How to preserve vitamins — and citrus fruit

At this time of year, everyone needs some vitamin C because everyone is on the edge of catching a cold or flu (everyone). 

Also at this time of year, there are lots of enticing citrus fruits at the grocery store. Clementine oranges (and the many new iterations of the clementine, such as Halos, Cuties and Satsumas) are abundant at every supermarket, and relatively inexpensive. This year’s crop, based on a completely limited and personal survey of available product, seems to be sweet and juicy. 

Last summer I began making my own jams, successfully preserving plums, peaches and the wild grapes that grew outside The Lakeville Journal’s former office in Lakeville (our new office is in Falls Village). 

I like marmalade, too, and would like to make some of the clementines into jam. Perhaps you are tempted to do the same. But take heed: If you cook citrus fruit, you destroy the vitamin C. 

Some vitamins and minerals get better when they’re cooked. For example, the cancer-fighting lycopene in tomatoes isn’t really accessible to our bodies until it’s been cooked.

Vitamin C is the opposite. The same holds true for most of the B vitamins, including folate (an essential vitamin for women who are pregnant; it helps the baby form a healthy spine, among other things). If you cook them (or expose them to too much oxygen) you destroy the nutrients.

I don’t think of the US Department of Agriculture as a very gourmet organization, but their guidelines for cooking fruits and vegetables emphasizes cooking techniques that I would associate with fine-dining restaurants. 

The USDA  recommends that you cook your fruits and veg as briefly as possible, so that they are crisp, not limp. They don’t want you to use a lot of water while you’re cooking, and they want you to cover your pot so steam doesn’t escape. Ideally, they’d rather have you just quickly stir fry your food, so that the nutrients don’t leach out into the water.

They also think microwaving is a good way to cook vegetables, but I don’t like microwaves so I don’t support that recommendation. But you do what you want.

The USDA also recommends that you leave your veg and fruit in big pieces when you cut them up; exposure to air destroys nutrients. If you’re storing them in the refrigerator, put them in an airtight container. 

Proteins are also impacted by cooking, but they are a little bit less delicate than the veg and fruits. But, again, you don’t want to overcook your meats and fish. I couldn’t find any definitive answer on whether a slow-cooked stew has fewer nutrients than a quick-cooked steak. But I think the answer is that when you make a stew, the nutrients remain in the cooking liquid. 

I also didn’t find a definitive answer on whether grains are less nutritious when you cook them, but it’s kind of a moot point because you’re never going to eat them raw. Interesting to note: Most nuts (including peanuts, which are technically legumes), are more nutritious after they’ve been lightly toasted.  

The marmalade recipe that follows ignores all the good advice that I’ve just shared with you, but it’s really delicious. I made it this weekend with Compass Arts and Entertainment Editor Anne Day at her house,  using tiny little citrus fruits called calamondins that she grows on a tree in her home. 

Anne has been making this marmalade for years, and it really is what you want a preserve to be: It tastes like the sweet essence of the fruit. She warns, though, that you would never actually eat a raw calamondin; the fruit is exceptionally bitter. 

I can’t confirm that this same technique would work with clementine oranges but in theory it should. This is such a quick, easy recipe that it would be worth making the experiment just to see how it goes. 

We did not “preserve” the marmalade; Anne notes that it never lasts long enough to need preserving. It’s so delicious that it’s all eaten up before the month is over. Just store it in the refrigerator (you can even freeze it, for up to three months).

The first step is to take your clean jars and lids and drop the jars in boiling water for about five minutes (Anne prefers to steam hers). Pour boiling water over the lids, in a bowl, and leave them in the hot water until you’re ready to put the jam in the jars.

Cut the tiny calamondins in half, and remove the center segment of pith and any seeds that you find. Put these in one bowl (you’ll get a lot of juice in this bowl too). 

Take a pair of sharp kitchen scissors and cut the fruit into thin strips, over a bowl, so you catch all the lovely juice as it drips out.

First put all the seeds and pith and any juice from that bowl into a saucepan. Add an equal amount of sugar to the pith; if you have one cup of pith, seeds and juice, add one cup of sugar. Boil it all until the sugar melts and it begins to thicken into a syrup. Remove from heat and strain out the juice and set it aside (you can throw out the pith and seeds now).

Take the strips of calamondin and put them in a measuring cup and add a little less sugar than fruit (one cup of strips of citrus should get three quarters of a cup of sugar). Add in the syrup that you made from the pith. 

Boil the sugar and citrus until they reach 219 degrees (measure it with a candy thermometer). 

Remove from heat and immediately pour into the jars that you’ve sterilized. Anne recommends that you eat some of the marmalade as soon as it cools off a little bit; it’s exceptionally good when it’s warm.