Intermediate postharvest training for horticultural crops


This set on online training modules is designed to support smallholder and subsistence farmers who may already be selling their horticultural crops but would like to move into larger or urban markets — with intermediate concepts that will enable them to meet higher quality standards.

Part of a three-level training series, this intermediate level is aimed at farmers with a working background or understanding of postharvest handling practices who want to increase their knowledge towards meeting higher standards. This module builds off the beginning postharvest training for horticulture crops by providing more detailed information on topics including postharvest basics, sanitation food safety, packaging and water loss.

These lessons were originally created for farmers and student audiences in Latin America, but are widely applicable to small-scale farmers and agriculturists elsewhere in the world. 

Users can control the progression of each narrated training topic by starting and stopping lessons as well as switching between topics. Notes are also made available for each topic that can be accessed at the top control bar of the video player. 

Postharvest basics for fruits and vegetables

This 12-minute postharvest basics lesson covers internal and external factors that influence the deterioration and loss of postharvest horticultural crops. Internal factors consist of composition, morphology, and physiology. External factors include temperature, physical damage, pathogens, humiditiy, and rodents/insects.

Understanding the different plant parts and which horticultural crops can be categorized by each part of the plant is another strategy that can help reduce postharvest losses. For example, leaves will have different postharvest handling procedures and management than roots or stem products. Treating crops based on what part of the plant they come from can better enable appropriate handling procedures to be used for that particular group of crops.

Factors affecting maturation and ripening are important to understand as horticultural crops undergo significant changes during postharvest handling. Certain measures can be taken to influence these stages.

For example, ethylene is a plant hormone that can help some fruits in ripening. Ethylene is a gas produced by some fruits during ripening and all fruits and vegetables when injured. Ethylene promotes natural ripening for bananas and avocados, but can also accelerate deterioration in other fruits and vegetables. 

Additional postharvest basics include the composition of horticultural crops and changes that occur. The color, flavor and nutrition will depend on the presence of carbohydrates, proteins, vitamins, pigments, volatiles or acids in the fruits or vegetables. Ripening can include changing colors and developing different flavors through increased sugar content and sweetness. 

Luis Cisneros, of Texas A&M University, is the presenter of this lesson.

Sorting and grading horticultural crops

This 6-minute sorting and grading lesson develops an understanding of how market demands for quality can better enable smallholder farmers to sell their produce in large or urban markets.

The main factors influencing market demand are shape, form, color, and food safety. This topic provides several images comparing fruits and vegetables suitable for markets vs. those that do not meed demand requirements. 

Many urban markets and distributors will have a specific set of standards for fruits and vegetables that are required to be sold at their market. These profiles show visual characteristics such as shape, color, and size of products that farmers can measure against their own crops. Markets can also be contacted to learn more about their required specifications when smallholders are interested in selling at their market.

Ivanna Vejarano, of the Panamerican Agricultural School, Zamorano, is the presenter of this lesson.

How to measure quality

This 10-minute quality measurement lesson focuses on standards needed for farmers to sell their horticultural products at larger markets. Farmers must maintain a certain level of quality that matches the demands of the consumer, distributor and market. Distributors primarily value visual appearance, firmness and storage life, while consumers focus on visual appearance, taste and smell. 

Several types of measurements or evaluations can be conducted to determine the quality of products. For visual appearance, color scales exists to help compare a farmer's products to market standards. These scales focus on uniformity of color and intensity. Other measurements of color use colorimeters which measure the reflection of light on the surface of the product.

Size and shape are also important parts of measuring visual appearance. Sizing rings, calipers, and visuals with detailed descriptions can help determine if products meet quality standards.

Texture can be measured using sensory analysis along with penetrometers that measure how hard a product is and the depth of penetration.

Flavor and aroma are typically evaluated using sensory analysis to develop profiles for taste. Solubles in fruits and vegetables impact taste, and using a refractometer to measure soluble solids can allow for the measurement of juice samples to determine the product's overall content.

Ana Silvia Colmenares, of Universidad del Valle Guatemala, is the presenter of this lesson.  

Curing roots, bulbs and tubers (underground storage organs)

This 10-minute lesson on curing bulbs, roots and tubers lesson presents alternative curing options for bulbs, roots and tubers. When weather may not permit the curing process to take place in the fields, crops can be stacked in small piles under a simple outdoor shed. This will protect them from the rain and other adverse weather conditions while providing sufficient airflow for drying. Adding fans attached to the shed's roof can speed up the drying process, if electricity is accessible.

