Free fatty acids and their esters modulate isothermal crystallization of anhydrous milk fat
Food Chemistry, 2017, 218, 22-29
The effect of free fatty acids with different chain lengths or unsaturation degree on anhydrous milk fat (AMF) crystallization was evaluated. The impact of esterification was also studied using three triglycerides. Melted blends containing the additives at concentrations lower than 12 wt.% were quenched at 25 degrees C and isothermal crystallization was monitored by pulsed low-resolution nuclear magnetic resonance. In parallel, polarized light microscopy was used to observe the microstructure. Compounds based on long chain saturated fatty acids, i.e. palmitic, stearic, eicosanoic acids, tripalmitin and tristearin accelerated crystallization. Conversely, propanoic, hexanoic and oleic acids slowed down the process, while triacetin had no impact. Interestingly, above a critical concentration, the addition of palmitic, stearic or eicosanoic acids caused a transition from a one-step to two-step process. Gompertz model was used to fit the experimental data and to assess the influence of the molecular properties of the additives on the kinetic parameters. (C) 2016 Elsevier Ltd. All rights reserved.
Tip-Enhanced Raman Spectroscopy to Distinguish Toxic Oligomers from Abeta1-42 Fibrils at the Nanometer Scale
Angew Chem Int Ed Engl, 2017, 56, 1771-1774
For the first time, natural Abeta1-42 fibrils (WT) implicated in Alzheimer's disease, as well as two synthetic mutants forming less toxic amyloid fibrils (L34T) and highly toxic oligomers (oG37C), are chemically characterized at the scale of a single structure using tip-enhanced Raman spectroscopy (TERS). While the proportion of TERS features associated with amino acid residues is similar for the three peptides, a careful examination of amide I and amide III bands allows us to clearly distinguish WT and L34T fibers organized in parallel beta-sheets from the small and more toxic oG37C oligomers organized in anti-parallel beta-sheets.