Magical marmalade

I am currently enjoying the diminishing contents of a large kilner-jar labelled Classic Seville Ornage Marmalade and dated January 2001. There is one more identical jar in our garden shed, labelled similarly but dated January 2005. When that is gone, my precious stock will finally be exhausted.

The seal on the jar I’m eating was broken several months ago, and since then it has been living happily on top of the fridge in our warm kitchen. But there isn’t a hint of mould or other spoilage - just the evidence in the deep brown colour, rich bitterweet taste and lively scent of oranges of seven years of slow maturation.

This was my first batch of home-made marmalade, made from Seville oranges I found by chance in Morrisons. The 2005 vintage was the second batch. The third - or at least its makings - are currently sitting on the bench in my workshop, in the form of a 16kg case of Sevilles delivered yesterday (25 January 2008) from A1 Fruiterers, three 5kg bags of ordinary granulated sugar bought today from Sainsburys and eight lemons also bought today from a local farm shop.

The reason my marmalade has survived without degradation - in fact, quite the opposite - over six years in sealed jars, followed by several months in a warm kitchen after opening, is that it’s a real preserve, unlike modern commercial jams that need refrigeration to keep the bugs at bay. Preserves like this live up to their name because of the concentration of sugar in the finished product. It is so high that any micro-organism finding its way onto the surface of the preserve will have all the water in its cell(s) sucked out by the process of osmosis. Osmosis is a vitally important part of life for all animal and vegetable organisms, and one of the few things I can remember clearly from fourth-form Biology. If two solutions with different concentrations of dissolved chemicals exist on either side of a semi-permeable membrane - a cell wall, human skin or even, in our school experiments, a slice of potato - water will be drawn from the weaker solution to the stronger one in an attempt to equalise the osmotic pressures on the two sides of the membrane. A mould spore or a single bacterium in contact with a proper preserve won’t have a chance, as all its water will be sucked out without making a significant difference to the sugar concentration in the jam. Thousands - possibly millions - would suffer the same fate before any damage would be done.

So how do we ensure that our jams have enough sugar to protect them? Simple, because as a sugar solution becomes stronger its boiling point rises. When this reaches 106°C we know that our preserve really will be just that. So we simply boil our preserves, removing water as steam, until the temperature shown on a sugar thermometer reaches the magic figure. Fortunately, this coincides pretty well with the concentration needed for a pectin gel to set, so provided we have fruit with enough pectin (a chemical called a heteropolysaccharide that occurs in the cell walls of plants and is a powerful gelling agent) in it, and all the other chemical requirements are met, we will have a set jam that is totally infection-proof. Provided we seal it tighly in its jars for storage and don’t leave it exposed to the air for long periods after opening, which would allow it to attract moisture from the air and form a thin film of a weaker solution to collect on the surface, it will stay infection-proof for a very long time, even after opening. The initial seal is easily achieved by tightening the lid when the jam and the air above it are still very hot: as they cool the they contract, forming a partial vacuum that sucks the lid down firmly on its rubber (kilner jar) or plastic (recycled jam jar) seal.

This is far superior to the traditional method of sealing jam-jars, with a disc of waxed paper stuck down onto the surface and a piece of cellophane stratched over the jar and held with a rubber band, regardless of whether an offcut of a pretty patterned fabric is added as a finishing touch.

My recipe

This is from Leith’s Cookery Bible (Pru Leith is the nice lady judge on the BBC’s Great British Menu, and her comprehensive Bible has mostly taken the place of my venerable Constance Spry Cookery Book, if only because it offers metric as well as Imperial measures), but it’s not a lot different from any basic marmalade recipe. The ingredients are:

• 900 grams of Seville oranges
• 2 lemons
• 2.8 litres of water
• 1.5 kilos of sugar

The book specifies preserving sugar, but I’ve always used ordinary granulated, which is virtually pure sucrose with some water-of-crystallisation.

The method is as follows:

1. Cut the fruit in half and squeeze roughly into a bowl - just enough to get the pips (which are numerous in Seville oranges) out
2. Remove the pips and tie them up in a piece of muslin - they are a valuable source of pectin
3. Slice the skins as roughly or finely as you like - I’ve always done this by hand, which is a wearisome task for a large batch, so I plan to try the slicing blade in our big Magimix food-processor this time
4. Add the juice-and-pulp mixture, the bag of pips and the sliced skins to the water in the preserving pan and soak for 24 hours or to soften the skins and so reduce the cooking time
5. Bring the pan to the boil and simmer gently until the skins are soft (about two hours)
6. Add the sugar (previously warmed in the oven) and stir while bringing the pan back to the boil - slowly, to avoid burning
7. Boil rapidly, checking the temperature after five minutes and then at three-minute intervals until it reaches 106°C
8. When this temperature is reached, turn down the heat and test a small sample on a previously chilled plate: when cold the surface should wrinkle when pushed to one side with a finger - if not continue boiling and test every few minutes
9. Allow the marmalade to cool a little before putting in jars and sealing

I fill the dishwasher with jars and lids and wash on a hot programme. The jars are then transferred to the oven set at something over 100°C until needed, ensuring absolute sterility (yes, I know I said the marmalade would be totally infection-proof, but there’s no point in asking for trouble).

