Methods for Storing and Cooling Onions After Harvest

As we cover methods for cooling onions, they are one of the most widely used food items in the US. They are an important flavoring component in countless dishes and are even eaten raw on sandwiches and salads. Onions are also rich in antioxidants and flavonoids which may bring a number of healthful benefits including anti-cholesterol, anti-inflammatory, and anti-cancer. For onions to properly serve their crucial culinary and nutrition niche, they must be stored, cooled and transported carefully in ways that take the quality and freshness needs of the onion into consideration.

General Facts About Onions

The phrase onions encompasses a wide array of different bulb vegetables in the Allium genus, including such exotic members as the Egyptian onion (A. ×proliferum), The Japanese bunching onion (A. fistulosum), and the Canada onion (A. canadense) to name just a few. However, most varieties of common onions are in the A. cepa species, including red onions, yellow onions, white onions, shallots, and potato onions, each of which has a different and distinct flavor.

Onions pose a unique challenge to growers because unlike many other fruits and vegetables which can go straight from harvest into cooling and storage, onions need to be dried first. In some regions onions are dried in the field; however, areas with high humidity and rainfall during onion harvesting season must instead dry the onions by other means such as in bins and barns, often with carefully regulated humidity and temperature.

General Information About Cooling and Storing Onions

Like other fruits and vegetables onions have specific cooling needs which include factors such as temperature, humidity, handling, and storage. As discussed above onions also require drying. Depending on the resources available some farmers have had success repurposing equipment and facilities used for drying tobacco, peanuts, and other crops into use for drying onions.

Drying – Drying is crucial to reduce the onion’s susceptibility to decay organisms, extend their shelf life, and vulnerability to bruising. Even dried onions are of course still subject to eventual decay and physical damage, but drying helps provide them with extra time and resistance. Drying times will vary from two or three days if heated air is used, to anywhere upwards of one or more weeks if only ambient air is used.

Humidity – During drying onions should be exposed to a relative humidity of about 65%. Higher humidity levels will lengthen drying times or even prevent full drying. This will also increase the onion’s risk of neck rot and other problems. Once the onions are dried and are in cold storage a slightly higher humidity of about 70% to 75% is generally acceptable.

Temperature – During drying heated air temperature should be 100°F. Higher temperatures should be avoided since anything over 110°F can damage the onion. Once the onion is dried it should be stored in a cooler or cool environment with a temperature between 32°F and 36°F. It is important to prevent the temperature from reaching 31°F or lower because his will subject the onion to freeze damage.

Storage – Temperature and humidity greatly impact how long an onion can viably be stored and at what rate the onion loses mass. Onions stored in temperatures 50°F or higher may be subject to sprouting.

Exposure to Other Produce – Onions should also be kept separate from other fruits and vegetables, both to protect the onion and the other food. That is because onions will readily leach moisture from other produce, drying out the other food and exposing the onion to too much moisture for proper storage. Onions also have a very pungent odor and many other types of produce may absorb the smell.

Cooling Method for Onions

Onions should be cooled using the room cooling method. This involves placing them in a refrigerated room or large walk-in cooler. It is important to continue monitoring temperature and humidity levels while the onions are in the cooler.

Long-Term Storage

Onions can also successfully be placed in controlled atmosphere storage for even longer-term storage. This involves carefully regulating not only temperature and humidity levels, but also the onion’s exposure to gases such as oxygen, nitrogen, and carbon dioxide. Onions in controlled atmosphere storage may last up to 8 months with minimal quality loss.

SEMCO/SEMCOLD LLC offers quality cooling equipment that can be customized and designed to fit the needs of onions. We can also tailor our systems to the particular capacity demands and other requirements of our customers. Please contact us for more information.

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Methods for Cooling Tomatoes After Harvest

Tomatoes are an extremely popular type of produce that are used in a wide variety of dishes and which may be eaten fresh and raw, turned into paste or sauce, or of course used for America’s favorite condiment: ketchup. However, for optimum taste and quality it is very important that the temperature of tomatoes be closely regulated. What follows is a discussion of general tomato information, factors that affect cooling and storage, and proper cooling methods.

General Facts About Tomatoes

One of the most popular tomato-related debates is whether tomatoes are fruits or vegetables. Botanically they are fruits of the nightshade family, specifically Solanum lycopersicum. In terms of culinary practices they are often used in ways similar to a vegetable. Tomatoes as a food originated in Mexico. However, due to their versatility, taste, and ability to grow in different regions, they quickly spread throughout most of the world following the Spanish colonization of the Americas in the 1500s.

Tomatoes are renowned for their nutritional value. They contain an important and powerful antioxidant known as lycopene. Lycopene has been shown to have a number of health benefits including possible prevention of cancer, particularly prostate cancer, and skin protect against UV rays. There is also research being conducted into whether or not tomatoes have heart-healthy benefits for people with type 2 diabetes and whether or not tomatoes can improve urinary tract function.

General Information About Cooling and Storing Tomatoes

Tomatoes are more complicated to cool and store than many other types of produce because there is a very wide variation of correct storage temperature depending on the ripeness of the tomatoes. Tomatoes also vary in shelf life depending on ripeness at the time of harvest and storage conditions.

