Sulfonation Reactions behind the Fate of White Wine’s Shelf-Life

1H NMR based sulfonation reaction kinetics of wine relevant thiols in comparison with known carbonyls

Sulfite addition is a common tool for ensuring wines' oxidative stability via the activity of its free and weakly bound molecular fraction. As a nucleophile, bisulfite forms covalent adducts with wine's most relevant electrophiles, such as carbonyls, polyphenols, and thiols. The equilibrium in these reactions is often represented as dissociation rather than formation. Recent studies from our laboratory demonstrate, first, the acetaldehyde sulfonate dissociation, and second, the chemical stability of cysteine and epicatechin sulfonates under wine aging conditions. Thus, the objective of this study was to monitor by 1H NMR the binding specificity of known carbonyl-derived SO2 binders (acetaldehyde and pyruvic acid) in the presence of S-containing compounds (cysteine and glutathione). We report that during simulated wine aging, the sulfur dioxide that is rapidly bound to carbonyl compounds will be released and will bind to cysteine and glutathione, demonstrating the long-term sulfur dioxide binding potential of S-containing compounds. These results are meant to serve as a complement to existing literature reviews focused on molecular markers related to wines' oxidative stability and emphasize once more the importance of S-containing compounds in wine aging chemical mechanisms.

Microfluidic formulation of food additives-loaded nanoparticles for antioxidation

Browning has many important implications with nutrition and the shelf life of foods. Mitigating browning is of particular interest in food chemistry. The addition of antioxidants has been a common strategy to extend shelf life of drug and food products. In this work, we report a microfluidic technology for encapsulation of three common food additives (potassium metathionite (PMS), curcumin (CCM), and β-carotene (β-Car)) into nano-formulations using low-cost and readily available materials such as shellac. The food additives encapsulated nanoparticles provide a microenvironment that can prevent oxidation during daily storage. The results showed that the produced nanoparticles had a narrow size distribution with an average size of around 100 nm, were stable at conventional storage conditions (4 ºC) for 18 weeks, and had sustained release ability at 37 ºC, pH= 7.8, 160 rpm. In addition, further experiments showed that the formulation of hydrophobic additives, such as CCM and β-Car did not only improve their bioavailability but also allowed for the encapsulation of a combination of ingredients. In addition, the antioxidants loaded nanoparticles demonstrated good biocompatibility, low toxicity to human cells. The longer release time of encapsulated food additives increases shelf life of foods and enhances consumer purchase preferences, which not only saves costs but also reduces waste. In summary, this study shows that such antioxidant-loaded nanoparticles provide a promising strategy in extending the shelf life of food products.

Chemical Stability of Thiol and Flavanol Sulfonation Products during Wine Aging Conditions

Bisulfite (HSO3-) is the predominant form of sulfur dioxide, present as free and bound to wine relevant electrophiles under wine acidic pH. While sulfonation reactions of flavanols and thiols have been recently reported as key for wine preservation against oxidation, the transient mechanisms and physicochemical parameters responsible for that remain unknown. In the present study, sulfonation reaction kinetics of thiols and flavanols were monitored under simulated wine aging conditions. The reaction products were then characterized by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis, and their chemical stability during time was determined by 1H NMR spectroscopy. Thiol and flavanol sulfonation reaction yields were both promoted by the presence of iron and oxygen, while their chemical stability was confirmed under the same conditions. The sulfonation derivatives of epicatechin and cysteine were synthesized and quantified in young and aged wines. Higher concentrations were reported for both metabolites in older wines, indicating their participation on the strongly bound sulfur dioxide fraction. These findings offer new prospects for more precise use of sulfur dioxide in winemaking.