Castelbuono Manna

Manna is the sugary exudate that the manna ash (Fraxinus ornus, and to a lesser extent Fraxinus angustifolia) releases when its bark is cut. In hot, dry air the sap hardens into white concretions that can be lifted off the tree.

It is not a syrup and not a resin. It is a sugar, dominated by mannitol, which exceeds fifty per cent in the purest grade, alongside glucose, fructose, mannotriose and other oligosaccharides. It is roughly half as sweet as table sugar and has a low glycaemic index.

Two grades exist and they are genuinely different products. Manna cannolo is the fine one: chalk-white stalactites up to twenty centimetres long, formed along a nylon thread strung under the cut so the sap dries suspended in air and never touches bark or ground. Manna in rottame is scraped off the trunk or gathered from below: darker, less pure, and historically sold to industry.

One clarification that always needs making: this has nothing to do with the manna of the Book of Exodus. The name is shared, the substance is not. This is a Sicilian farm product, cut and harvested by people who do it for a living.

Gently sweet, and far less sweet than you expect from something that looks like a sugar stick: about half the sweetening power of sucrose. The flavour behind it is what makes it interesting: cool and faintly minty, with a light resinous, almost eucalyptus edge and a clean finish.

The cooling sensation is real rather than suggested. Mannitol has a negative heat of solution, so it draws heat as it dissolves and the mouth registers it as cold. This is why it is transformative in granita and ice cream and only pleasant in a cake.

Texturally the cannolo is light, brittle and chalky, and it snaps between the fingers. It dissolves cleanly in warm liquid with no grittiness and no aftertaste.

Two things govern everything else: manna is about half as sweet as sugar, so you need roughly double the weight, and it has a pronounced cool minty aroma that does not cook out. It is a flavouring sweetener, not a neutral one.

Dissolve it in warm water or milk, not boiling, stirring for a few minutes. From there it goes into custards, ice cream bases, panna cotta and semifreddo. Crumbled straight over fresh sheep's ricotta, with nothing else, is the most direct and most Sicilian way to eat it.

In granita and gelato it does something sugar cannot. Mannitol absorbs heat as it dissolves, so the cold registers more sharply on the tongue. Castelbuono's gelaterie have known this for generations.

In coffee and herbal infusions it works very well and the balsamic note becomes an asset. Local bakers use it in enriched doughs, and manna panettone has become a signature of the town.

One honest caveat on quantity: mannitol is an osmotic laxative above roughly twenty to thirty grams in an adult, which is precisely why pharmacies sold manna for centuries. At the five to ten grams a portion that cooking uses, it is not an issue.

Manna is hygroscopic and fully water-soluble, which makes damp air the only thing that really acts on it. In a humid room the surface turns tacky, then the pieces mat together, and eventually the whole lot slumps into a sticky mass. Kept in an airtight glass jar, in the dark, dry and at room temperature, it holds around two years with no change. The refrigerator works against it: every time the jar comes out, condensation forms inside. In a seaside kitchen in August, a food-grade silica gel sachet in the jar earns its place, exactly as it does with saffron or coarse salt.

Handling is part of it. Never take manna out with damp fingers, and use a dry spoon. Softened cannoli can be dried again: half an hour in an oven at 40 to 50 degrees with the door propped open drives the water back off and the snap returns. If they have already fused into one block, the practical route is to dissolve the whole thing in warm water and keep the syrup refrigerated for about a week. Grade and dating belong to the producer on the jar.

Grade shows in the shape. The top grade, cannolo, is a stalactite five to twenty centimetres long, irregular in section and startlingly light, ivory white and matte to the point of looking chalky. Yellowing or a brownish cast means either the lower grade or a wet harvest year. The lower grade, rottame, arrives as irregular fragments and granules; it is a different grade rather than a fault, it costs less and it dissolves just the same. Good manna is brittle: it snaps between the fingers with a dry click, and a piece that bends or feels tacky has been taking water out of the air.

Taste is the last check. It should be lightly sweet with a cool minty edge and a faintly resinous base, melting on the tongue without grit; strong, medicinal or bitter flavours are not part of it. On the label look for the comune, Castelbuono or Pollina, the producer and the declared grade. Anything sold simply as manna with no origin may be industrial mannitol, chemically the same molecule and a different product. Expect roughly 8 to 15 euros for 100 grams of cannolo.

Italian specialist importers and online food shops carry Sicilian manna in the US and the UK, usually in 30 to 100 gram packs. Expect 40 to 65 dollars per pound in the US and 70 to 115 pounds per kilo in the UK for cannolo grade. In Italy the same grade runs 80 to 130 euro per kilo, with small packs at 6 to 15 euro; the fragment grade is 35 to 60 euro per kilo.

Read the grade before the price. Cannolo is the chalk-white stalactite form and is what you want for eating as it is; rottame or fragments are darker and cheaper and are perfectly good dissolved into a cream or a syrup.

Check the label names Castelbuono or Pollina and a producer. Generic 'manna' with no origin may be industrial mannitol, which is the same molecule and a completely different product.

One practical note before the price puts you off: recipes use five to ten grams a portion. A fifty gram pack covers around ten desserts, which puts it closer to the cost of saffron than of sugar.

Castelbuono, in the province of Palermo, inside the Madonie regional park. The town has a Ventimiglia castle, a serious pastry tradition and manna in every possible form: in ice cream, in enriched breads, in biscuits, and in jars in the shops on the main street.

Pollina, the other producing town, sits high above the sea between Cefalù and the Nebrodi mountains. There is a museum devoted to manna here, and between late July and August it is possible to watch the cutting in the groves, which is the thing genuinely worth planning around.

Cefalù, half an hour down on the coast, is the easiest base, with its Norman cathedral and its beaches. From there the road climbs inland to Petralia Soprana and Sottana, Geraci Siculo and Piano Battaglia: an hour takes you from the sea to seventeen hundred metres.

August if you want to see the work. Any month if you simply want to buy and eat it: manna is a dry product and the shops carry it year round.