Ripeness/Color – Tomatoes are often graded on ripeness based on the color of their skin. The colors and criteria are as follows:

  • Green – Green tomatoes have a surface that is completely green. The particular shade of green may range anywhere from light to dark. Tomatoes are called “mature green” when they have reached the stage of ripening that will allow them to fully ripen into red tomatoes. Immature greens are tomatoes that are not yet mature enough to ripen fully and should be avoided. Mature greens on the other hand will be indistinguishable from vine-ripened tomatoes by the end of the ripening process and come with the added benefit of a longer shelf life.
  • Breakers – Tomatoes are called breakers when their green skin features tannish yellow skin with pink or red spots that do not cover more than 10% of the tomato’s surface.
  • Turning – Tomatoes are said to be turning when they have tannish yellow, pink, or red skin that makes up more than 10% of their surface but less than 30%.
  • Pink – Tomatoes are said to be pink when they have more than 30% but less than 60% of their skin a pinkish red or red color.
  • Light Red – Light red tomatoes have a pinkish red or red skin that comprises more than 60% of their surface but less than 90%.
  • Red – Red tomatoes are those with more than 90% of their surface red.

Temperature – The correct storage temperature for tomatoes varies based on their ripeness/color. As a general rule the more ripe the tomato the cooler its correct storage temperature. Tomatoes stored at temperatures too cold for their ripeness stage will suffer cold damage, reduced taste and quality, and may never fully ripen. By contrast tomatoes stored at temperatures too high for their ripeness stage may be subject to premature spoilage, decay, and damage. Mature greens may be stored at 58°F to 60°F, while pink tomatoes may be stored at 48°F to 50°F. Fully ripe tomatoes may be stored at temperatures as low as 40°F.

Humidity – The correct humidity level for storing and cooling tomatoes is about 85% to 95%, with lower humidity levels running the risk of drying out or dehydrating the tomatoes and higher humidity levels making the tomatoes more susceptible to rapid decay. Some studies suggest an even more narrow range of about 85% to 90% with concerns that even humidity levels over 90% could hasten decay.

Ethylene – Like many other fruits and vegetables tomatoes produce and release ethylene as they ripen, which in turn further hastens the ripening process. Unripe tomatoes may be intentionally treated with ethylene to bring about more rapid ripening prior to being sold to consumers. By contrast unripe tomatoes not yet ready to be sold should avoid contact with ethylene.

Storage – Because tomatoes are sensitive to ethylene it is typically a good idea to keep them separate from other fruits and vegetables since these other types of produce may unintentionally hasten ripening or, likewise, ripe tomatoes may hasten the ripening of other produce. Along the same lines ripe tomatoes may also need to be kept separate from unripe tomatoes. Once a tomato fully ripens its shelf life is much lower.

Shelf Life – The shelf life of tomatoes varies based on their ripeness, as well as the other factors discussed above. Generally mature green tomatoes will have a shelf life of about 21 to 28 days. Pink tomatoes have a shelf life of about 7 to 14 days. Fully ripe red tomatoes only have a shelf life of about 2 to 4 days.

Methods of Cooling Tomatoes

Tomatoes should be cooled using the room storage method, which involves placing the tomatoes in a refrigerated room or cooler set to the correct temperature for the tomato’s given ripeness level. It is important to ensure that the tomato boxes are well ventilated to allow heat to escape and for proper air circulation. Tomatoes should also be handled carefully as they are very prone to physical damage due to bruising, dropping, or general mishandling. SEMCO/SEMCOLD LLC offers industry-leading cooling equipment that can be customized to handle the unique demands and cooling sensitivity of tomatoes.

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Ice and Cooling Methods for Cabbage and Leafy Greens

Cabbage and leafy greens such as collard greens, mustard greens, turnip greens, and kale are an important source of vitamins and nutrients. They are often discussed together due to similarities among planting, harvesting, and nutrition. However, there are some important differences with regards to the way cabbage should be cooled and stored versus these other greens. Recognizing these differences and employing the best cooling and storage method for each vegetable is crucial for getting the best taste, quality, and market value.

Factors Influencing the Cooling and Storage of Cabbage

Cabbages come in a variety of colors such as green, purple, and white; however, the green variety is of course the most popular and well known. It is closely related to cauliflower, broccoli, and brussels sprouts. It comes in closely packed groups of leaves called heads. A head of cabbage may range from 1 lbs to 9 lbs, depending on variety. Most cabbage varieties grown in the US fall in the range of 3 lbs to 5 lbs when mature.

Temperature – As with just about every fruit and vegetable, temperature is closely tied to shelf life and quality preservation in cabbage. The optimum temperature for cabbage to be stored is 32°F.

Humidity – Cabbage should be kept at a relative humidity of 95%.

Freezing – It is important to avoid subjecting cabbage to freeze damage. Cabbage will freeze at a temperature of 30°F.

Ethylene Gas – Decomposition of cabbage is accelerated when the cabbage is exposed to ethylene gas. Ethylene gas is released by many different types of fruits and vegetables as a byproduct of their own ripening and decomposition. Some such ethylene gas-producing fruits and vegetables include apples, pears, peaches, and tomatoes. Cabbage should be stored and cooled separately from these other foods to prevent this interaction.

Cooling Methods – Cabbage may utilize one of the following cooling methods

  • Room Cooling – The most common way to cool cabbage is by placing it in a refrigerated room such as a large cooler and allowing it to gradually cool to lower ambient temperatures. It will take a typical, medium-sized head of cabbage around 18 hours to cool from 80°F to 36°F.
  • Forced-Air Cooling – Though room cooling is typically sufficient, some people make use of forced-air cooling to accelerate the cooling of cabbage. This involves arranging the containers of cabbage around a fan and using the fan to pull air through the ventilated containers, thereby forcing air circulation and increasing the rate of cooling.

