Digestibility of modified milk proteins: nutritional implications.

Area of Science:

• Food Chemistry
• Protein Biochemistry
• Nutritional Science

Background:

• Milk protein structure undergoes chemical modifications during processing and storage.
• These modifications can significantly impact protein digestibility and nutritional value.
• Accurate methods are needed to quantify these changes and their effects.

Purpose of the Study:

• To develop and validate in vitro techniques for assessing chemical changes in milk proteins.
• To evaluate the impact of these structural changes on protein digestibility.
• To establish a link between processing-induced modifications and nutritional quality.

Main Methods:

• Developed and standardized an in vitro digestibility assay using immobilized enzymes (gastric, pancreatic, intestinal).
• Quantitated protein racemization using a bioreactor with immobilized D-amino acid oxidase and catalase.
• Assessed Maillard reaction extent and available lysine via fluorometric o-phthalaldehyde method.
• Utilized immobilized enzymes for complete protein hydrolysis, preserving key amino acids.

Main Results:

• The in vitro digestibility assay correlated directly with human feeding study results.
• Increased racemization and lysinoalanine content were directly related to decreased protein digestibility.
• Higher available lysine, post-Maillard reaction, correlated with reduced protein digestibility.
• Enzymatic hydrolysis yielded nutritionally meaningful chemical scores without degrading critical amino acids.

Conclusions:

• The developed in vitro techniques effectively quantify structural changes in milk proteins.
• These methods accurately predict the impact of processing and storage on protein digestibility and nutritional quality.
• The techniques provide a valuable tool for monitoring and controlling protein quality in the food industry.