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the nigerian palm-wine: science and socioeconomic importance

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THE NIGERIAN PALM-WINE: SCIENCE
AND
SOCIO-ECONOMIC IMPORTANCE
A FACULTY LECTURE DELIVERED AT THE
FACULTY OF SCIENCE,
UNIVERSITY OF CALABAR
CALABAR
ON 4th NOVEMBER, 2010
BY
FRANK MORAH
B.Sc., M.Sc., Ph.D. (Ibadan), MIPAN, FCSN,
FICCON
PROFESSOROFCHEMISTRY.
INTRODUCTION
Palm-wine is a very popular traditional
drink in West Africa. It is consumed by
more than ten million West Africans
(FAO, 1998). It is also consumed in
Central African countries like Zaire,
Congo and Cameroon etc. The
Nigerian palm-wine is made from
sugary sap of the oil-palm tree (Elaeis
guineensis) and Raphia palms. The
sap contains a lot of simple sugars in
solution. This is naturally inoculated
and fermented by wild yeast to give
palm-wine (Morah, 2004). In the real
sense of speaking, the palm trees do
not secrete or produce palm-wine.
They merely secrete the sap which is
fermented by wild yeast to produce
palm-wine.
Although different types of palms are tapped in Africa, only the oil-
palm and Raphia palm trees are tapped in Nigeria. There are four
different types of Nigerian palm-wine. There is the normal up-wine
tapped from the male inflorescence of “life” oil palm tree. This is
also known as emu and nkwu enu amongst the Yorubas and Igbos
respectively. There is also the “down-wine” tapped from felled oil-
palm tree and is destructive of the crop. This used to be popular in
Ghana (Soda-Ayernor and Mathew, 1971). This was probably
because the Ghanaian rural economy of over half a century ago did
not force the people to preserve their palms. The down-wine was
not so popular in Nigeria. Production of down-wine in both countries
has been reportedly discontinued (Sadah-Ayenor and Mathew,
1971). However, interaction with indigenes of Cross River State
shows that the down-wine is still very popular here, especially in
Boki area, where a lot of oil-palm trees still grow wild in their large
expanse of forest area. Stem tapping of standing oil-palm tree gives
another type of oil-palm-wine known as ItiinpartsofAnambra State
especially in Dunukofia, Idemili North and Idemili-south Local
Government Areas. The forth type of palm-wine is the Raphia
palm-wine known as g r ọ ọ, ngwo and uk t amongst the Yorubas,
Igbos and Efiks/Ibibios respectively. It is mainly tapped from Raphia
hookeri
TAPPING OF PALM-WINE
All common varieties of the oil-
palm tree are tapped except
the Virescens fruit-type
(Morah, 2006 and 2009)
known as akwuojukwu or
nkwuojukwu in Igbo and
efiakun amongst the Ibibios
and Efiks. Palm-wine from this
variety has unacceptable
organoleptic properties and it
is only used for adulteration of
good palm-wine. To tap up-
wine, the leaf subtending to
the immature male
inflorescence is cut off in order
to gain access to the
inflorescence still enclosed in
its spathes.
An incision is made near its apex and
the top of the tissues inside the
spathe is removed. Part of the
spathe is removed and a tapping
panel created by cutting the main
stem of the spadix horizontally.
Some fibrous fabric made from the
leaf sheath is used to cover the cut.
A very thin slice is taken on the cut
during daily tapping. A small pipe
fabricated from small bamboo stem
is used as the funnel for channeling
the exude from the slit into the
receiving calabash or bottle. It is
this exude that is called the sap and
is collected every morning,
afternoon and evening. The
unfermented sap is sweet and
colourless.
The quantity of palm-wine from a tree depends mainly on the number of male
inflorescence available for tapping and the season of the year. The highest
quantity of wine is produced during the March/April and October/November
seasons (Tuley, 1965a). High yield of palm-wine in October-November
corresponds to the period of production of high number of male
inflorescence while high yield in March-April (ie it beginning of the rainy
season) corresponds to the period of increase in the rate of development of
organs of the palm-tree.