Shelf Life – When properly harvested, handled, cooled, and stored cabbage has a shelf life of about 2 to 3 months.

Factors Influencing the Cooling and Storage of Leafy Greens

The term “leafy greens” is applied to various leaf vegetables such as collard greens, mustard greens, turnip greens, and kale. These greens may be harvested in leaf bunches or by the entire plant. Leafy greens are more perishable than cabbage and have a shorter shelf life.

Temperature – The optimum temperature for cooling and storing leafy greens is about 32°F.

Humidity – Leafy greens should be kept in a humid environment to prevent them from drying out. Their optimum relative humidity is about 95%.

Freezing – Leafy greens are easily damaged by freezing. As with cabbage they will freeze at about 30°F.

Cooling Methods – Leafy greens require faster cooling than cabbage to maintain their best quality. One of the following cooling methods may be employed:

  • Hydrocooling – One of the most successful methods of cooling leafy greens quickly and efficiently is with hydrocooling. This involves submerging the greens in near-freezing water.
  • Packing Ice – Leafy greens may also benefit from being placed in direct contact with packing ice to quickly and efficiently get their temperature down.

SEMCO/SEMCOLD LLC understand the needs of the produce industry and we are eager to go the extra mile to serve our clients with their industrial or commercial cooling needs. We offer a wide range of cooling systems that are ideal for cabbage and leafy greens and which can be customized to fit each client’s different capacity demands and other specifications.

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Methods for Cooling Sweet Corn After Harvest

Corn, also known as “maize” in many parts of the world, is one of the most popular and widespread crops on the planet. The United States produces about 332 million metric tons every year. There are two major types of corn: field corn, which is used as a starch-rich variety used in corn products such as cornmeal, corn oil, and other corn-based foods; and sweet corn, which is a sugar-rich variety which is eaten as a vegetable and prized for its taste. For sweet corn to be flavorful and high quality it must be rapidly and continually cooled otherwise the sugars will begin converting into starches.

General Information About Cooling and Storing Corn

Sweet corn is an extremely perishable crop which requires immediate and consistent cooling until it reaches end consumers. If it is not properly cooled it will rapidly become tough and starchy, losing its tenderness and sweetness and no longer being suitable for consumption. There are several important cooling factors which affect sweet corn.

Respiration and Degradation – Like many other types of fruits and vegetables a major source of quality loss for sweet corn is due to the rise in temperature caused by natural cellular respiration. The respiration rate is heavily dependant on temperature, making it crucial to quickly and thoroughly cool sweet corn to preserve its quality. The respiration rate at 90°F is a staggering eight times higher than at 32°F. Considering that field temperatures are often upwards of 90°F when sweet corn is harvested this can lead to almost immediate degradation if left unchecked.

One remedy to limit respiration is to harvest the sweet corn in the early morning, while temperatures are lower and while the moisture content is highest. This also helps reduce cooling loads for subsequent cooling and helps save energy. Another common method is to immediately begin covering the sweet corn with cool well water as soon as it is harvested.

Moisture Retention – Moisture retention is another important factor in sweet corn quality. To best retain moisture the sweet corn should be neatly and uniformly trimmed to remove long shanks and flag leaves. Loss of moisture can result in kernel denting as well as a loss of quality and taste. Once again treating the corn with cool water can help with moisture retention.

Sugar Content – Sweet corn has a high percentage of sugar which gives it its characteristic sweet, flavorful taste. However, almost as soon as it has been harvested the sugars present begin converting into starches. This process cannot be completely stopped, but it can be significantly slowed, preserving the quality and value of the corn for longer. Temperature is an important factor with the loss of sugar being about four times as rapid at 50°F as it is at 32°F. Once the sugars are converted into starches this process cannot be undone. That makes it crucial that the corn remain properly refrigerated for its entire journey from harvest into the eventual hands of the consumer.

Relative Humidity – The relative humidity of the environment plays an important role in moisture retention and proper cooling. Sweet corn does best with a relative humidity of about 90% to 98%.

Storage – Storage times will vary but under ideal storage conditions, those with low temperature and high humidity, sweet corn can be stored for around 5 to 8 days without a major loss in quality. Some newer, supersweet varieties are able to be stored for even longer.

Methods of Cooling Corn

Basic cooling methods such as room cooling, which involves placing the sweet corn in a refrigerated room or cooler, are not adequate to cool the sweet corn rapidly and efficiently enough. Instead hydrocooling and packing ice is recommended.

Hydrocooling – Hydrocooling involves rapidly cooling the corn by submerging it in near-freezing water. This is one of the most effective ways to quickly and efficiently remove the majority of field heat and help the corn quickly approach suitable cooling and storage temperatures. However, hydrocooling is most efficient when the temperature differential between the corn and the water is high. In other words when water temperatures are low, such as with freezing water, and when corn temperatures are high, such as with freshly harvested crops. After about 20 to 30 minutes of hydrocooling the temperature of the corn will have decreased by about 20 degrees or more. As a result the next 20 degree temperature drop would take twice as long as the first 20 degree drop and would require over an hour of additional hydrocooling.

Packing Ice – Because hydrocooling becomes less efficient the lower the temperature of sweet corn gets, it is recommended that after initial hydrocooling the remaining necessary temperature drop be attained through the use of packing ice over and around the sweet corn. This will help save energy and lower cooling loads. A good rule of thumb is to use about one pound of ice for every five pounds of sweet corn.

