Storing Rutabagas

Agdex#:	258/64
Publication Date:	January 1980
Order#:	80-001
Last Reviewed:	July 1983
History:
Written by:	E. C. Lougheed

Table of Contents

1. Quality Begins in the Field
2. Cultural Practices
3. The Weather
4. At Harvest
5. Directly Into Storage
6. Importance of a Very High RH
7. Importance of 0ºC Temperature
8. Waxing
9. Types of Storages for Rutabagas
10. Storage Construction

 

Quality Begins in the Field

Good rutabaga roots always store better than poor ones. Good storage results require that high-quality roots are harvested from the field. Both cultural practices and weather affect quality.

Cultural Practices

Registered seed, soil preparation, spacing, fertilizer and spray programs, use of herbicides, boron and sprout-inhibitor sprays, etc all have an effect on the quality of the roots and their freedom from disease and disorders. For details on recommended practices, consult Ontario Ministry of Agriculture and Food Publication 502, Rutabagas.

The Weather

The weather can affect the quality and storage behavior of roots. Too little rain will reduce the effectiveness of fertilizer applications and, in general, roots will be undersized. Nevertheless, the roots will have more flavor, be firmer, mature better and likely store better than roots grown in a wet year. Too much rainfall usually results in more storage problems. The roots are larger but less firm, more susceptible to mechanical injury and disease organisms, have less flavor, and their maturity at harvest is delayed. Immature roots do not store as well as properly matured ones.

At Harvest

Avoid excessive mechanical injury as much as possible. Bruises, cuts and scrapes exact a toll not only in appearance (the worst must be discarded) but also create focal points for disease organisms to enter and start rots. Furthermore, injured roots age at an increased rate, lose moisture faster and, in general, are a problem in storage. It is time well spent to study your harvesting and storage-filling operations for the purpose of reducing mechanical injuries.

Directly Into Storage

Unlike potatoes and onions that require a curing treatment before storing, rutabaga roots should go immediately into storage after harvest. For best storage results, the roots are cooled at 0ºC as soon as possible, and the relative humidity (RH) within the storage room must be maintained at a very high level (95%).

Importance of a Very High RH

The rutabaga root, similar to that of carrots, beets and parsnips, has no special protection against loss of moisture by evaporation. Exposure to low RH results in excessive water loss and shriveling. Consequently, it is essential to maintain a very high RH in storage. During cooling of the roots there is a considerable loss of moisture, so cool the roots to 0ºC as quickly as possible. At 0ºC it is much easier to maintain the RH at a very high level than at higher storage temperatures. An undersized evaporator (cooling coil) in the storage room can defeat the aim of maintaining very high RH. Because it is undersized, it is necessary to operate at a temperature much lower than that of the room to absorb the heat load. Consequently, the evaporator acts as a dehumidifier and maintains the RH in the storage room at a much lower level than desired. Undersized evaporators may be able to maintain the desired temperature, but only at the expense of lowering the RH. When installing refrigeration equipment, growers should insist on proper-sized evaporators to ensure that the system is capable of maintaining both a 0ºC temperature and a very high RH. Air-cooled systems should be equipped with adequate humidification systems.

Importance of 0ºC Temperature

There are many good reasons for storing rutabagas at 0ºC. As mentioned previously, it is easier to maintain a very high RH at 0ºC than at higher temperatures. The activities of disease organisms are sharply reduced as the temperature falls below 4ºC, and at 0ºC they are largely inactive. It has been proven that the brown surface discoloration called "storage burn" can be largely controlled by quickly cooling the freshly harvested roots to 0ºC, together with adequate air circulation. A very important effect of storing at 0ºC is that aging processes (chemical changes) are markedly slower than at high storage temperatures. The roots are firmer, have a better flavor, are more resistant to diseases, and have a longer shelf-life when marketed. Furthermore, roots do not sprout at 0ºC. Storing at 0ºC will slow down the development of soft rot and skin rot as well as retard the brown internal discoloration of roots affected with water core (boron deficiency). However, these diseases and disorders occur in the field and should be controlled there. Roots with disorders and diseases should never be placed in storage. Rutabagas freeze at approximately -1ºC and temperatures below -0.5ºC should be avoided in storage.

Waxing

Waxing of roots to reduce moisture loss during storage is not recommended. The wax coating will become unsightly and it may interfere with the normal living processes of the roots which require oxygen intake and carbon dioxide release. In a proper storage maintained at high RH, moisture loss from the roots will be minimal and there is no need for waxing them.
However, roots being marketed should be waxed to enhance their appearance and protect them against excessive moisture loss. Details concerning the waxing of rutabagas may be obtained from Agriculture Canada Publication 1120, The Waxing of turnips for the Retail Market.

Types of Storages for Rutabagas

In past years, large quantities of rutabagas have been stored in pits, barns, common or air-cooled storages and, more recently, refrigerated storages.

• Pits and Barns: Except for emergency reasons or for very short-time holding, these must be considered unsatisfactory and obsolete. In pits the RH will usually be very high (which is good) but the temperature is often too high (resulting in sprouting, rots and rapid aging) or too low (resulting in freezing injury). In barns the RH is often too low (resulting in shriveling) and temperature too high (storage burn, rapid aging, etc).
  
• Common or Air-cooled Storage: These can be useful for storing that portion of the crop to be marketed in the fall and early winter. However, this type of storage should be properly constructed, with adequate insulation and equipped with a forced-air ventilation and air-circulation system. The forced-air system must be carefully designed to permit full use of outside air for cooling purposes, and later permit regulation of the temperature and humidity with a minimum of air circulation.
  
• Refrigerated Storage: A refrigerated storage provides the best conditions of temperature and humidity for storing rutabagas. It can be especially useful for storing rutabagas harvested early, or in a warm fall when cold air is not available for operating an air-cooled storage. Its use is essential for maintaining the roots in a state of high quality for marketing in the spring and early summer.
  
• Jacketed Storage: This is a special type of refrigerated storage in which cool air from the evaporator circulates within a jacket, constructed close to the walls and ceiling of the storage room. Since the cool air does not contact the stored produce, the dehumidifying effect of the evaporator noted previously is eliminated. In a jacketed room it is much easier to maintain a very high RH. At present, an increasing number of jacketed storages are being constructed for carrots which also lose moisture readily and must be stored under very high RH. Jacket construction adds about 25% to construction cost.
  
• Combination of Air-cooled and Refrigerated Storages: Storages can be designed to use refrigeration in the fall and spring periods for which outside air temperatures are too high for adequate cooling. Air-cooled storage is used during the winter months. Such a combination must permit suitable control of temperature and humidity with both cooling systems.

Storage Construction

Whatever your requirements for rutabaga storage, information on construction is available from your closest Agricultural Engineer in an office of the Ontario Ministry of Agriculture, Food and Rural Affairs.