2 July 2009

Richard's Garden

Strawberry and Redcurrant Jam

Jam, conserve, preserve or jelly there are names for the same thing: a way to preserve fruit. The preservative is sugar. High concentrations of sugar prevent the action of the bacteria and fungi that makes the fruit rot. Jam is typically a gel. If the gel is solid it is often called cheese or jelly. Conserves and preserves are typically less solid, and can be quite sloppy. Jam is just a generic term covering all cases.

The solidity of the gel in a jam is caused by pectin. Pectin is found in most fruit but typically there are higher quantities of pectin in the more acid fruit: gooseberries, cooking apples and redcurrants.  Pectin is a long molecule and when you boil fruit you release the pectin so that the molecule can unravel and bind together the fruit, sugar and water. However, for a good gel, (and to aid the pectin), the jam must be acid and have a low water content. Most fruit have enough acid, but you can raise the acid content of other fruit by adding a fruit acid like lemon juice. To lower the water content you boil the fruit to boil off the water. The sugar content of a jam must be about two thirds. Most fruit does not have this much sugar and so you must add sugar. Adding sugar also lowers the overall water content.

Strawberries have low pectin, low acid, highish sugar and high water content. Typically you will find that strawberries are made into preserves: sloppy jams where the preserving agent is sterilisation by boiling. Consequently preserves must be bottled with an airtight seal and you typically have to store opened jars in the refrigerator and eat the preserve within a few days.

Redcurrants have a high pectin content and a high acid content. If you boil redcurrant juice for just 10 minutes with an equal weight of sugar, you'll find that when it cools it will set into a stiff gel. The gel will keep in a jar for a year or more without spoiling. You do not need an airtight seal on the jar because the high sugar content prevents the gel from deteriorating. Typically such jams are put into sterile jars and covered with cellophane covers, but the cellophane is merely to keep dust and insects away. Similarly, once opened, a jar of redcurrant jelly will keep for weeks at room temperature (if you can resist eating it for that long) and a lid is needed simply to keep the wasps out.

Since strawberries have a low pectin and low acid content, it makes sense to raise the pectin and acid to make a jam rather than a preserve. The taste of redcurrants compliments the taste of strawberries and so the two make perfect partners for a jam.

This is the recipe that I use: strawberries, redcurrants, sugar. Nothing more is needed. The quantities I used were in the ratio 2 : 1 : 3, that is, 2 Kg of strawberries to 1 Kg of redcurrant juice (about 1.3 Kg of redcurrants) and 3 Kg of sugar.

Some recipes recommend special types of sugar. This is unnecessary, and can add to the cost. Basically, you want the sugar to dissolve quickly, so either caster sugar or granulated sugar will do. Usually you will use white sugar, but this is only so that the sugar does not add a taste to the jam, and that it will not add impurities that will cause a scum. I tend to use whatever sugar is in the cupboard, and if it is organic, raw sugar, then I am not bothered - it simply means that there will be more scum to skim off. Preserving sugar usually has pectin added, and you can use this if you want to make strawberry jam without redcurrants. The labels on bags of preserving sugar also tells you that the crystals are larger and will dissolve more quickly, but I find granulated sugar dissolves quickly enough. Some recipes also tell you to warm the sugar to make it dissolve quicker. I have never tried this because, as I have said several times already: granulated sugar dissolves quickly enough! Warming the sugar seems extra effort that adds nothing to the final product.

If you are making jam (with high pectin content) then you do not need to provide an airtight seal. The jam pot covers that you buy from shops have four parts: wax disks, cellophane covers, rubber bands and stickers. The wax disk is put on top of the hot jam in the jar, wax side down. This basically forms a barrier against mould spores. The cellophane forms a lid and this is stretched across the top of the jar and secured with the rubber band. You do not have to make an airtight seal with the cellophane, but if you stretch it across the top then it looks better than if it is wrinkled. It is important to label each jar so that you know what is in the jar, and how old it is.

These are the details of the steps to make strawberry and redcurrant jam.

