Midterm

• POSTHARVEST -refers to the stage of crop production immediately following harvest.
• POSTHARVEST ENGINEERING AND TECHNOLOGY – Is the application of engineering principles for development of postharvest machinery for various postharvest operations of agricultural products.
• AGRICULTURAL PRODUCTS –  or product of agricultural origin means any product or commodity, raw or processed, that is marketed for human consumption or animal feed (excluding water, salt and additives).
• CROP PROCESSING – Is the transformation of raw materials harvested from the farm into a valuable marketable product.
• WHY DO WE NEED TO PROCESS AGRICULTURAL PRODUCTS? •Food security

  •Food safety

  •Minimize product loss
• Primary Processing – Any activity that involves the handling of crops to make them more suitable to manufacturers, processors or consumers and can still be changed into other forms. (In simple words, it is the conversion of raw materials.
• Secondary Processing – Postproduction activities that involve conversion of harvested crops into stable products that can no longer be changed into other forms. (Ex. Turning wheat flour into bread).
• Perishable Crops - refers to agricultural food produce which have short life-span and must be consumed or processed within a short-time after harvest.
• Examples of perishable crops include tomato, pepper, banana, potatoes, yams, carrots, onions and leafy vegetables.
• Post-production in Secondary Processing: Food Processing, Industrial Processing, Production of Medicinal Products from Plants, Production of Died Plant Art Forms
• Drying – Food drying is a method of food preservation in which food is dried. Drying inhibits the growth of bacteria, yeasts, and mold through the removal of water.
• Fermenting – is an ancient technique of preserving food. Fermentation  is a natural process through which microorganisms like yeast and bacteria convert carbs such as starch and sugar into alcohol or acids.
• Canning – refers to the preservation method where fruits or vegetables are sealed in airtight containers (usually cans or jars) and heated to destroy microorganisms that can cause spoilage.
• Freezing – Is a preservation method where crops are rapidly cooled to extremely low temperatures to halt enzymatic activity and microbial growth. Commonly used for fruits, vegetables and other perishable crops, allowing them to be stored for extended periods while retaining their freshness.
• Preserving – Typically involves methods such as canning, freezing, drying, and fermenting. These techniques help extend the shelf life of crops by inhibiting microbial growth and preserving their nutritional content.
• Common Storage Facility/Equipment: Grain Storage Facility, Cold Storage, Ventilated Storage, Evaporative Cooler
• Objective of Storage •At the food level: to permit deferred use of the agricultural products harvested.•At the agricultural level: to ensure availability of seeds for the crop cycles to come.•At the agro-industrial level: to guarantee regular and continuous supplies of raw materials for processing industries.•At the marketing level: to balance the supply and demand of agricultural products thereby stabilizing market prices.
• Grain Structure

  Germ – the embryo which, if fertilized by pollen, will sprout into a new plant.
• Grain Structure

  Endosperm – The germ’s food supply. It is by far the largest portion of the grain.
• Grain Structure

  Husk – The multi-layered outer skin of the grain, and is tough enough to protect the grain from pests and pathogens.
• Mechanisms of Drying

  When hot air is blown over a wet food, water vapor diffuses through a boundary film of air surrounding the food and is carried away by the moving air.
• Mechanisms of Drying

  The drying rate is dependent upon many factors:

  Airflow Rate

  Temperature

  Relative Humidity

  Exposure Time

  Types

  Variety of Grain

  Size of the Gain

  Initial Moisture Content

  Grain Depth
• Grain Drying Option

  Field Drying

  • Low cost
  • Ease of management
• Methods of Field Drying:

  Mat Drying

  Pavement Drying
• High Temperature Grain Drying

  Batch Type – mechanical grain dryer wherein the grain in fixed volume is held in the drying chamber in batches until the gain reaches the desired moisture content.
• Flat Bed Type – shallow bed batch type dryer wherein a fixed volume of grain is held stationary in a horizontal grain holding bin.
• Recirculating Type – batch type dryer equipped to circulate and/or mixed fixed volume of grain during the drying operation.
• Vertical Bin Type (Columnar Type) – batch type dryer wherein a fixed volume of grain is held stationary in a vertical grain holding bin.
• Continuous Flow Dryer – dryer in which the material being dried moves through the drying chamber in a substantially continuous stream and is discharged without being recirculated.
• a. Concurrent Flow Type (Parallel Flow Type) – the product being dried moves in the same direction as drying air.
• b. Counter-Flow Type – the grain being dried move in one direction and the drying air moves in the opposite direction.
• c. Cross-Flow Type – the flow of air is transverse to the direction of flow of the grain being dried.
• d. Mixing Type – the drying bin is similar to columnar drying bin except that it includes louvers causing mixing to occur as the grain flows through the system.
• e. Non-Mixing Type – the grains in the drying bin flows through the column in a straight path.
• Solar Drying – Has an absorber that receives and absorbs solar spectrum of radiation.
• METHODS OF DRYING

  1. Conduction Drying – The heat for drying is transferred to the wet solid material mainly by conduction through a solid surface usually metallic. The phenomena are known as conduction or contact drying.
• METHODS OF DRYING

  2. Convection Drying – The drying agent (hot gases) in contact with the wet solid is used to supply heat and carry away the vaporized moisture and the heat is transferred to the wet solid mainly by convection.
• METHODS OF DRYING

  3. Radiation Drying – It is based on the absorption of radiant energy of the sun. Heat energy can be supplied to wet products by electromagnetic waves.
• Physical Properties of Agricultural Crops

  1. Surface Area

  2. Porosity

  3. Bulk Density

  4. Angle of Repose

  5. Angle of Friction
• Surface Area – Surface area of the product, especially of the paddy grain, is regarded as cono-elliptical cylinders in shape.

  It affects the physical properties especially the porosity, angle of repose, and angle of friction of the product. It is important in designing, cleaning, and separating equipment, dryer and storage facilities.