Rose Hip Jelly (With a Brief Description of the Chemistry of Jellies)

When rose flowers wither and fall from the plant, they leave behind a little green ball called a rose hip.  In late summer those hips swell and turn red, and start to look like berries.

They are not berries, as you will discover if you open one up.  Rosehips are full of seeds and what looks like white hair.  If eaten raw those hairs will irritate your mouth and throat.  Don't eat those hairs raw.  The fleshy part around the seeds and hair can be eaten raw.  It has an interesting flavour; depending on the plant and the time of year it can taste like fresh cut grass, or a tomato, or possibly a plum.

Though rose hips can be eaten fresh, they are most commonly made into jelly. They contain little pectin, so the jelly usually contains another fruit, like apple.

Two hours have passed between when I wrote that last sentence and when I wrote this one.  It crossed my mind that I don't really know what pectin is, so I read a large section of On Food and Cooking to find out.  If you like, I can tell you what I found.


The Chemistry of Jellies

Unlike animals, plants get all their nutrients and energy from soil and air and sunshine.  They therefore stay in one place, and require a rigid framework on which to grow.  Like animal cells, plant cells are made of fluid enclosed in little sacks of a semi-permeable membrane.  Unlike animal cells, they also have a firm wall surrounding their cell membranes for additional structural support.

These cell walls are analogous to reinforced concrete.  Fibers of cellulose act as the iron rods, and hemicellulose and pectin act as the cement that cross-links the iron rods.  Hemicellulose is made of glucose and xylose sugars, while pectin is in fact "long chains of sugar-like subunits,"^[1] whatever the hell that means.

Here are some things that happen when we cut and cook fruit:

• the thermal and physical disturbance breaks the pectin chains in the cell walls apart,
• cell membranes rupture, spilling cell fuild everywhere, and
• the loosed pectin dissolves in that cell fluid (and any other liquid you have added to the mix).

The pectin does not re-form into its characteristic chains because it has been diluted, and the sub-units can't reach eachother.  To aggravate the matter, the pectin sub-units accumulate a negative electrical charge, and so are actually repelled by eachother!

As sympathic cooks we can help pectin chains re-form by doing the following:

• adding sugar - Sugar is hygroscopic and attracts water.  With water molecules flocking towards the sugar, the pectin molecules have an easier time finding eachother.
• boiling off excess water - This also reduces the distance between pectin molecules
• adding acid - Acidic solutions are full of hydrogen ions (H⁺) that neutralize the pectin molecules' negative charge.  After contact with a hydrogen ion, the pectin molecules no longer repel one another.

The three steps above that help reform pectin chains also happen to preserve the fruit!

With the pectin chains re-formed, there is now a network that traps water and gives the jelly its characteristic firm-but-wiggly texture.

Don't you feel empowered by all this information?  Put it to good use:


Rosehip and Apple Jelly
adapted from River Cottage Handbook No. 2 - Preserves

Ingredients

• 325 g rosehips
• 775 g apples, peeled and quartered (I used windfall apples from my questionable backyard apple tree, removing any severely damaged sections)
• roughly 550 g sugar

Procedure

Place the quartered apples in a straight-sided pan.  Cover with water.  Bring to a boil, then simmer until the apples soften and turn to pulp.

In the mean time, chop the rosehips in a food processor.

Add the rosehips to the pan and simmer for 10 minutes.

Remove the pan from the heat and let stand for 10 minutes.  Pour the mixture into a scalded jelly bag suspended over a bowl. Drain for several hours.  After 24 hours I ended up with about 800 mL liquid.

Measure the juice and put it into a pot. Bring to a boil, then add 400 g of sugar for each 600 mL of juice. (My 800 mL of liquid required 533 g sugar.) Stir until completely dissolved, then boil to setting point, 220F.

After boiling I had roughly 500 mL jelly. Pour into hot sterilized jars.

1.  McGee, Harold. On Food and Cooking. ©2004 Scribner, New York. Page 296.  This is the only direct citation I used, but really all of the scientific info is from this invaluable reference.