In addition to the most well known products, there are other agrofood products obtained by parts of citrus fruits. These applications are considered sometimes at high added value but they use only a minimum part of the world citrus fruit production.
Marmalade.
The citrus fruit marmalade is made of sour and small oranges with addition of lemon.
The juice is extracted from the fruits and it will be used afterwards. The peels must be cut in thin slides of about 1mm and boiled for about one hour during which the evaporated water shall be replaced with fresh one. Then the juice is added.
The classic English recipe include the entire juice while the American one prefers the filtered juice. To create suitable conditions for the gelatinization, some citric acid or lemon juice is added, till reaching a pH value of 3 - 3,4. Apart, in another container some pectin is mixed with sugar (1 pectin, 10 sugar) and this mixture is poured inside the saucepan with the peels, stirring and boiling everything. After some minutes other sugar is added and the ebullition goes on till obtaining a marmalade with the desired density. If you want an equal distribution of the peels you can use a pectin with quick hold. It's recommended to fill the pots at a temperature of at least 85°C and to close them immediately.
For the English market the marmalade is prepared with a mix of cooked torn pulp and peels of sour oranges. The sour oranges must be selected by quality and dimensions and scalded in hot water.
The endocarp, separated from the peel, is cut and cooked. Then is sieved with a sieve of 3 mm holes. The peels must be cut in slices between 38 and 63 mm long. Finally the torn pulp, slices and peels are cooked together in equal parts till reaching a content of soluble solids of 8%. If not hermetic pots are used, it's better to add sulphurous anhydride as preservative.
Comminuted.
The "comminuted" is a paste used to prepare thirst-quenching drinks. The raw material for the comminuted production is made of citrus fruit peel and juice, partially substituted by liquid mixed to citrus fruit residues and essential oil.
The production process consists in the grinding the citrus fruit parts, pasteurization and homogenization till obtaining an homogeneous paste, with colloidal aspect, quite fluid.
Candied peels.
It's a typical craft made working. The used peels mustn't have had any kind of damage (neither mechanical nor parasitic) and shall present the color of the ripe fruit. If the peels working is handmade, the fruit (citron, bitter or sweet orange, lemon) is de-pulped with an instrument called rake. Depending on the finished product characteristics, the peels can be totally or partially deprived by the essence or be natural. For the citrons, usually the whole fruits are pickled. The peels are undergone to a long working that makes them soft and quite elastic. In a first phase, they're put in cement tanks in big containers of paraffined wood , pressed and covered with sea water. The Mediterranean water, that has a salt tenor of 3,7-4°/oo, adding sodium chloride to reach the density of 7° Baumé, is considered optimal.
Recently, because of the increased pollution near the shores, it's used a sodium chloride solution at 5-7°/oo at a saline solution having he following composition:
Sodium chloride 27 g/l Potassium chloride 0,75 g/l Magnesium chloride 2,30 g/l Magnesium sulphate 2,30 g/l Calcium sulphate 1,40 g/l
Also this solution must reach 7° Baumé. In these tanks the fermentation occurs thanks to a yeast Saccharomyces citri medicae and to the bacteria Bacillus citri medicae. It's this biological process that makes the peels very soft and elastic.
After 5-6 days, the peels are transferred in definitive containers, that usually are barrels with a volume of 400 l. In these barrels the peels are put in spiral (each of them is put on the previous one to form concentric circles).
After having dripped the residual pickle, new pickle is added. The peels must always be covered by liquid, so every day pickle is added. So the fermentation goes on for a certain period (usually two months). After this period they're ready to be sold.
In these years the peels working (cut in cubes or round pieces, of standard dimensions). The cubes are cut with suitable equipments and selected through a series of vibrating sieves; the round pieces are obtained with proper moulds.
Also the slices obtained by hand cut peels can be pickled. Following a rational production method, that doesn't include the pickling, the slices are pre cooked in water at 60° C, then put in tins and covered by a sugar solution at 10-11° Brix. Afterwards there is the pasteurization in autoclave for about 45’ at 100° C and the cooling in water.
To candy the pickled peels it's important to wash them carefully. Then they're boiled many times in water for at least 5 minutes, changing each time the water. The duration of the washing and the numbers of cooking vary depending on the bitter flavor of the peels.
At the end of this preliminary phase, the peels are boiled for one hour in a sugar solution at 50° Brix, added with citric acid at 0,05% and at the end of the boiling the peels are let inside the solution for at least one night. In the final working phase, the peels are re-boiled at 104° C, drained and desiccated on racks in hot air current. The containers of the finished products must be hermetic because the peels suffer from the humidity.
Segments.
It's a typical Japanese product. The segments or slices are adequately prepared and firstly submerged in sugar syrup and then in milk.
Flavouring paste.
They're mixtures obtained by homogenized peels finely grinded, essences, sweetener, coloring agents and thickener. They're used to aromatize the drinks.
Vine and vinegar.
From the ripe orange and tangerine juices it's possible to produce wine. In fact these fruits are characterized by a high sugar tenor and a low acidity, that make them suitable to an alcoholic fermentation. The best ones are the dry ones. The oranges vinegar production reaction are similar to the reactions for the vinegars obtained from other fruits.
After the sugar fermentation, the ethylic alcohol is oxidized by bacteria of the Acetobacter genus, with production of acetic acid. The obtained vinegar contains volatile acids and citric acid that give a pleasant characteristic sign.
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