SEMCO/SEMCOLD LLC offers high quality hydrocooling and icing systems that are ideal for use on sweet corn cooling. Our systems and product lines can be customized to suit the capacity needs and other specifications of each our clients.

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Cooling and Storing Methods for Strawberries After Harvest

Strawberries are known the world over for their sweet, succulent flavor, juicy texture, and brilliant red color. They are the ideal dessert after a meal, a perfect afternoon snack, or a great flavoring for pies, jams, jellies, compotes, ice cream, and more. However, for strawberries to live up to their lofty potential they must be handled carefully, cooled quickly and thoroughly, and not allowed to re-warm. What follows is a discussion of strawberry-related information, general facts about cooling and storage, and ideal cooling methods.

General Facts About Strawberries

Strawberries as we know and love them today were first cultivated in the 1750s in Brittany, France by crossing two wild varieties of strawberries: the Virginian strawberry, native of the United States, and the Chilean strawberry, native of Chile and Argentina. The cross proved quite fruitful indeed and resulted in what we now refer to as the garden strawberry or simply strawberry. Despite the name, strawberries are not true berries at all; instead they are aggregate accessory fruit, meaning that the tasty flesh is not from the plant’s ovary itself but rather the adjacent tissue. Other accessory fruits include pineapples, figs, and mulberries.

Strawberries are a common ingredient in countless desserts, preserves, cereal bars, snack products, juices, and other foods and beverages. They are a great source of vitamin C and manganese, and contain small amounts of essential unsaturated fatty acids crucial to a healthy diet. It is believed that strawberries might improve heart health, fight cancer, and help with inflammation, though research on these purported benefits is on going.

General Information About Cooling and Storing

Strawberries are a highly perishable fruit which pose a number of cooling and storage challenges. That is because they are highly sensitive to heat, moisture levels, and mishandling. Even under ideal circumstances they have a fairly limited shelf life. This makes it important to eek out every bit of saleable life span they have by optimizing the way they are cooled and stored. The following are key considerations:

Respiration – Like most other fruits and vegetables, strawberries respire and give off heat as a byproduct of this respiration. Unfortunately respiration rates are directly tied to degradation and over-ripening and these effects are only accelerated at higher temperatures. For comparison a ton of strawberries releases about 3,300 Btu per day at a temperature of 32°F; however, at a temperature of 80°F the same ton of strawberries would release a whopping estimated 41,800 Btu – nearly 13 times as much heat!

Humidity – Strawberries are extremely sensitive to humidity levels. They require a relative humidity in the range of 90% to 95%. If humidity levels are too low the strawberry will shrivel up, losing its taste and quality. On the other hand, if the humidity is too high water and moisture may form on the strawberry which exposes it to decay organisms such as gray mold and rhizopus rot. These pests are extremely communicable and will readily infest an entire container of strawberries from only one small initial source.

Temperature – To reduce respiration and extend strawberry shelf life as much as possible the fruit should be cooled rapidly to about 32°F to 34°F as soon as it is picked, and it is crucial that these temperatures remain constant. If the strawberries are allowed to rewarm they are subject to spoiling. However, the strawberry will freeze at 31°F, which will also damage it.

Handling – Strawberries are delicate and very prone to bruising and physical damage. Once they are damaged the weak spot becomes a site vulnerable to decay organisms and rapid spoiling. This makes it essential that strawberries be carefully harvested and packaged and that any damaged fruit be discarded rather than be allowed to remain with the good strawberries and spoil them.

Shelf Life – Even when conditions are optimal strawberries only have a shelf life of about 5 to 7 days. This makes it very important for strawberry operations to be as efficient as possible and for strawberry farmers to arrange potential buyers before harvest.

Methods of Cooling Strawberries

Because of the various challenging elements of strawberry cooling, storage, and handling strawberries have a limited number of options in terms of what cooling methods can be employed. Basic room cooling is not suitable because it is essential for strawberries to get their temperature down quickly, within 2 hours or less, after harvest. Room cooling would cool them too gradually. Hydrocooling is not suitable either because the water and moisture would make them more susceptible to threats from decay organisms like gray mold. Slush ice and packing ice would risk physical damage. That leaves strawberries with one viable cooling method: forced-air cooling.

Forced-Air Cooling – Forced-air cooling involves arranging the strawberries around a fan and pulling, rather than blowing, air through the containers. This thus forces cool air circulation and cools the strawberries much more quickly than non-forced air methods would allow. Once again because of the strawberries’ sensitivity to humidity levels it is important to monitor air moisture and ensure that the process doesn’t dry the strawberries out or allow condensation to form on them.

SEMCO/SEMCOLD LLC understands the unique challenges associated with strawberry cooling and storage. Our forced-air cooling systems are versatile and can be custom designed to fit each client’s particular capacity and scale demands.

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Methods for Cooling Apples After Harvest

Apples are one of the most popular fruits in the world. Estimates place the amount of apples grown worldwide to have been about 69 million tons in 2010. Proper apple handling, cooling, and storage is essential to the overall quality and taste of the ultimate apple or apple product that makes its way to end consumers. Fortunately there are several excellent cooling and storing methods available to those who grow, ship, and sell apples.

General Facts About Apples

There are over 7,500 known varieties or cultivars of apples. Each different variety comes with its own set of characteristics; however, just about all are susceptible to some extent to bruising and mechanical damage. As such it is important for harvesters and workers to avoid dropping apples, or over-stuffing boxes.

