How to preserve vegetables without a fridge

In this brief guide, we are going to answer the question “How to preserve vegetables without a fridge?”, and discuss the different methods of preserving vegetables without a fridge.

How to preserve vegetables without a fridge 

Dating back from 1986 to 1995, about 0.95% of vegetables per capita and 0.38% fresh fruits per capita consumption were recorded, with China leading with the highest consumption of fruits accounting for 6.4%. (e lowest consumption of fresh fruits and vegetables was recorded to be 0.19% of vegetables in Sub-Saharan Africa, and there was a decline in consumption rate in Africa and Near East Asian countries. It has been revealed that the production of fresh produce such as fruits and vegetables has experienced a tremendous increment of about 94% from the year 1980 to 2004 (1).

Vegetables can be preserved without a fridge by :

  • Using proper storage temperature and humidity.
  • Storing ethylene producing and ethylene absorbing vegetables separately.
  • Using techniques such as pickling and dehydration for long term storage

Selecting the right vegetables to preserve without a fridge

It is important to select the proper vegetables to preserve without a fridge.

  • Purchase fresh vegetables: Once vegetables are refrigerated once, they perish faster at room temperature. Always purchase fresh vegetables.
  • Do not wash the vegetables before storage: Washing vegetables before storage increases the moisture which causes microbial growth and faster spoilage.
  • Pick and choose fresh, unspoilt vegetables: Do not buy bruised, overly ripe vegetables since they will perish faster.   

Some types of fresh produce last longer when stored unwashed. Beans and berries, for example, are sensitive to moisture and washing before storage can cause them to mold and rot more quickly. When storing unwashed produce, safe handling is essential. Allowing unwashed produce to come into contact with other refrigerated items could allow the spread of pathogenic microorganisms that may be present in any dirt or debris on produce. When washing produce before storing thoroughly dry with a clean paper towel and package in plastic bags or storage containers. Refrigerating produce in a vegetable bin or crisper will help maintain best quality (4).       

Storage conditions for vegetables without a fridge

Tt is possible to minimize with some precaution such as low temperature, relative humidity control during storage. Vegetables that are not refrigerated must always be stored away from direct sunlight. Other factors to be considered are :

  • Storage temperature: Optimum storage temperature depends on the type of vegetable.
  • Storage humidity: Most vegetables require a humid atmosphere to avoid drying out. Temperature by 10-15°C (50-60°F) and maintain high humidity of about 95% that can increase shelf life and retain quality of horticultural produce (5).
  •  Light intensity: Most vegetables must be kept in dark places to prevent spoilage. If vegetables such as onions are kept in sunlight, they will sprout. The general lack of use of shade contributes to high pulp temperatures and high water losses (5).
  • Ethylene sensitivity: Ethylene sensitive vegetables must be stored away from ethylene producing fruits and vegetables. As a gas, ethylene is hard to contain and many things respond in negative ways if stored with ethylene generating fruit. Cabbage and Brussels sprouts will turn yellow or crack and start to grow, carrots develop a bitter flavor due to ethylene-induced isocoumarin production and cucumbers deteriorate quicker (3).

Storage temperature

Most vegetables preserve well in cool temperatures. Generally, vegetables harvested in the warm season could be stored at higher temperatures than vegetables grown in the cool season. Potatoes, sweet potatoes, bananas, watermelon, tomatoes, squash, pineapple, lemons and avocados can be stored at higher temperatures (> 50°F) (3).

Ethylene and spoilage

Ethylene is a colourless, odourless gas released by certain fruits and vegetables during the ripening process. Fruits and vegetables are either ethylene producers or absorbers.Ethylene is produced endogenously by perhaps all plants and their organs. At very low concentrations it can induce a wide array of physiological responses, including altered geotropic growth, abscission, ripening, senescence, and physiological disorders. These responses can be beneficial or detrimental, depending upon the response and one’s need (2).

Fruit and vegetables are categorized as climacteric or non-climacteric. Climacteric fruit reach a certain developmental stage and once attaining that stage, continue to develop to full physiological maturity, even when removed from the plant. Climacteric fruit such as peaches, plums, cantaloupe, bananas, pears and tomatoes continue to gain flavor and get sweeter by changing starch into sugar. Many also go from firm to soft and juicy (peach and plum), or at least softer (avocado and cantaloupe). They are also sensitive to ethylene gas, which they self-generate, further aiding the ripening process (3).

It is important to store ethylene producing fruits and vegetables away from ethylene sensitive ones.

For example bananas, apples and melons are ethylene producers while cabbage, broccoli and cauliflower are ethylene absorbers.

Effects of ethylene on vegetables

Effect of ethylene varies from one type of vegetable to another. Ethylene will have the following effects on these common vegetables :

  • Green leaves and broccoli: Yellowing
  • Fruits disorders: apples may develop “core browning” during storage, and 6 ppm ethylene accelerates this disorder.
  • Carrots: Bitterness: The compound responsible for the bitterness is isocoumarin, which can be formed when the ethylene level is only 1 ppm (2).

