Pectin in fruit

Pectin is a plant cell wall polysaccharide consisting of a linear chain composed of D-galacturonic acid residues linked via α(1-4)-glycosidic bonds. Pectin or pectin solutions may be manufactured or obtained from dried apple peels and cores.

When pectin molecules come in contact with fruit acid, chainlike structures in the pectin become charged and these chain fold in on themselves. The folded chains trap water from the fruit or juice, forming gel.

Fruit contains pectin substances in a form that is not water dispersible and in this form cannot be used for the manufacture of jams, jelly, and other foods.

Pectin, which is released from the middle lamella of apple cell was by the mechanical action of milling and pressing is present in all fresh apple juices to a varying extent.

In early season fruit, amounts of soluble pectin may low, in the order of 0.1% by weight of juice. In later fruit, or in fruit from cold store, pectin may rise as high as 1-25% in the juice.

Commercial pectin comes in two forms, liquid and powdered. Liquid and powdered pectins are not interchangeable. Each requires a different balance of fruit, sugar and acid to attain the proper set.
Pectin in fruit 

Strawberries Used for manufacturing of Other Foods

Strawberries Used for manufacturing of Other Foods
Large amounts of strawberries are frozen to be sold to the consumer as such to be used for the manufacture of jams and jellies or for use in the bakery trade. Few strawberries for retail are sliced, mixed with sugar. Some strawberries are frozen individually on wire mesh and packaged in carton and overwrapped and placed in shipping cases for holding in frozen storage.

Strawberries used for the manufacture of other foods are usually frozen whole, in wooden barrels, mixed with sugar. A proportion of fruit to sugar of 3:1 or 2:1 may be used. The barrels of fruit are placed in cold rooms at 10 degree F or below. In order to mix the sugar with the fruit, the barrels are rocked during filling and rolled periodically during the several days required for freezing. The frozen fruit is sometimes stored at 10 degree F. Strawberry and sugar mixtures may also be packed in slip cover cans holding 30 lb of product.

In the manufacture of strawberry jam, water is added to the defrosted fruit mixture, as well as more sugar. The amount of sugar depending on how much sugar was added to the frozen product. About 0.25% - 0.3% of dispersed pectin is added, and the product is heated in open kettles to a soluble solids content of 65%. The pH is then adjusted to 3.3 with citric acid solution and the preserve is packaged in glass jars and vacuum capped. The sealed jars are then heated to a temperature of about 160 degree F, then cooled. In manufacturing strawberry jelly, about 0.3 – 0.35 % dispersed pectin is used, and the pH is regulated to 3.0 – 3.2.
Strawberries Used for manufacturing of Other Foods

Processing of Raspberries

Processing of Raspberries
At the processing plant, the fruit is washed with gentle sprays of water and drained on a metal mesh belt. If the product is to be handled in the fresh state, it is placed in small, retail sized baskets usually with a cellophane over wrap and quickly cooled to 31 to 32 degrees F. In this condition, the fruit has a storage life only 5 – 7 days.

Some raspberries are frozen for the bakery trade and many for the manufacture of raspberry jam and jelly. To prepare them for freezing, the washed and drained berries may be placed in wooden barrels without sugar, and then placed in a room at 0 degree F or below and allowed to freeze slowly. Usually however, they are mixed with sugar (three parts fruits to one part sugar) then packed in slip cover cans of 50 Ib capacity. The covered fruit is allowed to freeze in cold rooms at 0 degree F or below.

In the manufacture of jam, the deforested fruit is passed through a pulper that allows essentially all the berries with the seeds to pass through the strainer. Sugar and water are then added the amount of sugar depending on whether the frozen product was packed with or without sugar. About 0.1 – 0.15% dispersed pectin is then added and the product is heated in open kettles to concentrate it to soluble solids content about 68%. Citric acid solution is then added to adjust the pH to 3.3 and the fruit is packed in glass jars and vacuum capped. The jars of product are then heated to bring the temperature of all parts to about 160 degree F after which the product is cooled.
Processing of Raspberries

How grape juice is manufactured

How grape juice is manufactured
The Concord variety is chiefly used for the manufacture of grape juice. The grape are washed in acid or alkaline solution, then in water to remove spray residues, then destemmed and crushed by mechanical means. The crushed grapes are heated to about 180 F to extract pigment from the skins, after which the heated materials subjected to mechanical pressure while enclosed on cotton press cloths. The juice is then filtered, pasteurized by heating to 1790 F, and stored in bulk in covered tanks at about 40 F. This provides for the separation of tartaric acid slats. The juice is then siphoned off from the tartrate and treated with enzymes, which break down pectin, or with casein for purposes or clarification. It is then filtered and bottled. The bottles are capped and then pasteurized by heating in water at 170 F for 30 min.

To produce grape juice concentrate, grape juice is subjected to heat and evaporation until concentrated. Volatile components can be recovered from the process, and they can be added back to the concentrate. The concentrated juice may be frozen in retail sized containers, or it may be shipped in large tanks to food processors for remanufacturing process.
How grape juice is manufactured