Stem tapping of standing oil-palm tree also gives very high yield during
the March – April season. The stem tapping by amateur tapper may lead to
damaging of soft tissues around the growing point and may kill the palm tree
or provide entry for injurious insects and bacteria (Tulley, 1985a). Such a
thing hardly happens with seasoned tappers. The palm fronds are cut off
leaving only a few (about ten or so) around the growing tip. The side to be
tapped is cleaned and smoothened. The tapping starts from the end closer
to the apex and a very thin slice removed each day of the tapping as the
tapping proceeds downwards. This gives higher yield of sap per day and
may be tapped for several weeks until it stops producing. The same palm
tree may be tapped again after one or two years. The palm-wine produced
in this case contains less sugar than the inflorescence palm-wine. It is
therefore not very sweet (when fresh) and the stale palm-wine is not as
strong or alcoholic as that tapped from the male inflorescence.
COMPOSITION OF PALM-SAP AND WINE
The sap collected during tapping of
these palms is colourless and sweet due to
its content of simple sugars in solution
(Epem, 1982). The sap is fermented mainly
by wild yeast to give the palm-wine. The
fresh up-wine contains sucrose (4.29),
glucose (3.31) and ammonia (0.038g/100ml)
as well as lactic acid and amino acids
(Bassir, 1962). The Down-wine has different
composition from the up-wine as it contains
glucose, sucrose, fructose, maltose and
raffinose. The presence of the last two
sugars is thought to be due to post-felling
changes (Bassir, 1968). The following nine
sugars were identified in Raphia palm-wine
(Faparusi, 1981): sucrose, glucose,
fructose, cellobiose, maltose, xylose,
rhamose, arabinose and galacturonic acid.
Sucrose, glucose and fructose decreased in
concentration during the first twenty two day
period of tapping. Cellobiose, maltose and
xylose showed slight increase during the
period while rhamose, arabinose and
galacturonic acid were inconsistent in the
days of their appearance. It is these sugars
present in the collected palm-sap that are
fermented to give palm-wine. Other
constituents of the sap and wine include
vitamins, proteins, amino acids and mineral
elements etc.
Another difference is that the up-wine contains only ethanol while down-
wine contains very small amounts of two additional but undesirable
alcohols-methanol and propanol. These two undesirable alcohols must
have arisen due to post-felling formation of trace amount of stirring agents
which must have diverted part of the fermentation process to give methanol
and propanol. A metabolic intermediate of methanol in the body is
formaldehyde whose aqueous solution is known as formalin. Methanol is
therefore highly poisonous, attacks the central nervous system and causes
blindness. It is therefore not advisable to drink down-wine or methylated
spirit or even local gin made from the down-wine.
FERMENTATION
Fermentation is the breaking down or decomposition of organic molecules
through the activity of enzymes contained in microorganisms to simpler
organic molecules. Many organic compounds are prepared through
fermentation.
Alcoholic fermentation is the breaking down of sugars through the agency
of microbial or yeast enzymes to give ethanol (ie alcohol). Alcoholic
fermentation is one of the oldest and most important of all industrial
processes. The discovery of the process is lost in the mist of antiquity
(Tooley, 1971). It was probably discovered by the early man who carefully
observed the spontaneous fermentation of the sugar containing fruit juice
which he gathered.
To the best of my knowledge, the
oldest documented account of alcoholic
fermentation is contained in the book of
Genesis 9:21-22 “And Noah began to
be a husbandman and planted a
vineyard: and he drank of the wine, and
was uncovered within his tent.” This
being the first recorded task which
Noah undertook when he came out of
the ship does not merely indicate that
he knew how to do it during the first
world but rather shows that wine
making through fermentation was a
most important industry before God’s
destruction of the first world with flood.
Palm-wine yeast includes
Saccharomysescerevisiae,S.
chevalieri,S.pastriorianus,S.
ellipsoide,S.vaferand S.prombe
(Bassir, 1962; Okafor, 1972; Abalaka
and Okpala, 1990; Morah 1995 and
2007). These yeast cells accumulate in
millions around the flower stalks and
inoculate the sap naturally.
Abalaka and Okpara (1990) showed that the palm-wine yeast gives low
biomass but high yield of ethanol. The disaccharide sugars are hydrolysed
by the yeast enzymes to monosaccharides which are subsequently
fermented by another yeast enzyme to ethanol with evolution of carbon
dioxide.
