GARLIC 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 be interactive and will use live specimens for demonstration. It will 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 trainees will also be taken on a tour of the two levels of markets.

Garlic belongs to the onion family, the Allium family and is more related to the shallot onion and the leek. The harvesting and post-harvest characteristics are therefore similar to those of the onions. The main post-harvest handling to extend shelf life include drying, curing and treatments to extend storage life. The main difference between garlic and the bulb onion is the structure of the bulb. Whereas the onion consists of a compact bulb, garlic consists of bunched up components referred to as the cloves.

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.

Contamination of vegetables such as garlic can occur with unclean water, contact with the ground or dust, or contact with farm animals. Contaminants that can cause illness include pathogens, most commonly from animals, or chemical residues from pesticides. Contamination can be prevented by applying the proper food safety practices. These include:

• Water management
• Personal hygiene
• Cleaning and sanitizing materials
• Prevention of contamination from animals
• Proper use of animal fertilizer
• Preventing contamination with chemicals

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

1. Identify the maturity indices for harvesting garlic at the optimum quality.
2. Practice harvesting of garlic.
3. Perform the processes of drying and curing to extend shelf-life of the garlic bulbs.
4. Practice the processes of sorting and grading for the market.
5. Carry out the processes of packaging and storage of garlic.

2.0 Pre-Harvest considerations

Garlic varieties differ considerably in their inherent duration of dormancy, either as measured by the time to sprout in storage or after planting.  The stage of maturity of cloves at harvest has significant influence in dormancy.  Cloves lifted when the leaves are still green, require more time to sprout than mature cloves harvested when the foliage has dried.  Delay in harvesting of garlic bulbs before the tops have fallen over indicating full maturity, results in poor storage.  Delay in harvesting bulbs results in splitting and sprouting of bulbs.  The higher nitrogen application and use of more irrigation in the later part of growth and development is detrimental for garlic storage.  Sprouting is a major problem of garlic storage.

3.0 Harvesting

The harvesting of garlic is similar to that of bulb onions. Garlic is harvested when the tops have fallen and are completely dry. This is usually 100 to 140 days from the day of planting. Farmers should make sure that during harvesting, they are using clean materials for collection such as bins or crates, knives, gloves, bags, or other items used to gather vegetables. Local materials can be used for collection such as wooden crates, baskets made out of palm leaves, or other receptacles to ensure products are out of contact with the ground.

Farmers should also identify suitable locations on the farm for collection that are clean and provide ample shade.  Harvesting can be done by hand pulling or using garden forks. After lifting, the bulbs must be left in windrows to cure for 7 to 10 days in the field. High quality bulbs are clean, white (color is dependent on the variety grown) and well cured. A well-cured bulb is one with a dry neck and outer leaves. The bulb should be firm to touch. The minimum bulb diameter required on the fresh market is 4cm.   The following are some aspects to consider:

Crop matures 4-6 months after planting.

Harvest in August to October when conditions are dry.

Lift bulbs and leave to cure on the ground for a week.

4.0 Post harvest handling

4.1 Drying and curing

These two operations are essential in post-harvest management of garlic. Drying is done to remove excess moisture from the outer skin and neck with a view to reduce storage rot. Sufficiently dried and cured garlic has dry skin tight fitting on each clove, especially the outer ones, and a well-sealed neck on each clove. Curing is an additional process, which helps in development of skin color and bulbs to become compact and go into dormant stage. Curing bulb crops such as onions or garlic entails drying the neck of the crop for up to five days, exposing it to warm and dry temperatures.

Since curing frequently commences before drying is complete, these two distinct processes are collectively called 'curing'. It is considered that the garlic has been properly cured when the neck is tight, the outer scales are dry and it has lost 3 to 5% of its original weight. Garlic bulbs, after harvest, are cured naturally in the field by windrowing in such a way that the bulbs of one row are protected from the sun by the foliage of the adjacent row. This is practiced in places where the temperature is mild.

When curing bulb crops in the field, they can be left in the field exposed to the sun or put in stacks. Crops can be lightly covered to prevent sun burning and should be checked each day to monitor the drying of the neck. Bulb crops can also be cured in burlap sacks. This process may take longer as less airflow passes through, but can provide a uniform curing process. Exposure of bulbs to the sun for longer period may cause damage to the skin making them more vulnerable to storage rot. Normally, it takes about a week for drying of foliage and outer scales.

After field curing, the bulbs are cured in a ventilated shed for 7 to 10 days either with tops or after cutting the tops leaving about 2.5 cm neck intact. The roots are removed completely. It has been reported that garlic with intact leaves has more storage life than the topped garlic. Artificial curing can be done by blowing hot air at 27 to 35"C through the curing room. It takes about 48 hours for complete curing process if relative humidity is between 60-70%. Curing of bulbs is important and beneficial as it extends the storage life of crops for several months.

4.2 Sorting and grading

Garlic bulbs after curing are run over a grader or graded manually before their storage or marketing. All thick necked, split, injured, diseased and insect infested bulbs are removed before storage. Size grading is done after sorting. Knowing what consumers want in terms of taste, aesthetics, and quality standards can better inform what products are suitable to be sold in local markets. Individual markets have their own specific demands for shape, form, color, and food safety. Farmers who understand these standards can focus on harvesting their best products to be sold at the market and use products that don't meet these standards for alternative purposes such as livestock feed or compost. The garlic is graded according to their size (diameter) in three grades; big (30-35 mm), medium (25-30 mm) and small (10-25mm). Only big and medium grade bulbs should be stored. Grading is very necessary for getting better price and to minimize losses on account of decay.

