A nut roaster to solve shelf-life problems due deterioration in the quality of hazelnuts

macchinario lavorazione cioccolato

A leading confectionery firm, that uses significant amounts of whole hazelnuts in its products, has requested Tecno 3's cooperation in addressing shelf-life issues connected to the qualitative deterioration of this ingredient. Preservation of toasted whole nuts is generally critical due to the high content in fat content that tends to migrate to the surface and is oxidised by atmospheric oxygen. Turning rancid is the cause of the short shelf life of all products containing whole nuts, roasted using traditional methods. Packaging, however careful, is able to perceptibly slow down the phenomenon but does not significantly improve preservation.

THE STUDY
Toasted nuts contain a certain residual amount of water, generally between 4 and 7%. This is contained in the product's structural cells, where is also the composition oil. When the nuts are rapidly heated at high temperature, water turns to the gaseous state with a very high vapour pressure, which causes the rupture of cell walls. The phenomenon allows oil to escape and migrate to the surface, thus coming into contact with the oxygen in the air. The solution to the problem is to allow water to evaporate leaving cells intact, so that their walls act as barrier for the oil they contain.
THE SOLUTION
Toasted nuts contain a certain residual amount of water, generally between 4 and 7%. This is contained in the product's structural cells, where is also the composition oil. When the nuts are rapidly heated at high temperature, water turns to the gaseous state with a very high vapour pressure, which causes the rupture of cell walls. The phenomenon allows oil to escape and migrate to the surface, thus coming into contact with the oxygen in the air. The solution to the problem is to allow water to evaporate leaving cells intact, so that their walls act as barrier for the oil they contain.
THE REQUEST
Tecno 3 has produced a hot air, continuous vertical roaster divided into 3 stages. 1st stage: gradual water evaporation, with heating at moderate temperature to prevent high tensions. Most of the hot air is recirculated to assure energy savings. A small percentage if fresh air allows moisture to be removed. 2nd stage: heating at the desired temperature according to the desired degree of roasting. In addition to assuring energy savings, air recirculation prevents excessive loss of aroma. 3rd stage: cooling with air at ambient temperature.

The result

The nuts gently go through the three stages without being subject to any harmful rolling or impacts. In products intended for peeling the peel remains on until roaster outfeed, acting as protection against the action of the air and the loss of aroma. Roasting only starts after the drying stage and leaves the cell structure perfectly intact. On outfeed, the foodstuff has no trace of surface oiliness. This makes peel removal easier (in nuts where this is possible) with the specific “Peeler” machine developed by Tecno 3, without soiling the brushes, without damaging the surface and with excellent results. The customer who made the request is now satisfied, as are many more who experienced the same issues and have decided to use the Tecno3 roaster. Positive results are obviously also had with nuts intended for grinding to make paste.

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