Agricultural/Bioengineering Post-Harvest Technology 1 — Questions and Answers
Question 1: What is the primary purpose of grain drying in post-harvest management?
- Increase grain protein content
- Reduce moisture to safe storage levels and prevent spoilage (Correct answer)
- Improve grain color for marketing
- Speed up germination during planting
Correct answer: Reduce moisture to safe storage levels and prevent spoilage
Drying reduces grain moisture below the threshold (typically 13–15%) at which mold, insects, and bacteria thrive.
Question 2: Equilibrium moisture content (EMC) of grain is defined as the moisture level at which:
- Grain absorbs maximum water
- Grain neither gains nor loses moisture to the surrounding air (Correct answer)
- All grain pathogens are eliminated
- Drying airflow reaches its peak
Correct answer: Grain neither gains nor loses moisture to the surrounding air
EMC is reached when the vapor pressure of grain moisture equals that of the surrounding air, resulting in no net moisture transfer.
Question 3: Which type of grain dryer passes heated air upward through a moving grain column?
- Bin dryer
- Cross-flow dryer (Correct answer)
- Concurrent-flow dryer
- Counter-flow dryer
Correct answer: Cross-flow dryer
In a cross-flow dryer, heated air moves horizontally through a vertically moving grain column, which is the most common commercial design.
Question 4: Controlled atmosphere (CA) storage of fresh fruits and vegetables involves modifying which gases?
- Nitrogen and hydrogen
- Oxygen and carbon dioxide (Correct answer)
- Ethylene and sulfur dioxide
- Methane and water vapor
Correct answer: Oxygen and carbon dioxide
CA storage reduces Oâ‚‚ and increases COâ‚‚ levels to slow respiration and delay ripening of fruits and vegetables.
Question 5: The process by which fresh produce continues to consume oxygen and release COâ‚‚ after harvest is called:
- Transpiration
- Photosynthesis
- Respiration (Correct answer)
- Translocation
Correct answer: Respiration
Post-harvest respiration is the metabolic process that consumes stored carbohydrates and generates heat, reducing shelf life.
Question 6: Heat of respiration from stored grain is a concern because it can cause:
- Increased protein synthesis
- Hotspots that accelerate mold growth and grain deterioration (Correct answer)
- Reduction in grain density
- Improved milling quality
Correct answer: Hotspots that accelerate mold growth and grain deterioration
Localized heating (hotspots) in grain bins accelerates moisture migration and mold development, leading to grain spoilage.
Agricultural/Bioengineering Post-Harvest Technology 1
What is the primary purpose of grain drying in post-harvest management?