For roots and tubers, semi-controlled structures can be used for curing. These structures can be curing sheds that are covered to prevent excess heat and rain exposure, as well as enclosed rooms with ventilation such as a greenhouse. 

Water loss plays an important component in curing of bulbs, roots and tubers for longer term storage. The curing process will exhibit initial water losses around 5 percent, but will ultimately prolong excessive water loss during storage. Reducing the amount and time of water loss will maintain high quality products prior to being sold in the market. 

Lisa Kitinoja, of the Postharvest Education Foundation, is the presenter of this lesson.

Water sanitation and food safety

This 15-minute water sanitation and food safety lesson teaches the importance of preventing contamination of horticultural products that are intended for sale at markets. One such practice is water management. Water can transmit various agents capable of causing disease or illness.

The use of water for postharvest processing typically includes some form of washing that requires potable water. Wash water should be regularly cleaned or replaced with clean water. Many cleaning operations that use water will add chlorine to help prevent bacterial growth. Chlorine measurements need to be taken regularly to manage the concentration within the water. 

Personal hygiene is another practice that can help to prevent food contamination. This includes making sure workers regularly wash their hands, wear proper clothing, and use designated restroom facilities. These procedures also apply to visitors who may be on the farm engaging with produce or equipment. Utensils and equipment used in postharvest need to be adequately sanitized and cleaned.

Another source of contamination are animals and livestock. Animals should be prevented from accessing crop fields during plant growth and harvest to prevent contamination from animal feces.

Chemical and microbial contamination should be prevented and monitored during production. Soil microbial tests can be conducted to detect any harmful microbes in the soil that may have resulted from animal feces. Chemicals such as pesticides should only be used if approved and farmers should carefully follow the application instructions provided. 

Alejandro Castillo, of Texas A&M University, is the presenter of this lesson.

Packaging materials for fresh produce

This 18-minute lesson on packaging fresh produce provides a deeper assessment of the types of materials and packaging that are best suited to maintain the quality of horticultural crops. Wooden crates and sacks are commonly used in developing countries as the materials are low cost and more readily available. This lesson provides a detailed chart of the types of sacks that can be used and how they impact the storage of horticultural crops. Sack materials are assessed against tearing and snagging, protection against moisture absorption and insect invasion, as well as contamination.

Another type of packaging that provide benefits to producers are cardboard boxes. Cardboard is relatively lightweight, inexpensive and collapsible for easier transport. Cardboard packages are rigid enough to be stacked and also provide appropriate surfaces for labeling to aid in identification. Some disadvantages of cardboard containers include careless stacking that can cause containers to collapse as well as susceptibility to moisture absorption and damage if significantly exposed to water. 

High density polyethylene containers, or plastic crates, are commonly used for storage and shipment of fruits and vegetables. This material is easy to clean allowing them to be reused, are sturdy enough to be stacked, and are smooth to prevent damage to produce. Some disadvantages are higher costs, they may need to be imported, are used for many alternative purposes which can cause food safety concerns, and can deteriorate rapidly when exposed to sunlight. 

Eleni Pliakoni, of Kansas State University, is the presenter of this lesson. 

Cooling and temperature management

This 11-minute cooling and temperature management lesson shares methods for keeping fruits and vegetables cool during postharvest to maintain their quality. Several methods that can keep produce cool during lag periods between harvest and storage are to provide ample shade during transportation. This is often a period where horticultural crops are at significant risk of high temperatures and damage. Shaded vehicles can help to maintain temperatures during movement. Receiving facilities also need to ensure that shade is provided when fruits and vegetables arrive at their facilities. When products are transferred to cooling structures for storage, it is important that products receive significant exposure to air and cool temperatures.

Additional methods for cooling include portable forced-air coolers in cold rooms. These machines use a high velocity fan to pull cool room air over products at a higher speed. Fruits such as berries can be organized in pallets where plastic sheeting covering the sides of the products are aligned with the air cooler at the end. This increases the cold air flow over the products ensuring that they receive good contact. Hydrocooling can accomplish cooling even faster than using cold air. Products can be immersed itself or in bags in cold or ice water. Refrigeration can also support the cooling of water for hydrocooling by maintaining the temperature of cold water in which products are submerged. Sanitizing equipment can also be used to ensure water used for hydrocooling is clean and frequently disinfected.

