Final (Part 2)

• Porosity - has an important role in the drying and storage of the product. It indicates the percentage volume of spaces over the volume of the product plus the volume of spaces within the product.
• Porosity - it is dictated by the shape and dimension of the product as well as the

  roughness of the product surface.
• PSYCHROMETRY – The study of the properties of the air, and use of the psychrometric chart are essential for an understanding of the processes involved in drying and storage of grains and other agricultural crops, and for analyzing individual requirements for a particular climatic condition.
• PSYCHOMETRIC CHART - device that simplifies the measurement of air properties and eliminates many time-consuming and tedious calculations that would otherwise be necessary. Any psychometric chart is simply a graphic presentation of the conditions or properties of air, such as temperature, humidity, and dew point.
• Dry-Bulb Temperature - temperature of the air as measured by an ordinary thermometer such as a household thermometer. The bulb is the sensitive portion of the instrument. As the temperature of the bulb increases, the liquid in the bulb expands and rises in the stem.
• Wet-Bulb Temperature - temperature of the air as measured by an ordinary thermometer whose glass bulb is covered by a wet cloth or gauze. The clean cotton wick absorbs water.
• Dewpoint Temperature -temperature at which moisture condenses on a surface. It is the temperature at which condensation occurs when air is cooled at constant humidity ratio and constant atmospheric pressure.
• Relative Humidity - is the ratio of the partial pressure of water vapor in the to the pressure that saturated water vapor exerts at the temperature of the air. The relative velocity is expressed as decimal or a percentage. In agricultural process such as grain drying, relative humidity values between 0 to 100% are often encountered.
• Humidity Ratio - weight of the water vapor contained in the moist air per unit weight of dry air. Other terms used for humidity ratio are absolute humidity and specific humidity.
• Specific Volume -specific volume of moist air is defined as the volume per unit weight of dry air.
• Enthalpy - enthalpy of a dry air-water vapor mixture is the heat content of the moist air per unit weight of dry air above a certain reference temperature.
• Milling - is the process of converting paddy into rice. It is to be carried out with outmost care to prevent breakage of the kernel and improve the recovery of the paddy.
• Milling Process

  • Cleaning -removing foreign materials such as rice straws, stones, seeds, etc. from the paddy.
• Milling Process:

  • Dehusking and Husk Separation - removing the husk from the paddy with a minimum damage to the grains, and separating the husk from paddy.
• Milling Process:

  • Paddy Separation -separating dehusked paddy from the remaining grains. Most dehusker removes about 90% of the husks.
• Milling Process:

  • Bran Removal - removing all or part of the bran layer from the grain to produced polished rice.
• Milling Process:

  • Grading – separating or grading broken grains from unbroken rice. Broken grains are separated into different sizes.
• Abrasive-Type Whitener

  - type of whitener consisting of an abrasive-coated cylinder or cone which rotates inside a perforated steel housing.
• Frictional-Type Whitener

  -type of whitener consisting of a fluted roller rotating inside a hexagonal chamber with slot-type perforations.
• Maximum Input Capacity - maximum quantity of paddy that the rice mill can process to a specified quality over a given period, expressed in kg/h.
• Output Capacity - mass of milled rice per unit of milling time, expressed in kg/h.
• Coefficient of Husking -ratio of the mass of brown rice to the total mass of paddy input to the husker.
• Coefficient of Wholeness - ratio of the mass of head brown rice grains to the total mass of brown rice (head broken) produced by the husker.
• Husking Efficiency - product of coefficient of husking and the coefficient of wholeness.
• Percentage Cracked Brown Rice - number of grains showing cracks of fissures per 100 grains of hand- husked paddy.
• Hardness of Grains - compressive strength of a full head, uncracked and hand-husked, brown rice as measured by a hardness tester.
• Milling Degree - extent or degree by which the bran covering the brown rice is removed as result of the whitening process.
• Head Milled Rice - percentage mass of head milled rice recovered from the mass of the corresponding input paddy to the rice whitener.
• Head Milled Rice Recovery Index - ratio of the head milled rice recovery from the test rice mill to that from the laboratory whitener.
• Percentage Broken Milled Rice - percentage of milled rice grains measuring less than ¾ the size of its full head rice from the mass of the corresponding input paddy to the rice husker then to the whitener.
• Broken Milled Rice Index - ratio of the percentage broken milled rice recovery from the test rice mill to that from the laboratory whitener.
• Total Milling Recovery - percentage total mass of milled rice (head and broken rice) to the mass of the corresponding input paddy to the rice mill (husker or huller and whitener).
• Total Milling Recovery Index - ratio of the milling recovery from the test rice mill to that from the laboratory whitener.