  1. Strip the redcurrants from the stalks. Some recipes say that this is not necessary, but I just don't like the idea of boiling sticks with the fruit. I started with about 1.3 Kg of redcurrant fruit to produce 1 Kg of juice.
  2. Put the fruit in a pan with enough water to cover the bottom of the pan (say, about 100ml). Heat until it starts to boil, then reduce the heat and simmer for 10 minutes. The fruit will soften and disintegrate.
  3. Sieve the fruit. This removes the pips, skin and the few stalks that were in the mixture. You can squeeze the pulp through the sieve to get more juice. Normally you should not do this for a redcurrant jelly since it will make the jelly cloudy, but this does not matter because the strawberries will make the jam cloudy anyway.
  4. Weigh the juice (it should come to about 1Kg) and return to the pan.
  5. Remove the stalks from the strawberries and cut them up into small pieces. The size depends on your preference. Think how big you like the strawberries to be on your toast, and cut the fruit to this size. Weigh the strawberries and make sure that you have about twice the weight of the redcurrant juice (2 : 1 strawberries to redcurrant juice). Start heating the fruit on high.
  6. To the pan, add an equal amount of sugar. That is, the weight of the sugar should be the same as the weight of the combination of the strawberries and redcurrant juice. Stir the mixture until the sugar has dissolved - this should only take a minute or so.
  7. At this point you should look carefully in your pan. When the mixture comes to boil it will boil up to twice the volume. If you do not have the volume in the pan for this to happen then remove some of the warmed mixture and set it aside for a second jam making session. (I have tried two pans boiling at the same time, but I find it difficult to monitor two pans, so it is best to have two jam making sessions.)
  8. Bring the mixture to the boil. This may take 10 minutes or more. As the mixture boils, water is removed. In addition, scum will form at the edge of the pan. With a large spoon skim off this scum. Stir the mixture regularly. This is important for large fruit like strawberries, because you do not want them to stick to the bottom of the pan and burn. If the fruit burns then it will taint the entire pan and you'll have to throw the lot away.
  9. There are various methods to tell if the mixture has boiled enough. Some people measure the temperature to see if it has reached a temperature between 103C to 105C (this indicates that the sugar content has reached 65%). A simpler method is to take a teaspoon of the liquid and drop it on a cool saucer. When the liquid has cooled to room temperature it should form a skin that you can see wrinkling as you push the gel. To be honest, my eyesight is not good enough for this method, so I simply boil the mixture rapidly for for 10 minutes, which seems to work.
  10. While you are waiting for the mixture to heat up, wash the jars. It is always good to over estimate, so if you have 5 Kg of fruit and sugar, clean 12 one pound jars (5 Kg is 11 lbs). Wash them clean, then rinse, then let them dry for a couple of minutes. Now put them on a tray in the oven. Switch the oven on and set it to 100C (hence the jars are heated up from room temperature to 100C, don't pre-heat the oven). This will dry them completely and it will make sure that the jars are sterile. In addition, it will also make sure that the jars are hot when you pour hot jam in them.
  11. When the jam has been boiled enough, take the pan off the heat. Take the jars out of the oven and put them on wooden boards (chopping boards are good for this). Use several boards even if you can fit all the jars on one board.
  12. Using a ladle skim off the fruit floating on the surface and put an equal amount of fruit in each jar. Do the same with half the jam in the pan, that is, ladle it out equally between the jars. The idea is to try and make sure that there are equal amounts of fruit pieces in each jar. Now with the remainder of the jam fill each jar to within 1cm of the top. You may find that you had too many jars, so that some of the jars are half full. No matter, you can pour jam from one jar to another to fill them up: holding one jar with oven gloves pour the jam into the other ones.
  13. You will find that pouring jam into jars is not easy and jam will drip down the side of the jars. Don't worry: it always looks more than there is. Use a clean damp dishcloth to clean the sides. Take several layers of dry kitchen towel folded over and use this to hold the lip of a jar while you quickly wipe the side. The idea is to remove most of the spilt jam, the sides of the jars may still be a little sticky, but don't worry about this. As you clean a jar, you can put it onto the clean chopping boards that I mentioned above.
  14. You now need to put the wax disks on the surface of the jam, wax side down.
  15. You have a choice. You can put the cellophane lids on the jars while the jam is hot (in which case the lid stretches better, but you have to deal with hot jars) or you can wait until the jam is cold (in which case the lid will not stretch so well). If you choose to do this when the jam is hot wipe the lip clean with damp kitchen towel. If you put on the lid when the jam is cold then wipe the lip clean while the jam is still hot since it will wipe easier.
  16. When the jars are cold use a clean damp dishcloth to clean the sides so that they are no longer sticky. Then, when the sides are dry stick on the label with the contents and date. Store tha jam in a cupboard with the newest jars at the back.

Do not worry too much about this jam setting: there should be enough pectin and acid in the redcurrants in this recipe. You'll find that the jam will not be set when warm. Even when cold the jam may still be a little liquid. However, after a day you'll see that it will have gelled, and over time it will get more solid. If the jam is too sloppy then you need to empty the jars into the pan and bring it to the boil again.

Strawberries in my Garden

Five years ago I bought four Elsanta strawberry plants. These are perhaps not the most tasty of strawberries, but they grow well and keep well - most strawberries sold in UK supermarkets are Spanish Elsanta. I planted them in tubs. They fruited well the first year and grew runners. Every year I have potted the runners and the following spring planted the runners. In the first few years I planted them in more tubs, but last year I planted some twenty plants in a border in the garden, and this uyear I planted another twenty more. In total I must have over a hundred plants - just from the four original plants.

The fruit become ripe mid-June and then for two or three weeks we can have strawberries for dessert every other day (if you have them every day then they kids get bored). This year there has been too many to eat fresh, so we have frozen the excess. When you thaw frozen strawberries the result is a mushy fruit. It tastes like strawberry, but it does not have the firm texture of the fresh berry. This is not an issue if you want to cook them. Summer pudding is tasty, and, of course, so is jam.

So far we have had about 4 Kg of strawberries and will probably get another 2 Kg in the next couple of weeks.

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(c) 2009 Richard Grimes