Petha — the translucent candied ash gourd of Agra

i. Origin & history

The ash gourd (Benincasa hispida) is a large, pale green gourd with a waxy white bloom on its skin — the 'ash' of its English name. Its flesh is white, watery and almost flavourless, which makes it an ideal blank canvas for candying, and it is grown widely across the plains of north India. In English it goes by several names: ash gourd, white gourd, winter melon, wax gourd and white pumpkin, and the sweet itself is sometimes sold simply as 'Agra petha'.

Agra's claim to the sweet is strong. The city has a whole trade built on it, centred on old bazaars where the gourds are peeled, cut and simmered in huge vats, and petha is the standard edible souvenir carried home from a visit to the Taj Mahal. A popular story says it was first made in the kitchens of the Mughal emperor Shah Jahan, or to feed the workers building the Taj Mahal in the seventeenth century. These stories are widely told in Agra but are not documented, and the technique of candying gourds in syrup is much older and more widespread.

Ash gourd has a long place in Ayurvedic tradition as a 'cooling' food, and petha is often offered as a sweet suitable for fasting days and hot weather. It is also notably light compared with most north Indian sweets: there is no ghee, no milk and no flour, just vegetable and sugar.

The confusion worth clearing up is with pumpkin. The orange pumpkin (kaddu) is a different plant, and recipes that say 'pumpkin' for petha mean the white ash gourd. Orange pumpkin will not turn translucent or hold its shape in the same way. Petha should also not be confused with the Chinese winter-melon candy used in mooncakes and wife cakes, though it is made from the same gourd by a very similar method.

ii. What the lime water does

Ash gourd flesh is over 95% water and very soft. Simmered straight in syrup, it would collapse into a mush. The step that makes petha possible is soaking the cut cubes in a solution of edible lime — calcium hydroxide, known in India as chuna, the same slaked lime used in paan.

Calcium ions from the lime cross-link the pectin in the gourd's cell walls, forming calcium pectate, a firmer gel that holds the cells together. The cubes come out of the soak noticeably stiffer, and they keep their sharp edges and slightly crunchy outer layer through long cooking in syrup. The same principle is used to make crisp pickles and in Mexican candied pumpkin (calabaza en tacha).

Pricking the cubes all over with a fork lets the lime solution — and later the syrup — penetrate evenly to the centre. After soaking, the cubes must be rinsed several times in fresh water and then boiled, both to remove the alkaline taste and to soften the flesh just enough that it can absorb sugar.

The candying itself is slow osmosis. Cooked in syrup and left to stand, the gourd gradually swaps its water for sugar; this is what changes it from opaque white to glassy and translucent. Done in stages — cook, rest, cook again — the sugar penetrates all the way through. Rush it in one go and the outside candies while the centre stays watery and spoils quickly.

iii. Ingredients

Makes 20 servings · scroll the side panel to adjust

• 1 kg ash gourd (white pumpkin), weighed after peeling and seeding
• 1 tbsp edible lime paste (chuna)
• 2000 ml water, for soaking
• 750 g sugar
• 400 ml water, for the syrup
• 1 tsp lemon juice
• 1 tbsp rose water or kewra water
• ¼ tsp green cardamom, ground (optional)

Choose a mature ash gourd with a heavy, firm feel and a powdery white bloom; young gourds are too soft and watery. You will lose about a third of its weight to skin and seeds. Edible lime (chuna) is sold in small tubs at Indian grocers as paan lime; use only food-grade lime, wear gloves and keep it away from eyes, as it is caustic before dilution. The lemon juice stops the syrup crystallising. Rose water or kewra (screwpine) water is the classic Agra perfume; saffron makes kesar petha.

iv. Method

1. Peel the ash gourd thickly, remove the soft seedy core, and cut the firm flesh into 3–4 cm cubes or rectangles. Prick each piece all over, deeply, with a fork.
2. Stir the lime paste into the 2 litres of water in a large glass or steel bowl until dissolved. Add the gourd pieces, making sure they are submerged, and soak for 6–8 hours or overnight. They will turn whiter and feel noticeably firmer.
3. Drain and rinse the pieces under running water, then soak in fresh water for 10 minutes; repeat the rinse and soak three or four times until no lime residue remains.
4. Boil the pieces in plenty of fresh water for 12–15 minutes, until they are slightly translucent at the edges and a knife slides in easily. Drain well.
5. In a wide pan, dissolve the sugar in 400 ml water with the lemon juice. Add the boiled gourd and simmer gently for 25–30 minutes, until the pieces look glassy and the syrup thickens. Skim any foam.
6. Turn off the heat, cover and leave the petha to stand in the syrup for 6–8 hours or overnight so the sugar penetrates to the centre.
7. Bring back to a simmer and cook for another 15–20 minutes until the syrup reaches one-string consistency and the pieces are fully translucent. Stir in the rose water and cardamom.
8. For syrupy (angoori-style) petha, cool and store in the syrup. For classic dry petha, lift the pieces onto a rack and leave them to dry at room temperature for 6–12 hours, until the surface crystallises into a firm white coat.

v. Tips & common mistakes

• Do not skip the lime soak. Without calcium the pieces dissolve into a sweet mush in the syrup. If you cannot find chuna, alum (fitkari) is used by some cooks as a substitute, but lime gives the classic bite.
• Rinse thoroughly. Any lime left on the gourd gives a soapy, bitter aftertaste. Several changes of water are worth the time.
• Prick deeply and evenly. Unpricked pieces candy only on the outside and stay opaque and watery in the middle.
• Candy in two stages. The overnight rest in syrup is what turns the pieces translucent right through. One long boil makes them tough outside and raw within.
• Do not boil the syrup hard. A fierce boil caramelises the sugar and colours the petha; it should stay pale and glassy.
• Dry petha needs air, not heat. Leave the pieces on a rack in a dry room. An oven sets a hard sugar crust before the inside is ready.

vi. Variations

Agra's sweet shops sell dozens of versions. Sada petha is the plain dry original. Angoori petha is small cubes kept in syrup. Kesar petha is saffron-yellow and scented, paan petha is green and flavoured with betel leaf, and chocolate, coconut and dry-fruit petha are filled or coated with nuts. Gilori petha is folded into triangles around a filling like a paan.

Related candied sweets include the syrupy fruit preserves called murabba made across north India and Pakistan, the Gujarati mohanthal for a contrasting rich fudge, and Southeast Asian candied fruits. For a similar translucent, gently chewy texture in a Middle Eastern sweet, see Turkish delight, and for another regional icon of Indian sweet-making, Mysore pak.

vii. Serving & storage

Petha is eaten as it is, at room temperature, as a sweet with tea, an offering at temples, a fasting-day treat or a gift. Angoori petha is often served chilled in its syrup in summer. Because it contains no dairy and is relatively light, it is one of the sweets that travels best, which is why it is bought by the box in Agra.

Dry petha keeps for about two weeks in an airtight container at room temperature and for three to four weeks in the fridge. Syrupy petha keeps for two to three weeks refrigerated in its syrup. If dry petha becomes sticky in humid weather, leave it uncovered on a rack for a few hours. It does not freeze well — the gourd turns watery on thawing.

ix. More from Indian & South Asian

• Kaju Katli — cashew fudge diamonds
• Gulab Jamun — milk dumplings in syrup
• Rasgulla — spongy chhena balls
• Soan Papdi — flaky threaded sweet
• Pedha — milk fudge rounds
• Turkish Delight — rose-scented starch jelly