Cucumber Post-Harvest Cooling Methods

Cucumbers are a classic ingredient in salads as well as many other dishes and sauces. Cucumbers are also arguably the most popular of all pickled foods and in the US the term “pickles” refers exclusively to pickled cucumbers. There are in fact three main varieties of cucumbers that have each been cultivated to improve the cucumber’s suitability for different purposes: slicing, pickling, and burpless. Regardless of the variety and ultimate use, starting with a healthy, high quality cucumber and carefully cooling and storing it after harvest is critical.

Facts About Cucumbers and Cucumber Varieties

Cucumbers are members of the gourd family and are thus closely related to squash, zucchini, watermelons and other melons. Like their relatives cucumbers are classified as a fruit in botanical terms; however, like squash they are often used more as a vegetable for culinary purposes. Cucumbers grow on creeping vines and produce thin, spiraling tendrils that climb trellises and other supporting frames. Eventually the vines develop flowering blossoms, which eventually produce the cucumber fruit. Like many other types of fruit they have a very high water content, usually about 90% or higher.

Cucumbers originated in India and from there spread throughout Southern Asia, the Middle East, and Mediterranean. They have been cultivated for at least 3,000 years and are mentioned in the Bible as well as in the writings of the ancient historian Pliny the Elder. The Roman Emperor Tiberius is known to have had such a great fondness for them that special measures had to be taken during his reign so that he could eat them year round. The main varieties of cucumbers are as follows:

Slicing – Slicing cucumbers are long, smooth,and uniform in color. They are harvested while green, though if allowed to continue ripening will turn yellow and become bitter and sour. As the name implies they are typically cut into round slices and are commonly used in salads and other dishes. In North America slicers have a thick, tough skin; however, the ones grown in other countries have a more delicate, thinner skin and are also typically smaller. Slicing cucumbers may also be pickled if desired.

Pickling – Pickling cucumbers are a specially developed cultivar that are more suitable to pickling. They have a longer shelf life than slicers as well as several other key physical differences. Pickling cucumbers are typically shorter and thicker than slicers, have a less uniform shape, and usually have bumpy skin. They also have varying colors and may be creamy yellow, light, pale green, or dark, deep green. Many different pickling processes exist which yield different flavors and textures.

Burpless – Burpless cucumbers have been cultivated to be easier to digest than slicing and pickling cucumbers and are less prone to causing digestive gas for the people who consume them. They are typically seedless or nearly seedless, have a thinner, sweeter taste than other varieties, and often grow considerably larger. They may be eaten raw, sliced into salads, chopped up into yogurt, fried, or braised with meat.

Gherkin – The gherkin belongs to the same species as other cucumbers and has been specially cultivated for use in pickling. However, gherkins are their own cultivar and are distinct from other pickling cucumbers. Gherkins are so popular for pickling than in some parts of the world such as the United Kingdom and Australia the term “gherkin” is used generically to refer to a pickled cucumber instead of the typical American term “pickle.” In this way the term may be applied to other cultivars that are not technically gherkins.

Information About Cooling and Storing Cucumbers

Cucumbers are at their most delicious when they have been harvested at their prime, carefully picked and stored, and properly cooled. What follows are key factors that affect the cooling and storing of cucumbers:

Temperature – For maximum freshness and quality cucumbers should be stored at a temperature of about 50º-55ºF. They may suffer chill damage if over-cooled and will freeze at 31ºF. However, temperatures that are too high will hasten decay and reduce shelf life and quality.

Relative Humidity – As discussed above, cucumbers have a very high moisture content; typically 90% or more of the cucumber’s weight comes from water. Thus, if cucumbers are exposed to dry air they will rapidly shrivel and shrink, losing both mass and quality. For best results cucumbers should remain in an environment with about 95% relative humidity.

Ethylene Sensitivity – Cucumbers are highly sensitive to ethylene and will rapidly yellow and decay in response to even low levels of ethylene. For this reason it is important to keep cucumbers isolated from ethylene-producing fruits and vegetables such as tomatoes, bananas, and other melons.

Handling – Cucumbers should be cut, not pulled from the vine. Pulling cucumbers from the vine may result in tearing. Cucumbers are also prone to bruising and other defects if they are mishandled or treated too roughly.

Shelf Life – Cucumbers have a shelf life under optimal conditions of about 10 – 14 days. If pickled the cucumber’s shelf life is dramatically extended.

Methods of Cooling Cucumbers

Hydrocooling – Hydrocooling is a pre-cooling method that involves rapidly submerging the cucumbers in near freezing water. This results in a very fast and effective removal of field heat and quickly lowers the cucumbers’ temperatures to levels that can be more easily managed with other cooling methods such as room cooling or forced-air cooling.

Room Cooling – Room cooling involves placing the cucumbers in a refrigerated room such as a cooler and allowing them to gradually acclimate to the ambient temperature. For this method to be effective the cucumbers should not be over-packed, which might result in fruit near the center of the bunch never fully reaching the desired temperature or in doing so too slowly to prevent quality loss.

Forced-Air Cooling – Forced-air cooling involves placing the cucumbers in a refrigerated room around a large fan which then pulls cool air through the cucumbers, thereby forcing airflow and more rapidly cooling the cucumber than room cooling alone.

SEMCO/SEMCOLD LLC is an industry leader in the manufacturing and installation of industrial cooling equipment that is ideal for use with cucumbers and other produce. We know that our clients are trusting us with the quality of their crops and we are committed to earning that trust with dependable, effective cooling systems. Our systems can also be fully customized to best fit the capacity needs and other specs of our clients.