A motile rod-shaped and high-alcohol anaerobic bacterium closely related to
Zymonomasmobilis has been reported to occur in palm-wine (Van Pee and
Swings, 1971). Different strains of Zymonomas isolated from palm-wine
have been shown to effect alcoholic fermentation of sugars
(Van Pee and Swing, 1971; Obire, 2005).
The palm-wine is cloudy and whitish in colour due to suspension of yeast
cells (Morah, 2004). It is usually accompanied with heavy white sediment of
yeast cells constituting the main bulk of the dreg. The palm-wine is mostly
consumed fresh along with the growing yeast culture (Morah, 2004). The
fresh palm-wine is usually sweet due to the dissolved sugars in solution.
C
12
H
22
O
11
+ H
2
O 2C
6
H
12
O
6
C
6
H
12
O
6
2C
2
H
5
OH + CO
2
hydrolysis
disacchor ide
ferm entation
monosaccharide
The wine becomes more alcoholic and less sugary on standing as its
constituent sugars gradually get converted into alcohol. It also becomes
sour on standing because of production of organic acids due to activity of
microorganisms in the palm-wine (Morah, 1986, 1995 and 2007). The
Raphia palm-wine usually has higher concentration of dissolved sugars
and is therefore expected to give higher yield of local gin. Raphia palm
grown upland gives lower yield of wine which is much more sugary than the
one tapped from Raphia palms grown in swamps.
MICROFLORA OF PALM-WINE
A number of microorganisms, some of which are pathogens, have been
isolated from Nigerian palm-wines. These include Lactobacillus,
Micrococcus,Lieuconostoc,Klebsiella,Streptococcus,Acetobacter,
Sereratia,Bacillus,Zymononas and Brevibactrium species as well as
Eschereichiacoli (Okafor, 1975; Morah, 1995 and 2007; Faparusi and
Bassir, 1977; Ogbulie, etal¸2007). Palm-wines, especially Raphia palm-
wine are greatly diluted with waterof questionable quality from brooks,
gutters and streams etc. It is believed that some of these microorganisms
enter the palm-wine through such contaminated water as well as
unsterilised tapping equipment and receiving containers which are rarely
washed. The abundance of these microbes in up-wine is quite low but very
high in Raphia palm-wine. This is attributed to the fact that up-wine is not
normally diluted or at most diluted to a very little extend whereas Raphia
palm-wine is normally diluted with large quantities of water of questionable
quality (Ogbulie etal, 2007).
Sacoglottisgabonensis stem bark extract has been shown to inhibit
the growth of Leuconostocmesenteroides and Lactobacillus
planetarium (Faparusi and Bassir, 1972; Morah, 2007). It also has
inhibiting effect on Micrococcus species, Escherichiacoli,
Staphylococusaureus and Streptococcus species isolated from palm-
wine (Morah, 2007). E.coli causes stomach ache while the
Leuconostoc and Micrococcus species cause intestinal and urinary
problems. A number of these microbes isolated from the palm-wine
are pathogenic and this poses public health problem. They are
believed to be responsible for the unstable bowel movement
commonly associated with consumption of untreated Raphia palm-
wine as claimed by many palm-wine drinkers. It is a common practice
in southern Nigeria to treat Raphia palm-wine with powdered or
crushed stem bark of Sacoglottisgabonensis also known as edad and
nche amongst the Ibibios/Efiks and Igbos respectively. Most Raphia
palm-wine drinkers have attested to the fact that the wine without
Sacoglottisgabonensis stem bark gives stomach upset but the one
which contains the stem bark is quite innocuous. Sacoglottis
gabonensis stem bark is also added to the palm-wine to prevent or
reduce souring which occurs in stale palm-wine.
FERMENTATION KINETICS OF PALM-WINE
Palm-wine production is a batch fermentation process with the dissolved
sugars acting as the substrate. As the substrate is not replenished,
ethanol production rises to a maximum and slows down with depletion of
the substrate until it eventually stops (Morah, 1995). Acidity of palm-
wine also increases continuously with time due to the activity of
microorganisms, such as Acetobacterspecies, which convert the
produced ethanol to ethanoic acid (Morah, 1986). With combined
activities of these microorganisms, palm-wine fermentation process
becomes reduced to a consecutive reaction type (Deinfoerfer, 1960) in
which produced ethanol, acting as the intermediate product,
accumulates to some extent before being converted into the final
product, ethanoic acid (Morah, 1995 and 2007).
