Must is fresh unfermented grape juice. If, like the Ancient Romans, you have no access to cane sugar, and honey is in short supply, grape juice is a useful substitute. The sugar and acidity of must varies according to the ripeness of the grapes from which it comes. Unripe grapes (from which Verjus is made) contain in the region of 5 to 8% sugar and their juice can be almost as tart as lemon juice, whereas must from grapes ripe enough to be made into wine will contain 10 to 15 % sugar and taste proportionately sweeter.
There are advantages and disadvantages to cooking with must. It is not as intensely sweet as honey, but then nor does it have honey’s sometimes cloying sugariness. Its distinctly fruity flavour can add interest to both sweet and savoury dishes. For desserts and confectionary or any dish where a more concentrated source of sugar is required, must can be reduced by boiling. In Roman times this yielded Caroenum (must reduced to approximately 50% of its original volume) and Defrutum (sometime spelt Defritum) which was boiled down by two thirds. Defrutum in particular was often given additional flavour by the addition of figs or other fruit during the reduction.
The production of grape juice reductions, once so widespread, has not entirely died out. In Southern Italy Mosto Cotto (cooked must) and Vin Cotto (usually a mixture of cooked must and wine) are produced as regional specialities and used to enhance meat and cheese dishes and also to make a variety of traditional desserts.
If you are curious what Ancient Roman cookery was like, the following 2,000 year old recipe for Duck with turnips from De Re Coquinaria by Marcus Apicius will give you some idea:
DUCK WITH TURNIPS ~ Wash and truss the bird and boil it in a large saucepan with water, salt, dill until half done. Cook the turnips so that they lose their pungency. Remove the duck from the pan, wash again, and put into another saucepan with oil, liquamen and a bouquet of leek and coriander. Put over it one washed and finely chopped (raw) turnip and braise. When it has been cooking for a while add defrutum to give it colour. Then prepare the following sauce: pepper, cumin, coriander, asafoetida root, add vinegar, and some of the cooking liquor; pour over the duck and bring to the boil. When it boils thicken with cornflour, and add to the turnips. Sprinkle with pepper and serve.
You will note that, as is generally the case with these ancient recipes, quantities are not given. For more information on how to cope with this and other peculiarities of Ancient Roman cooking, you might like to visit our www.vinumvetustum.com.au website. If you would like to buy Roman grape reductions made from must from our vineyard, or you would like to hear about Roman dinner parties at the Mount Terrible vineyard, please contact me, John Eason.