So about a month or so ago I took a ride out to the Green Briar Nature Center and Jam Kitchen in Sandwich, Massachusetts. It's a small sanctuary and working artisanal preserves factory just off Route 6A, and it's owned and run by the
Thornton W. Burgess Society and is the home of Burgess' Peter Cottontail character. They produce a great many types of preserves, including jams, jellies, chutneys, and even suncooked fruit sauces, but the thing they're best known for is the Cape Cod tourist specialty, beach plum jelly. It's quite tasty, pleasantly sweet with a bit of a tannic twang, and although beach plums are a long way from a mainstream fruit, it's a nice little diversion from the usual grape/strawberry/apple/orange marmalade thing.
Anyway, the Green Briar is a pretty cool place -- something like what you imagine a commercial kitchen of a hundred years ago looking like, with the surprising addition of easily the largest gas stove I've ever seen -- a long table, roughly 20 feet long with at least thirty vintage cast-iron burners, room enough for an immense array of pots. If you walk through the kitchen, at the far end there's a decent sized gift shop, with many books and toys, as well as the centerpiece: a wall of their many preserves, including, for the sum of $6.85, beach plum. There's one other thing they have: a slim, $5 pamphelet that happens to be the Green Briar cookbook, with all the recipes for their most popular jams and jellies. In that book are some of the simplest and most basic recipes for making fruit jellies, including not only their beach plum, but also basic ones like apple and grape. The recipes are surprisingly simple -- for jams, fruit and sugar, and sometimes a bit of acid (usually citric or tartaric). For jellies, it's mostly a matter of crushing and cooking the fruit and then letting it drip through... and then it just gels. The book makes a point of saying that they don't use pectin. Well... there's a little more to it than that.
When making a jam or jelly, someone versed in technique but not kitchen chemistry might assume that it's a simple reduction process -- start with a relatively thin feedstock and concentrate the flavor, usually with heat, as with maple syrup. There is in fact an element of reduction in making jams and jellies, but the end result of a straight reduction process with fruit or fruit juice isn't going to be a preserve so much as a piece of fruit leather (Fruit Roll-Ups for you 80s kids like me) or, if you're careless, a puddle of highly caramelized glop. Either way, the reduction process has a tendency to neutralize all but the least volatile of flavors in the liquid being reduced, which is a major problem when you wish to preserve the character of a fruit. A piece of apple leather is quite tasty, but it doesn't have the same flavor as a fresh apple, and a gentle process like sun-cooked preserves leaves the resulting product more syrupy than jammy. So what's really happening?
Pectin.
Pectin is a component of many plant cell walls, and it's... a little different. It is, more or less, a complex carbohydrate, but unlike substances like starch, cellulose, and more obscure relatives like inulin, it's not a polysaccharide. Instead, it's a chain made up primarily of units of galacturonic acid, a derivative of the glucose isomer galactose. Pectin, in fact, happens to be one of the reasons that we cook food in the first place -- in its natural form, it's rather indigestible and serves primarily to keep the insides of the plant cells in.
Pectin is essentially glue; it's the substance that keeps the cellulose and other substances (like
lignins and sometimes inulins) held together as a cell wall in a plant. Without pectin, the plant softens and eventually disintegrates as the cells rupture and dessicate. This is actually a natural part of the ripening process of many fruits -- the incompletely-ripened tomatoes you find at the market, for example, are often an example of what happens when you pick a fruit before it's ripe, with a distinctly cottony, mealy texture. This happens with many fruit, and is caused by both
hemicellulose (an insoluble cellulose-like polysaccharide that is also broken down in cooking) and complex pectin. The process by which enzymes break down pectins and hemicelluloses are an important part of making the fruit go from a mere seed capsule to being something birds and mammals will actually seek out and want to eat. In other words, pectin, like the animal collagen I mentioned in my last post, is fairly easy to break down, and readily breaks into shorter chains under heat (i.e. cooking) or enzymatic (i.e. dead plant) action.