I then fill the jars using a jam funnel and a ladle, leaving about a centimetre of space (you need some air to get enough contraction on cooling to create the vacuum that ensures a good seal. I put the tops on almost immediately.

Labelling

I like to put attractive labels on my jars, so I print them on the computer, on coloured paper. Then, believe it or not, I stick them on with ordinary milk - a trick I first learned from my friend Jeff, who introduced me to the fine art of buying wine in bulk and bottling it at home. This is done by floating each label blank-side-down on a saucer of milk then turning it over and leaving it to absorb the milk for a few minutes - I usually do about 20 at a time. The label can then be applied lightly to the jar or bottle, slid around until it is aligned and smoothed down with a just-damp cloth. It will stick tightly but come off very easily in warm water when the jar is to be re-used.

Update 7 February 2008 This is really bizarre: I?ve tried both semi-skimmed and whole milk as a label adhesive, and my labels keep falling off! How can ordinary milk change its composition over three years? Currently experimenting with stock sugar syrup...

The 2008 vintage

Monday 28 January 2008 I started the new batch this morning. After a bit of measurement, I concluded that our ’huge’ 15-litre stockpot would only handle the following quantities, which should yield about 12 pounds of marmalade:

• 3kg oranges
• 6½ lemons ( actually used six big ones and one small one)
• 9.3 litres water
• 5kg sugar

First, the water was measured into the pan.

The citrus fruits were all cut lengthways into quarters, which were then held over a large bowl, folded in half and squeezed to get the juice and most of the pips out (Sevilles have loads of pips!). A good feel around amongst the pulp got the rest out (I hope). The quarters were then packed into the feed-chute of the Magimix until it was full. A gentle push down the chute with the machine running rapidly sliced each batch into the bowl The result was coarser and less neat than I would have produced with one of my beautiful Tojiro knives, but once cooked I hope the result will be acceptable (it’ll have to be, I suppose!). Each time the bowl was full it was emptied into the pan.

Finally, the juice from the bowl was sieved into the pan, and the pips were tied in a new J-cloth and dropped in.

At one point, while processing the oranges, a had a taste of the juice: it was unbelieveably bitter and acid, which bodes well for the finished product.

The pan has now been left for the peel to soak for 24 hours, aided by an occasional stir. MY only concern is that it is pretty full. The level will need to drop quite a way to make room for the 5kg of sugar.

Tuesday 29 January 2008 At 9:15am the pan was brought to the boil. Initially the peel and the bag of pips tended to float up, forming a ’head’ that was clear of the liquid, but after about 40 minutes it had all sunk. At the end of two hours the skins looked translucent and were very soft. The heat was turned off. The sugar, which had been left in a roasting tin in the the oven at 100°C, was added and stirred in, and the mixture was brough to a fast rolling boil on the wok-burner of our range cooker.

I used both the old sugar thermometer and the digital thermometer to check temperature, and it took ages for this to rise to anywhere near 106°C. As this point got close I started using the old-fashioned technique for testing - putting a little of the syrup on a chilled plate, cooling it and pushing with my finger to look for wrinkles. To my annoyance, this didn’t happen, and eventually I got worried. Stirring the mixture, which by now had reduced by between a third and half its original volume, I found that the solids were sticking to the bottom of the pan and were heavily caramelised. I thought that perhaps the loss of sugar in the change to caramel was impairing the working of the pectin and decided to cut my losses, so I went ahead and filled the jars - a total of 11 750-gram and two 370-gram Bon Maman jars. This gives a total of almost nine kilos - far more than the recipe, which says I should have the same weight of finished marmalade as the starting weight (5 kg) of sugar. I suspect an error in the recipe, Pru!

The marmalade in the first jars has now set, though it is still warm, so hopefully no great harm has been done.

I think the problem may have been that the stockpot is too deep and narrow to reduce the mixture quickly, and this may be why the solids stuck at the bottom and caught. For the next batch, I may have to use our big stewpan - the same diameter but haf the height - for a smaller batch. I remember that our old preserving pan (which must have left home with Wife Number Two) was shallower, wider and tapered, as well as being made of light aluminium rather than heavy stainless steel with a thick aluminium layer on the bottom, as our professional Bourgeat pans are.

Wednesday 6 February 2008 I have made two smaller batches in the shallower pan, which limits me to four litres of water, and both boiled to a set much more quickly. Since they didn’t burn, they also came out a paler orange colour instead of the first batch’s murky brown. For the second of the two, I omitted the soaking phase: the peel softened fine with simmering. I also decided not to bother pre-heating the sugar: it took a little longer to get to the boil, but saved a lot of faffing about! I haven’t tasted anything except the gooey scrapings from these two batches - a tasting report will follow in due course.