CHILI POST HARVEST

1.0Introduction

This training module will be used for training Field Staff (TOT), who will then train the farmers. The training at both levels will be interactive and will use live specimens for demonstration. The training will therefore be based near a farm or at least the trainees will be able to visit a farm of the produce at the period when harvesting and post-harvest handling are being carried out for practical demonstration.

The maturity indices for chili can vary considerably depending on the type and variety, and the intended use. The most common harvests are of mature green and ripe chili for the fresh market. and harvested ripe and dried chili. The post-harvest management involves handling of these two categories.

Both quantitative and qualitative losses occur in horticultural commodities between harvest and consumption. Qualitative losses, such as those in edibility, nutritional quality, caloric value, and consumer acceptability of fresh produce, are much more difficult to assess than are quantitative losses. Quality standards, consumer preferences and purchasing power vary greatly across countries and cultures and these differences influence marketability and the magnitude of post-harvest losses.

This module therefore intends to help the horticulture smallholder farmers gain knowledge:

1. And be able to identify the maturity index for harvesting of the chili of the two categories (fresh market and dried).
2. And practice the appropriate methods of harvesting the chili.
3. And practice the sorting and grading of chili.
4. On the deteriorative factors of chili and methods of control.
5. On the precooling of chilis.
6. And practice of drying chilis.
7. And practice of parking and storage of chilis.

2.0Pre-Harvest considerations

Chili pepper (Capsicum annuum L.) belongs to the Solanaceae family. There are a lot of cultivars that belong to C. annuum having fruits of varying color, shape and degree of pungency (hot or sweet). The chili crop should be inspected throughout the growing season to estimate whether the crop’s yield and quality will meet market standards. However, several quality criteria can be assessed postharvest, including maturity, freshness, freedom from diseases, mechanical injuries, insects, blossom-end rot, sunscald, and freeze injury. 

In general, chilies harvested late in the season will have inferior quality, and therefore a shorter shelf life, than early or midseason harvests. Fruit firmness or degree of dehydration is the primary indicator of chili freshness.  Fresh green chili loses water very quickly after harvest and begins to shrivel and turn color within a few days if not refrigerated. Chili stems should be firm and green.  Darkening, shriveling, or rotting of stems indicates that the chili was not harvested recently.  Select chilies with the desired maturity for the intended market. Maturity is generally judged according to physical traits such as size, shape, color, and texture. Most mature green chilies should be firm and dark green in color. If the chilies are light green and yield easily to pressure when squeezed, they are immature. Green chili for canning should be flat with two locules and about 6 in. (15 cm) long. Bell types should be large, firm, crisp, and blocky, with four lobes. Jalapeños should be thick-walled, conical, glossy green, and about 2.75 in. (7 cm) long and 1 in. (3 cm) wide.

3.0Harvesting

During harvest and handling, it is important to remember that chili fruits soften easily and develop postharvest diseases if they are damaged, bruised, or subjected to sustained high temperatures. All chili types, especially New Mexican green chilies, are highly susceptible to water loss, sunscald, and heat damage. These problems are likely to occur if chilies are allowed to sit for more than an hour in direct sunlight. Fresh chili harvested in the summertime can have pulp temperatures of 90°F (32°C) or more. For these reasons, chilies should be harvested in the early morning, placed in the shade, and cooled as soon as possible. If the chilies are not cooled within 1 to 2 hours, they will begin to show signs of water loss and softening.

Fresh chili is harvested either mature green or ripe to a color dependent on the variety. The harvesting is mainly by hand into buckets or sacks and then emptied into bulk bins for transport to the packing shed or processor. A field of long green chilies can be harvested in early August and then again in September. A third harvest will typically yield small fruits and may not be profitable. Once at the shed, the chili is either dry-dumped onto padded ramps or moving conveyor belts, or wet dumped into a chlorinated (500 – 600ppm) wash tank.

