Ginger
Product Care

Harvest Maturity

Ginger Post-harvest Handling and Market Preparation Information Sheet (1.14MB)

The principal indices used to determine ginger harvest maturity are foliage senescence and rhizome size. Ginger should be harvested once the foliage begins to turn yellow and starts to dry. This natural aging process typically begins between 7 to 9 months after planting. One sign of maturity for the rhizome is yellowing foliage. Rhizomes will not continue to enlarge and grow without healthy foliage. Delaying harvest until all of the leaves have died is not recommended as it will reduce rhizome quality, increase fiber content, decrease storage life, and increase the incidence of sprouting.

When market demand for ginger is high, it is more cost-effective to harvest prior to the beginning of natural senescence. In this case, several randomly selected plants should be sacrificed and dug up to determine average rhizome size. If the size is acceptable, the remaining plants can be harvested. If the rhizomes are too small, they will require additional time to grow. The early harvest of non-senescent plants can result in more weight loss and decay. The skin of early harvested ginger is very tender. Furthermore, the fresh wound created at the point of separation between the stem and rhizome will be difficult to heal.

Harvest Methods

Ginger is almost entirely harvested by hand in Guyana, although mechanical digging devices are available for use on large-scale plantings. The initial step in harvesting is to remove a significant portion of the senescent foliage with a machete to make the rhizomes more accessible. Ginger is dug by hand using a fork or cutlass to loosen the soil around the crown of the plant. The process should be done carefully in order to avoid damaging the rhizomes. The rhizomes should be gently pulled out of the soil using the remaining length of stem as a handle. Care should be taken not to injure the ginger, which has a delicate skin and is easily wounded during harvest and handling. Ginger harvested early will still have an actively growing green stem attached to the rhizome which needs to be snapped or cut off slightly above the point of attachment to the rhizome (Figure 1).

Excess soil and roots should be removed by hand before placing the rhizomes in the field container. Cotton gloves are typically worn to facilitate field cleaning. The rhizomes should never be thrown or dropped. Ginger should be pre-graded in the field and any unmarketable, damaged, or diseased rhizome should be discarded (Figure 2). Wounded tissue is an entry point for decay causing bacteria and fungi.

Avoid leaving the rhizomes exposed to direct sun for longer than 30 minutes. The harvested ginger should be placed directly into strong well-ventilated wooden or plastic field crates for removal from the field (Figure 3). Transporting ginger in mesh sacks will increase the level of skin damage due to rubbing of the delicate skin against the mesh. Harvesting during very wet or very dry conditions is not desirable as this will increase the amount of skinning and make removal of the rhizomes from the soil much more difficult.

Larger scale growers may elect to use a modified potato digger to mechanically harvest ginger. These diggers perform best when the ginger is grown on raised beds in straight rows. The rhizomes are lifted out of the ground with a metal shovel which undercuts the rhizomes and lifts them to the top of the soil. Rhizomes are then picked up by hand after excess soil and roots are removed.

Preparation for Market

Cleaning

Relatively clean rhizomes sold in the domestic market may not require any further cleaning. However, ginger intended for export must be thoroughly cleaned before packing. Also, the ginger intended for long-term storage should be washed immediately after harvest and then cured. A considerable amount of hand labour is required. Soil adhering to the rhizome should be removed and the roots and stem may have to be trimmed back. Ginger should be scrubbed by hand or with a soft-bristled brush in clean water sanitized with 150 ppm hypochlorous acid (Figure 4). The rhizomes should be washed as soon as possible after harvesting, as soil is more difficult to remove when dry. Care is required during this operation to prevent rhizome breakage. Broken, split, or bruised rhizomes are susceptible to decay and shrinkage.

The water pH should be maintained at 6.5 for optimal sanitizing activity of the hypochlorous acid. The water needs to be changed after it builds up with soil particles and the 150 ppm hypochlorous acid concentration cannot be maintained. A fungicide treatment is also recommended and can be applied in the wash tank or as a separate overhead spray application after cleaning (Figure 5). Recommended fungicides are benomyl (500 ppm active ingredient) or thiabendazole (1000 ppm). After the cleaning process, the ginger should be air dried, sorted, and packed.

