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Assignment
On
Properties of Dry & Moisture Air & its Importance for a Food Industries
Submitted To
A. K. M. Sarwar InamAssistant ProfessorDepartment of NFE
Daffodil International University
Submitted By
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.
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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.
Yield determining.
Drying process confirming the end.
Reference:
https://www.masterflex.com/tech-article/why-food-moisture-content-is-importanthttps://www.usaemergencysupply.com/information-center/self-reliance/food-storage-frequently-asked-questions/why-moisture-is-important