Steve Sargent, of the University of Florida, is the presenter of this lesson.

Storage practices for fresh horticultural crops

This 9-minute storage practices lesson focuses on four types of storage structures that are beneficial for short-term storage. These four structures are low cost and use locally available materials for construction allowing smallholder farmers the ability to set these storage rooms up on their farms. The four structures suitable for short-term storage are the charcoal cool room, zero energy cool chamber, ventilated onion storage, and a small ready made or self-built cool room.

Evaporative cooling systems like the charcoal cool room or zero energy cool chamber are best suited for fruits and vegetables grown in dry regions or for storage during dry seasons when relative humidity is low. Ventilated onion storage structures are beneficial for produce such as onions, garlic, shallots, or other bulb crops that require very dry conditions and high air flow. These structures use mesh walls that increase the permeability of air through the products to keep relative humidity between 65-75%. These storage systems can be designed with individual compartments allowing for easy access to certain quantities of produce. 

Unlike evaporative cooling and ventilated structures, cold rooms can be significantly more expensive to build. Cold rooms are best suited for produce that require lower storage temperatures such as apples or carrots around zero degrees celsius. They require more energy to power cooling systems and have more material to maintain insulation. One low cost option utilizes a small window style air conditioning unit and a CoolBot system.  Local materials can be used for the construction of walls and panels for insulation. The cost of these structures is estimated at 10% of other commercial systems. 

In addition to the types of storage structures, it is important to understand the types of produce being stored. Certain fruits and vegetables are considered ethylene producers and others are sensitive to ethylene. Ethylene is a plant hormone that can increase ripening and mixing these two groups of crops can have negative results during storage. 

Lisa Kitinoja, of the Postharvest Education Foundation, is the presenter of this lesson. 

Transportation of fresh horticultural crops

This 5-minute transportation of fresh fruits and vegetables lesson introduces simple tips to improve postharvest handling in preparation for transportation as well as during transportation. Harvesting fresh fruits and vegetables should be conducted during earlier times of the day when temperatures are cooler. When produce is harvested and is at the collection point for transportation, ensure that they are kept in a shady and cool area to prevent excessive sun and heat exposure. 

Preparing fruits and vegetables for transportation should be conducted in an organized and efficient manner. Staging produce so they can quickly be loaded onto a vehicle to be brought to the packing area will help prevent delays or the amount of time that horticultural crops are sitting prior to being loaded. The main modes of transportation for horticultural crops are the use of hand trucks or carts to carry the produce from the field, trucks to bring them to an accumulation point or cool storage area, as well as using a refrigerated truck to transport them to the market. Refrigerated transportation is best used for travel distances that are more than a few hours away from the field. Maintaining a low temperature will help prevent the loss of quality during transport to the next location.

During transportation, uniform containers should be used for storage of the produce to prevent injury. Using the same containers ensures that there is little movement during transportation and that stacking is uniform. Mixing fruits and vegetables within a vehicle during transportation should be organized based on the types of produce that are being combined. Fruits and vegetables should be mixed during transportation based on similar temperature needs, ripening rates, as well as their moisture compatibility and proper relative humidity. 

Jeffrey Brecht, of the University of Florida, is the presenter of this lesson. 

Water loss during postharvest

This 10-minute postharvest water loss lesson examines the impact water loss may have on postharvest processes such as packaging, transportation, and market acceptability as well as provides a more detailed explanation of methods to reduce water loss. As products lose water, they shrink and can ultimately fit less snug in packaging. Products that do not fit well in their packaging can increase the probability of damage during transportation as the fruit or vegetable itself can easily be bruised as they are shifted around during transport. As prices are often paid based on weight, farmers may receive less if their crops experience too much water loss. 

Horticultural crops that have the ability to get wet can be sprinkled with water. This allows the water that is evaporated into the air to come from water that is misted, not water within the product itself. Dryer air will pull water out of a product and introducing water into the environment can reduce the amount of water pulled out of the product. Because colder water evaporates more slowly than warmer water, and cooler air holds less water than warmer air, quickly cooling fruits or vegetables after harvest minimizes water loss. Water loss is also enhanced when air flows over the surface of a crop. Reducing the amount of air flow can help to reduce evaporation and water loss. 

Mark Ritenour, of the University of Florida, is the presenter of this lesson.


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