Why Nige­ria should pro­mote ste­via plants pro­duc­tion – RMRDC boss

Sunday Trust - - AGRIC BUSINESS - By Hus­sein Ya­haya

Ste­via is a sweet­ener and sugar sub­sti­tute ex­tracted from the leaves of the plant species Ste­via re­bau­di­ana, na­tive to Brazil and Paraguay. Dr. Ibrahim Hus­saini Dogo, the Direc­tor-Gen­eral of the Raw Ma­te­rial and Re­search De­vel­op­ment Coun­cil (RMRDC), in this in­ter­view, ex­plained why Nige­ria must fully em­brace its pro­duc­tion for bio sugar ex­trac­tion. Ex­cerpts:

RMRDC in­tends to go into pro­duc­tion of ste­via, which I doubt many Nige­ri­ans know much about. Can you give us a vivid de­scrip­tion of the plant and its cul­ti­va­tion po­ten­tials in Nige­ria?

Ste­via re­bau­di­ana is a nat­u­ral sweet­ener with zero calo­ries that has re­cently been found in wide­spread use in food and phar­ma­ceu­ti­cal in­dus­tries glob­ally. It is a nat­u­ral sweet­ener with high medic­i­nal and com­mer­cial im­por­tance.

Ste­via is a sub­trop­i­cal peren­nial herb, be­long­ing to the fam­ily, aster­aceae. It has an­nual, sub­lig­neous, more or less pubescent stems with ex­ten­sive, fi­brous and fil­i­form root sys­tem. The cul­ti­vated ste­via plant grows vig­or­ously, giv­ing a branched bushy shrub­like ap­pear­ance. Ste­via is na­tive to Paraguay and Brazil and is of­ten re­ferred to as sweet herb, horny leaf, honey yerba and candy leaf. The leaf has been used for cen­turies as a sweet­ener to coun­ter­act the bit­ter taste of var­i­ous plant medicines.

In 1964, this crop was cul­ti­vated com­mer­cially for the first time in Paraguay and later in­tro­duced to a num­ber of coun­tries. It is now suc­cess­fully grow­ing un­der dif­fer­ent cul­ti­va­tion con­di­tions and cli­matic lo­ca­tions of the world. Ste­via seeds re­main vi­able for a lim­ited pe­riod and have very low ger­mi­na­tion rate be­cause of their small size. Be­ing a highly het­erozy­gous specie, there is also vari­a­tion in the plants raised from the seeds. They do not pro­duce true-to-type plants, and there­fore con­stant re-se­lec­tion for type is re­quired in mother-seed plots.

Ste­via is mainly prop­a­gated veg­e­ta­tively by stem cut­tings, al­though it is a labour in­ten­sive pro­ce­dure. Care­ful se­lec­tion of the plant is re­quired to get more pro­duc­tiv­ity and prof­itabil­ity.

Ste­via prefers a well-drained fer­tile sandy loam or loam soil high in or­ganic mat­ter. It prefers lighter acidic to neu­tral (pH 6-7) soil for bet­ter growth. It re­quires con­sis­tent sup­ply of wa­ter, but ex­ces­sive ir­ri­ga­tion in wa­ter log­ging soils can cause stem rot disease. It re­quires par­tial shade dur­ing very hot and long sunny days.

Fer­tiliser re­quire­ment for ste­via is mod­er­ate and varies ac­cord­ing to the en­vi­ron­ment and soil type. The plant prefers low lev­els of ni­tro­gen, but high lev­els of phos­pho­rus and potas­sium. Un­der av­er­age cli­matic con­di­tions and soil type, 70kg Ni­tro­gen, 35kg Phos­pho­rus and 45kg Potas­sium per hectare has been rec­om­mended.

Why does the coun­cil in­tend to go into pro­duc­tion of ste­via when Nige­ria has so many plant species that are yet to be de­vel­oped?

This is a very bril­liant ques­tion. It is true that Nige­ria has more than 500 plant species. A lot of work has been done on plant bio­di­ver­sity lo­cally. It is also true that the in­dus­trial po­ten­tials of some of them have not been ad­e­quately stud­ied. Let me, how­ever, say that global in­ter­est in ste­via is be­cause of its spe­cial at­tributes. To­day, ste­via is be­ing pro­moted in most parts of the world for use in bio-sugar pro­duc­tion. The World Health Or­gan­i­sa­tion (WHO) is of the opin­ion that within the next few years, 20 per cent of the sugar con­sumed in most coun­tries would be re­placed by bio-sugar. Em­pha­sis is be­ing shifted from sweet­en­ers pro­duced from chem­i­cal com­po­nents as they can­not con­trol the in­ci­dence of di­a­betes that is rav­aging the world.