C
6
H
12
O
6
CH
3
CH
2
OH CH
3
-CO
2
H
Glucose
(substrate)
Ethanol
(interm ediate
product)
Ethanoic acid
(final product )
As the growth of Acetobacterspecies continues, the ethanol is
consumed while concentration of ethanoic acid builds up. A certain
critical period results in a maximum level of ethanol. After this point a
decline in concentration of ethanol sets in (Morah, 1995 and 2007).
Addition of Sacoglottisgabonensis stem bark to fermenting palm-wine
increases the concentration of ethanol in the palm-wine. This is
attributed to the antimicrobial effect of the stem bark. It inhibits the
growth of the bacteria responsible for the conversion of ethanol into
ethanoic acid. For the same reason, the usual changes in flavour and
taste of palm-wine with time is drastically reduced in the presence of
the Sacoglottisgabonensis stem bark. The presence of crushed
Sacoglottisgabonensis stem bark in Raphia palm-wine is therefore
advantageous. Morah (2007) has recommended it as a suitable,
cheap, natural, environmentally friendly and locally available
preservative for palm-wine. Addition to sodium metabisulphite, which
is a conventional preservative for wine and fruit juice, acts in a similar
way as Sacoglottisgabonensisstem bark (Morah, 1986 and 1995).
PR ESERVAT I ON AN D BO T T LED PA LM - W I N E
Fig . 1 : Flow ch art for bott le d pa lm - w in e .
Fresh palm -wine
Analy sis of palm - wine
Addition of preservat ive
Palm-wine is normally taken fresh and unbottled. Some people,
especially men, prefer the stale (overnight) palm-wine which is less
sugary with little sour taste and much more alcoholic. This gives them
the desired “kick”. Research has shown that sodium metabisulphite
(Morah, 1995) and Sacoglottisgabonensis stem bark (Morah, 2007)
are suitable preservatives for palm-wine. Although benzoate has been
detected in some locally bottled palm-wine at Onitsha (Morah, 1985),
benzoic acid is not often recommended for preservation of wines.
There is an insignificant quantity of bottled palm-wine in the
Nigerian palm-wine market. The essence of bottling is to preserve the
organoleptic properties of the palm-wine such as taste, flavour and
mouth feel and to extend its shelf-life. The flow chart for bottling of
palm-wine is given in Fig. 1. The fresh palm-wine is first tested for
oganoleptic properties, chemical composition and microbial assay.
Calculated quantity of the preservative is added and thoroughly mixed
with the wine. The resulting mixture is filled into clean bottles and
corked. The corked wine is given hot temperature treatment in hot
water. This pasteurizes it by killing the yeast and other microorganisms
present in the wine. The pasteurized wine is now labeled, packaged
and sent to the market. Raphia palm-wine is locally bottled along Palm
Street, Calabar and marketed under the trade name, PalmBooze.
PALM-WINE PRODUCTS AND USES
Local gin: The local gin goes by such names as kaikai, ogogoro, akpetesi,
kinkana, sapele water, numberone and ufofob etc. It is normally obtained through
repeated simple distillation of about four-day old Raphiapalm-wine in the traditional
way with local distillation apparatus. The percentage of alcohol in the local gin
varies depending on the source and extent of distillation and may be over 40% (v/v)
alcohol. The yield and quality of gin have been shown to be significantly improved
by allowing the palm-wine to ferment in the presence of metabisulphite ion (Morah,
1995) or Sacoglottisgabonensis extracts (Morah, 2007). The gin is used in Ghana
for large scale production of branded spirits (Sodah-Ayernor and Mathew, 1971).
The local gin made from palm-wine could therefore serve as a locally available
raw-material for the industrial production of assorted brandy, whisky and rum etc.
