“…Ultrahigh temperature (UHT) processing ensures a long shelf life for milk stored at ambient temperature; however, such thermal processing will cause negative impacts on flavor quality. − Flavor changes in UHT milk are mainly associated with Maillard reactions, lipid oxidation, and proteolysis. , Maillard reactions start by a condensation reaction between carbonyl groups of reducing sugars and amine groups of proteins, peptides, or amino acids, forming a Schiff base. After enolization, the Schiff base is transformed into Amadori compounds (or Heyns compounds in the case of ketoses), which can be degraded to form highly reactive α-dicarbonyls, including glyoxal (GO), methyglyoxal (MGO), and deoxyosones. , Further rearrangement and dehydration reactions lead to formation of 5-(hydroxymethyl)furfural (HMF) and furfural, , which are regarded as indicators of Maillard reactions in foods. − α-Dicarbonyls may also react with free amino acids to form Strecker aldehydes, such as 2-methylbutanal, 3-methylbutanal, phenylacetaldehyde, and acetaldehyde. , α-Dicarbonyls can also form advanced glycation end products (AGEs) by reacting with nucleophilic side chains in proteins . The reaction between α-dicarbonyls and proteins may lower the nutritional value of foods. , Strecker aldehydes, HMF, and furfural contribute to the formation of off-flavor in UHT milk during long-time storage. , …”