How to preserve yams

In this brief guide, we are going to answer the question “how to preserve yams” and discuss the different methods of preserving yams.

How to preserve yams

Studies show that consumer demand for sweet potato (yam) is growing exponentially, thanks to the rising interest in ethnic vegetables mediated by globalization and by nutraceutical research. For these reasons, both imports and consumption are rapidly growing, increasing by 100% over the last five years (1).

Yams can be preserved by :

• Raw yams: Storing raw yams under proper conditions
• Cooked yams: Refrigerating and freezing 
• Dehydrating 
• Canning

Yams, often confused with sweet potatoes, are dry, starchy, tubers native to Africa and Asia.

Yams are very versatile as their flavor can be altered to match the needs of a recipe.

Yams are usually served boiled, baked or mashed. They are also served as a side dish with vegetables and meat.

How to preserve raw yams

Raw yams must not be refrigerated or frozen as the cold temperature may cause them to develop hard centers along with an unpleasant taste. Yams preserve well under the proper storage conditions.

At room temperature, raw yams will only last for about a week. However, in a study, unpeeled and peeled yam tubers were kept in different storage temperatures. Unpeeled tubers stored at 17 and 25°C (62 and 77°F)  could maintain saponin content and composition until 35 days later. During 80 days storage, the content and composition of furostanol and spirostanol glycosides in peeled and unpeeled tubers at -18°C (0°F), and peeled tubers at 4°C (39°F) did not show significant differences (2).

Ideally, raw yams must be stored at a temperature of 45-55° F, in a dark and dry area. Raw yams must not be kept in a covered container. They must be kept in a crate or loose bag that allows air circulation. Under these conditions, raw yams will be preserved for about a month.

Once cut, raw yams will spoil quickly. Cut raw yams must be immersed in water and refrigerated. They must also be used within 24 hours. However, a study showed that minimally processed yam stored at 10°C (50°F) may be sold for up to six days, and yam stored at 5ºC (40°F) for up to 14 days. Yam was selected, peeled and cut into slices of approximately 3 cm thickness. The slices were rinsed with water, sanitized and then drained in kitchen strainers (3).

Once cooked, yams can be either refrigerated or frozen.

How to preserve cooked yams by refrigerating

Cooked yams are very susceptible to spoilage. They must be refrigerated within 2 hours of cooking. If left out for longer than 2 hours, it is best to discard the yams.

Cooked yams can be refrigerated for 2 to 3 weeks in an airtight container of a ziplock bag.

How to preserve cooked yams by freezing

Freezing is the best method to preserve the flavor and texture of cooked yams. Cooked yams can be frozen for about 1 year (4). Textural properties of the frozen yam French fries are affected by root storage, and the problem can be overcome by calcium treatment and low‐temperature blanching (5).

Yams can be either boiled or baked before freezing. Boiled yams can also be mashed in the same manner as mashed potatoes and then frozen.

To freeze yams:

• Boil or bake the yams until they are tender.
• Allow the yams to cool down to room temperature.
• Slice the yams into desired thickness. Baked yams can also be frozen whole, wrapped in aluminum foil and then placed in an airtight container or a ziplock bag. If you want to mash yams, mash and season them at this stage. A little lemon juice can be added to prevent discolouration.
• Place the yams into airtight containers or ziplock bags and squeeze out the excess air.
• Seal, label and place in the freezer.

Frozen yams can be thawed in the refrigerator before use. After being thawed the yams can be further refrigerated for a maximum of 3 days before being used. If frozen yams are thawed using cold water or a microwave, they must be used immediately and must not be refrigerated.

How to preserve yams by dehydrating

Dehydrating yams will preserve them for 6 to 12 months. Yams must be blanched before dehydrating. If yams are dehydrated without blanching, the enzyme activity will result in a change of color and flavor in about 3 months. Dried food should be stored in a cool, dry, dark place. Most dried vegetables can be stored for 6 year at 60° F, 3 months at 80° F (6).

Dehydrating can be done in a food dehydrator or an oven.  The slices may be subjected to metabisulfite treatment before or during blanching to prevent browning. The blanched or unblanched slices are sun‐dried until the slices reach a moisture content of about 6–10%. Drying times vary from 4 hours to 5 days, depending on climatic conditions (5).

Dehydrating yams is time-consuming and there is a loss of nutrients during the blanching stage. However, dehydrated yams have a long shelf-life and can be a healthy snack.

To dehydrate yams:

• Wash the yams and peel them.
• Slice the yams into slices of about ¼ inch thickness.
• Blach the yams in boiling water for about 5 minutes. 
• Sprinkle with seasonings such as salt and cinnamon if needed.
• Arrange the yam slices on a dehydrator tray or place them on a baking sheet.
• Dehydrate the yams according to instructions of the dehydrator manual or at the lowest temperature setting of the oven.
• The dehydrating process takes about 6 to 12 hours.
• Store the dehydrated yams in an airtight container, away from direct sunlight.

How to preserve yams by canning

Canning is a preservation method that results in a long shelf-life. There are several recipes for canned yams. However, if you are planning to store them for over a year at room temperature, follow a recipe that uses pressure canning.

Sweet Potatoes can be canned whole, halved, or cut into chunks, in either syrup or water. Sweet Potato roots are peeled, cut and blanched. Blanching in water at 77°C for 1–3 minutes. Immediately after blanching, the material is packed in cans and covered with syrup at 95°C to prevent discoloration. Sugar (20–40%) or water is used, depending on consumer preferences. Cans should be exhausted long enough for the internal temperature to reach 77°C to ensure a good vacuum of the finished cans. After closing, the cans should be retorted according to the processing schedules and quickly cooled after retorting to an internal temperature of 35°C to avoid “stackburn” and slow drying of the can, which may lead to rusting (5).

Disadvantages of canning yams include the long time taken for preparation, processing and sterilizing and the need for special canning equipment.

Canning candied yams is an unusual and delicious way to preserve yams. 

If canned into sterilized jars and stored properly, these candied yams preserve for about 3 years.

A complete recipe for making candied yams can be found here.

Other FAQs about Yams that you may be interested in.

Can you eat raw yams?

Conclusion

In this brief guide, we answered the question “how to preserve yams” and discussed the different methods used to preserve yams.

If you have any questions or comments, please let us know.

References

1. Galvao AC, Nicoletto C, Zanin G, Vargas PF, Sambo P. Nutraceutical Content and Daily Value Contribution of Sweet Potato Accessions for the European Market. Horticulturae. 2021, 7, 23. 
2. Yang, Deng-Jye, and Jau-Tien Lin. Effects of different storage conditions on steroidal saponinsin yam (Dioscorea pseudojaponica Yamamoto) tubers. Food Chem, 2008, 110, 670-677.
3. SIMÕES, ADRIANO, et al. Quality of minimally processed yam (Dioscorea sp.) stored at two different temperatures. Rev Caatinga, 2019, 29, 25-36.
4. Home Food Storage. University of Nebraska Lincoln.
5. Truong, V. D., et al. Sweetpotato production, processing, and nutritional quality. Handbook of vegetables and vegetable processing, 2018, 2.
6. Harrison, J. A., and E. L. Andress. Preserving food: drying fruits and vegetables. University of Georgia cooperative Service, 2008, 2.