Sorting

Remove all damaged and injured rhizomes. The remaining marketable rhizomes should be sorted according to size and overall appearance. The ginger surface should be clean, bright yellow-brown, and appear fresh. It should not be wilted or have any evidence of sprouting. The rhizomes should be free from bacteria or fungal infection and not have any objectionable skin blemishes. High quality ginger is characterized by large thick rhizomes with limited branching, light skin colour, and a glossy appearance (Figure 6). The skin colour will slowly darken and lose its shine during storage.

The minimum rhizome size for export is 250 g (9 ounces). There is no maximum size limit. The main stem should not be less than 3 cm (1.25 in) thick and 12 cm (5 in) long. Market requirements demand that rhizomes be large and well-formed with limited branching. Rhizomes which have more than 4 side branches should not be packed for export (Figure 7). The skin should be tight and light brown. Export quality ginger should be smooth and firm, with uniform shape and size, be free from insect damage and decay, and have a uniform peel colour typical of the variety. The internal flesh should be firm and uniformly coloured, without any indication of darkening. Depending on type and cultivar, ginger flesh colour should either be cream or pale yellow.

Packaging

Ginger of roughly similar size per rhizome should be packed in each market container. The container should be strong, well-ventilated, and capable of being stacked without damaging the rhizomes. For the domestic market, wooden crates provide better protection to the ginger than mesh or synthetic sacks. For the export market, ginger rhizomes should be placed in a clean, strong, well-ventilated fiberboard carton (Figure 8). The carton should have a minimum bursting strength of 275 lb per square inch. A two-piece full telescopic corrugated carton is preferred. A double-walled self-locking waxed carton is also acceptable. The surface of the rhizomes should be thoroughly dry prior to packing. Wet or damp ginger should not be packed into cartons destined for export, as surface mould will soon develop. Ginger destined for export should be loosely packed in layers inside the carton. The carton should not be overfilled. Net carton weight is typically 10 kg (22 lb) for the U.K. export market and 14 kg (30 lb) to North American destinations. However, carton size and weight may vary depending on the market destination and importer requirements. For marine shipments, an additional 5% packing weight is needed to account for weight loss during transit.

Curing

Ginger intended for storage should be cured by air drying the rhizomes at ambient temperature (22°C to 26°C or 71°F to 79°F) and 70% to 75% RH for several days to allow the skin to thicken and the cut surfaces to suberize. Curing will help reduce postharvest weight loss and decay. Following this brief curing treatment, the ginger should be put in well-ventilated containers for long-term storage.

Temperature Management

Ginger may be successfully stored for several months if the correct postharvest handling and storage procedures are utilized, and healthy, undamaged rhizomes are initially selected. The optimal temperature for storing and transporting ginger is 12°C (55°F). At this temperature, the rhizomes will remain in marketable condition for at least 3 months, depending on initial rhizome vigor and condition. Holding ginger at ambient temperatures (25°C to 30°C or 77°F to 86°F) will result in high moisture loss, surface shriveling, and sprouting of the rhizome. Market life under these conditions is less than 1 month. Therefore, ginger exports from Guyana can be made in non-refrigerated marine containers if the rhizomes are shipped within a week of harvest. At the other temperature extreme, ginger is very sensitive to chilling injury and should not be stored below 12°C (55°F).

Relative Humidity

Dehydration is a common postharvest disorder of ginger held under low relative humidity (RH) conditions (i.e. less than 65% RH). Shriveling of the rhizome becomes noticeable after the loss of more than 10% of the initial harvest weight. On the other hand, surface mould will begin to grow at a RH above 90% and sprouting will be stimulated, especially if the temperature is above 16°C. In order to minimize weight loss but avoid surface mould, a compromise RH range of between 70% to 75% is recommended for storing ginger. Ginger stored at 22°C (72°F) and 70% RH for 3 months will lose about 20% of its initial weight.

Principal Postharvest Diseases

Postharvest disease in ginger is normally due to rough harvesting and handling practices which result in injury to the skin and flesh of the rhizome. Holding ginger at a less than optimal temperature and RH will accelerate postharvest decay. Postharvest losses from diseases are caused by various fungi and bacterial soft rot. Decay can be kept to a minimum by following careful harvesting and handling practices, sanitation of the wash water, curing of the rhizomes after washing to promote wound healing, application of a postharvest fungicide, and holding the rhizomes at 12.5°C (55°F) and 70% to 75% RH.

