For anyone who has ever tried to make it at home, perfect fruit jelly can seem like a truly elusive substance. When it works, you end up with a quivering solid of beautiful, translucent color and great fruit flavor. When it doesn’t, you get a runny (though still flavorful) syrup.

为了制作果冻，您可以用水煮熟水果，直到柔软，并开始失去颜色，将固体压紧，然后煮汁，添加糖。然后煮沸直到液体达到220°至222°F，或直到它变厚到足以掉入勺子侧面，然后倒入灭菌的罐子中。(Another doneness test is to put a small amount of the hot jelly or jam on a chilled saucer, freeze for a minute or so, and then push the cooled liquid with your finger. If it wrinkles, it’s done.) Jams and preserves are less work; you just boil the fruit with sugar until the mixture thickens or reaches temperature.

听起来很容易（而且）；但是，有时是水果果冻凝胶，有时不是。关键是要有足够的果胶，糖和酸。您需要平衡所有三个元素才能使水果果冻，果酱，蜜饯和果酱固定。（要区分果酱和果酱，请查看这些术语的词典.)

Pectin is the thickener

所有果冻和果酱中最关键的成分是果胶，它由自然存在于所有水果中的巨大分子组成。果冻和果酱制造的目标是使这些大果胶分子在凝胶网络中连接，捕获和固定在其中的甜果汁。

一些水果 - 苹果，黑莓，蔓越莓 - 有很多果胶。其他水果，例如桃子和杏子，还没有足够的时间来凝胶。

So the first step is knowing whether you have a high-pectin or low-pectin fruit. If it’s the latter, you’ve got two choices. You can supplement it with a commercial pectin, or you can add a high-pectin ingredient like lemon rind (be sure to include the pectinrich white pith) when you boil the fruit.

For all fruit, pectin levels are highest when the fruit is mature but still slightly underripe; pectin amounts start to drop off as the fruit continues to ripen. Therefore, you’ll get a better gel from almost ripe rather than from fully ripe fruit. Or you might want to use some of both, getting the higher pectin from the less ripe fruit and the more intense flavor from riper ones.

Acid is the matchmaker

Even better than adding lemon rind and pith to the fruit is to toss in a whole slice of lemon to a small batch of fruit. The lemon juice in the pulp provides acid, which is the second essential component of any fruit jelly or jam.

Without acidity, pectin molecules won’t build that crucial gel network. Pectin molecules are charged; they repel one another just like the same ends of magnets do. Acids neutralize the charge, so the pectin molecules no longer repel one another and can join.

酸和果胶中高的水果会自行凝胶，而酸水平较低的水果不会。为了补偿低酸水果，请尝试将1-1/2茶匙在2板的新鲜柠檬汁中添加到一小批果冻或果酱中。

Fruits become less acidic as they ripen, so again, from a gelling standpoint, it’s best to choose those that are not fully ripe.

有些水果比其他水果更好

Pectin content and acidity will vary depending on the ripeness, growing conditions, and variety of the fruit—berries are especially hard to pin down. The list below can help you figure out whether a batch of fruit jam or jelly might need a pectin or acid boost, but keep in mind that it’s an approximate guide.

高果胶和高酸凝胶的水果更多；低果胶和低酸凝胶的水果较少。

高果胶，高酸
酸苹果，螃蟹，蔓越莓，黑莓，醋栗，柠檬，红醋栗，东方康科德葡萄

高果胶，低酸
Sweet oranges, tangerines, sweet apples, ripe quince

低果胶，高酸
杏子，石榴，草莓，酸樱桃，菠萝，覆盆子，大黄

低果胶，低酸
Peaches, nectarines, pears, blueberries, ripe mangos, sweet cherries, any overripe fruit

糖绑在水中

在我们可以期待完美的果酱或果冻之前，我们还有一个问题要解决。果胶分子宁愿与水分子连接，也不愿彼此连接。这是糖进来的地方。糖是吸湿性的 - 它可以将水绑起来，使其无法使用果胶分子，而果胶分子现在别无选择，只能彼此连接。

大多数果酱和果冻配方在日本须贺不要吝啬r, so it’s unlikely that you’ll fall short in this area. I usually add 3/4 to 1 cup sugar for every 4 cups unreduced juice for jelly. If you add too much sugar, there’s a risk that it will crystallize out of the mixture or that the jelly will become too stiff. Occasionally, even when you think you have enough pectin, acid, and sugar in the jelly or jam, it still won’t set. You could try reboiling it; it may gel better the second time, and eventually, it will start to thicken through evaporation. But be aware that extended cooking (or excessive heat) can damage the pectin and prevent gelling altogether, though having enough sugar in the mixture should help.

One more tip for gelling jellies: Calcium increases gel strength and can help ensure that a jelly sets. The easiest kitchen source of calcium that I know of is molasses, so if you expect trouble with a particular batch of fruit, you might try adding a half teaspoon of molasses to a small batch of jelly.