Every year, a significant share of harvested fruits and vegetables never makes it to the consumer’s plate. The Food and Agriculture Organization estimates that roughly 32% of all food produced globally is lost or wasted, with fresh produce accounting for a disproportionate share of those losses. Much of this waste is preventable. The moment a fruit or vegetable is harvested, it becomes a race against biology – respiration, water loss, sprouting, greening, and microbial decay all begin working against quality from that point forward. Understanding the core principles of storage is about knowing how to slow down or suppress these processes long enough to get fresh produce to market in good condition.
Table of Contents
- Why storage is about controlling biology, not just temperature
- Temperature: the most important variable in storage
- Optimum temperature ranges
- Preventing undesirable processes through temperature
- Humidity control and managing transpiration
- Ethylene management in storage
- Controlled and modified atmosphere storage
- Protective coatings and packaging
- Integrating storage principles: a systems approach
Why storage is about controlling biology, not just temperature
Fresh fruits and vegetables are not inert objects – they are living tissues that continue to breathe and change after harvest, even though they are no longer attached to the parent plant. The central challenge of storage is managing the biological processes that drive deterioration. The three most visible and economically damaging of these are sprouting (such as potatoes developing shoots), rooting (onions growing new roots), and greening (potatoes turning green and forming toxic glycoalkaloids when exposed to light). Each of these processes diverts stored energy and nutrients away from the edible portion, reduces marketability, and in the case of greening, raises food safety concerns.
Alongside these visible changes, respiration – the breakdown of sugars, starches, and other compounds to generate energy – is perhaps the most critical underlying process. The higher the rate of respiration, the faster the produce deteriorates. Products with very high respiration rates, such as asparagus, mushrooms, peas, and sweet corn, deteriorate far more quickly in storage than low-respiration crops like apples, onions, and garlic. The goal of all storage systems is to reduce the rate of these processes to the minimum safely achievable.
Temperature: the most important variable in storage
Throughout the period between harvest and consumption, temperature control has been found to be the most important factor in maintaining product quality. Lower temperatures slow respiration rates, delay ripening and senescence, and inhibit the growth of spoilage-causing fungi and bacteria. The general principle is to keep produce at the lowest temperature it can safely tolerate.
Optimum temperature ranges
There is no single storage temperature that suits all crops. The optimum postharvest temperature for most fruits and vegetables is the lowest temperature that does not freeze the commodity. However, many tropical and subtropical crops – including bananas, mangoes, tomatoes, cucumbers, and sweet potatoes – are sensitive to chilling injury, which occurs at temperatures above freezing but below a threshold specific to each crop. Symptoms include failure to ripen, surface pitting, internal discoloration, and development of off-flavors. This is why storage facilities are typically divided into three broad categories: cold storage (0-2°C), cool storage (4-13°C), and warmer storage (13-16°C) for chilling-sensitive crops.
The risk of chilling injury is cumulative – multiple low-temperature exposures, even before harvest, can contribute to the development of injury symptoms. This makes pre-harvest growing conditions relevant to storage planning, not just post-harvest decisions.
Preventing undesirable processes through temperature
Temperature management directly suppresses sprouting and rooting. Potatoes stored at appropriate cool temperatures can be held for weeks without sprouting, but if stored too cold, starch-to-sugar conversion accelerates, leading to excessive browning during cooking. Greening in potatoes is driven not by temperature but by light exposure – even low-intensity light over one to two weeks can stimulate chlorophyll and toxic glycoalkaloid formation. Darkness in the storage environment is therefore a non-negotiable requirement for potato storage.
Humidity control and managing transpiration
Transpiration – the loss of water from plant tissues – is the second major driver of postharvest quality loss. Water loss or dehydration leads to a reduction in fresh weight, which affects appearance, texture, and in some cases flavor. It also affects crispiness and firmness – qualities consumers strongly associate with freshness.
Transpiration rate is determined by several external factors: temperature, relative humidity, air velocity, and atmospheric pressure. High temperatures, low relative humidity, and high air velocity all increase transpiration rates. Conversely, maintaining high relative humidity in the storage environment directly slows water loss. Most fresh produce requires a relative humidity between 85 and 95% during storage. Leafy vegetables with large surface-to-volume ratios, injured produce, and immature fruits lose water far more rapidly than mature, intact crops.
The key challenge is balance: too much humidity creates conditions favorable for fungal growth and decay, while too little leads to rapid wilting and weight loss. Monitoring should be done using a hygrometer or sling psychrometer – not by visual inspection of the produce itself, which is unreliable. Humidity can be managed through humidifiers, misting systems, or perforated packaging that limits airflow while maintaining adequate moisture around the produce.
Ethylene management in storage
Ethylene is a naturally produced plant hormone that regulates ripening and senescence. The overall impact of ethylene in a storage environment is to accelerate ripening, aging, and eventual spoilage – manifesting as brown spots, decay, sprouting, yellowing, bitterness, and loss of color in common fruits and vegetables.
One overripe apple releasing ethylene can accelerate the deterioration of an entire pallet of fruit – a practical reality that makes segregation of ethylene producers from ethylene-sensitive crops a foundational storage rule. Ethylene-producing crops like apples, bananas, avocados, and tomatoes should never be stored alongside ethylene-sensitive ones like leafy greens, cucumbers, kiwifruit, and broccoli. Ethylene exposure can also cause sprouting of potatoes, and damage in vegetables includes leaf spotting, yellowing, bitterness, and development of off-flavors.
At the commercial level, ethylene scrubbers – devices that actively remove ethylene from the storage environment – are used when levels rise above 0.005 µL/L in sensitive storage situations. Using electric forklifts instead of combustion-engine equipment in storage areas is another practical measure, since internal combustion engines release ethylene in their exhaust.
