Improvement of traditional processing of local monkey orange (Strychnos spp.) fruits to enhance nutrition security in Zimbabwe
Improvement of traditional processing of local monkey orange (Strychnos spp.) fruits to enhance nutrition security in Zimbabwe
Ruth T. Ngadze 1 2
Ruud Verkerk 1 2
Loveness K. Nyanga 0 1 2
Vincenzo Fogliano 1 2
Anita R. Linnemann 1 2
0 Institute of Food, Nutritional and Family Sciences, University of Zimbabwe , Harare , Zimbabwe
1 Food Quality and Design, Wageningen University and Research , Wageningen , The Netherlands
2 Department of Food Science and Technology, Chinhoyi University of Technology , Chinhoyi , Zimbabwe
Although the monkey orange (Strychnos spp.) tree fruit is widely distributed in Southern Africa and particularly in Zimbabwe, it is underutilized and little attention has been given to its potential commercialisation due to limited knowledge and information. Most of the fruits and their products are wasted because of limited harvest time, process control and storage conditions, leading to variability in shelf life and sensory quality, thereby impacting nutritional quality. Traditional processing techniques make insufficient use of this food resource within rural communities. This study aimed at identifying the existing bottlenecks by means of a survey among 102 smallholder farming respondents in the wet and dry regions of Zimbabwe. Results revealed that S. cocculoides and S. spinosa were used by 48% of respondents as a functional ingredient in porridge, by 25% in fermented mahewu drink and by 15% of respondents as a non-alcoholic juice. The fruits of S. innocua and S. madagascariensis are preferably processed into dried products. Taste, flavour and colour were the important quality characteristics for all processed products, and constraints to be solved are seed-flesh separation, long processing times, separation of juice and pulp during storage as well as pulp viscosity. Respondents reported monkey orange products to have health benefits for children and immune-compromised people, who, on regular consumption, have reportedly increased weight and resistance to disease. The positive perception about the processed products of Strychnos spp. offer a good opportunity to improve nutrition security by capitalizing on these not-yet-fully-exploited resources, but technological solutions to improve sensory quality and shelf life must be developed.
Traditional processing; Monkey orange; Strychnos cocculoides; Strychnos spinosa; Strychnos innocua; Strychnos madagascariensis
Indigenous fruit trees in Africa supplement the diet of many
rural families by providing essential nutrients (Bille et al.
2013; Nhukarume et al. 2010) and serve as a livelihood
source, especially in times of famine (Legwaila et al. 2011;
Mithöfer and Waibel 2003; Packham 1993). Hundreds of
indigenous fruit species exist in Africa that are locally
significant, although they might be unknown in global markets
(Jamnadass et al. 2011). These locally important species are,
however, frequently underutilised, leading to erosion of their
usefulness and restricting development options for poor
communities (Ekué et al. 2010). Some studies have been
conducted to assess knowledge by local communities in Zimbabwe on
processed products of indigenous edible fruits such as
beverages derived from sand apple (Parinari curatellifolia), marula
(Sclerocarya caffra) (Gadaga et al. 1999), baobab (Adansonia
digitata) (Mpofu et al. 2014), and ber (Ziziphus mauritiana)
(Nyanga et al. 2008).
Strychnos spp. (monkey orange) have been identified
among the top priority fruit species in Southern Africa through
ethnobotanical surveys (Mkonda et al. 2002; Saka et al. 2004),
particularly in dry areas of Zimbabwe such as Binga (Mpofu
et al. 2014). This fruit tree proliferates in areas with a
prolonged dry season, remains dormant when water is
unavailable and bears fruit in abundance (Mwamba 2006;
National Research Council 2008). The excess production of
the fruit leads to its underutilization and this can be seen in the
veld around Zimbabwe where fruit remains littered and
unpicked when in season. Five common Strychnos species
grow wildly across the agro–ecological regions of the country,
with wide distribution patterns. S. cocculoides is found in the
north, west, central and south, S. spinosa in the north, west,
central, east and south, S. innocua in the north, central, east,
and south, S. madagascariensis in the north, west,
central, east and south, and S. pungens in the north, west
and central parts of Zimbabwe (Mapaura and Timberlake
2004; Van Wyk and Van Wyk 1997). Though the
Strychnos spp. fruit is widely distributed in Zimbabwe,
it is underutilized and little attention has been given to
its potential commercialisation due to limited knowledge
and dissemination of information about propagation,
agronomic practices and product processing techniques.
Strychnos spp. fruits ripen and are harvested from
September to December (Akinnifesi et al. 2007), a time when
intense agricultural labour coincides with low maize stocks
and the unavailability of freshly-gathered vegetables
(McGregor 1995). The season of prolonged food scarcity
often increases reliance on consumption of indigenous fruits by
the entire family (Shackleton et al. 2000). In addition to the
consumption of fresh fruit, traditional fruit processing is most
common in drier climatic areas for the supplementation of
food requirements (Saka et al. 2004). An estimated 46% of
rural households have reported processing indigenous fruit
into juices and/or porridges (Kalaba et al. 2009), along with
several other food products that can be used as a complement
and substitute for the local cereal-based staple foods.
