The making of Sirop de Liège
The making of Sirop de Liège spread involves two stages:
I. The making of concentrated juice
II. The making of the finished product
The fruit (pears, apples, dates, apricots, prunes) are processed separately in order to produce the concentrated juice which will serve for the day to day production of the finished product.
I. The making of the concentrated juice
The production of the concentrated juice involves 3 main operations:
1. cooking of the fruit
2. extraction of the juice
3. concentration of the juice
1. Cooking of the fruit
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150.000 to 200.000 kg (or 150 to 200 T) of fruit are processed every 24 hours.
After being washed and crushed, the fruit is continuously fed into the cooker. Cooking time is about one hour.
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The cooked pulp is then filtered in order to separate the prime juices, after which it is cooked again in traditional cookers. Steam, which is necessary for the cooking process, is allowed to pass into the adapted coil in the bottom of the cooker.
The time necessary for perfect cooking depends on the variety and maturity of the fruit. |
2. Extraction of the juice
The fruit compote is pumped towards the presses in order to extract the juice from it. Each press is made up of hurdles between which filtering bags of 3 metres high and 1 metre wide are placed.
In 20 minutes, 12 tons of fruit are pumped and pressed for an hour under a pressure of 10 kg/cm2.
Before being concentrated, the juice is collected in waiting reservoirs, then sent on to rotary filters.
After the pressing process, the flesh of the fruit, called the pulp, is evacuated. 100 kg of fruit yeld about 12 kg of pulp, which will be used as cattle feed. |
3. Concentration of the juice
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The triple-effect evaporators, which run continuously, can process 15.000 litres of juice every hour, which yields about 2.500 kg of concentrated juice.
This concentrated juice, cooled down to 15° C in a heat exchanger, is pumped into the storage tanks, where it is kept in reserve for use in the making of the finished product throughout the year. The concentrated juice is kept at a low temperature (5 to 8° C), and thus conserved. |
II. The making of the finished product
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Among the constituents of the apple, the one which interests us the most is pectin. It has the property of provoking gelatination when a mixture of apple juice and sugar is concentrated.
The quantities of each constituent, determined by computer, are pumped from the storage reservoirs into the mixers.
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Once it is homogeneous, this mixture is sent into the refiners where it is boiled in order to evaporate any excess water and to obtain the concentration necessary for a good gelatination. This stage is called the refinement.
In order to ensure that the product is of consistent quality, these different operations are controlled by computer. All the production data is recorded and printed out for the internal quality control department.
Chilled to 65° C and still liquid, the syrup can then be pumped towards the filling machine, which can turn out 250 g, 300 g, 450 g and 900 g pots at the rate of 2000 to 5000 every hour, that is an average of 50.000 pots a day.
These pots are then conveyed automatically into a chilling tunnel. This tunnel, which is 10 m long, 5 m wide and 3 m high is fitted with six levels of aerated conveyor belts. Progress is very slow : 3 hours to travel 10 metres. During this time, 10.000 m3 of cold (10° C) and sterile air gradually lowers the temperature of the syrup which, when it emerges from the tunnel, has reached 15° C at the heart of each pot.
This slow and gradual chilling, in conditions of perfect hygiene, is vital to ensure a good gelatination and to seal the surface of the syrup against any exterior contamination.
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This slow and gradual cooling is vital to ensure proper jellying.
Upon emerging from the tunnel, the pots are conveyed to the packing machine. Finally, the wrapping machine coats them with a plastic film. Then they are loaded onto pallets, ready for delivery.
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