Apples are susceptible to sun and heat damage. For this reason it is crucial that harvested apples not be allowed to sit in the sun for hours and that apple boxes and crates be well ventilated. Apples should also be cooled as soon as possible after harvesting to slow deterioration and quality loss.

General Information About Cooling and Storing Apples

For the successful cooling and storing of apples it is important to keep the following considerations in mind: respiration and its effect on degradation, relative humidity and its effect on the apple’s water and weight loss, chilling and re-chilling and how it can contribute to bacteria or fungi growth, and cooler and equipment maintenance and the impact this has on apple cooling and storage.

Respiration and Degradation – Apples continue to respire even after they are picked. It is this respiration which is largely responsible for their degradation and general loss of quality. However, respiration can be slowed if the apples are properly cooled, thereby minimizing degradation, maintaining quality, and extending shelf life.

As a general rule of thumb, the higher the holding temperature the greater the respiration and softening rate. Most varieties of apples will respire and degrade at twice the rate when they are kept at 40°F versus 32°F. At 60°F apples will respire and degrade a startling six times faster than at 32°F. It is generally a good idea to avoid subjecting the apples to temperatures more than a degree or two below 32°F, however, because they could suffer freeze damage.

Another important point to remember is that most coolers and thermometers will measure the temperature of the air rather than the temperature of the apples themselves. The actual apples are often a few degrees higher in temperature.

Relative Humidity – Relative humidity is an important factor in apple cooling and storage because if the relative humidity is too low it will cause the apples to dry out and suffer weight loss. Most varieties of apples need a relative humidity of about 90% to 95%. In some cases this will require the use of humidifiers in the storage rooms to add water vapor to the air.

Storage – Apples are known to “sweat” when they are removed from a cool storage environment and abruptly exposed to warm air. Likewise this sweating may occur if the cooler or storage facility is opened and warm air is allowed to enter. What is actually happening is that moisture is condensing on the apples. While this does not itself directly harm the apples, it can contribute to bacterial and fungal growth. Chilled apples should also not be allowed to warm up and then be re-chilled, since this can also contribute to the problem.

To prevent the growth of pathogens it is crucial that storage rooms and containers be kept clean and sanitary. Likewise, while apples prefer high relative humidity levels of 90%-95% the humidity should not be allowed to reach the saturation point of 100% since this too can cause moisture and condensation to form and once again promote bacterial growth.

Cooler Maintenance – Good cooler maintenance is also crucial to the proper cooling and storage of apples. The thermostats and humidistats should be periodically checked for accuracy, fans, ducts, and refrigerations coils should undergo routine cleaning and inspection, and gaskets should be checked to confirm a good seal. It is also important to monitor the cooler for potential air leaks or damaged insulation. Good upkeep and cooler maintenance will also help keep energy costs as low as possible and extend the service life of the cooler.

Methods of Cooling Apples

There are several different appropriate methods for cooling apples including: room cooling, forced-air cooling, and hydrocooling. Apples that are being stored long-term may also be subject to controlled atmosphere storage. What follows is a brief description of each as they relate to apples.

Room Cooling – Room cooling involves placing the apples in a chilled room such as a cooler to allow them to cool gradually as a result of ambient conditions. When it comes to room cooling it is important that the apples be well-ventilated, otherwise apples near the center of the boxes may not properly cool. The bulk apple boxes themselves should be stacked at least six inches apart from each other and at least eight inches away from an external wall or ceiling.

Room cooling is one of the least expensive methods of cooling apples and it also has the benefit of requiring little extra handling and labor since the apples are also likely to be stored, at least short-term, in the same refrigerated room that did the cooling. However, room cooling also has the disadvantage of being one of the slowest methods of cooling apples and it generally takes anywhere from several days to two or more weeks to fully cool the apples. Apples in the middle of the box may never fully cool since there is a natural heat increase from respiration and these internally located apples may be too far away from the cool air to fully benefit.

Forced-Air Cooling – Forced-air cooling involves forcing cool air past the apples to ensure contact and greatly increase the rate of cooling. Forced-air cooling is about four to ten times faster than room cooling. Because forced-air cooling relies so heavily on air flow, it is essential that the apple containers have plenty of open space and are well-ventilated. It is common for the apple crates to be arranged in a shell-type formation around the fan.

Using the correct fan for the job is crucial. Not all fans are able to generate enough pressure to fully move the air through the apples. A general rule of thumb is that the fan will need to be able to deliver around two to three cubic feet of air per minute per pound of apple being cooled. It is also worth noting that the fan will pull the air through the apples, rather than blowing it around them. This helps reduce damage and water loss. However, forced-air cooling nevertheless does run the risk of drying the apples out. That is why it is particularly important to monitor and maintain relative humidity levels when using forced-air cooling.

Hydrocooling – Hydrocooling is one of the fastest methods of cooling apples, faster than both room cooling and forced-air cooling. Hydrocooling involves submerging the apples in cold water to cool them. The larger the apple the longer it must be kept in the water. A general rule of thumb is that as the diameter of an apple doubles the amount of time it takes to cool the apple will also double.

Since the water is such a crucial element of hydrocooling it is very important that it be kept as cold as possible, generally as near to freezing as it can get while still being liquid. The water should also be very pure to avoid contaminating the apple and it must come into full contact with each of the apples. The water should also move past the apples quickly. Since hydrocooling requires a higher cooling load than other methods it is common to only cool the apples to about 45°F then finish the cooling using a different method.

