Chemical and Proteolysis-Derived Changes during Long-Term Storage of Lactose-Hydrolyzed Ultrahigh-Temperature (UHT) Milk

Proteolytic activity in milk may release bitter-tasting peptides and generate free amino terminals that react with carbohydrates, which initiate Maillard reaction. Ultrahigh temperature (UHT) heat treatment inactivates the majority of proteolytic enzymes in milk. In lactose-hydrolyzed milk a β-galactosidase preparation is applied to the milk after heat treatment, which has proteolytic side activities that may induce quality deterioration of long-term-stored milk. In the present study proteolysis, glycation, and volatile compound formation were investigated in conventional (100% lactose), filtered (60% lactose), and lactose-hydrolyzed (<1% lactose) UHT milk using reverse phase high-pressure liquid chromatography–mass spectrometry, proton nuclear magnetic resonance, and gas chromatography–mass spectrometry. Proteolysis was observed in all milk types. However, the degree of proteolysis was significantly higher in the lactose-hydrolyzed milk compared to the conventional and filtered milk. The proteins most prone to proteolysis were β-CN and α_s1-CN, which were clearly hydrolyzed after approximately 90 days of storage in the lactose-hydrolyzed milk

Lactose-Hydrolyzed Milk Is More Prone to Chemical Changes during Storage than Conventional Ultra-High-Temperature (UHT) Milk

The enzymatic hydrolysis of lactose to glucose and galactose gives rise to reactions that change the chemistry and quality of ambient-stored lactose-hydrolyzed ultra-high-temperature (UHT) milk. The aim of the present study was to investigate and compare chemical changes in lactose-hydrolyzed and conventional UHT milk during a 9 month ambient storage period. Several complementary analyses of volatiles, free amino acids, acetate, furosine, and level of free amino terminals were concluded. The analyses revealed an increased level of free amino acids and an increased formation rate of specific compounds such as furosine and 2-methylbutanal in lactose-hydrolyzed UHT milk compared to conventional UHT milk during storage. These observations indicate more favorable conditions for Maillard and subsequent reactions in lactose-hydrolyzed milk compared to conventional UHT milk stored at ambient temperature. Furthermore, it is postulated that proteolytic activity from the lactase-enzyme preparation may be responsible for the observed higher levels of free amino acids in lactose-hydrolyzed UHT milk

Substituted 7‑Amino-5-thio-thiazolo[4,5‑<i>d</i>]pyrimidines as Potent and Selective Antagonists of the Fractalkine Receptor (CX₃CR1)

We have developed two parallel series, A and B, of CX₃CR1 antagonists for the treatment of multiple sclerosis. By modifying the substituents on the 7-amino-5-thio-thiazolo­[4,5-<i>d</i>]­pyrimidine core structure, we were able to achieve compounds with high selectivity for CX₃CR1 over the closely related CXCR2 receptor. The structure–activity relationships showed that a leucinol moiety attached to the core-structure in the 7-position together with α-methyl branched benzyl derivatives in the 5-position displayed promising affinity, and selectivity as well as physicochemical properties, as exemplified by compounds <b>18a</b> and <b>24h</b>. We show the preparation of the first potent and selective orally available CX₃CR1 antagonists