2.2 Harvesting
Harvesting is the primary process of collecting the target crop product from the field, where it is open to the vagaries of the climate and the growing environment, and placing that product in controlled processing and stable storage conditions environme nt. The harvesting requirements will differ for the final product sought, and there are specific needs such as maturity and evenness, that will dictate the harvesting management and timing [13] , [14-16] .
Plants should be harvested during the optimal season or time period to ensure the production of plant materials and finished spice products of the best possible quality. The time of harvest depends on the plant part to be used. Detailed information concerning the appropriate timing of harvest is often available in published standards, official monographs and major reference books. However, it is well known that the concentration of biologically target active constituents varies with the stage of plant growth and development. The best time for harvest should be determined according to the quality and quantity of biological target constituents.
During harvest, care should be taken to ensure that no foreign matter is mixed with the harvested plant materials. When possible, p Plant parts should be harvested under the best possible conditions, avoiding dew, rain or exceptionally high humidity. If harvesting occurs in wet conditions, the harvested material should be transported immediately to a drying shed and drying started to expedite drying so as in order to prevent any possible deleterious effects due to increased moisture levels, which promote microbial fermentation and mould. Cutting devices, harvesters, and other machines should be kept clean and adjusted to reduce contamination from soil and other materials. They should be stored in an uncontaminated dry place , free from insects, rodents, birds and other pests, and inaccessible to livestock and domestic animals.
Soil can have a high microbial content, and contact between the harvested crop and the soil should be avoided so as to minimize the microbial load on the harvested plant materials. Where necessary, large drop cloths, preferably made of clean muslin, should may be placed on the soil surface before the plants are used as an interface between the harvested . plants and the soil. If the underground parts (such as the rhizomes roots) are harvested used, any adhering soil should be removed from the plant material as soon as possible it is harvested. Mechanical damage or compacting of raw plant materials as a consequence of overfilling or stacking of bags may result in fermentation composting or rot other damage and should be avoided. Rotting plant materials should be discarded during harvest, post-harvest inspections and processing, in order to avoid contamination and loss of product quality. (modified from the WHO guidelines on good agricultural and collection practices (GACP) for medicinal plants).
2.2.1 Harvesting Seeds and Fruits
i). Maturity - The selection of seed or fruitto harvest which is at the correctmaturity or ripeness, based on colour, is critical to obtaining a product of even high quality. Three examples are given here but maturity standards should be adopted locally for each spice.
Allspice (Pimenta) fruit is harvested 3-4 months after flowering when mature but not ripe (green) fruit is most strongly flavoured . Small or over-ripe berries should be removed as they detract from the appearance of the finished product. Harvesting is undertaken manually by breaking off the twigs bearing the berry clusters. The berry clusters should be placed in a container and not placed on the ground, as soil contamination aids microorganism growth. Leaf oil is also produced from the material collected during the berry harvest or from specialized plantations.
Colour is important for vanilla pod harvest and d aily picking of mature vanilla pods is essential to obtain the correct maturity for processing , as immature pods produce an inferior product and over-mature pods split at curing. The right picking stage is when the distal end of the pod turns yellow and fine yellow streaks appear on the pods. Vanilla pods, when green, are almost odourless but they develop a faint phenolic odour as the beans reach a stage of harvest maturity. The beans are ready to harvest 6-9 months after flowering.
The harvest time of coriander fruit is of paramount importance in determining the quality of the spice. Immature fruit contain higher volatile oil than ripe fruit but have a disagree able aroma. Fruit ripening is progressive from the primary umbels down and judgement is required in deciding the optimum harvest time. The crop should be harvested when the majority of the umbels are a ripe chestnut colour.
ii ). Maturity forend use and pre-drying treatment. The time of harvest maturity is often dependent on the end usage for the spice. Pepper spikes from the vines are hand-picked when one or two berries begin to turn bright orange or red on the flower spike. These are taken to the threshing floor where the berries are separated from the spikes. White pepper is harvested fully ripe; black pepper is harvested fully mature and near ripe; canned pepper at 4-5 months growth; dehydrated green pepper at 10-15 days before full maturity; oleoresin at 15-20 days before maturity; pepper oil at 15-20 days before maturity; and pepper for powder is harvested when the berries are fully mature with maximum starch. In quality terms, the volatile oil percentage (%) decreases with maturity but piperine % and starch % increase. The harvested spikes are collected into clean sacks. Post-harvest handling is crucial to obtain a high quality product Blanching with hot water for one minute is required. This process cleans the fruit and removes other contaminants, and gives a shining black colour to the fruit by activating the phenolase enzymes responsible for producing the black colour. Blanching allows the fruit to dry at a faster rate. Mechanisation of these processes has been undertaken by spraying boiling water onto the fruits as they move on a conveyor belt fitted with mechanical brushes. The blanching time can be adjusted by the speed of the conveyor. The washed and blanched berries pass through sieves where the fruit are graded into selected sizes. The graded peppers are air-dried to remove the surface moisture and then placed in a drying yard or in a drier.
iii) Cultivar difference. The correct harvest maturity is often dependent on the choice of cultivar. Cardamom fruits ripen over an extended period and are harvested every 3-5 weeks. There are maturity differences between cultivars. Fruits are individually picked with their pedicels when they are fully developed but unripe. Some cultivars change colour as they mature while others do not and local experience is necessary to judge the correct harvest time. After harvest, capsules are washed thoroughly in water to remove adhering soil. A pre-soaking of the capsules in hot water at 40°C and dipping the capsules for 10 minutes in a 2% sodium carbonate solution helps increase the green colour of the capsules.
iv) Continuous harvesting In the tropics, a crop can produce and ripen continuously. Nutmeg & Mace trees bear fruit all year. The fleshy drupe turns yellow when ripe. The pulpy outer husk (pericarp) splits into two halves exposing a purplish-brown seed surrounded by a red aril. The fruits are often allowed to split and fall to the ground before harvesting when they should be collected as soon as possible to prevent discolouration and the risk of mould or insect damage. A long pole may be used to take partially opened pods directly from the tree and this ensures a better quality aril but can result in damage to flowers and younger fruit. The frequency with which nutmegs are harvested is dependent on the availability of labour, level of production and the market price, but a daily harvest to every 2-3 days in off-peak times is typical.
v) Chemical manipulation of ripeness. Colour stage, that is the ripeness, dictates the harvesting maturity of chilli peppers for spice production. Chilli fruit on the bush have a wide range of ripeness due to the growth habit of the chilli plant and choice of cultivar. Fruit ripen from green, to green with some light red, to all light red, to deep red. Fruit of deep red colour are used for spice production. Partial drying of fruit on the plant does not reduce quality, as fruit will be dried in processing. Immature light red chilli has low colour content and spice quality, while the colour stability of red chilli spice is best when harvest is delayed. As the plant grows there is an increasing number of fruit set as branchlets develop and thus there is also a sequential maturity of fruit. To obtain high yields there is a need to allow the last fruit set to ripen. This can be done by either harvesting mature fruit repeatedly or by leaving fruit on the plant for an once-over harvest. The latter is needed for machine harvesting. Heat levels of fruit of the first fruit set is also likely to be higher than the last fruit set because of increased competition for the pungency precursors. Ethylene, a natural ripening hormone, in the form of ethephon sprays, is used to synchronize chilli ripening to make mechanical harvesting possible.