Wash tanks should be cleaned daily, and the chlorination levels should be monitored frequently. These sanitation practices are necessary because chilies are highly susceptible to bacterial diseases that could be introduced through the wash tanks. Fruits are then sorted to remove diseased, overripe, immature, or otherwise defective pods. Alternatively, the chilies can be given a sulfur dioxide dip (0.4% sodium or potassium metabisulphite in clean water. Both dips should take at least two minutes. The dips should be followed by drip drying of the produce before packing or drying. The action helps to clean the product and prevent it from spoilage by microorganisms during storage and drying (if done).

4.0Post-harvest handling

4.1 Pre-cooling and storage

Fresh chili is a highly perishable commodity. Proper cooling extends the shelf life by slowing respiration, water loss, color change, and decay. Temperatures higher than 70°F (21°C) greatly accelerate ripening through respiration and ethylene production. Preferred cooling methods for chilies are room cooling and forced-air cooling. Cooling and storage are independent operations and the specific requirements for rapid cooling should therefore be considered separately from cold storage needs.

Precooling is meant to remove field heat from the produce. Room cooling in a cold or refrigerated room exposes fresh produce to cold air and lowers the temperature. Bins or boxes must be stacked properly to permit airflow between the individual storage units.  Room coolers can be partitioned into sections so that recently harvested chilies with high field heat are kept separate from previously cooled produce. Powerful fans and ceiling jets can be used to increase the airflow and, consequently, the cooling efficiency of room coolers.

Forced-air cooling is an active cooling process and is much faster at removing field heat than room cooling. With forced-air cooling, fans pull cool air through the boxes or bins of produce. Room coolers can be modified into forced-air coolers relatively quickly and inexpensively by adding extra fans and partitions.  The produce can also be cooled by using cold morning water from the river or tap. This can be combined with the chlorine dip or sulfur dioxide dip. For a small holder, the most practical practice that eliminates cooling is to harvest very early in the morning to take advantage of the low temperatures at the time, then bring to shade immediately.

The optimum storage conditions for fresh chilies are 45 to 50°F (7-10°C) and 90 to 95% relative humidity. Chilling injury occurs at lower temperatures. The symptoms of chilling injury are softening, pitting, and an increased susceptibility to decay. Freeze damage occurs at 32°F (0°C). Most fresh chilies can be stored for 2 to 3 weeks if kept cool at the proper temperature. Chilies should be shipped in refrigerated trucks, but these vehicles should not be used for pre-cooling because refrigerated trailers do not have adequate cooling capacity or ventilation to remove field heat quickly. Transit cooling is intended only to keep previously cooled produce cold during shipping.

Poor temperature management and ethylene accumulation during storage or transit promote ripening and decay. Some fruits and vegetables produce much larger quantities of ethylene than chilies. For that reason, chilies should never be stored or shipped with crops such as tomatoes, apples, or melons. Storage rooms should be ventilated properly to reduce the accumulation of ethylene in the environment. Placing ethylene scrubbers containing potassium permanganate in the storage room or transit vehicle can also decrease ethylene levels.

4.2 Sorting and grading

Sorting is part of post-harvest handling that is done with the aim of ensuring quality chili that conforms to the market demand. This is because consumers within the household, food industry, hotels, supermarkets, and restaurants have different specifications.

The red chili is considered fresh chilies when they are ripe and reddish, in fresh condition, not rotten, deformed or damaged, and free from pest and disease. Based on the percentage amount of defect, chilies are classified into three quality levels; super, the first, and second class.  Today, sorting and grading of red chilies is still done manually through visual observation. This method has some weaknesses, such as that it produces inconsistency due to the limited capacity of human visual sense, fatigue, and the divergence of quality perceptions from different observers.

Determining the chilies’ quality after sorting all of them takes a long time, and this can also affect the quality of the chilies after harvesting. This must be anticipated by applying a method and using tools for initial decision makers before the chilies are properly sorted. For this reason, a faster post-harvest handling technology with a low error rate is needed to help equate or standardize perceptions of the quality of sorting and chili grading among the parties involved. 

