FOOD HAVEST MANANGEMENT

&PROCESSING

POSSIBILITIES OF CLOVES

YOHANANTH SIVANANTHAN

CLOVE

Clove, Syzygium aromaticum, is a monoecious (both male and female flowers on the same plant) evergreen tree in the family Myrtaceae grown for its aromatic flowers.

The many branches of the tree are semi-erect with smooth oval shaped leaves.

The branches end with a 3–4 flowers near the tip with one terminal flower and the others opening below it.

The leaves, flowers and bark all have a distinct smell. The clove is the unopened flower buds. The tree grows 8–15 m (26–50 ft) tall and can live to be more than

100 years old. The clove tree may also be referred to as tropical myrtle and are

native to the Molucca Islands. 

Clove is mainly grown in Mid Country wet zone of Sri Lanka.

Kandy, Kegalle and Matale districts are major growing areas

The clove tree is a small evergreen tree that grows to a height of 12-20 metres.

Clove Tree

It thrives in coastal regions with temperatures between 15 and 30oC,average rainfall and a distinctive dry season(the optimum level of rainfall is 1750 to 2500mm a year).

It is a low altitude plant that grows best at altitudes lower than 300m above sea level although it will also grow at altitudes above 900m.

The young leaves of the clove tree are bright pink and change to a greenish yellow as they mature.

The flowers develop in cluster of three to ten groups,each will three flowers per group.

These flowers are dried and grinded to use for cooking. Euglenol is responsible for that distinct aroma and taste

that the cloves have. Eugenol is a phenyl propene,an allyl chain-substituted

guaiacol, Eugenol is a member of the phenylpropanoids class of

chemical compounds. It is a clear to pale yellow oily liquid extracted from certain essential oils especially from clove oil,nutmeg,cinnomon basil and bay leaf..

It is slightly soluble in water and soluble in organic solvents.

Clove tree Clove buds

Clove foliage Clove fruit

Clove flower

Dried Clove

Clove fruits in tree

Soils and Climatic need

Soil

Clove thrives well in a variety of soils.Deep and rich loams with high humus content are best suited for the crop.It also grows satisfactorily on laterite soils.Pure sandy soil is unsuitable for this crop. Clove does not tolerate water logging and therefore land selected for this crop should be well drained.

Climate

Clove grows well in a humid tropical climate from sea level up to 1000m elevation.An average rainfall of 1750- 2500mm,per annum is sufficient. It is however, necessary that dry periods alternate with moist ones for good flowering.The annual average temperature should be 20 o - 30o C without much seasonal and diurnal variation.Persistent strong winds are harmful. Shade is essential during the first two or three years of growth. Thereafter full exposure to light is beneficial.

Crop Establishmentplanting material

Clove is propagated through seeds. Tree ripe fruits should be sown immediately since the viability of seeds is rapidly lost within 48 hours of collection.

Seeds obtained by removing outer pulp show early and uniform sprouting. The seeds are sown in perforated polythene bags consist of equal parts of well decomposed farm yard manure, top soil and coarse sand. The size of the polythene bags may vary from 10 Χ 20cm to 25 Χ 40cm depending on the time kept in nurseries before field planting. Bigger plants (15-20 months) establish better in the field.

Field plantingSpacing: 20’Χ20’(250 plants/ha)Temporary shade for 2-3 years is necessary. Artificial shade for newly established plants may be required during sunny seasons. Whenever possible ground cover crops such as leguminous sps, which do not compete with clove, should be established as a soil conservation measure.

PropagationClove is commercially propagated from seeds which are planted soon after harvest.

Seeds should be collected and extracted from the fruits of healthy mother plants exhibiting desirable characteristics.

The seeds are extracted by soaking the fruits in water and peeling the skin from the fruit.

The seeds can be planted in prepared nursery beds or polyethylene bags containing a mixture of soil and aged manure and should be planted to a depth of 2 to 5 cm (0.8-2.0 in) and spaced 12 to 15 cm (4.7-5.9 in) apart.