Loss of green color is initiated or accelerated when plant tissue is exposed to ethylene. Ethylene at a 5 ppm level causes the green color of cabbage to fade significantly after 1 mo of storage, and 1 ppm can have an undesirable effect on cabbage stored for 5 m. The rate of color loss differs among commodities, as noted with various types of citrus (2).

How to reduce spoilage due to ethylene without a fridge

Vegetable spoilage due to ethylene exposure can be reduced by :

  • Storing ethylene producing fruits and vegetables away from ethylene sensitive ones.
  • Storing vegetables in a well-ventilated area so that the ethylene concentration surrounding the vegetables is lower.

It was concluded that ventilation with air is still, up to now, the best available method for the removal of ethylene gas (7).

Vegetables that naturally preserve well without a fridge

Some vegetables naturally preserve well without requiring a fridge. Good examples are potatoes, onions and garlic (3,6).

  • Potatoes: Potatoes must be kept in a cool, dark place. In fact, storing potatoes in a fridge produces toxic chemicals.
  • Onions: Onions must be stored in a cool dark place.
  • Garlic : Garlic must not be kept in plastic containers. Garlic will preserve at room temperature for about a month if kept away from plastic.
  • Tomatoes : Tomatoes bruise easily so they must be stored and handled with care. Tomatoes are best stored in a plastic bag with holes for ventilation.
  • Cabbage, broccoli and cauliflower: These vegetables will last for about a week without refrigeration, provided they are kept away from moisture and direct sunlight.

 

Vegetables that are hard to preserve without refrigeration

Some vegetables are hard to preserve for over a few days without refrigeration. A good example is green leaves.

Preserving green leaves without a fridge

Green leaves such as kale, spinach and spoil very quickly without refrigeration. Rapid spoilage is due to their high rates of respiration and transpiration and the possibility of enzymatic and microbiological deterioration (10). They can be kept without refrigeration for about four days. The best way to store green leaves is in a bag with a little air and away from sunlight. Exposure to direct sunlight will cause the yellowing of leaves.

Green leaves must be kept in a cool environment with high humidity. Spraying them with cold water every hour will prolong the preservation time.

In a study, the shelf life of spinach was of 3 days packed stored in LDPE bags with 5% perforation at room temperature and RH 55 % to 65 %, while at cold storage conditions the shelf life was extended to 14 days (10).

Dehydration

If vegetables must be preserved for a long time without a fridge, they can be dehydrated to remove all moisture and stored in airtight containers. Vegetables can be dehydrated by sun-drying or by using a dehydrator.

Drying removes the moisture from the food so bacteria, yeast and mold cannot grow and spoil the food. Drying also slows down the action of enzymes (naturally occurring substances which cause foods to ripen), but does not inactivate them (8).

Commonly dehydrated vegetables include corn, carrots and potatoes.

Pickling

Some vegetables can be preserved by pickling. Pickling is the process of preserving fresh produce in an acid solution such as vinegar or in a salt solution

Pickling is one of the oldest known methods of preserving foods. Commonly pickled vegetables include cucumbers, cabbages and olives. 

Both pickling and dehydration enable the preservation of vegetables for a significant time without a fridge but they cause significant changes in the flavour, texture and nutrient content of vegetables.

Fermented pickles — also called crock pickles — are produced by curing cucumbers or other vegetables in a salt brine for several weeks. During this treatment, salt-tolerant bacteria convert carbohydrates (sugars) in the vegetables into lactic acid by a process known as fermentation. Lactic acid preserves the pickles and gives them their characteristic tangy flavor (9).

Conclusion

In this article, we addressed the question “How to preserve vegetables without a fridge?”. We also discussed the different conditions to be taken into account when preserving vegetables without a fridge such as storage temperature, humidity, light intensity and ethylene sensitivity.

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

References

  1. Balali, Gadafi Iddrisu, et al. Microbial contamination, an increasing threat to the consumption of fresh fruits and vegetables in today’s world. Int J Microbiol, 2020.
  2. Watada, ALLEY E. Effects of ethylene on the quality of fruits and vegetables. Food Technol, 1986, 40, 82-85. 
  3. Goldy, R. All fruit and vegetables are not created equal when it comes to proper storage conditions. 2019. Michigan State University.
  4. Hoyle, E.H. Selecting and storing fruits and vegetables. 2013. Clemson University.
  5. Hailu, Gebru, and Belew Derbew. Extent, causes and reduction strategies of postharvest losses of fresh fruits and vegetables–A review. J Biol Agri Healthcare, 2015, 5, 49-64.
  6. Preserving Onions and Garlic. Clemson University.
  7. Keller, Nicolas, et al. Ethylene Removal and Fresh Product Storage: A Challenge at the Frontiers of Chemistry. Toward an Approach by Photocatalytic Oxidation. Chem rev, 2013, 113, 5029-5070.
  8. Andress, Elizabeth L., and Judy A. Harrison. Preserving food: Drying fruit and vegetables. University of Georgia, 2000.
  9. Ingham, Barbara H. Homemade pickles & relishes. University of Wisconsin–Extension, Cooperative Extension, 2008.
  10. Kakade, Avinash, et al. Shelf life extension of fresh-cut spinach. Int J Agri Environ Biotechnol, 2015, 8, 609.