Properties of Dry & Moisture Air & its Importance for a Food Industries
A. K. M. Sarwar InamAssistant ProfessorDepartment of NFE
Daffodil International University
Md Sohel Rana
ID No- 163-34-562
Department of NFE (Evening)
Submitted Date 22.07.2018
Properties of Dry Air:
Is the specific heat, ratio of specific heats, dynamic viscosity, thermal conductivity, density and kinematic viscosity is the dry air properties, dry air properties temperatures at ranging 175 – 1900 K.
Air is a mixture of several constituent gases. The composition of air varies slightly, depending on the geographical location and altitude.
The apparent molecular weight of standard dry air is 28.9645. The gas constant for dry air, Ra, is computed as 8314.41/28.9645 = 287.055(m3Pa/kgk).
Specific Volume of Dry Air is the ideal gas laws can be used to determine the speci?c volume of dry air. Therefore, V’a =RaTa/pa.
Specific Heat of Dry Air is the 1 atm (101.325 kPa), the speci?c heat of dry air Cpa in a temperature range of -40 to 60 degree C varying from 0.997 to 1.022 kJ/(kg K) can be used.
Enthalpy is the heat content of dry air, is a relative term and requires selection of a reference point. Ha = 1.005(Ta-To)
Dry bulb temperature is the properties of dry air it measured by a thermometer.
Importance of dry air in food industries;
Drying (dehydrating) food is one of the oldest and easiest methods of food preservation. Dehydration is the process of removing water or moisture from a food product. Removing moisture from foods makes them smaller and lighter. Dehydrated foods are ideal for backpacking, hiking, and camping because they weigh much less than their non-dried counterparts and do not require refrigeration. Drying food is also a way of preserving seasonal foods for later use.
Properties of Moist Air:
It is the dry bulb temperature, dew point temperature, wet bulb temperature, relative humidity, absolute temperature, vapor pressure, heat content, specific volume ; density.
Importance of moist air in food industries:
Three Ways Humidity and Moisture Affects Food Processing;
1. Accelerated Growth of Microorganisms
2. Compromised Product Quality and Reduced Shelf Life
3. Packaging is Affected
For In bakeries: For dough proofing, relative humidity is a critical factor for consistent results. Too low humidity reduces the volume of the dough, producing a smaller product.
For smoked meats: high humidity helps disperse heat and smoke flavor evenly throughout the product.
Cheese producers; use controlled humidity to accurately control the ripening process for brie, camembert, and blue cheeses, providing uniform humidity throughout the year. Culture producers recommend 70-80% RH for drying and 90-95% RH for ripening. Roquefort cheese requires 98% RH
There are important of moist air, such as:
Quality measurements of Food.
Shelf life determination of food.
Requirements Legal and labeling.
Dry weight establishing of food.
Drying process confirming the end.