Passion fruit nectar figures prominently in many tropical drinks created by the inimitable Trader Vic. In his Trader Vic's Bartenders Guide, Revised, he states:
If you have occasion to buy some passion fruit nectar (we distribute it), you can pretty well be assured that any drink made with it will be good...
Trader Vic does indeed sell a product called Passion Fruit Syrup, which up until about a year ago was a reasonably quality product made with real fruit juice. Ingredients are HFCS, water, passion fruit concentrate, citric acid, natural flavors, xanthan gum, red #40 (11% fruit juice).
Unfortunately, the Trader Vic brand has decided to replace this product with a new recipe made from artificial ingredients. I have not tried this newer version based on some of the comments here in the Tiki Central forums. I tried a bottle of Finest Call passion fruit syrup, but this turned out to be a sub-par, if not, just-plain-bad call.
Instead, as with grenadine, I was left to devise my own recipe for passion fruit nectar.
The starting point for this effort is a bottle of Looza brand passion fruit Nectar. It is readily available at many specialty stores such as Whole Foods. It is a Belgian brand and contains only water, concentrated passion fruit juice and sugar (25% juice). Many of the recipes for passion fruit syrup that I ran across on the forum required some amount of cooking. As with the grenadine, I tried to avoid any heating, lest it strip the acidity and give the resulting syrup a more "cooked" flabby flavor. Using the "cold process" involves simply shaking the mixture until the sugar is dissolved.
Comparing sugar levels, the Trader Vic's contains 21g/oz. Looza contains 4g/oz. Cutting the Looza with 50% water (12.5% juice) results in 2g/oz. Therefore each oz. of Looza syrup requires an extra 18g or so of sugar or 1.5 tablespoons of cane sugar.
The resulting product is clean and fruity with a definite passion fruit flavor that is more focused than the Trader Vic's version, but not overpowering. It is notably less viscous, owing to the lack of xanthan gum, but I have not found this to have a negative impact on any tropical drinks made with it.
Passion Fruit Nectar
2c Looza Passion Fruit Nectar (approx. 1/2 bottle)
2c Bottled or otherwise neutral pure Water
3c White granulated sugar
2 drops red dye (totally optional, only if you're going for the original look)
Combine ingredients in a glass bottle or pour-top plastic juice bottle (closable top recommended) and shake vigorously until sugar dissolves. Refrigerate. Substitute 1:1 per Trader Vic recipes.