Controlled Atmosphere Storage – Controlled atmosphere storage allows apples to be stored very long-term with only a slow, gradual loss in quality. As the term implies it involves keeping the surrounding conditions – the atmosphere – around the apple in a very controlled state. Temperature and humidity levels are closely regulated as are oxygen, carbon dioxide, and nitrogen levels since all of these gas concentrations can also affect the speed of degradation.

When selecting a cooling and storage method for apples it is important to consider factors such as the apple’s particular variety, the temperature at harvest, energy efficiency, how long the apples will need to be stored, and how much handling will be required. Naturally choosing a method which accomplishes your goals while keeping energy and labor costs to a minimum and apple quality to a maximum will be desirable. SEMCO/SEMCOLD LLC offers a full range of cooling devices ideal for apples which can be customized to fit each customer’s capacity needs.

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Methods for Cooling Blueberries After Harvest

Research has shown that blueberries tend to be an impulse buy for most consumers rather than a planned purchase. For this reason it is imperative that the blueberries which eventually make it to grocery stores be fresh, high quality, and visually appealing. In order to accomplish this goal the blueberries must be well cared for from planting, growth, and harvest, right on through to cooling, storage, transport, and display. The cooling and storage segment is especially important because it is during this crucial phase when the blueberries will either shrivel, rot, and decay or maintain their quality and thrive.

General Facts About Blueberries

Blueberries are commonly classified as either highbush or lowbush, with the term highbush referring to larger varieties of cultivated blueberries, including the vast majority of those commercially sold, and the term lowbush referring to smaller, wild varieties of blueberries, which are not as commonly sold. Blueberries are an early summer fruit and are highly perishable with a relatively short shelf life compared to many other types of fruits of vegetables. Depending on the weather and other conditions a blueberry field may be harvested as many as four times during the season, typically in intervals of about five to seven days. If the fields are harvested less often the result is typically over-ripe blueberries which are not as suitable for transport and sale, while harvesting more often is typically an inefficient use of labor and resources.

Blueberries are very susceptible to physical damage from careless or rough handling, picking, or mechanical harvesting. They should thus be handled very carefully and it is imperative that they be cooled rapidly and efficiently to preserve quality and extend shelf life. A successful cooling and storage system for blueberries is paramount.

General Information About Cooling and Storing Blueberries

If blueberries are allowed to remain at field harvest temperatures they are extremely perishable and will being to decline in quality very quickly. Visible signs of decay may be evident in warm, wet blueberries as soon as 12 hours or less after they have been harvested. For this reason they should never be held all day without proper cooling and storage. They should also not be picked while wet, such as immediately after or during a rainstorm, because wet blueberries are more susceptible to postharvest decay organisms such as the ones that cause gray mold and Alternaria rot. As a general rule of thumb blueberries should never go more than four hours without being cooled, but should be cooled sooner still if possible.

Respiration – Like other fruits blueberries are alive at the time of harvesting and continue to respire even after they have been picked. There is a natural rise in temperature due to this continued respiration. It has been estimated that blueberries generate about 22,000 Btu of heat per day per ton due to respiration. This is enough to raise their temperature by as much as 6°F. If that extra heat is not removed by cooling it will hasten the ripening and decay process.

Proper cooling will dramatically increase shelf life and slow the decay caused by respiration. That is because the respiration rate is directly impacted by the temperature of the blueberries. Blueberries respire at almost 20 times the rate at 80°F compared to 40°F. That means that they have almost 20 times the shelf life as well. The optimum temperature to slow respiration and increase shelf life is about 33°F to 34°F.

Humidity – Blueberries have a high water content and require a high relative humidity to remain moist and flavorful. If there is not adequate humidity in the air this can result in the blueberries becoming dried out and suffering water-related weight loss. The optimum relative humidity for blueberries is between about 90% and 95%.

Freezing – Blueberries will freeze at about 28°F. Freezing is a viable method of extending shelf life, but it must be done intentionally and quickly and the temperature should then be maintained below 0°F. Blueberries may suffer freeze damage if they are unintentionally subjected to temperatures below 28°F and then allowed to warm up again.

Correct Method of Cooling Blueberries

One of the most common cooling methods is called room cooling. In room cooling the product is placed in a refrigerated room and allowed to gradually cool to the ambient temperature. However, this method is not suitable for blueberries because the cooling rate is too slow to prevent continued degradation and quality loss. A large part of the problem is that the containers, wrappers, and plastic needed to hold the blueberries acts a kind of insulation, keeping the heat in. Room cooling not only results in inadequate cooling, but also non-uniform cooling, with some blueberries getting significantly cooler than others.

Forced-Air Cooling – The solution to this problem is forced-air cooling. In forced-air cooling, the blueberries are arranged around fans which then pull cooled air through the berries. This results in a much faster, and more uniform rate of cooling. Depending on the particular circumstances, forced-air cooling is about 16 to 20 times faster for cooling the blueberries than attempting to use still-air room cooling alone. This results in blueberries that have a much longer shelf life and which will reach the end consumer in much better condition.

For businesses that sell blueberries and blueberry products, be they farms, factories, or grocery stores, quality is of the essence. It is the quality of the product around which the business will build and maintain its reputation and keep customers coming back. SEMCO/SEMCOLD LLC can help with this crucial area by supplying industry-leading, efficient, customizable blueberry cooling equipment and systems. Our products and product lines are versatile and can be developed to suit each customer’s unique requirements.

