|Strawberry jam, one type of common fruit preserve|
Many varieties of fruit preserves are made globally, including sweet fruit preserves, such as strawberry or apricot, as well as savory preserves of vegetables, such as tomatoes or squash. The ingredients used and how they are prepared determine the type of preserves; jams, jellies, and marmalades are all examples of different styles of fruit preserves that vary based upon the fruit used. In English the world over the plural form "preserves" is used to describe all types of jams and jellies.
The term 'preserves' is usually interchangeable with 'jams'. Some cookbooks define preserves as cooked and gelled whole fruit (or vegetable), which includes a significant portion of the fruit. In the English speaking world, the two terms are more strictly differentiated and, when this is not the case, the more usual generic term is 'jam'.
Jam apart from being a particular type of preserve (spreadable containing the fruit) is also used as a general term (in British and Commonwealth English) for any type of fruit preserve (e.g. "the jam factory in Tiptree") while in the US the term jelly is preferred; e.g. a jam donut or a jam sandwich in the UK, Ireland and Canada is a jelly donut and a jelly sandwich in the US.
The singular preserve or conserve is used as a collective noun for high fruit content jam, often for marketing purposes. Additionally, the name of the type of fruit preserves will also vary depending on the regional variant of English being used.
In general, jam is produced by taking mashed or chopped fruit or vegetable pulp and boiling it with
|Five varieties of fruit preserves:|
Commercially produced jams are usually produced using one of two methods. The first is the open pan method, which is essentially a larger scale version of the method a home jam maker would use. This gives a traditional flavor, with some caramelization of the sugars. The second commercial process involves the use of a vacuum vessel, where the jam is placed under a vacuum, which has the effect of reducing its boiling temperature to anywhere between 65 and 80 °C depending on the recipe and the end result desired. The lower boiling temperature enables the water to be driven off as it would be when using the traditional open pan method, but with the added benefit of retaining more of the volatile flavor compounds from the fruit, preventing caramelization of the sugars, and of course reducing the overall energy required to make the product. However, once the desired amount of water has been driven off, the jam still needs to be heated briefly to 95 to 100 °C (203 to 212 °F) to kill off any micro-organisms that may be present; the vacuum pan method does not kill them all.
During commercial filling it is common to use a flame to sterilize the rim and lid of jars to destroy any yeasts and molds which may cause spoilage during storage. Steam is commonly injected immediately prior to lidding to create a vacuum, which both helps prevent spoilage and pulls down tamper-evident safety button when used.
Glass or plastic jars are an efficient method of storing and preserving jam. Though sugar can keep for exceedingly long times, containing it in a jar is far more useful than older methods. Other methods of packaging jam, especially for industrially produced products, include cans and plastic packets, especially used in the food service industry for individual servings. Fruit preserves typically are of low water activity and can be stored at room temperature after opening, if used within a short period of time.