Lesson 3 Flashcards
It is the presence of a liquid, especially water, often in trace amounts. Moisture is defined as water in the adsorbed of absorbed phase.
Moisture
Amount of moisture in the grain expressed as percentage of the total weight of the sample, wet basis.
Moisture Content
It is lightly entrapped and therefore easily pressed or squeezed from food. It acts as a dispersing agent and solvent and can be removed by drying foods. Can promote the growth of microorganisms. Examples are citrus fruits, tomato, pineapple.
Free Water
This water associates in layer through intermolecular hydrogen bonds around hydrophilic food molecules. Water is held tightly to proteins or cell walls or protoplasm. It is not readily squeezed out of food. It refers to the hydration proteins such as starch. Examples are carrots, singkamas, radish, kamote.
Absorbed Water (Capillary Water)
Cannot be boiled or the water remains unfrozen below 0 degrees Celsius, usually -20 C. Water in food that is unavailable as a solvent. Examples are egg white, egg yolk, meat and fish, cheese.
Bound Water
Based on direct measurement of the amount of water removed from a food simply by evaporation. Its major uses in the food industry are for concentrating essential oils, flavours and alcoholic beverages, and in the deodorization of fats and oils.
Distillation Methods
A thermogravimetric method (water losses on drying) in which the sample is dried for a defined period of time at constant temperature. The moisture content is determined by weighing the sample before and after drying and determining the difference.
Oven Drying Method
It allows dehydration to be carried out at low temperatures in a closed system.
If the drying temperature is below 10 °C, it can inhibit the growth of microorganism. To increase the drying rate, heating plates/trays or heating chamber wall may be installed to allow conductive heat transfer.
Vacuum Drying
The heat transfer mode in vacuum drying is by?
Radiation
It is suited for drying high value liquid foods such as coffee and juices, as well as high value solid foods such as strawberries, shrimp, diced chicken , sliced mushrooms, and even steaks
and chops. The main principle of this is facilitating the sublimation of water from the sample under reduced pressure and temperature conditions.
Freeze drying or Lyophilization
Method of grain moisture determination
based on actual extraction of water either by convection heating (oven method) or distillation.
Primary Method
Method of grain moisture determination based on some characteristics of the grain sample such as electrical resistance and capacitance which are related to moisture content and must be periodically calibrated against and official primary method.
Secondary Method