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Produce That Benefits Most from Hydrocooling

Proper cooling is essential for almost any type of produce in order to ensure that quality is preserved as fruits and vegetables begin their journey to the end consumer. Here at SEMCO/SEMCOLD LLC, we offer many different kinds of cooling systems and different cooling methods are better suited to different types of produce. In this article let’s take a look at hydrocooling and the produce that benefits most from this method.

Hydrocooling-Produce

Why Produce Cooling Is So Important

Good produce cooling is important for a number of reasons. Field heat, or the ambient temperature that permeates a plant while it is growing, can have many detrimental effects that begin to affect the produce as soon as it is harvested. These include wilting due to water loss, rapid cellular respiration that leads to softening, and high levels of ethylene production, which can make the fruit overripe. In addition, warmer temperatures are more hospitable to decay-causing microorganisms such as molds and bacteria.

Proper cooling as soon as the crop is picked can slow, delay, or even prevent many of these undesirable processes. It is important to ensure that field heat is rapidly dissipated as soon as possible after the produce has been harvested. This keeps fruits and vegetables fresher for longer, decreasing the urgency to sell and improving overall quality once it is purchased.

Hydrocooling Basics

Hydrocooling is a cooling method in which produce is directly cooled by chilled, near-freezing water. This cold water runs over the fruits and vegetables, quickly dropping their temperature and eliminating problems due to heat. The water is cooled either with ice, a refrigeration system, or a system specially designed for hydrocooling.

The Advantages of Hydrocooling

There are many benefits to hydrocooling. One of the biggest is that it is very rapid; water transfers heat away from food up to 15 times more rapidly than air does. Hydrocooling systems can be designed for a range of operation sizes, capable of handling both small loads and very large ones. Also, hydrocooling helps prevent moisture loss in produce, ensuring that the fruits and vegetables will not dry out—a common concern with some other types of cooling systems.

In addition, depending on the design of the system, hydrocooling can also act as a way to partially wash the produce. This is not true, however, for hydrocooling systems where the water is recirculated without being purified. These are a few of the reasons why hydrocooling is a popular option among produce growers.









Important Considerations for Hydrocooling

A number of factors should be taken into account when trying to decide if hydrocooling is the best option for a crop. One of the biggest is concern about rot and disease. Although colder temperatures discourage decay, wet environments are friendly to microorganisms, meaning that some of the disease-prevention benefits of cooling can be reduced. For many types of produce, this difference is negligible, but foods that are especially susceptible to disease should not be hydrocooled.

In addition, the type of packaging should also be considered. Hydrocooling should be avoided for packages that are not water permeable, preventing the water from flowing inside and around the produce. Also, the packages must be designed to drain well, so that the water does not collect and pool in the storage area. Mesh bags, bulk bins, and wire crates are well-suited for hydrocooling; palletized produce can be hydrocooled if it is stacked correctly.

Finally, it is important to note that hydrocooling is primarily a pre-cooling method meant to remove field heat rapidly. Hydrocooling is not advisable as a standalone cooling method because at lower temperature it is not energy efficient. Hydrocooling is often done in conjunction with room cooling or forced-air cooling.

Best Produce for Hydrocooling

There are many types of fruits and vegetables that respond particularly well to hydrocooling. These include:

  • Apricots
  • Peaches
  • Plums
  • Nectarines
  • Cantaloupe
  • Apples
  • Pears
  • Cherries
  • Spinach
  • Lettuce
  • Endive and other greens
  • Leeks and Green Onions
  • Asparagus
  • Broccoli
  • Snap Beans
  • Pea Pods
  • Brussel Sprouts
  • Cauliflower
  • Turnips
  • Cucumbers
  • Corn

Foods that should not be hydrocooled include those that are highly susceptible to wetting, such as berries, potatoes, bulb onions, and garlic. This type of cooling should also be avoided for citrus fruits, mushrooms, grapes, and squash. For information regarding cooling methods for particular types of produce be sure to check out our past articles.

SEMCO/SEMCOLD LLC Designs Great Hydrocooling Systems

Here at SEMCO/SEMCOLD LLC, we are proud to offer a wide variety of cooling solutions to our clients with our specialty design, manufacture, and installation services. Hydrocooling is just one excellent option for keeping your produce fresh and your quality high. Contact us for more information regarding the system that is best for your crop.

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4 Reasons Ice Cooling May Not Be Best for All Produce

Keeping fruits and vegetables at their optimal temperatures is vital for maintaining freshness and nutritional value. Temperatures that are too warm could cause certain types of produce to go bad. Keeping your produce cool with ice cooling is beneficial in many cases. However, not all produce will fare well with ice cooling. Let’s take a look at 4 reasons why ice cooling isn’t always the right choice.

Large Ice Chunks Could Be Problematic

Some types of fruits, such as tomatoes, plums and peaches, have very thin skins that are prone to bruising, bursting and other types of damage. If you choose to use solid ice to keep these types of produce cool, there is a good chance you’ll end up with produce you either have to sell at a discount or can’t sell at all. Still the produce experts emphasize that stone fruits especially have to be stored at temperatures equaling 0 degrees Celsius or 32 degrees Fahrenheit. If they are too warm, they will continue to ripen, greatly diminishing their shelf life.

