How to preserve kumquats

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

How to preserve kumquats?

Kumquats can be preserved by: 

• Refrigerating
• Freezing whole or sliced kumquats
• Freezing whole kumquats in sugar syrup
• Dehydrating
• Preserving kumquats with salt

Kumquats are a citrus fruit originating from China. Fortunella spp is the smallest of the true citrus fruits. Kumquats look similar to oranges but are oval and smaller. Unlike oranges, kumquats are eaten whole without peeling because the peel is what gives a unique sweet flavor while the pulp is tart. 

Like all citrus fruits, kumquats are rich in vitamins and minerals. Kumquats are also an excellent source of nutrients and phytochemicals, including ascorbic acid, carotenoids, flavonoids, and essential oils. From a dietary viewpoint, essential oils represent an added value for kumquat fruit because, in addition to their contribution to the flavor, they play an important role in human health, like other non-nutritive phytochemicals such as polyphenols and flavonoids. Recent discoveries indicate additional therapeutic properties against allergies and other inflammatory diseases, anticancer activity, beneficial effects on capillary fragility and arteriosclerosis, and antiviral activity (1).

The short shelf life is as a result of high transpiration rate and spoilage losses caused mainly by Penicillium spp. Fresh kumquats will keep only for a few days at room temperature so they must be preserved in one of the methods we are going to discuss (1).

How to preserve kumquats by refrigerating

Refrigeration will preserve fresh kumquats for a few days. It is not necessary to wash the kumquats before refrigerating. If you do wash them, wipe them down with a paper towel to make sure they are completely dry before storage. 

On the other hand, studies showed that hot water treatments (dipping the fruit in hot water at 50°C or 120°F for 2-3 minutes) or water with chlorine were effective to improve the shelf life and quality of kumquat fruit with the accumulation of scoparone, a natural antifungal compound, in the skin (2).

To refrigerate kumquats:

• Place the kumquats in a ziplock bag or airtight container.
• Store it in the crisper drawer of the refrigerator.

Refrigerated kumquats must be used within 2 weeks.

How to preserve kumquats by freezing

Kumquats can be frozen for a few months. It is recommended to slice and remove the seeds from the kumquats before freezing as this makes them easier to use. However whole kumquats have a better shelf-life when frozen. A study showed that freezing at −20°C (-4°F) did not have significant effects on the carotene composition of citrus fruits stored for 13 months, although the amount of vitamin C decreased (3).

Freezing kumquats will alter their texture and they will be soggy when thawed, but they can still be used for cooking and baking.

How to freeze sliced kumquats

• Wash the kumquats and wipe them with paper towels.
• Slice the kumquats into halves and remove the seeds.
• Place the kumquats slices on a tray lined with parchment paper and freeze them for a few hours.
• Transfer the frozen kumquats inside a ziplock bag or an airtight container.
• Label, and return to the freezer.

How to freeze whole kumquats

• Wash the kumquats and wipe them with paper towels.
• Place the kumquats on a tray lined with parchment paper and freeze them for a few hours.
• Transfer the frozen kumquats inside a ziplock bag or an airtight container.
• Label, and return to the freezer.

Sliced, frozen kumquats must be used within 4 months.

How to freeze whole kumquats in syrup

• Wash the kumquats and wipe them with paper towels.
• Make a sugar syrup by heating and dissolving 2 parts of sugar in 4 parts of water.
• Place the kumquats inside a ziplock bag or an airtight container.
• Pour the sugar syrup to cover the kumquats.
• Label and freeze.

Kumquats in sugar syrup can be stored in a freezer for up to 1 year.

How to preserve kumquats by dehydrating

Drying is one of the most important preserving methods used in the food industry. This process is mostly used to minimize chemical, microbiological and enzymatic reactions which limit shelf life of fresh fruit and vegetables (4).

Kumquats can be dehydrated using a food dehydrator or an oven.

Kumquat slices can be dehydrated with both pulp and peel. Kumquats peel can also be dehydrated after removing the pulp.

Dehydrated kumquats can be stored for about 6 – 12 months in an airtight container. They can also be refrigerated in a ziplock bag.

To dehydrate kumquats:

• Wash the kumquats and wipe them with paper towels.
• Slice the kumquats into desired thickness. You can also squeeze out the pulp and seeds and dehydrate just the peels.
• Arrange the kumquats slices on a dehydrator tray.
• Dehydrated at 135 °F for about 6 hours until the slices are completely dry and crispy.

Alternatively, kumquats can be dried using a domestic microwave oven. A study showed that microwave drying using a power of 900 W significantly shortened the drying duration when compared to hot air and vacuum drying. The fruit slices were dried in 42 minutes. In addition, microwave dried samples had the highest antioxidant activity (4). 

How to preserve kumquats with salt

Kumquats can be preserved in salt for years. Preserving kumquats in salt is the method with the longest shelf-life and it only requires 2 ingredients,  kumquats and salt.

To preserve kumquats in salt:

• Wash the kumquats and wipe them with paper towels.
• Slice the kumquats in half.
• Lay the kumquats and salt alternatively in a sterilized mason jar.
• Seal and allow to ferment for a few months.

Kumquats preserved with salt have no proper expiration date. As long as they are immersed in brine, they won’t spoil.

Kumquats preserved in salt can be added to cooking recipes and is traditionally used as a home remedy for sore throat.

Fermented, preserved, or “pickled” citrus, also called msayer, are typical products of the Moroccan and other North-African countries culinary tradition. The process of making msayer, described in popular recipes, by adding cut citrus fruit peel, lemons or kumquat to a brine of NaCl and to let the fermentation occur for about 30 days, generally at room temperature. The naturally fermented products are preserved by the bacteria and yeast growth and the acids produced by them (5). 

A detailed recipe for kumquats preserved in salt can be found here.

How to select the best kumquats for preservation

Select ripe kumquats. Ripe kumquats range in color from bright yellow to bright orange. Avoid green unripe kumquats.

Selects kumquats that are glossy and have a smooth rind.

Avoid kumquats with blemishes or wrinkled skin.

Avoid kumquats that are soft and mushy as they may be bruised.

If possible, select freshly plucked kumquats with leaves still attached to the stems.

Conclusion

In this brief guide, we answered the question “how to preserve kumquats”, and discussed the different methods used to preserve kumquats. We also looked at how to select the best kumquats for preservation.

References

1. Schirra, Mario, et al. Influence of postharvest hot water treatment on nutritional and functional properties of kumquat (Fortunella japonica Lour. Swingle Cv. Ovale) fruit. J Agri food chem, 2008, 56, 455-460.  
2. Kassim, A., et al. The effects of different pre-packaging treatments on the quality of kumquat fruit. CyTA-J Food, 2016, 14, 639-648.
3. Bonat Celli, Giovana, Amyl Ghanem, and Marianne Su-Ling Brooks. Influence of freezing process and frozen storage on the quality of fruits and fruit products. Food Rev Int, 2016, 32, 280-304.
4. Ozcan-Sinir, Gulsah, et al. The effect of hot air, vacuum and microwave drying on drying characteristics, rehydration capacity, color, total phenolic content and antioxidant capacity of Kumquat (Citrus japonica). Food Sci Technol, 2018, 39, 475-484.
5. Deba-Rementeria, Shuyana, et al. Characterization of salt-preserved orange peel using physico-chemical, microbiological, and sensory analyses. LWT, 2021, 148, 111769.