杏吧原创

Soggy pud

Question: The traditional way to cook a boiled pudding is to tie it in a
cotton or linen cloth and immerse it in boiling water. If the water goes off the
boil, water gets into the pudding and it goes soggy.

What prevents the simmering water鈥攗ndoubtedly a liquid鈥�
penetrating the cloth, when the cloth lets in water when the temperature is only
a few degrees lower?

Quite a few Christmases have come and gone since this question was first
asked on 15 November 1997. Now, at long last, we are not only printing some of
the answers but we are also taking the boiled pudding into the New
杏吧原创 lab鈥擡d

Answer: Many years ago my wife added warm water to my mother鈥檚 Christmas
pudding and I don鈥檛 think my mother has ever forgiven her. I can confirm that
Christmas pudding is not at its best when it is eaten through a straw!

The secret of keeping the water out of the pudding lies in the preparation,
and you must use the best beef suet.

When the pudding mix is ready, lay a rectangular piece of sheeting on the
table. Carefully sift a thick layer of plain flour over this sheeting and place
the pudding mix in the centre. Now, in a container large enough to hold both
pudding and displaced water add boiling, boiling, boiling water.

Two people are required for the next step. One carefully picks up the edges
of the sheeting and twists them together, making sure that there is a layer of
plain flour all over the pudding mix. The other person winds strong string
tightly around the sheeting below the hands of the person holding the
pudding.

Then you slowly lower the pudding into the boiling water and cook for the
required time. Keep the pan topped up with with boiling water. It is absolutely
essential that you use boiling water at every stage.

As well as the boiling water, the flour plays a very important role. The
boiling water denatures the protein in the flour so that, rather than being
clumpy molecules, the protein stretches out. This makes an effective water
barrier by entangling water molecules and preventing their further inward
movement. Water that is merely warm simply soaks through the flour into the
pudding.

The floury water barrier is assisted by the beef suet in the pudding which
melts and slowly moves outwards to join it. Here it makes a kind of 鈥渉ot water
pastry鈥�. This skin is flexible when warm but becomes more rigid when cool and
helps provide some physical strength to hold the pudding together.

Malcolm Oliver

Brushgrove, New South Wales

Answer: When water reaches its boiling point it begins to boil throughout its
volume. The steam bubbles that are generated are created at points of
imperfection (nucleation sites) on the vessel wall or on microscopic particles
in the water.

Cotton or linen fibres act as nucleation sites for the bubbles on their
surface, which push the bulk of the surrounding water outwards. This in turn
creates a barrier to the passage of water through the cloth, although there is
still a small percentage that passes through.

If the water is allowed to cool below the boiling temperature, the bubbles
disappear, allowing more of the water to soak through the cloth to the pudding
inside.

Alan Dawes

Swindon, Wiltshire

Answer: As long as the temperature of the pudding is going up, all the gas
(water vapour and carbon dioxide from the baking powder) is expanding and
migrating outwards, pushing water from its pores. As soon as the temperature
starts to drop, the gas starts to contract, drawing water in from the edges.

Michael Stanford

Dallas, Texas

These three answers focus on three different effects that occur while the
pudding is cooking: the formation of an impermeable layer, bubbles created at
nucleation sites slowing water entry, and expansion of gas within the pudding
driving water out. Are all correct? We turned to our lab鈥擡d

To recreate a boiled pudding sitting below the surface of the cooking water,
New 杏吧原创 carried out the following experiment.

Four old, 100 per cent cotton airtex T-shirts (minus sleeves), with an area
of about 1.7 square metres, were wrapped around cricket balls鈥攚hich are
heavy enough not to float鈥攖o form spheres that were about 15 centimetres
in diameter. The T-shirts were held in place by elastic bands.

Two of the 鈥減uddings鈥� were rolled in a mixture of melted butter and olive oil
until their surfaces were totally covered. Then all four puddings were wrapped
in pudding bags made from an old cotton sheet and tied with string.

Water was heated in a large aluminium pan until it was boiling ferociously.
One non-oily and one oily pudding were lowered into the boiling water for 15
minutes. The two remaining puddings (one oily, one non-oily) were immersed in
cold water for 15 minutes.

When the 15 minutes were up, the puddings were removed from the boiling
water, the pudding bags stripped away and the T-shirts unfolded. On the non-oily
pudding, there was a noticeable dry area of T-shirt鈥攁bout 0.4 square
metres鈥攊n the centre surrounding the cricket ball. The oily pudding had a
larger dry area, about 0.5 square metres. What was also noticeable about these
two puddings was that, as they boiled, a layer of bubbles built up beneath the
outer pudding bag and the T-shirt, making them more buoyant as they 鈥渃ooked鈥�.
This suggests that the layer of air contributed to making the pudding far less
saturated with water in the middle and that the layer of butter/oil added to
this effect.

Both of the puddings placed in cold water were totally saturated with water
and no dry area of T-shirt remained.

It would appear that both air bubbles and fat help to keep the pudding dry as
it cooks.

Anyone who would like to make a real pudding rather than boil old T-shirts
and cricket balls can take a look at a number of 19th-century recipes for
traditional boiled puddings in SOAR, the Searchable Online Archive of Recipes at
www.recipesource.com.