milk and six types of animal milk, respectively. Both similarities and differences were observed among the species. Human milk contained more immunoglobulins involved in the adaptive immune response, playing a crucial role in mucosal defense in newborn babies. In contrast, ruminant milk contained higher amounts of antimicrobial proteins, which protect newborns from bacterial infections. The most dominant difference in MFGM proteins between human and animal milk was related to protein processing in the endoplasmic reticulum. Goat milk and camel milk were more similar to human milk in terms of skim milk and MFGM proteins compared to the other five types of animal milk. Moreover, immunoglobulins and complement and coagulation cascade proteins in goat milk were most similar to those in human milk. A higher content of immunoglobulin A was observed in donkey milk, which could be considered as a source of IgA in infant formula. These results provide more comprehensive and novel insights into protein variation among animal milk, which may support improving dairy products such as infant formula.

Milk fat globule membrane (MFGM) proteins are receiving increased attention due to their reported benefits for human health, particularly in infant populations. Challenges exist in MFGM protein quantification due to their low quantities, complex chemistry, interactions with other matrix components, and the high matrix complexity. In this study, a subset of four MFGM proteins were selected as relevant targets for identification and quantification in an infant formula (IF) matrix: butyrophilin, mucin 1, xanthine dehydrogenase/oxidase, and perilipin 2. An analytical protocol for absolute quantification of these four MFGM proteins in IF was successfully developed and validated. Additionally, the feasibility to apply the method in selected MFGM ingredients was also demonstrated. The method demonstrated good performance; high accuracy and robustness, low LOQ and uncertainty, while controlling the matrix effect. This study represents a report of an analytical method to quantify selected MFGM proteins in IF., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interest or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)