Do you think it can be com­mer­cialised in a coun­try like Nige­ria?

Ste­via can be com­mer­cialised in de­vel­op­ing coun­tries in view of its in­her­ent value. Presently, it is com­mer­cially cul­ti­vated in China, Ja­pan, Brazil, Canada, USA, UK, Spain, Bel­gium, Aus­tralia, South Korea, Thai­land, Is­rael and Tai­wan. China and Ja­pan are the world’s ma­jor pro­duc­ers and ex­porters of diter­pene gly­co­sides. Ja­pan has ap­proved the use of ste­vio­side in many food prod­ucts, in­clud­ing ce­re­als, teas and soft drinks.

In In­dia, ste­via was in­tro­duced in the last decade as a re­sult of high de­mand due to its huge di­a­betic pop­u­la­tion. It has been suc­cess­fully cul­ti­vated in many In­dian states like Rajasthan, Ma­ha­rash­tra, Pun­jab, Ker­ala and Orissa. High de­mand for nat­u­ral sweet­en­ers as com­pared to ar­ti­fi­cial ones drove the farm­ers in In­dia to­wards large-scale ste­via cul­ti­va­tion.

In these economies, ste­via cul­ti­va­tion and pro­cess­ing are fast de­vel­op­ing into multi-mil­lion dol­lar en­ter­prises. If ad­e­quately pro­moted, I am sure a num­ber of phar­ma­ceu­ti­cal com­pa­nies will latch unto it. Presently, the Na­tional Agency for Food, Drug Ad­min­is­tra­tion and Con­trol (NAFDAC)-reg­is­tered im­ported bio-sugar is sold in many su­per­mar­kets in the coun­try.

Con­sid­er­ing the high rate of post-

har­vest losses in Nige­ria; which is about 30 to 70 per cent on an­nual ba­sis, how do you in­tend to en­sure that this ini­tia­tive does not go the same way?

Ste­via leaves are ready for first har­vest­ing af­ter four months of plant­ing, and sub­se­quent har­vest­ing can be done af­ter ev­ery three to four months. On an av­er­age, one can get three to four com­mer­cial har­vests in a year, depend­ing on land type, va­ri­ety and cli­matic con­di­tions. Young ac­tively grow­ing shoot sec­tions and leaves have high gly­co­side con­tent and over-ma­tured leaves show­ing chloro­sis have less gly­co­side con­tent.

Shoot tips can also be clipped off along with leaves while har­vest­ing as they con­tain same amount of diter­pene gly­co­sides as leaves. The to­tal gly­co­side con­tent of the leaves starts de­creas­ing with on­set of flow­er­ing, so har­vest­ing should be done be­fore the on­set of flow­er­ing or im­me­di­ately af­ter flower bud for­ma­tion.

Dry­ing is the most im­por­tant ac­tiv­ity in post-har­vest han­dling of ste­via. The coun­cil has de­vel­oped var­i­ous types of dri­ers. Some of these have been de­ployed com­mer­cially. This is im­por­tant as freshly har­vested leaves of ste­via con­tain high mois­ture con­tent and de­te­ri­o­rate if not dried prop­erly. Dry­ing of leaves should be com­pleted im­me­di­ately af­ter har­vest­ing by plac­ing leaves on a screen or net. Sun dry­ing method can also be used. This can be done in mod­er­ately warm con­di­tions in about 12 hours. Proper aer­a­tion with low den­sity of load­ing is re­quired for quick dry­ing in the sun. It can also be dried in a sim­ple dryer by pass­ing hot air just above room tem­per­a­ture. It has also been re­ported that the qual­ity of leaves dried at 50°C in hot air dryer for six hours is bet­ter in terms of colour, sweet­ness and nu­tri­ents. Dried leaves with three to five per cent mois­ture con­tent should be packed in air-tight con­tain­ers and stored in cool and dry places.

How do you in­tend to process the leaves in view of the low level of tech­nol­ogy ad­vance­ment in Nige­ria?

Ex­trac­tion of ste­viol gly­co­sides from leaves in­volve only con­ven­tional pro­cesses and pu­rifi­ca­tion pro­ce­dures. It is some­what sim­i­lar to the ex­trac­tion process used in sugar mills. Ex­trac­tion of gly­co­sides from leaves of ste­via in­volves aque­ous or sol­vent ex­trac­tion, ion ex­change pu­rifi­ca­tion, pre­cip­i­ta­tion, fil­tra­tion, crys­talli­sa­tion and dry­ing. Ex­trac­tion pro­to­col in­volves dis­solv­ing leaves in hot wa­ter or al­co­hol.

