Pectin

Pectin is a natural component of all edible plant material. Pectin is located in the plant cell walls and in a layer between the cells called middle lamella. Pectin gives firmness to the plants and influences growth and water household. Pectin is a soluble dietary fibre. Pectin is a polymer of galacturonic acid and with that an acidic polysaccharide. Part of the acids are present as methyl ester. Pectin is a hydrocolloid and binds a lot of water resulting in thickening and gelling properties.
Pectin was discovered in the nineteenth century, and has been used at home and in industry for many years.
Most commercial pectins are extracted from fruits. Today there is a range of different pectins for different uses.
Pectin is regulated by official specifications in most countries.

STRUCTURE


Galacturonic Acid Unit
Pectin for use in food is defined as a polymer containing galacturonic acid units (at least 65%). The acid groups may either be free, combined as a methyl ester, or as sodium, potassium, calcium or ammonium salts, and in some pectins amide groups may also be present.

Pectin in the plant starting material is part of a very complex structure, which gives shape to the soft non-woody parts of the plant. Plant cell wall structure diagram Pectin in this state contains a range of neutral sugar molecules, in a complex non-random structure, containing blocks of homogalacturonic acid (sometimes called "smooth regions"), and blocks containing many neutral sugar molecules (rhamnose, galactose, arabinose, and lesser amounts of other sugars) in a highly branched structure (sometimes referred to as "hairy regions").

DISCOVERY & HISTORY

Jams and Jellies have been produced for many years, at least since the 18th Century. Recipes were published in the "London Housewife's Family Companion" of 1750 which described jellies made from apple, currant, and quince, all fruits rich in gelling pectin.
Pectin was first isolated in the 1820s, and shown to be the key to making jams and jellies.
Gradually, people mixed pectin rich fruits or fruit extracts with fruits which do not set jams well - strawberry with gooseberry or with red currant, for example. Extracts of apple peels and cores were also used for "difficult to set" jams.
Commercial jam producers sought further supplies of pectin source materials. In Germany, apple juice producers started to dry the pomace residue left after pressing juice for sale to jam makers, who would cook the pomace in water with or without fruit juice to make a jellying juice.
The first commercial production of a liquid pectin extract was recorded in 1908 in Germany, and the process spread rapidly to the United States, where a classic patent was obtained by Douglas (US Pat. 1.082,682, 1913). This was followed by a rapid growth of the pectin industry in the United States, and also somewhat later in Europe.
In recent years, the centre of production has moved to Europe and to citrus-producing countries like Mexico and Brazil.
Further changes of structure and location of the industry continue, but are constrained by the need for large capital investment to set up a plant of economic size, and the need for a large-scale source or sources of raw material.

COMMERCIAL PRODUCTION

Process details vary between different companies, but the general process is as follows:

1. The pectin factory receives pineapple from our own farm or a number of juice producers. In most cases this material has been washed and dried so it can be transported and stored without spoilage. If the raw material is dry, it can be assessed and selected from store as required for different purposes. If wet citrus peel is used, it has to be used as received, as it deteriorates very rapidly.

2. The raw material is added to hot water containing a processing aid (usually a mineral acid, although others such as enzymes could be used).
Water alone will only extract a very limited amount of pectin.

3. After time to extract the pectin, the remaining solids are separated, and the solution clarified and concentrated by removing some of the water.
The solids can be separated by filter, centrifuge, or other means. The solution is then filtered again to clarify it if necessary.

4. Either directly, or after some further holding time to modify the pectin, the concentrated liquid is mixed with an alcohol to precipitate the pectin.
The pectin can be partly de-esterified at this stage, or earlier or later in the process..

5. The precipitate is separated, washed with more alcohol to remove impurities, and dried.The alcohol wash may contain salts or alkalis to convert the pectin to a partial salt form (sodium, potassium, calcium, ammonium).The alcohol (usually isopropanol) is recovered very efficiently, and reused to precipitate further pectin.

6. Before or after drying, the pectin may be treated with ammonia to produce an amidated pectin if required. Amidated pectins are preferred for some applications.

7. The dry solid is ground to a powder, tested, and blended with sugar or dextrose to a standard gelling power or other functional property such as viscosity or stabilising power. Pectins are also sold blended with other approved food additives for use in specific products.