Figure 1 Sorted chilies

One alternative technology that can be used is image processing as this is a non-destructive (without damaging materials) quantitative method.  Digital image processing can be used for factors, such as shapes, sizes, and color recognition, texture extraction, body strength, smell and handling. Mechanization, rapid screening, and reduction of human error are considered as the main advantages of the image processing, which has been emphasized in industries and factories. With the development of this alternative, it is hoped that it can be a system of early decision making in determining the quality of red chilies. In addition, the buyer also would not need to wait for the sorting to be carried out by the seller to find out the quality of the chilies to be sold.

4.3 Packing

Different kinds of packaging containers are used for chili for in domestic markets, including bamboo baskets, wooden crates, plastic crates, and plastic bags. Plastic crates offer better protection against physical injuries than the other containers due to their smooth surface, rigidity, and ease in handling. If bamboo baskets or wooden crates are used, protective measures must be applied such as using liners such as fresh leaves and old newspapers and proper strapping or binding of the container.

Baskets of produce should not be stacked on top of one another unless a rigid divider is provided in-between layers in a stack. Plastic or mesh bags and sacks are not recommended unless they are placed in a rigid container. For retail, the fresh chili can be packed in sealed and perforated plastic bags, which can show them in display. These should be specifically manufactured and branded.

4.4 Transport and Market Handling

Chili is susceptible to mechanical damage, particularly if transported in sacks or bags. Any cracks, splits, or punctures will cause the soft rot in figure 2. Fruit transported in sacks is easily bruised. Rigid plastic containers are better; they protect the fruit from cracking and splitting. Handle chili carefully during transport to avoid damage to the fruit. Cracks or splits promote the growth of bacteria and mold, which lead to rapid decay, rapid deterioration of chili, discoloration, decay, and finally, tissue breakdown, which are the common symptoms of damage. Except for ripening treatment, transport, and market handling, the recommendations for tomatoes can be applied to fresh chili. At the market, keep chili dry. Do not allow rain or moisture to collect on the fruit. Protect them from dust and insects to ensure the fruit is wholesome and clean. Loading into the transportation vehicle should be such that the fresh chili should not be compacted as they will bruise and spoil faster.

5.0Causes of Post-Harvest Loss in Chili

Loss of water leading to shriveling and loss in weight – controlled by proper packaging and storing in a cool room with RH greater than 80%.

Microbial damage – controlled by chlorine and Sulphur dioxide dip.

Physical injury leading to easy spoilage by loss of water and microorganisms – avoid compacting and rough handling.

6.0Post-Harvest diseases & pests

1. Bacterial soft rot

Bacterial rots are caused by Erwina sp. While rotting expresses itself in the postharvest environment during storage the pre requisites for this disease actually occur during harvesting and subsequent handling through bruising, damaged stems, finger nail damage and so on. In fact, any kind of damage to the pericarp or stem increases the susceptibility of the fruits to be invaded by bacterial organism which will cause rotting. The application of chlorinated sprays at a rate of 50-75 ppm or Milton at a rate of 500 ppm have been shown to significantly reduce postharvest bacterial rotting.

1. Anthracnose

This is a problem that starts on the field. Anthracnose is a fungal disease that is seen mainly on the pericarp of the fruits. The predominant symptom is concentric black spots. Fruits that have just started to turn show these symptoms more readily than mature green ones. The presence of these symptoms on turning fruits may indicate that the mature green fruits might also be inoculated but the visible symptoms only express itself during storage. A proper field management program using the principles of integrated pest management is the best way to manage this disease.

Figure 3 Chili with Anthracnose

7.0Evaluation of the training

This evaluation can be done as a quick written test during training of field staff. For farmer training, it can be done as a guided discussion of the answers to the questions by the trainer, in a plenary session. It is meant to assess the extent of learning.

1. Describe the maturity indices of harvesting fresh chili.
2. Describe the method of harvesting fresh chili.
3. Describe the sorting and grading of fresh chili.
4. Enumerate the factors involved in spoilage of fresh stored chili and the methods of control
5. Describe the disinfection of fresh chili and the reason for the action
6. Describe how fresh chili are precooled and the reason for the action. How can the action be avoided by a small farmer?
7. Explain the drying of chilies and its importance.
8. Give the appropriate packages for storing and retailing of fresh chili.
9. Give the appropriate conditions for storing fresh and dry chili.