Sometimes you want this. Fruit preserves, to take the opening example, are highly dependent on fruit pectin to thicken and gel; cooked apple pulp in fact happens to be a fairly common ingredient, not only in apple jelly, but in several other preparations where the high concentration of free pectin and the relatively neutral flavor of apple juice serves to reinforce a more delicate, syrupy preserve (as is often the case with many berries). Essentially, the fruit is pulped and cooked with massive doses of sugar, then allowed to cool. The pectins will bond with each other and some of the sugar in the mixture, gel and cause the preserve to thicken; in order to make a jelly, the process is essentially the same, though the cooked pulp is filtered while still hot to remove cell detritus; there is even a special type of filter used when this is done by hand, mentioned in the Green Briar cookbook, called a jelly bag. The procedure is somewhat similar to working with sugar syrup, in that the fruit mixture needs to be cooked to a point where it "sheets" -- i.e. thinly covers -- the stirring spoon. A similar effect allows tomato sauce to go from a sloppy, readily separated mix of pulp and juice to a thick, more homogeneous finished product. If the jam or jelly doesn't set up enough, more-or-less pure, refined pectin is also available; add sugar and acid, and it will gel just like fruit. Those who use refined pectin, however, are advised to be sparing in their use of it; too much will turn the jelly into rubber. (When the Green Briar authors say they don't use pectin, this is what they mean -- they don't use purified pectin to help things along.)
Sometimes, however, you don't want to break down the pectin -- you may like your tomato sauce on the chunky side, for example, or you want whole fruit in a syrupy base rather than a preserve. There's a couple of ways to accomplish this. For one thing, pectins seem to like calcium and aluminum ions a lot -- tomato canners, for example, use a great deal of calcium chloride (the same stuff used in ice melt) as a stabilizer in diced and whole tomatoes, since it causes the pectin chains to relink in a somewhat stiff web that causes the tomato fragments to remain in roughly the same shape as when they were cut. The use of aluminum hydroxide and aluminum salts in certain types of pickles have a similar result, creating an extra-crisp pickle that sometimes has even more crunch than the original vegetable. As appealing a result as it can be, though, metal-pectin interactions become something of a problem when people make Boston baked beans. Molasses is a critical ingredient in Boston baked beans, and ot contains a fair amount of metal salts, particularly calcium, and while those salts serve to keep the beans intact during the long, slow cooking process, they can seriously impede things if the molasses goes into the baking dish too early, since the beans may not break down at all. When I've made baked beans, I tend to par-cook the beans in salted water until they're somewhat soft before adding other ingredients; I've never seen an authentic recipe that does this, but dammit, it works.
The other way involves sugar and is demonstrated rather startlingly by Shirley Corriher on page 325 of
CookWise, where she contrasts a recipe for smooth applesauce with chunkier apple wedges. The trick is to add massive doses of sugar before cooking -- in Corriher's applesauce recipe, the apples are cooked by themselves and the end result is a distinctly mushy, easily mashed texture. The wedges, on the other hand, are cooked with a relatively high proportion of brown sugar, which both bonds the pectin chains together and provides trace amounts of calcium ions from the molasses in the brown sugar, increasing the firmness of the finished wedges in a way that white sugar, which is essentially chemically pure sucrose, can't. (I've always used white sugar in my applesauce, which invariably comes out more mushy than chunky.) In extreme cases, such as candied fruit, the pectins are actually augmented by an incredibly high sugar concentration, which is drawn into the fruit by way of osmotic pressure from the syrup the fruit is cooked in, since the sugar concentration will try to equalize itself both inside and outside the fruit.
So we see that pectin, like many other proteins and carbohydrates in the food we eat, is one of those things that serves a function to the life form the food came from, and that can be repurposed to do something entirely different in the kitchen. More importantly, the breakdown of complex cell wall pectins into simpler pectins during the cooking process is also one of the main things that makes cooked plant matter far more appealing to the human tongue (and mouth, particularly the teeth) than raw plants. And one of these days I'll take some time to go into further detail about why the raw food movement is out of its mind, but in the meantime, I'm going to give you a very rough-and-ready recipe for chunky applesauce.
Start with 3-4 lb (1.5-2 kg) of tart, firm apples (I prefer Granny Smith). Cut into chunks (the larger the chunkier; go for thin slices if you want smooth) and place in a stockpot or dutch oven, with sugar to taste and water about halfway up the apples. Bring to a boil and cook at a high simmer till the apples are soft (20-40 minutes), then add a teaspoon or so of cinnamon, cook a little bit more, mash if necessary, then serve or scoop into jars or plastic storage containers and chill. This is particularly good mixed with whole milk yogurt.
Hat tip, as always, to the works of Harold McGee and Shirley Corriher (without
On Food and Cooking and
CookWise, none of these columns would be possible), as well as the Thornton Burgess Society for keeping a great local, artisanal product alive and being willing to share their wisdom with anyone willing to make the trip. Credit also goes to the many authors who have brought the ancient wisdom into the modern age, as well as the many nameless fingers who fight on a daily basis to keep
Wikipedia a worthwhile source of knowledge.
