beta-lactoglobulin in native and nanoparticle forms could be used to tackle wine?s astringency

IGNACIO CABEZUDO; JUMOKE B. OLATUJOYE; PAULA JAUREGI

Norwich

Simposio; Total Food 2014; 2014

Institute of food research

Milk whey is a by-product of cheeseproduction,for that reason is produced in large amounts,and it?s mostlyapplied toanimal feed.As it is a source of very valuable proteins, much effort is being dedicatedto their extraction and application in food. In this work we investigate theapplication of the major whey protein,betalactoglobulin (β-Lg) in the treatmentof astringency in wine.Astringency isa puckering sensation, a rough or dryingmouth-feel, associated withinteractions between some phenolic compounds (tannins)andsalivary proteins, which leads to precipitation. In red wine, this effect isoften tackled by fining, which involves the addition ofa compound and settlingof wine?s partially soluble compounds.Some proteinsare known to interact withphenolicsin this way,influencing clarity, sensory characteristics, and aging capacity.Unfortunately,the antioxidant, cancer preventing and anti-inflammatory properties of wine aremostly attributed to phenolic compounds, and part of them can be lost in the finingprocess. Our objectivewas to first investigatethe potentialof β-Lg, in its native form and as nanoparticle aggregates, as wineastringency reducing agents.We aim to study the most promising proteins whichreduce astringency by complexation with tannins, yet maintaining otherpolyphenols in solution keeping in this way the health beneficial propertiesofwine.β-Lg nanoparticles were produced by asimple heat-induced denaturation method. A solution of β-Lg0.2 % w/vwasprepared, pH was adjusted to 6.0 and the protein was heated at 60°C during 10minutes, and then at 75°C for 15 minutes. β-Lg nanoparticlesize wascharacterised by dynamic light scattering (DLS).Different commercial winesampleswere evaluated before and after protein treatments, by assessment oftheir astringency. For that purpose astringency was measured by a method that reliesonmeasuring tannic acid as a tannin equivalent in wine upon precipitation withovalbumin. Tannins in wine were determined by the MethylCellulose Precipitation(MCP) method, relying on the precipitation of tanninswith the named polymer. Theresultswere contrasted withthe total phenolicconcentration of wine on each sample, evaluated by theFolin-Ciocalteaumethod.Eachprotein was evaluated at two different concentrations,0.1 and 0.5 mg/ml, and thereduction in astringency wasgreater at higher concentration of protein.β-Lginboth forms, showed highaffinity for the red wine polyphenols, reducedpolyphenols in the wine,hence decreasing astringency as measured by the Llaudymethod.Moreover, an importantamount of soluble phenolicscould be kept insolution, which is a plus to the bioavailabilityof polyphenols.