Germination usually occurs within 1 to 6 weeks. The seedlings should be shaded to protect them from harsh sunlight. The seedlings should be kept moist through regular watering and can be transplanted when they reach at least 30 cm (11.8 in) in height. The seedlings should be hardened off by exposing them to increasing amounts of sunlight before the are transplanted to the field. 

Clove nursery

Crop managementfertilizer applicationRecommended mixture - 625 kg / ha at the 10th year and after (density 250 plants/ha)

Crop protectionDiseasesNo serious diseases and pests have been reported in Sri Lanka

PestsNo serious pest and diseases have been reported in Sri Lanka except wilting of nursery plants in large proportions. The incidence of wilting can be controlled by controlling shade and water application. Leaf spotting due to Pestalots sp. and Collectotrichum sp is fairly common in nurseries and during wet weather, but do not seem to have any serious effects. 

 

COMMON PESTS AND DISEASES

Dieback (Eucalyptus canker) Cryphonectria cubensis

Symptoms- Once fungus enters a wound on a branch it moves downward until it reaches the branch junction; all branches above the junction die backcause – FungusComments - Fungus attacks wounded areas of the plant 

Management - Avoid causing damage to trees with machinery and tools; protect pruning wounds with appropriate fungicide; infected parts of trees should be pruned out and burned; any resultant wounds should be treated with fungicide paste

Nematodes (Ring nematode, Reniform nematode, Common spiral nematode) Criconemoides spp. Rotylenchulus reniformis Helicotylenchus dihystera

Symptoms - Dark lesions on roots; stunted plant growth; yellow leaves; slow growth and low yield

Cause – Nematode

Commen - Damage from nematodes often promotes root infection by bacteria and fungi

Management - Solarizing soil can reduce nematode populations in the soil and levels of inoculum of many other pathogens

 

Coconut scale Aspidiotus destructorSymptoms - Pale yellow spots on leaves; entire leaves yellowing; leaves turning brown and dropping prematurely; adult insect is a flattened oval, resembling a scale, which is red-brown in color

Cause – Insect

Comments - Insect also attacks other crops such as coconut, tea and mango

Management - May be possible to control coconut scale by pruning infested parts of trees and destroying by burning; chemical control may be necessary

Oriental fruit fly Bactrocera dorsalis

Symptoms - Dark brown to black lesions on foliage; adult insect is a small fly with a bright yellow abdomen with a distinctive dark "T-shape" pattern; larvae are cream-white maggots which burrow into fruit

Cause – Insect

Comments - Oriental fruit flies are serious pests of many crops including mango, avocado, guava, pineapple and papaya

Management - One of the most effective methods of controlling the oriental fruit fly on many crops is to bag the fruit in paper bags or polythene sleeves to prevent oviposition by female flies; chemical sprays are most effective when combined with a protein bait to attract the insect

Soft scale Ceroplastes floridensis

Symptoms - Reduction in plant vigor and viability; wilting leaves with abnormal coloration; stick residue on leaves; insect is a a rounded scale covered in white or pink-white waxy substance

Cause – InsectComments - Large populations of soft scale promote the development of sooty mold

Management - Natural enemies of the soft scale can generally provide good control of the pest; application of horticultural oil may be applied if scales become problematic; healthy plants are less susceptible to scale damage than those which are stressed so adequate irrigation and fertilization are important in scale management

Sumatra disease Ralstonia syzygii

Symptoms - Dieback of trees which begins in the crown and leads to tree death within 3 years of initial infection; leaves turn chlorotic and drop from the tree or may wilt and remain attached; discoloration of vascular tissues evident as gray-brown streaks in new wood; bacterial exudate may ooze out of tissue when cut

Cause – Bacterium

Comments - Bacteria are limited to the water-carrying vessels in the tree (xylem); the disease is thought to be transmitted by Hindola striata and Hindola fulva, both sucking insect species

Management - An antibiotic - oxytetracycline - can be injected into the tree to slow the decline of infected trees but there is currently no known cure for the disease; several insecticides can give control of Hindola insect species which are believed to spread the disease

 

PROCESSING OF CLOVES Clove must be dried before they are stored

and sold for market.This brief outlines the important steps that should be taken pre-harvest and post-harvest to ensure that the dried cloves are of top quality for the market.

