Lychee fruits of optimum maturity are washed and peeled. The treated fruits are taken out, followed by pulping in a pulper. Then the lychee fruits are drained into a bucket for 4–8 hours at 10~15 °C, and then cooled to 8–10 °C and drained for another 10 hours. The sugar contents are adjusted to 22° Bx by dilution with water and then mixed thoroughly together with 100 mg/L sulfur dioxide and 80~120 mg/L activated liquid pectinase. The treated lychee juice is then frozen to obtain the condensed juice that is full of a sweet and sour flavor. Afterward, the condensed juice is warmed up to 10–12 °C. A 24h-old active culture of yeast (
Saccharomyces cerevisiae is added at 5% to the sterilised lychee juice to carry out the alcoholic fermentation. The fermentation is carried as a routine practice and allowed to continue until the TSS comes to 7° Bx; this procedure usually takes several weeks. The wine is filtered and stored at 10–15 °C, and the ideal maturation process takes about three months. Slight adjustments are often made based on the flavor and alcohol content of the wine, followed by sterilization and then the beverage is dispensed into glass bottles, which are closed with crown corks. The initial lychee juice contains a large amount of fermentable sugars and high acid content which make the liquid suitable for winemaking. Lychee wine produced from reconstituted lychee juice concentrate under optimized conditions contain 11.6% ethanol, 92 mg/L total esters, 124 mg/L total aldehydes, and 0.78% titratable acidity. Sensory evaluation reveals a clean, light amber color, an attractive aroma of the natural lychee fruit, and a harmonious wine taste.
Lychee processing It is the first step in lychee wine production. After picking, the lychee fruits of optimum maturity are washed, peeled and seeded by hand or husking machine. The treated fruits are taken out, conveyed by a screw mechanism, followed by pulping in a pulper.
Crushing After peeling, the lychees are lightly or fully crushed. Crushers usually consist of several stainless steel rollers and gaps. They can be adjusted to different modes, light, strong or no crushing, depending on the winemaker's preference. The mix of lychee fruit and juice is then transferred to a vessel, usually a tank made of stainless steel or glass for fermentation.
Additions Sulfur dioxide is added when the lychee pulp is pumped to the containers. The addition rate varies from 0–100 mg/L. The purpose of sulfur dioxide is to prevent oxidation and delay the onset of fermentation. Pectinase is added at this stage to improve the extraction of the color and flavor from the lychee and to facilitate pressing. The addition rate of macerating enzyme ranges from 80–120 mg/L. According to the previous experiment, 0.2% activated liquid pectinase is usually the preferred reception. Tannin is the optional addition in the winemaking process. It can contribute to help stabilize color and prevent oxidation to remove the effects of rot. The sweetener may be added now, later or even not at all according to the preference of winemakers.
Fermentation It is a process of transferring the sugar present in the fruit into alcohol with heat as the byproduct. The natural yeast from the fruit and the environment start to carry out the alcoholic fermentation once the lychee pulp is in the fermentation vessel. Different winemakers have their own choices of specially selected yeast and the addition rate of yeast. There are hundreds of different strains of wine yeast are commercially available, many winemakers believe that specific strains of yeast are more or less suitable for different lychee varieties and different types of wine. The fermentation is carried as a routine practice and allowed to continue until the total suspended solid rate comes to 7°Bx, this procedure usually takes several weeks for lychee wine.
Bottling Most winemakers choose to filter the wine before bottling, although some of them use the absence of filtration as a marketing tool. Filtration is designed to clarify the wine and eliminate any remaining yeast and bacteria, which can stabilize the microenvironment in the bottled wine. Lychee wine is often dispensed into glass bottles with cork stoppers, but sometimes aluminium screw caps. == Classification ==