4.3 Packing

The types of packaging materials selected for storage are important to maintain quality and prevent damage. Natural materials may be selected, as they are low cost and readily available, but may not travel well over long distances. Natural materials can also be of lower quality and be less uniform in size or texture, which can cause damage to products.

Some specific materials for packaging that are typically used include wood, paper, plastic or other natural or synthetic materials. Wood has been historically used for the construction of crates, but has recently been replaced by other materials due to their heavy weight and higher costs. Wooden crates are also difficult to clean well, making them harder to use multiple times. Wood packaging can have sharp edges that can damage produce.

Garlic is packed in open mesh jute bags of varying sizes normally between 40kg and 60kg.  According to garlic grading and packing rules, packing should be done in nylon netted bags of 8kg, 25kg and 50kg sizes.  For export purpose, packing should be done in perforated 10 ply corrugated fiberboard boxes of 18kg and 25kg capacity.  Garlic packed in Nylon netted bags have less storage losses because of good ventilation'.

 

Figure 1 Packed garlic

4.4 Storage

Fruit and vegetable storage is helpful to extend product marketability, avoid price drops, keep produce for processing, and reduce losses during long-term storage. While storage provides many benefits for farmers, several issues can arise that lead to reduced quality or increased losses. Certain types of fruits and vegetables may not be suitable for storage.

Poor storage conditions and packaging can also reduce produce quality. At any level of storage, domestic or commercial, garlic should be stored in a cool and dry environment and kept well aerated. This helps to continue the process of drying and curing of any that were not adequately done so. In a commercial store the following can be noted. First, the storage room should be cool and dry. Secondly, to avoid sprouting in storage, the garlic should be stored for a period within dormancy or treated with a sprout inhibitor like maleic hydrazide. The temperature and humidity conditions for storage are as highlighted below:

At higher temperatures of (26 –30°C) garlic can be stored for 1 month

Intermediate temperatures (4.4 –18°C) favors rapid sprouting and high relative humidity cause molding

At 0°C and 65% relative humidity, garlic stores for 28-36 weeks

4.4.1 Points to be considered when constructing storage structures for garlic

It should be constructed in such a manner so that it can maintain the required temperature and relative humidity.

There are two type of storage structures; one row and two row storage structures. The type of structure determines the direction of erecting it as this is an important factor. One row structure should be erected against the flow of wind whereas; two-row structures should be erected along the direction of wind. Therefore, single row should be constructed in North-South direction while double row structure should be constructed in East-West direction.

The width of one stake should not be more than 4 feet. The maximum height at the sides should be 5 feet and at the centre, it should be 8 feet. The length of two-row structure should not be beyond 40-60 feet whereas in one row it can be according to requirement. There should be a minimum 4 feet working space in between two-row structure.

Bottom ventilation of I tool 7u feet should be provided for proper aeration.

The floor and sidewall should be constructed with wooden bantam or bamboos.

The roof should be constructed with asbestos sheet or mangaloro tiles or thatches. Galvanized iron sheets are not suitable for roofing material for storage structures. In case asbestos sheet or if galvanized sheets are used it should be thatched with dry sugarcane leaves or grasses during hot periods.

The structures should be construction at an elevated place. There should not be any waterbody or water stagnation around the storage.

5.0 Deteriorative factors and controls for garlic in storage

Loss or gain of moisture – packaging and control of RH.

Microbial decay or rotting, mainly molds – proper drying and neck sealing.

Sprouting – store within dormancy and/or apply anti-sprout (maleic hydrazide).

Physical injury – gentle harvesting, drying, curing, packaging and stacking in store.

6.0Post-Harvest diseases & Pests

The important storage diseases of garlic include the following:

1. Blue Mold

Penicillium corymbiferum causes this disease. The affected clove becomes soft, shrivels and is covered with blue-green powdery spores. This disease also attacks the crop in the field. The infection is carried from the field and healthy bulbs may carry fungus on the outer scales. Injury to the cloves at harvest should be avoided to control the rots. Proper drying and field sanitation reduce the infection of disease.

Figure 2 Blue mold on garlic

1. Black Mold

 This is caused by Aspergiltus species that causes deposition of black mold on the outer layer of bulbs ancl cloves. The infection can be cured by proper shade curing of bulbs.

Figure 3 Black mold on garlic

1. Mites

Sometimes mite, Aceria tulipae, which is a common pest sucking sap of the leaves causes damage to the cloves in storage. Two other species of mite, Rhizoglyphu.s sp. and Glycohaqus sp. also attack bulbs in the storage. Fumigation of bulbs with methyl bromide after harvest and before storage can control the mite. Fumigation is done with 35 gram of methyl bromide per cubic metres of storage space and the store should be airtight for two hours.

Figure 4 Mite-infested garlic

7.0Evaluation of 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 stage at which garlic is ready for harvesting.
2. Describe the appropriate methods of harvesting garlic.
3. Describe the drying and curing of garlic and give reasons for the action.
4. Describe the sorting, trimming and grading of garlic.
5. Enumerate the deteriorative/spoilage factors for garlic in storage and give the control of each.
6. Describe the conditions for packaging and storage of garlic for market and storage.