Food Technology Glossary

Heating food by passing an electric current directly through it, so the food itself acts like a resistor and heats evenly from the inside.

The combined conductance of all resistances between two fluids — convective films, wall conduction and fouling — used as Q = UAΔTlm.

A chart relating dry bulb temperature, wet bulb temperature, humidity ratio, relative humidity and enthalpy of moist air.

The ratio of the partial pressure of water vapour in air to its saturation pressure at the same temperature, as a percentage.

A pressure vessel used to sterilise food after sealing in its container, allowing temperatures above 100 °C.

A filtration method that pushes water through a very fine membrane under pressure, removing dissolved salts, minerals, and other impurities.

The dimensionless ratio of inertial to viscous forces, Re = ρvD/μ.

The mechanical energy delivered to unit mass of material in an extruder, in J/kg.

Atomising a liquid feed into a hot air stream so droplets dry almost instantly into powder.

The relation giving the settling velocity of a sphere in a fluid, proportional to the square of particle diameter and the density difference, and inversely proportional to viscosity.

The direct transition of a solid to vapour without passing through the liquid phase, occurring below the triple point of water — 0.0098 °C and 611 Pa.

A curve relating equilibrium moisture content to water activity at constant temperature, typically sigmoidal.