Harvesting

Pretreatment

Winnowing

Grinding

Packaging

Storage

CLOVES FIELD TO FACTORY

HARVESTING

Cloves trees are first harvested when the tree is 6-8 years old.

The timing of harvest of the clove buds is critical.

The buds should be harvested before the purple or crimson flowers start to develop.

The correct time of harvest is when the outer green leaves of the flower bud change from olive green to yellow pink and before the petals fall to expose the stamens.

Clusters of flower buds are hand picked from the branches.It is important that the branches are not removed or damaged as this will reduce the yield of future crops. .

The harvesting season commences usually in December and extends up to the end of April depending upon the locality.

The average yield of dry cloves in Sri Lanka is about 250kg/ha.Under good management conditions a yield of abut 850kg/ha can be obtained

PRE TREATMENT

harvest the buds are detached from the stalks by holding a cluster in one hand,pressing it against the palm of the other hand and slowly twisting so that the buds fall off.

The hands of the processor and the room in which the buds are separated must be very clean to prevent contamination of the cloves.

The stems and buds are separated and dried separately.The stems can be used for oil distillation.

DRYING The buds have to be dried quickly or

they will start to ferment.

They are usually dried in the sun,spread on clean mats.The cloves should be raked and turned frequently to ensure they develop an even brown colour.

The colour of buds changes from pale russet to a darker brown as the clove dries.The drying process takes about four or five days.It cannot be speeded up or the cloves will become dry,brittle and withered rather than plump.

The final moisture content of the dried cloves should be 8-10%.Experienced clove dries will know when the cloves are fully dry as the buds will snap easily.during the rainy season,cloves should be dried using a mechanical drier such as a tray drier.

badly dried cloves are pale brown and classified as khuker.

WINNOWING AND GRINDING Winnowing

The dried buds are winnowed using a traditional winnowing basket to remove dust and other foreign matter.Small cleaning machines are available that use a blower to remove the dirt and dust.

Grinding

Grinding can be a method of adding value to a product.

However,it is not advisable to grind spices.

After grinding,spices are more vulnerable to spoilage.The flavor and aroma compounds are not stable and will quickly disappear from ground products.The storage life of ground spices is much less than for the whole spices.It is very difficult for the consumer to judge the quality of a ground spice.It is also very easy for unscrupulous processors to contaminate the ground spice by adding other material.Therefore most consumers,from wholesalers to individual customers,prefer to buy whole spices.Dried cloves are usually sold whole.

PACKAGING

Cloves can be packaged in polythene bags of various sizes according to the market demand.

The bags should be sealed to prevent moisture entering.

Sealing machines can be used to seal the bags.Attractive labels should be applied to the products.

The label needs to contain all relevant product and legal information the name of the product,brand name,details of the manufacturer,date of the manufacture,expiry date,weight of the contents,added ingredients plus any other information that the country of origin and of import may require

STORAGE Dried cloves must be stored in moisture proof containers

away from direct sunlight. It is essential that the cloves are fully dry before they

are stored.Any moisture within the bags will cause the cloves to rot.

The stored cloves should be inspected regularly for signs of spoilage or moisture.

If they have absorbed moisture,they should be re dried to a moisture content of 10%

The storage room should be clean,dry,cool and free from pests.

Mosquito netting should be fitted on the windows to prevent pests and insects from entering the room.

Storing smelling foods,detergents and paints should not be stored in the same room as they will spoil the aroma and flavor of the cloves.

PROPAGATION

Seed propagation is commercially practiced in clove.

Seeds are collected from selected ripe fruits of the ‘mother tree’ and then they are soaked overnight before sowing them in the nursery beds.

Seed pericarp is removed before sowing. It is advisable to sow the seeds immediately

after harvesting. Another propagation method adopted for

commercial cultivation of cloves is ‘approach grafting’.

Approach grafting of clove on its own rootstock is successful