ACADEMY SERIES · EPISODE 23Chocolate & Confectionery

Dehumidification in Cooling Tunnels

In chocolate and confectionery production, gloss is often lost at the end of the cooling tunnel. If the cold product surface is below the dew point of the tunnel air or the room air at the exit, moisture condenses on it and sugar bloom begins. This episode covers where condensation begins, why relative humidity can mislead, dew point targets by product, the buffer zone at the exit, infiltration, a worked moisture load and dry-air flow, and choosing the right dehumidification technology.

Published: 13 October 2026Narration: Turkish and English4:41

In this video

  • Condensation starts where the product surface is coldest, at the end of the tunnel and at the exit; the air dew point is kept at least 3 degrees below the lowest product surface temperature.
  • A water film on the surface dissolves sugar, which then recrystallises as coarse crystals (sugar bloom); fat bloom comes from temperature swings, not humidity.
  • For coated chocolate the dew point is held at +4 °C at most, preferably +2 °C; +6 °C for tablets and +2 °C for pralines and filled products. A buffer zone at 18 °C and 45% RH, with a dew point of about +6 °C, prevents condensation at the exit.
  • In a 32 m example tunnel with two openings, a +2 °C target and 32 °C / 75% summer air, the total moisture load is 27.5 kg/h including a 20% margin; supply air at a −20 °C dew point needs about 6,400 m³/h of dry air.
  • Almost all of the load comes through the openings, so strip curtains, air curtains and 5–20 Pa positive pressure also shrink the unit. These targets lie below the +5 °C limit of condensing units, so a silica gel rotor or hybrid system is needed.

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