How to preserve Italian prune plums

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

How to preserve Italian prune plums 

Italian prune plums can be preserved by:

• Freezing with or without sugar
• Dehydrating 
• Canning in sugar or as jam

Italian prune plums are small, oval-shaped plums.

Ripe Italian prune plums have a sweet flavor and can be eaten on their own. They also hold up well when heated. So they are commonly used to make jams.

Unripe Italian prune plums are reddish-purple and they will turn black as they ripen.

They must be stored at room temperature until they ripen. After ripening, they can be refrigerated for a few days.  

Low temperature storage of plums recommended to extend fruit postharvest life and maintain quality. However,extended storage of plums at low  non-freezing temperature is limited and leads to physiological disorders such as gel formation,abnormal fruit ripening and development of chill injuries such as internal and external browning, flesh breakdown,reddish discoloration and loss in consumer acceptance (1). 

Polysaccharide based coatings have been studied to extend shelf-life of fruits and vegetables. Edible coatings based on polysaccharide materials such as chitosan, and carboxymethyl cellulose have been  investigated for delaying ripening (1).

How to freeze italian prune plums for preservation

Italian prune plums can be frozen either with or without adding sugar. Freezing preserves Italian prune plums for about 1 year. Freezing will significantly extend shelf life (2).

Freezing will lead to tissue damage and loss of quality due to chilling injury. In freezing, the formation of ice within the cell may cause damage to the delicate organelle and membrane structures of the cell. As one consequence, enzyme systems may be dislocated. This may result in uncontrolled enzyme action, leading to a variety of effects, including the production of off-flavors. Frozen fruit is used in the production of jams and desserts (2).

To prepare the Italian prune plums for freezing: 

• Chose ripe, and firm plums.
• Cut the plums into halves.
• Remove the pits.

To freeze Italian prune plums without sugar:

• Place the plums in a ziplock bag or an airtight container.
• Label and freeze.

To freeze Italian prune plums in sugar or sugar syrup:

• Pack the plums in sugar: Use 1 part of sugar for every 5 parts of the fruit. 

Or

• Pack the plums in sugar syrup: Use 50% sugar syrup.
• Label and freeze.

How to dehydrate italian prune plums for preservation

Dehydrating is one the most commonly used methods to preserve Italian prune plums. Dehydrated prune plums make a great snack. They can also be added to salads, cereals, and bread.

Among drying methods, solar drying is still an affordable and easy way to preserve food. Solar energy is one of the most attractive and cost-effective drying methods for fruits. Alternatively, drying in an oven can be done at 50°C with similar results. However, these processes are time consuming. The nutritional profile of the fruit will change by drying. A study showed that, although there was little loss of vitamin C, the antioxidant level of dried plums decreased compared to the fresh fruit (3).

Also choose ripe, fresh plums for dehydration. Do not use plums with blemishes and soft spots.

To dehydrate Italian prune plums:

• Choose ripe, firm plums.
• Cut the plums into halves and remove the pits.
• Slightly flatten the plums.
• Blanch the plums. Blanching is not necessary, but it will speed up the dehydrating process. The plums can be blanched for 1-2 minutes in steam.
• Spread the blanched plums on a dehydrator tray.
• Set the temperature for 130-135 F
• Dehydrate until the plums are dry.
• Store the dehydrated plums in an airtight container, in a cool, dark place.

How to preserve Italian prune plums by canning

Organisms that cause food spoilage – molds, yeasts and bacteria – always are present in the air, water and soil. Also, enzymes that may cause undesirable changes in flavor, color and texture are present in raw fruits. Use recommended processing methods and times when canning fruits to destroy spoilage organisms and stop the action of enzymes (4).

Canning will preserve Italian prune plums for about 1 year

Italian prune plums can be canned in sugar, water, or fruit juice.

To prepare the Italian prune plums for canning:

• Wash the plums and allow them to dry. 

• You can choose to can either with or without the peel. Usually, they are canned whole and unpeeled.

If you are canning whole plums: Prick the skin of the plums with a fork. This will prevent the plums from splitting open.

If you are canning, cut plums: Cut the plums into halves and remove the pits.

Canning in sugar can be done by either the hot-pack method or the cold-pack method.

Hot pack method: 

• Prepare sugar syrup by mixing water with sugar. You can decide the sweetness and adjust the amount of sugar as needed. Alternatively, you can simply use fruit juice such as grape or apple juice, or even water.

• Boil the Italian prune plums in the sugar syrup or fruit juice for at least 2 minutes.
• Cover and allow to cool down for about 30 minutes.
• Pack the plums into sterilized jars
• Pour the syrup to cover the plums.
• Leave about ½ inch of headspace.
• Process the jars using a water bath

Cold pack method:

• Prepare a sugar syrup as in the hot pack method, or use fruit juice or water.
• Pack the Italian prune plums into sterilized jars. You must not boil the plum for this method.
• Pour the syrup to cover the plums.
• Leave about ½ inch of headspace.
• Process the jars using a water bath.

Italian prune plums can be made into delicious jams, jellies. There are several recipes for making jams from Italian prune plums. The basic ingredients in all recipes include Italian prune plums, lemon juice, and sugar. 

Tips for preserving Italian prune plums

• Select fresh fruit. Do not use bruised and damaged plums. 
• Use ripe plums. To speed up ripening, place the Italian prune plums in brown paper with a banana or an apple. Bananas and apples produce ethylene gas that speeds up the ripening process. It will take about 2 weeks for Italian prune plums to ripen after being plucked from the tree.
• Make sure there is no water in the plums when refrigerating or freezing. Moisture will cause quick spoilage.
• For canning, make sure that the jars are sterilized properly. Jars can be sterilized in water or by heating in an oven.

Other FAQs about Prune plums that you may be interested in.

Can you eat plum seeds?

How long can you keep plums in the fridge?

How long do plums last in the fridge?

Can you keep plums in the fridge?

Conclusion

In this brief guide, we answered the question, “how to preserve Italian prune plums” and discussed the different preservation methods.

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

References

1. Hussain, Peerzada R., et al. Retention of storage quality and post-refrigeration shelf-life extension of plum (Prunus domestica L.) cv. Santa Rosa using combination of carboxymethyl cellulose (CMC) coating and gamma irradiation. Rad Phys Chem, 2015, 107, 136-148.
2. Reid, David S., and D. M. Barrett. Fruit freezing. Processing fruits: science and technology 1 1996: 169.
3. Vangdal, Eivind, et al. Effects of the drying technique on the retention of phytochemicals in conventional and organic plums (Prunus domestica L.). LWT-Food Sci Technol, 2017, 85, 506-509.
4. Garden-Robinson, J. Home Canning Fruit and Fruit Products. North Dakota State University Extension. 2020.