Mandarin oranges are high in citric acid and contain a fair amount of sucrose. They have a distinctive taste and it doesn't take much juice to make a gallon of wine. However, it oxidizes easily, so juice the oranges, add them to the water and immediately add a crushed Campden tablet per gallon. The recipe below uses only a pint of Mandarin orange juice per finished gallon of wine, but you can make it stronger by adding 1½-2 pints per gallon. Rest assured, though, that a pint of juice makes a flavourful wine. If you add more juice, decrease the water proportionally.
MANDARIN ORANGE WINE
1 pt Mandarin orange juice
2¼-2½ lbs finely granulated sugar*
6½ pts water
½ tsp pectic enzyme
1 tsp citric acid
1 tsp yeast nutrient
1 crushed Campden Tablet
1 pkt wine yeast
*Float a hydrometer in the combined juice and water and add enough brewing sugar to achieve a starting specific gravity of 1.085.
Juice the oranges and add all ingredients except pectic enzyme and yeast to primary. Stir well to dissolve sugar, cover primary and set aside for 12 hours. Add pectic enzyme, stir, recover, and set aside additional 12 hours. Add activated yeast and cover primary. Stir daily until vigorous fermentation subsides, then ferment covered until s.g. drops to 1.010 or below. Transfer to secondary and fit an airlock. Ferment to dryness, racking once or twice, and then stabilise and bulk age 4-6 months (check the airlock from time to time to make sure it doesn't dry out). You'll probably want to sweeten it a bit before bottling. Don't over-do the sweetening.