Yeast: The palm-wine yeasts have been found to be high alcohol producing with
low biomass. It has been found to be very suitable for the fermentation of sugar
molasses (Abalaka and Opara, 1990). With the abundance of sugar molass
wasting away in our local sugar factories and the abundance of palm-wine yeast,
Nigeria has an abundance of local raw materials for industrial production of edible
alcohol for the nation’s distilleries and vinegar production plants. High-ethanol
resistant yeast isolate from Nigerian palm-wine has also been successfully used in
lager beer production (Agu etal, 2007). Palm-wine yeast is a good source of
baker’s yeasts (Ejiofor etal, 1994) and brewers yeast, which are currently imported
into Nigeria. Up to twenty five amino acids have been identified in the Nigerian
palm-wine. There is abundance of vitamins A, B
2
, B
12
and C etc in palm-wine
(Ankra, 1973: Bassir, 1967). It also contains a lot of essential minerals (Ulshun et
al, 2005). It is against this background that Professor Bassir (1967) recommended
inclusion of palm-wine in the diet of pregnant women and teenage girls.
MEDICAL USES OF PALM-WINE
Due to the high mineral and vitamin contents of palm-wine, it is used for
correction of vitamin and mineral deficiency diseases. It is said to lower blood
pressure and hence a lot of hypertensive patients in the rural communities go
for palm-wines instead of lager beer. Udokang and Akpogomeh (2005)
established potassium sparing diuresis in human subjects after consumption of
Raphia palm-wine.
TRADITIONAL VALUE OF PALM-WINE
Palm wine occupies a very prominent position in traditional activities and life-
style of the inhabitants of the south-west, south-east and south-south geo-
political zones of Nigeria. It is used in traditional marriage ceremony,
traditional worship, festivals such as New Yam festivals etc and for
consultation with our ancestors, ancestral spirits and deities. Palm-wine is also
presented to seal agreements and land transactions. Consultation and
renewal of covenant with our ancestral spirits is usually done with native
kolanut (seed) followed by the fermented palm-wine (or sometimes its distillate,
local gin). It is believed that this renews and strengthens the covenant
between the living human beings and the ancestors and also brings one in
atonement with the spirit world. This is analogous with the conventional holy
communion as practiced in the Christendom where bread (made from seed)
followed by fermented wine are served to renew and strengthen the covenant
between us and our Lord, Jesus Christ.
Native law and custom marriage is
the traditional tying of nuptial
(marriage) knot. On identifying a
young lady to marry, the young man
goes with his family members to the
girl’s family with kolanut and palm-
wine for the “knocking on the door”.
The door can only literally be
opened on sighting the palm-wine.
All other visits to the in-laws before
the actual marriage ceremony must
be accompanied with palm-wine.
The acceptance of the groom by the
bride is usually done with good
palm-wine. During the occasion, the
bride’s father gives her a full cup of
palm-wine with the instruction to
hand it over to whom ever she
identifies as her Mr. Right. She
goes on Mr. Right pseudo-search in
the crowd of men. As soon as she
identifies the person, whom she has
been looking and waiting for, she
kneels down before him kisses the
palm-wine and hands it over to him.
This is an open giving of her hand
into the proposed marriage.
The young man declares his
acceptance by consuming the
palm-wine in appreciation of the
most beautiful offer; he stuffs the
emptied cup of palm-wine with
some money which is now
returned to his father-in-law. The
actual traditional marriage
ceremony is filled with pomp and
pageantry with both family
members coming out on their best
outing dresses. The ceremony is
climaxed by the pouring of libation
with palm-wine with blessing of the
young couple.
CONCLUSION
Production of palm-wine involves indigenous
science and technology developed and
practiced by Africans. Millions of southern
Nigerians consume the palm-wine and local
gin produced from it. The industry has
provided gainful employment for hundreds of
thousands of Nigerians in both rural and
urban areas. Its nutritional value is such that
it is almost a complete food in itself and
hence its recommended inclusion in the diet
of pregnant women, teenage girls and
convalescents. Its diuretic effect makes it
useful for hypertensive patients. The local
gin produced from palm-wine could serve as
locally available raw material for the large
scale production of branded spirits, while the
palm-wine yeast could serve as a local
substitute to the imported yeast for lager
beer brewing and bakeries etc. Palm-wine
and its distillation product, local gin, occupies
very important position in our culture as well
as traditional African religion. Concerted
effort should therefore be made towards
further development of the palm-wine
technology and industry.
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