Blue Mould

Blue mould, caused by the fungus Penicillium, is a common postharvest rot of ginger stored at a high RH. Blue mould generally requires moisture condensation on the rhizome surface, or storage at a RH above 95%. Mild surface infestations may be superficial only and not cause decay. However, the ginger has an unsightly appearance. Blue mould which develops on cut ends and injured areas will typically result in internal tissue decay (Figure 9). The rotted tissue is pale to dark brown, and may be firm or soft. Decay is particularly rapid at temperatures between 15°C and 20°C (59°F and 68°F).

Dry Rot

Dry rot, caused by the soil-borne fungus Fusarium, is a common postharvest disease of ginger. Infection is typically associated with wounds or insect and nematode damaged tissue. External symptoms of dry rot include off-coloured dry sunken lesions on the rhizome surface. The lesions are typically bordered by a brown margin. The fungus subsequently invades the entire rhizome, which becomes brown, dry, and shriveled. In humid environments, the ginger surface may become covered with a dense white mould (Figure 10). Internal symptoms include a pale brown discolouration of the vascular tissue.

Watery Rot

Watery rot, caused by the fungus Rhizopus, is one of the most rapidly developing storage rots of ginger. Symptoms include a soft, watery rot that progresses rapidly and may rot an entire rhizome in a week. Infected tissue is mottled brown and soft, and in a humid atmosphere the infected area is soon covered with large amounts of white mould. The mould will eventually turn black. Rhizopus is a wound pathogen and is not effective in colonizing healthy tissue. The postharvest fungicide 2,6-dichloro-4-nitroaniline (Botran) applied just prior to packing may reduce watery rot during transport to export market destinations.

Pythium

Pythium is another common soil-borne fungus that can be severe on ginger harvested during the rainy season or on rhizomes grown in poorly drained soils. Symptoms appear as small brownish spots on the skin, which may rapidly enlarge into sizeable lesions. As the decay progresses, the tissue breaks down into a soft and watery mass.

Armillaria Rot

Armillaria rot, caused by the fungus Armillaria mellea, can be a problem on ginger grown in recently cleared forest land. Symptoms include the development of tough, dark, string-like growths which adhere to the rhizomes (Figure 11). These structures are aggregations of fungal strands, commonly called the ‘shoe-string fungus’. Control involves the uprooting of all remaining tree stumps.

Sclerotium Rot

Sclerotium rot, caused by the soil-borne fungus Sclerotium rolfsii, is most commonly found on rhizomes harvested from stressed plants. Symptoms of decay include a well-defined separation between rotted and healthy tissue. A white mould forms on the ginger surface and noticeable shrinkage of the rhizome occurs. Small spherical fungal resting bodies about 1 to 2 mm (0.04 inch to 0.08 inch) in diameter develop on the mould. They are initially white but later turn brown.

Bacterial Soft Rot

Bacterial soft rot, caused by Erwinia carotovora, is the principal postharvest bacterial disease of ginger. These bacteria are widespread, especially in poorly drained soils, and enter the ginger rhizome via wounds in the tissue. Symptoms of bacterial soft rot include a soft wet rot of the tissue, which has a strong foul odour. Development of this disease is rapid under warm, humid conditions.

Postharvest Disorders

Sprouting

Ginger rhizomes will sprout at temperatures above 15.6°C (60°F). Sprouting may begin after several weeks at ambient temperature (Figure 12). The rate of sprouting grows as the temperature increases. Keeping temperatures at 12.5°C (55°F) will prevent sprouting. There is no effective chemical sprout inhibitor for ginger.

Chilling Injury

Ginger rhizomes are very sensitive to chilling injury (CI) or low temperature breakdown if stored below 12°C (54°F). CI is a physiological disorder that results in pitting and sunken lesions on the rhizome surface, shriveling, softening, flesh darkening, and postharvest decay (Figure 13). Shelf life is significantly shortened and eating quality of chilled rhizomes is inferior to non-chilled rhizomes.

The amount of CI damage to the ginger rhizomes depends on the specific temperature and the duration of exposure to the low temperature. The lower the temperature and longer periods of exposure will result in more CI. Also, the damage is cumulative. Slight injury may occur after 5 days at 7°C (45°F). Uncured rhizomes are more susceptible to chilling injury than properly cured rhizomes. Two weeks of exposure at 7°C (45°F) will result in significant CI and decay to uncured rhizomes.