I know this is a common topic but I bottled a Muscato that I racked three times. It was crystal clear when I bottled it but now, after three weeks it still has a cloudy haze to it. I didn't use any isinglass because I figured it was clear enough. Anyone know how it can become hazy like this? I made it from juice, too, if that's any help. It sat in my basement at about 65 degrees for five months before I bottled it.
Your Muscato might have a protein haze. Grapes contain small quantities of protein, and the protein is carried over from the grapes into the wine during fermentation. Originally, the protein molecules are much too small to be visible in the wine. However, under certain conditions protein molecules link together (polymerize) and grow larger. After many protein molecules have linked together, the protein particles are large enough to be visible. This growth process is very slow at normal cellar temperatures, but when wine becomes warm, the protein molecules grow more rapidly. At temperatures of about 120 degrees, protein molecules can link together and form large particles in a short time. When white or blush wines are subjected to warm storage conditions, protein hazes can form quickly, so all commercial white and blush wines are specifically treated with Bentonite to remove the excess protein before bottling. Winemakers call protein haze hot instability because warm storage conditions trigger the phenomena. Leaving a bottle of Sauvignon Blanc in a car trunk on a hot summer day can easily produce a graphic demonstration of hot instability.
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