Controlled and modified atmosphere storage
Once temperature, humidity, and ethylene are managed, the next layer of storage science involves controlling the gas composition around stored produce. Optimum oxygen and carbon dioxide concentrations in storage can lower respiration and ethylene production rates, reduce ethylene action, delay ripening and senescence, and retard the growth of decay-causing pathogens.
Controlled Atmosphere (CA) storage involves actively maintaining specific gas concentrations inside a sealed, gas-tight room. CA storage monitors and adjusts CO₂ and O₂ levels at the optimum storage temperature – in most cases, CO₂ concentrations are elevated and O₂ concentrations are reduced relative to normal air. Typical CA conditions involve O₂ levels of 2-3% and CO₂ concentrations of 5-15%, depending on the commodity. CA storage is most commercially significant for apples and pears, and is also widely applied to kiwifruit, avocados, persimmons, and nuts.
Modified Atmosphere Packaging (MAP) is a more accessible version of the same concept, typically applied at the consumer package level using polymeric films. MAP is widely applied in extending the shelf life of fresh-cut fruits and vegetables, usually designed to maintain 2-5% O₂ and 8-12% CO₂ levels, and can include absorbers of ethylene, carbon dioxide, oxygen, and water vapor.
An important caution: CA conditions that are not appropriate for a given commodity can trigger physiological disorders rather than prevent them. Each crop has a specific optimal gas range, and moving beyond safe limits – for example, oxygen below 1.5% for potatoes – can cause off-odors, off-flavors, and internal discoloration.
Protective coatings and packaging
Surface coatings applied to fresh produce create a semi-permeable barrier that regulates gas exchange and slows water loss. Edible coatings act as barriers to oxygen, carbon dioxide, and ethylene, thereby modifying the internal atmosphere of fresh fruits and vegetables – this selective permeability helps regulate respiration rates, mitigate oxidative stress, and delay senescence, preserving firmness, color, and flavor.
The practice of waxing fruits and vegetables for storage dates back centuries. The commercial waxing of fruit and vegetables began on a large scale in the USA in 1922, and today’s coatings range from natural waxes like carnauba (derived from Brazilian palm leaves) and shellac, to polysaccharide-based formulations using chitosan, alginate, and starch. Carnauba wax coatings effectively enhance postharvest shelf life by reducing water loss and respiration rate while maintaining firmness and consumer acceptability in fruits such as oranges, guava, apple, tomato, and eggplant.
Research on mandarin oranges found that natural wax-based coatings doubled the shelf life of the fruit during ambient storage – extending it to 30 days compared to only 15 days for uncoated control fruits, while also reducing mold and yeast counts. The choice between coating types involves trade-offs: lipid-based wax coatings offer lower oxygen permeability and superior water vapor resistance, while polysaccharide-based coatings allow more gas exchange, making them better suited to high-respiration fruits where excessive CO₂ buildup would be harmful.
Packaging materials work alongside coatings. The shelf life of fresh fruits and vegetables in packaging depends on two variables: the respiration rate of the commodity and the permeability of the packaging film. Modified atmosphere packaging using specially designed films acts as a protective barrier by simultaneously controlling respiration and gas permeation. Perforated plastic bags or containers with calculated vent areas are commonly used for retail-scale packaging to maintain the 85-95% humidity range while preventing condensation and mold.
Integrating storage principles: a systems approach
No single factor operates in isolation. Temperature affects respiration, which affects ethylene production, which affects ripening – and all of these interact with humidity, packaging, and coating choices. Effective postharvest management means establishing appropriate cold chains that maintain optimal temperatures and relative humidity, slowing respiration and ethylene production, while utilizing appropriate packaging and following safety and sanitation protocols. Produce should be harvested at optimum maturity, handled carefully to avoid mechanical injury, cooled quickly to remove field heat, and placed into appropriate storage conditions as rapidly as possible after harvest.
It is also worth noting that losses of horticultural crops due to improper storage and handling can range from 10 to 40 percent, and once a crop is harvested, it is almost impossible to improve its quality – only maintain or slow its decline. This is why every decision made at harvest and in the first few hours afterward has a disproportionate influence on the final storage outcome. A well-designed storage system does not compensate for poor pre-harvest practices or rough handling at harvest.
What do you think? Given that temperature, humidity, ethylene management, coatings, and atmosphere control all contribute to storage success, which of these factors do you think is most frequently neglected in small-scale or farm-level storage settings – and what would it take to address that gap? If you were advising a small farmer storing perishable crops like tomatoes or leafy greens in a tropical climate, which storage principle would you prioritize first, and why?
References
- https://pmc.ncbi.nlm.nih.gov/articles/PMC4006172/
- https://extension.umaine.edu/publications/4135e/
- https://www.fao.org/4/ae075e/ae075e13.htm
- https://edis.ifas.ufl.edu/publication/HS1270
- https://postharvest.ucdavis.edu/produce-facts-sheets/potato
- https://www.fao.org/4/y4893e/y4893e06.htm
- https://www.postharvest.com/blog/what-is-ethylene-gas-how-it-affects-fruits-and-vegetables
- https://extension.usu.edu/vegetableguide/production/postharvest-handling
- https://www.postharvest.biz/felix-instruments/how-does-controlled-atmosphere-storage-extend-fruit-shelf-life
- https://www.fao.org/4/y5431e/y5431e06.htm
- https://www.mdpi.com/2223-7747/15/1/132
- https://www.mdpi.com/2076-3417/14/23/11074
- https://www.sciencedirect.com/science/article/abs/pii/S0924224422003983
- https://pmc.ncbi.nlm.nih.gov/articles/PMC11889960/
- https://www.researchgate.net/publication/279810222_Protective_Coatings_for_Shelf_Life_Extension_of_Fruits_and_Vegetables
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