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The moisture content of grains is an essential property in food storage. The moisture content that is safe for long-term storage is 12% for corn, sorghum, rice and wheat and 11% for soybean [1] At a constant relative humidity of air, the EMC will drop by about 0.5% for every increase of 10 °C air temperature. [2]
This relationship between water activity and moisture content at a given temperature is called the moisture sorption isotherm. These curves are determined experimentally and constitute the fingerprint of a food system. [2] BET theory (Brunauer-Emmett-Teller) provides a calculation to describe the physical adsorption of gas molecules on a solid ...
Related: 11 Freezer Storage Mistakes That Are Ruining Your Frozen Food. The Safe Zone. The correct temperature for your freezer is 0 degrees Fahrenheit—if you set it to 0 degrees (-18 degrees ...
Food storage in refrigerators may not be safe unless there is close adherence to temperature guidelines. In general the temperature should be maintained at 4 °C (39 °F) or below but never below 1 °C (34 °F). [8] Safe storage times vary from food to food and may depend on how the food has been treated prior to being placed in the refrigerator.
In food science, water activity (a w) of a food is the ratio of its vapor pressure to the vapor pressure of water at the same temperature, both taken at equilibrium. [1] Pure water has a water activity of one. Put another way, a w is the equilibrium relative humidity (ERH) expressed as a fraction instead of as a percentage.
To compute the VPD, [2] we need the ambient (greenhouse) air temperature, the relative humidity and, if possible, the canopy air temperature. We must then compute the saturation pressure. Saturation pressure can be looked up in a psychrometric chart or derived from the Arrhenius equation; a way to compute it directly from temperature is
where temperature T is in degrees Celsius (°C) and saturation vapor pressure P is in kilopascals (kPa). According to Monteith and Unsworth, "Values of saturation vapour pressure from Tetens' formula are within 1 Pa of exact values up to 35 °C." Murray (1967) provides Tetens' equation for temperatures below 0 °C: [3]
The wet-bulb temperature is the lowest temperature that may be achieved by evaporative cooling of a water-wetted, ventilated surface.. By contrast, the dew point is the temperature to which the ambient air must be cooled to reach 100% relative humidity assuming there is no further evaporation into the air; it is the temperature where condensation (dew) and clouds would form.