Christmas means various things to totally different individuals. For me, it’s a chance to eat celebratory meals that aren’t obtainable all yr spherical.
The highest of my record is glazed ham, however a really shut second is a nicely matured Christmas pudding with totally different dairy-rich trimmings.
However what chemical transformations are concerned in making a Christmas pud? Right here’s the science.
Advanced flavour profiles
A Christmas pudding is a steamed dessert consisting of dried fruits, sugar, flour, fat, spices, eggs and alcohol. It’s usually cooked nicely in superior and left to mature, then steamed or reheated earlier than serving.
Fashionable puddings have a tendency to make use of dried grapes (raisins, currants and sultanas) and candied fruits comparable to cherries and citrus peel.
Dried fruits have totally different flavour profiles in contrast with recent fruits. Most of the unstable flavour compounds are misplaced however new flavours develop. These will be fashioned by enzymatic browning (like when reduce fruit turns brown), reactions with gentle, and transformations of fatty acids and even pure colors into flavour compounds.
Candied or glacé fruits comparable to cherries and citrus peel are made by heating the fruit in a sugar syrup. The water content material of the fruit is changed by sugar, leaving a chewy, candy, however much less vibrant product.
This sugary atmosphere is inhospitable to microbes. The water from micro organism and fungi is eliminated on contact with the sugary floor as a consequence of a course of generally known as osmosis.
Dried fruits for a Christmas pudding are sometimes soaked in alcohol for hours, days or even weeks, relying on the recipe. This ensures the fruits are moist within the closing pudding, whereas additionally including flavour.
Soaking rehydrates the fruits, guaranteeing they don’t draw moisture from the pudding combination. The presence of ethanol (from brandy, rum or cognac) additionally inhibits the expansion of microbes.
Suet and spice and all issues good
The most typical spices in pudding are cinnamon, nutmeg, allspice, mace and cloves. Every spice brings a singular chemical signature to the dish.
Some notable chemical compounds are cinnamaldehyde from cinnamon, eugenol from cloves and allspice, and sabinene from nutmeg.
A pudding isn’t a cake nevertheless it accommodates most of the typical cake elements: flour, baking powder, eggs and fats. The flour helps to soak up moisture and offers texture (the “crumb”), whereas the baking powder acts as a elevating agent. The lecithin from the egg yolks acts as an emulsifier, serving to preserve the combination collectively.
Suet (which comes from the fats across the loins and kidneys of beef cattle) is the normal fats utilized in Christmas puddings. The fats provides richness and might preserve the crumb moist by binding to starch from the flour. Many fashionable industrial puddings exchange suet with vegetable oils.
As soon as blended, the pudding combination is positioned right into a pudding basin, sealed or wrapped, then steamed.
Scientifically, steaming has benefits over different cooking strategies for reworking the batter right into a set pudding. The temperature of boiling water and the steam it produces is a constant 100°C, so there’s no hazard of burning the sugar-rich combination and fruits or drying it out.
At this temperature, the starches within the flour are gelatinised, egg proteins unravel (generally known as denaturing), and the baking powder is activated. This makes the pudding rise and set.
As soon as cooked, the pudding will be saved for weeks and even longer. Cooks will usually “feed” their pudding weekly with extra alcohol, bolstering the flavour and retaining microbes from spoiling the pudding.
A dramatic (and usually pointless) addition to the Christmas pudding custom is to pour over a warmed, high-percentage alcohol and light-weight it on hearth. The flame of burning ethanol is usually blue.
The blue color signifies a full combustion, the place all of the ethanol is consumed. The orange flame we normally affiliate with hearth is because of incomplete combustion, the place carbon soot fashioned within the flame emits gentle as a consequence of being heated (this course of is called incandescence).
Photograph by You Le on Unsplash
Liquid gasoline fires, significantly these with near-invisible flames, will be very harmful, so plan forward if you wish to set your pudding on hearth. By no means transfer round a flaming dessert and keep in mind: extra gasoline isn’t all the time higher.
Cash and plum puddings
One other Christmas custom was to incorporate good luck tokens and trinkets (together with a rooster wishbone!).
A typical inclusion was threepence and sixpence cash, which in Australia had been produced from alloys of silver and copper. The conversion to decimal forex within the Nineteen Sixties, and the “debasement” from silver cash, prompted a examine on the consequences of puddings on cash.
It turned out the brand new copper-nickel alloy made the encompassing pudding inexperienced and imparted an disagreeable flavour. The 5 and ten cent cash had been thought-about appropriate for inserting after cooking however simply earlier than consuming, however might current a choking hazard.
Silver pudding cash are offered for these eager to hold on the custom. Simply ensure that your friends are knowledgeable, for the sake of each their enamel and digestive tract.
Wikimedia/Kurzon, CC BY
As a younger chemistry scholar, I keep in mind studying in regards to the “plum pudding” mannequin of the atom – a now-defunct thought floated within the early 1900s by British physicist J.J. Thomson. He envisioned the atom as a sphere with electrons lodged in it like plums in a pudding.
Fashionable chemistry has moved on from this mannequin – however I’ve not moved on from puddings. I nonetheless love them.
Whether or not you go for a pudding or a contemporary pavlova, make sure to embrace the chemistry that makes your Christmas deliciously jolly.
