Investigation of the compositional and structural changes in the proteins of cow milk when processed to cheese

Various treatments applied during dairy processing strikingly affect milk proteins, the major structural determinants, thus causing modifications in some techno-functional and biological properties of the final dairy product. Cheeses, with a variety of types, are mostly consumed processed dairy foods worldwide. The purpose of this study was to investigate the effect of heating, culture/enzyme activity and other treatments on the composition and molecular structure of cow milk proteins during the processing of different cheeses through electrophoresis, chromatography and spectroscopy. Electrophoretic patterns of the samples successfully indicated differences in protein content through process steps and in the final products. Curdling after pasteurization at 85 degrees C revealed many newborn peptides not detected in raw cow milk and other dairy samples. High and low similarities in peptide profiles of cheeses to that of raw cow milk indicated high-temperature pasteurizationinduced unfolding facilitated extensive proteolysis subsequently. Significant conformational changes including loss of alpha-helices and exposure of beta-strands observed in the secondary structure of proteins especially through curdling might offer alterations of reactive/functional groups. In total, pasteurization, curdling, salting, and ripening treatments remarkably altered the content and structure of cow milk proteins through unfolding, denaturation and aggregation, strongly suggesting modified functionality when milk was processed to cheese.

Automated summary

Various treatments during dairy processing significantly affect the composition and molecular structure of cow milk proteins, leading to modifications in the final dairy product properties. Techniques like electrophoresis, chromatography, and spectroscopy can successfully indicate differences in protein content, showing changes induced by heating, culture/enzyme activity, and other treatments. The conformational changes observed, such as loss of alpha-helices and exposure of beta-strands, suggest that processing treatments like pasteurization, curdling, salting, and ripening alter the content and structure of cow milk proteins, affecting their functionality in the final cheese product.