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Potato Storage Management for Quality Potatoes

Potato Storage Management for Quality Potatoes. Roger Brook Extension Engineer Michigan State University. Potato Storage Ventilation. Use ventilation to control potato the storage environment potato temperature supply and/or control humidity remove surface moisture

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Potato Storage Management for Quality Potatoes

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  1. Potato Storage Management for Quality Potatoes Roger Brook Extension Engineer Michigan State University

  2. Potato Storage Ventilation Use ventilation to control potato the storage environment • potato temperature • supply and/or control humidity • remove surface moisture • provide oxygen and remove CO2

  3. Things Affecting Potato Storage Environment • Tuber respiration • Heat transfer thru building • Tuber variety and condition • Disease

  4. Respiration “ Respiration is, in a way, the opposite of photosynthesis. Energy stored in sugars is now released for use in maintenance of the tuber.” 6O2 + C6H1206 6CO2 + 6H2O + Energy (85% is heat) Oxygen Glucose Carbon Dioxide Water

  5. SEP NOV JAN MAR MAY Respiration Changes • Over time • With tuber temperature • With variety • With season 30 35 40 45 50 55 60 65

  6. The effect of stress on respiration • In general, any type of stress causes respiration to increase. • Stresses to watch for: • lack of fresh air (O2, CO2) • handling • temperature fluctuations • exhaust gases (CO, C2H4)

  7. Gas exchange in potato tubers O2 O2 H20 CO2 O2 H20 H20 O2 CO2 H20 CO2 O2 H20 CO2 O2 Lenticel and epidermis of potato tuber

  8. Wall cross-section vapor barrier steel cladding Plywood 1" extruded polystyrene house wrap Insulation and structural TYPICAL WALL SECTION

  9. VentilationUniformity • openings too small • underpile ducts too small • duct openings too large • workable 750-1500 fpm

  10. Ventilation Uniformity • openings too small • size for 1000 ft/min • plenum too small • plenum air velocity no more than 85% of the underpile duct velocity • underpile ducts too small • size ducts so that air velocity is 85% of the air outlet velocity • duct openings too large • size outlet for 1000 ft/min

  11. Sprinkler hose without endcap Sprinkler hose - too many holes / too large Sprinkler hose - correct holes / uniform distribution

  12. Ventilation System Builds Pressure for Distribution 100 FT 30 FT Distribution Ducts Loading and Work Area 8ft. c/c Plenum Fan Room Check distribution with food grade smoke

  13. PVC Solid Tubing 4 - 8 ft. long End Cap Monitoring Tuber Temperature Thermometer, hanging on string

  14. Understanding Moist Air in Potato Storages • dry air-water vapor mixtures • relative humidity • condensation and dew point • humidification equipment

  15. Relative humidity • The ratio of the actual amount of moisture in the air to the maximum amount of moisture the air could hold at that temperature. Relative humidity (RH) is expressed as a percentage

  16. Effect of warming air on RH 50 oF 95% RH 55oF 78% RH 60 oF 66% RH

  17. Surface temperature and condensation • condensation occurs at dewpoint temperature • potatoes or ceiling may be cooler than surrounding air; result can be “wet” surface. • Remedy: circulate air above bin or add insulation to ceiling.

  18. Calculated Dewpoint RH in a Potato Storage

  19. HumidificationSystems • High humidity • critical for curing process • minimal weight loss • maximum quality out of storage • Need 1 gal. water per 800 - 1000 cfm of design air flow

  20. Example of humidification required System has two 5-HP fans: need ~ 1 gal / 800-1,000 cfm airflow To determine humidifier capacity: water = 32,000 cfm/1,000 cfm/gal = 32 gal. water = 32,000 cfm/800 cfm/gal = 40 gal. Set water flow rate so that humidifier runs 80-85% of the time

  21. Centrifugal humidifier • also known as “spinning disk” • most common; moderate cost • low to moderate maintenance • low operating cost • excess water in plenum • prone to mineral buildup

  22. High pressure nozzles • moderate cost • moderate maintenance • some excess water in plenum • moderate operating cost • prone to nozzle plugging

  23. High pressure air/water nozzles • high cost • high maintenance • low excess water in plenum • high operating cost • excellent humidification

  24. Air washers • high initial cost • may require additional humidifier in dry climates • design size and placement • minimum size by face velocity • minimum distance for air spread

  25. POTATO STORAGE MANAGEMENTLooking for the Secrets • understand your crop • prepare your storage • prepare your crop • manage your system during HARVEST • manage your system during STORAGE

  26. UNDERSTAND YOUR CROPCommon Sources of Losses • breakdown due to disease • damage during harvest • equipment maintenance • harvest pulp temperature • weight and quality losses • cooling air temperatures • humidification • differences in respiration rates

  27. PREPARE YOUR STORAGEStructural Checks • Framing for decay and rot • Doors for good seals • Insulation for intact and dryness • infra-red thermometer in summer • Storage sanitation • steam clean • surface sanitize

  28. PREPARE YOUR STORAGEVentilation Checks • Thermometers and thermostats for accuracy • Humidifiers for operation and water flow • Fans motors for operation and lubrication • Fresh air doors for operation and lubrication • Control systems for correct functions • Electrical systems adequate voltage and safety • Ducts in need of repair or replacement

  29. PREPARE YOUR CROP • Remove dirt and vines • Grade to remove • rot and rocks • undesirable material • Size for Market • Record pulp temperature each load

  30. Manage during HARVEST • suberize ( wound healing ) • 55oF temperature • 90+% relative humidity • 10 - 14 days • weight loss control • humidification when fresh air • ventilation air temperature • modify for disease pressure

  31. Harvest Conditions Influence Management

  32. Weight loss vs. Relative Humidity 12 10 75% 8 85% % Weight Loss 6 95% 99.50% 4 2 0 0 1 2 3 4 5 6 7 8 9 10 Months in storage

  33. Manage for Disease / Decay Conditions • dry tuber surfaces • lower RH helps some • cool tubers quickly • watch temperature difference • manage humidity - condensation • keep air moving • through the pile • over the pile

  34. Manage during STORAGE • cooling versus holding • cool rapidly after suberize • control temperature difference • don’t overcool early • holding conditions • 38oF seed/table stock • 95% relative humidity • fresh air every day • will vary with physiological age

  35. Thank You -- Questions? Roger Brook Agricultural Engineering Department 210 Farrall Hall Michigan State University E. Lansing, MI 48840 brook@msu.edu

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