Melting Ice Could Ruin Produce

Some types of produce cannot get wet. Strawberries, blueberries and similar produce items will quickly become soft and decay once they get wet. Lettuce and other leafy vegetables are also prone to problems once they become wet. They will lose their freshness and begin to wilt within a few hours, leading to lost profits because of unusable vegetables. Even if the produce itself would be ok in water, melting ice could damage the packaging. Some fruits are stored in cardboard containers that degrade and fall apart when they become wet, leaving spilled produce as the result.

Ice Cooling Isn’t Always Economically Viable

Block ice is a common way to keep produce cool, but depending on where you are located and on the time of year, it isn’t always readily available. During peak seasons, agricultural areas usually have more demand than supply for block ice. While this type of ice is easy to transport long distances, doing so usually costs much more between the laws of supply and demand and the extra labor and transportation. One alternative is chip or flake ice, but it is only viable if you make your own with a machine such as the ones we sell at SEMCO/SEMCOLD LLC or if an ice plant is nearby. This type of ice cannot travel long distances since it melts and refreezes in one large ice chunk.

Ice Requires Enough Laborers

Small businesses simply might not have enough people on hand to work with large amounts of ice. Ice is heavy, and especially when working with large enough chunks or bags to cool large amounts of produce, it is practically impossible for one or two people to move alone. It is also time consuming to ensure the ice is still solid enough to do its job and that produce is at an optimal temperature. A business owner who already has a full plate could need to hire another person just to handle the care of produce.

All in all ice cooling is an excellent method of preserving freshness and quality. However, it is important to understand the limitations and drawbacks of ice cooling and to realize that for some types of produce, ice cooling isn’t necessarily the right choice. SEMCO/SEMCOLD LLC manufactures a wide range of cooling systems and whether ice is right for your application or not, we can design a fully customized system that meets your needs.

Flexible Financing Options for All Equipment

At SEMCO/SEMCOLD LLC, we strive to make acquiring high-quality industrial equipment more accessible with our LEAF Leasing financing options. This flexible “Lease-to-Purchase” program allows you to spread the total cost of any equipment over affordable monthly payments. Whether you need ice crushers, rotary valves, hydrochillers, or any of our advanced systems, financing through LEAF ensures you can enhance your operations without upfront financial strain. At the end of the lease term, you fully own the equipment—no hidden fees or extra costs. Additionally, LEAF Leasing offers tailored payment schedules, including options that align with your business’s cash flow cycles. Contact us today to explore how our financing solutions can help you grow your business with ease.

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Forced-Air Cooling Mistakes to Avoid When Cooling Produce

Many types of produce, like strawberries, apples, beans and blueberries, have to be drastically cooled after harvest in order to keep their freshness. Putting every different type of produce under the right cooling method will lengthen their freshness and ensure that a high quality product is given to consumers. There are a lot of different types of post-harvest cooling methods out there, like forced-air cooling, room cooling, hydrocooling and icing. Each of these cooling methods has a proper use when it comes to different types of produce. SEMCO/SEMCOLD LLC understands that you’ll need different equipment depending on the type of produce you deal with. However, in today’s article let’s take a look at forced-air cooling and some common mistakes to avoid when using this cooling method

What Is Forced-Air Cooling?

Forced-air cooling uses fans to pull cool air through the packages and pallets of produce. Because the cold air is actually forced around the room and into the heart of the pallets, this cooling method is typically 75% to 90% faster than room cooling. Forced-air cooling is thought of as being effective because:

  • It reduces how long produce stays at warmer temperatures, which decreases deterioration of the product.
  • It is energy efficient because of its shorter cooling times.
  • It is particularly more efficient when it comes to cooling large volumes of produce.
  • It cools produce without adding moisture or requiring excessive handling of the product.
  • It can be retrofitted from an existing room cooling facility.

 

Potential Forced-Air Cooling Mistakes

While forced-air cooling systems can be really effective, you have to avoid making certain mistakes that would drastically reduce the effectiveness of this cooling method.

Humidity Mistakes

The movement of the air can cause the produce to get dried out if the humidity levels are not properly regulated and monitored. Lack of water on the surface of the produce can result in shrinkage, wilting and overall loss of quality. Too much water can lead to the growth of mold and other fungi. This type of mistake can be avoided by incorporating more coils or larger coils used in the system and using a wet-bulb thermometer to monitor the humidity levels. You can also use industrial humidification systems to help keep the room at the right humidity level.

Ventilation Mistakes

Another mistake is not having enough ventilation between the packages, in the pallets and in the room in general. This lack of air flow can reduce the efficiency of the forced-air cooling system. If there is not enough ventilation, the cooling time will be longer. If there is too much ventilation, the products may not stay at a consistent temperature.

Overcrowding Mistakes

Another common mistake is over packing the pallets. When the pallets themselves are too full, the center produce is not able to get cooled as well as the other produce. You can avoid this type of mistake by not filling the individual pallets too full.

Produce Mistakes

Finally, many people use this type of system for the wrong types of produce. Some produce is not supposed to get as cold as quickly as others. At SEMCO/SEMCOLD LLC, we can help you get the right system for the right produce. It is appropriate to use a forced-air cooling system for apples, beans, blueberries, brambles, cabbage, cucumbers, eggplant, okra, peaches, peas, peppers, potatoes, squash, strawberries and tomatoes among others.

Using the most effective cooling system is important, but even an effective system has to be used in the right way. Turn to professionals who can help you get the best equipment for your line of work. Turn to SEMCO/SEMCOLD LLC. We provide fully customized cooling systems including forced-air cooling systems.

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