Review
Development and performance evaluation of a medium-scale system for processing Bitter leaf
J.k.  Tangka P.M. Penda
Department of Agriculture Engineering,University Of Dschang,FASA, P.O. Box 373,Dschang,Cameroon
A R T I C L E   I N F O                                          A B S T R A C T                             Article History:                                                       In this review article,the  importance
Received 3 Aug 2005                                         importance  of vernonia leaf and its post harvest         
Accepted 17 Nov 2006    technology are discussed.This
Available online 21 jan 2007                                 review reveals the possibility of
Keywords:                                                                cultivation of vernonia plant in
Vernonia leaf                                                            Nepal.The difficulties in post-
Post harvest processing                                        harvest processing is also discussed
Bitterness                                                                 and after analysis found that
Vegetable    manual processing of vernonia is
Juice                                                                           better to practice machinery
Machinery system                                                    system.
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
                                                                

                                                                                                                                           
    1.Introduction
    Bitter  leaf (Vernonia spp.) is a vegetable with dark green leaves belonging to the family Asteraceae.It is abundant in tropical countries (stevels,1990)occurs in wild but some domestication efforts have been tried in some countries (Misari,1992Tagwira,1996Fomum,2000Akachuku,2001).Among 1000 species (stevels),some species like Vernonia pobeguini, V. galamensis are rich in Vitamin A,B,C &K,cellulose ,fibres,iron ,Mg,Mn,Ca and proteins(Njonga,1984Akachuku).In some regions of the world are cultivated for their leaves ,and in others for oil extracted from their seeds.Almost all the species are very bitter in taste,the bitterest species being V.pobeguini (Kalanda &Lisowski,1995). The bitterness of the leaf is caused by the presence of saponines and sesquiterpene lactones (Kuo et al., 2003 Erasto et al.,2006) a considerable quantity of this vegetable are exported annually to Europe and America from Africa (Besong & Abia ,1998).Before exportation, the bitter leaf is processed.Processing involves chopping the leaves very finely and washing them until the bitterness is reduced to an acceptable level.It is difficult to qualify the end point of processing because this is normally done using organoleptic tests.After washing,the vegetable is dried and packaged for storage ,refrigerated or cooked immediately.The manual processing of Vernonia is very tedious,time consuming and has very little yield per effort  employed. In some markets,the processed Vernonia commands a price of 5 times more than that for fresh leaves . Despite,the high demand for this vegetable in the international market ,there is no machinery for post-harvesting processing.There is the need for the mechanization of process in order to increase productivity.Some species are known as iron weed.They are known for having intense purple flowers.The Genus is named for English botanist William Vernon.      
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doi:10.1016/j.biosystemseng
2.Practical utilization of of vernonia
The juice extracted from Vernonia can be used in the production of beer(Mbinglo,1998).Vernonia is used as fuelwood in the smoke treatment of seeds against rot caused by fungi such as Curvularia,Aspergillus,Fusarium and Penicilium(Misari). This plant has also great medicinal value . The bitter juice from leaves is taken for stomach problems and infertility(Njonga). Both the leaves and juice are consumed as a laxative (stevals). For malaria treatment , the roots are boiled and the concoction is used in vapour bath(kalanda &Lisowski).
The juice from the leaves of this plant is used as an iodine tincture  on wounds.(Misari)and for the treatment of intestinal nematodes in animals and humans.It is used to treat schistomiasis,a disease caused by parasitic worms,it also work well in treating diarrhea and malaise(koshimizu  et al.,1994). It is also used in toothache and diabetes patient,blood purifier and uterus toner.Vernonia spp. are used as food plants by the larvae of some Lepidoptera sps. They are very effective in contolling insect-pest.Vernonia is applied in abortion and cancer.Howevr it is worth noting that some species V.galamensis have antinutritional components such as tannins,enocetol phosphates(Malathus and Angelini,2005) and fatty acids (Baye et al.,2005)

3.Post-harvest processing of Vernonia
The harvested leaves are washed and macerated with a mortar and pistel.After that the leaves are wshed until the bitterness reduces to an acceptable level.In some communities,after choppin the leaves are put into warm water and some KOH is added . Salt helps to maintain the green colour of the vegetables that determines acceptability of the processed product. The processed vegetable is exported in refrigerated form or dried &package form . It takes at least 3 hrs to do with loabur intensive,copious quantities of weter to completely process about 1Kg of the leaves.
     Owing to all these problems this research exercise was carried out in order to design,fabricate  and test a machinery system that would cut, wash and spin the bitter leaf in one batch . Compared with the manual method of processing Vernonia ,the machine reduced processing time by a factor of about 60.




4.Concluding remarks
This review revealed the importance of Vernonia leaf and is located especially in different Asian countries such as Nepal,India and Bangladesh.This plant don?t need much care to grow but manual processing is difficult so,machinery system should be practiced which makes processing easier and faster.
References
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