Also, the leaves can be treated with non­po­lar sol­vents such as chlo­ro­form to re­move oil, lipids, chloro­phyll and other non-po­lar sub­stances. It has been re­vealed that methanol is the best sol­vent for the ex­trac­tion of Re­bau­dio­side-A from the leaves in terms of com­po­nent yield. Also, ethanol and aque­ous ace­tone have also been found suit­able to ex­tract Re­bau­dio­side-A, but yield may be less com­pared to methanol. Ex­tracts would then be clar­i­fied by pre­cip­i­ta­tion with salt or al­ka­line so­lu­tions, con­cen­trated and re-dis­solved in methanol for crys­talli­sa­tion of the gly­co­sides.

The com­mon steps in­volved in the ex­trac­tion pro­ce­dure are soak­ing of the leaves in warm wa­ter to dis­solve the gly­co­sides, pre­cip­i­ta­tion and fil­tra­tion of the re­sul­tant so­lu­tion, con­cen­tra­tion by evap­o­ra­tion, ion ex­change pu­rifi­ca­tion, spray dry­ing and crys­talli­sa­tion to pro­duce white pow­der/ crys­tals.

To­day, most of the com­mer­cial pro­cess­ing of ste­via leaves for the ex­trac­tion of ste­viol gly­co­sides are mainly con­cen­trated in China and Ja­pan where fac­to­ries are lo­cated near ste­via cul­ti­vated ar­eas.

As a new ini­tia­tive, has rel­e­vant bod­ies ap­proved the con­sump­tion ste­via prod­ucts glob­ally?

Yes; many bi­o­log­i­cal and tox­i­co­log­i­cal in­ves­ti­ga­tions have been car­ried out on ste­viol com­pounds of ste­via in the last 50 years. Eu­ro­pean Com­mis­sion’s Sci­en­tific Com­mit­tee on Food (SCF) eval­u­ated safe­tyre­lated is­sues of this nat­u­ral sweet­ener in 1985 and 1999 and raised ques­tions about lack of ac­cept­able pu­rity spec­i­fi­ca­tions.

In 2004, the Joint FAO/WHO Ex­pert Com­mit­tee on Food Ad­di­tives (JECFA) es­tab­lished ten­ta­tive pu­rity spec­i­fi­ca­tions which were later made per­ma­nent. JECFA es­tab­lished the Ac­cept­able Daily In­take (ADI) of 4mg/kg body­weight/day for pu­ri­fied ste­viol gly­co­sides in 2008 and val­i­dated its use as a sweet­ener in food and bev­er­ages.

The plant and its ex­tracts have also been used for sev­eral years as a sweet­ener in South Amer­ica, Asia, Ja­pan, China and in dif­fer­ent coun­tries of the Eu­ro­pean Union. In Brazil, Korea and Ja­pan, ste­via leaves, ste­vio­side and highly re­fined ex­tracts are of­fi­cially used as low calo­rie sweet­en­ers.

Presently in the US, leaf or ex­tracted forms of ste­via are used as a di­etary sup­ple­ment.

How do you in­tend to en­sure the suc­cess of this ini­tia­tive con­sid­er­ing that there are no ste­via agron­o­mists in Nige­ria?

The coun­cil has been col­lab­o­rat­ing with Kong As­so­ciates Shaghai (China) Lim­ited to pro­mote the de­vel­op­ment of dif­fer­ent va­ri­eties of the plant. The com­pany has in­tro­duced more than 100 im­proved cas­tor seed va­ri­eties from China to the Ahafo Re­gion of Ghana for multi-lo­ca­tional tri­als.

In Novem­ber, 2017, the tri­als were fi­nalised and Kong As­so­ciates se­lected the most adapt­able va­ri­eties to the trop­ics for com­mer­cial cas­tor seed plan­ta­tion de­vel­op­ment. In view of ex­tant col­lab­o­ra­tion be­tween RMRDC, Kong As­so­ciates and the Cas­tor Pro­duc­ers, Pro­ces­sors and Mar­keters As­so­ci­a­tion of Nige­ria (CPPMAN); Kong gave Nige­ria ap­pre­cia­ble quan­tity of the seeds for multi-lo­ca­tional tri­als in Nige­ria in 2017.

Kong is also pro­mot­ing saf­flower and ste­via in Ghana. The com­pany has agreed to give us im­proved ste­via va­ri­eties for mul­ti­lo­ca­tional tri­als in the coun­try. It is also plan­ning to send ste­via agron­o­mists to the coun­try to di­rect plant­ing op­er­a­tions. The com­pany is in­ter­ested in buy­ing the leaves from and farm­ers that par­tic­i­pate in the pro­gramme. This will guar­an­teed the off take for the pro­duce.

Ste­via plant

Dr. Ibrahim Hus­saini Dogo

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