Strychnos spp. has been identified to contribute more than
100% of the recommended daily intake for vitamin C, Fe and
Zn; especially for children between four and eight years old
and for pregnant women (Ngadze et al. 2016). Gadaga et al.
(2009) noted that over 65% of Zimbabweans live in rural areas
and are food insecure, especially during prolonged dry
periods, while malnutrition problems through vitamin and
mineral deficiencies have public health significance in the
country. Because of their wide availability and nutritional
composition, monkey oranges have potential for
contributing to the alleviation of vitamin and micronutrient
deficiencies of the vulnerable rural population, particularly
children and women, by complementing the monotonous
staple food diet. In Zimbabwe, extension services of
government and Non-Government Organizations (NGO’s)
are a bridge for the transfer of information on the
contribution of indigenous fruit species to health and
nutrition to the end user, through training of women groups
and cooperatives in new processing possibilities.
To date, indigenous knowledge on the collection and
processing of Strychnos spp. products in Zimbabwe has received
limited attention. Usually indigenous fruits are considered to
be a Bpoor man’s food^ or famine food. Erosion of cultural
norms through urbanization and increased cultivation of
exotic fruits and their marketing have led to further reduction of
the use of indigenous fruits. The lack of awareness of the
potential health benefits and standardized processing of these
fruits keep them away from most diets and adversely affect the
utilization of the fruits and nutrition security.
Thus, our present study aimed to assess and document
specific traditional processing techniques and their bottlenecks in
identified rural communities and regions in Zimbabwe with
the objective of determining which food technological
improvements would support the role of indigenous monkey
orange fruits as a way to improve nutrition security.
Strychnos spp. has the potential to generate income for actors
in the value chain within local and regional markets, as in the
case of baobab fruit and other African indigenous fruits that
reportedly reduce poverty by 33% during the critical period of
the year (Chadare et al. 2008; Mithöfer and Waibel 2003).
Aspects explored in our study include processed products,
processing steps, constraints and consumption patterns of the
fresh fruits and their products. The study also provides
information on local food uses of Strychnos species, which is
important for further research on the implications of processing
and storage for nutritional health benefits and sensory quality.
Study area and sample size
The study areas (Fig. 1) were chosen on the basis of the
abundance of Strychnos spp. fruits, in wet and dry regions of
Zimbabwe. For exhaustive data collection on the different
species, areas that cover the five agro ecological regions of
Zimbabwe (Vincent et al. 1961) were chosen carefully using
information gathered initially with assistance from NGO
extension services on the basis of community utilization of
Strychnos spp. The objective of this research was primarily
based on indigenous knowledge, where a limited
number of people served as primary data sources. Thus,
holders of information about indigenous fruit processing
and about village chiefs were identified and purposively
selected on account of their experience and past
participation in other surveys. Villages were visited prior to
the survey for familiarization with the community.
Consent from the village chief was obtained after clear
demonstration of research intentions and protocols.
Monkey oranges are underutilized, not commercialised
and commonly consumed and processed locally in rural
homesteads. Thus, often the actors that process the
Fig. 1 Study areas surveyed for indigenous knowledge of Strychnos spp.
fruit collection and product processing in Zimbabwe (annual rainfall
region I > 1000 mm, II 750–1000, III 650-800, IV 450–650 and region
fruits are concealed leading to the ‘snowballing method’
a s t h e b e s t m e t ho d t o u nc o v e r t h at po p u l a t i o n .
According to Katz (2006), BSnowball sampling is a
special nonprobability method for developing a research
sample where existing study subjects recruit future
subjects from among their acquaintances and where a
sampling frame is hard to establish^. Though snowballing is
not statistically representative, the sampling technique is
suitable when the human populations being surveyed are
difficult to pinpoint and locate because of their limited
numbers. Village chiefs, elders and leaders of women’s
groups suggested the initial participants for the survey,
then the identified respondents suggested other
households, where selection was based on their knowledge
of processing Strychnos spp. Informed consent was
obtained from all individuals in each participating
household in this study. With an estimated average size of
150 inhabitants per village, at least five % of the
population of the village were interviewed as a
representative sample (Mpofu et al. 2014). A total of 102
respondents were interviewed, where 20–40 informants were
recruited in each community.
V < 450), namely Gweru (region III and IV), Marondera (region II),
Chimanimani (region I, II and III) and Bikita (region II, IV and V)
Data were obtained during field visits using questionnaires
administered through face-to-face interviews, in detailed
focus group discussions and by observations during the monkey
orange season from September through December 2014.
Observations during the harvesting and processing of monkey
oranges were made as follow-ups to the information obtained
from the respondents. The interviews were either with
individuals or in group discussions in the local Shona and Ndebele
languages (with the assistance of local translators), which
were well understood by all respondents, so as to obtain
indepth information. Detailed discussions were used to generate
data from groups of between 10 and 15 participants in selected
communities. A relevant leader of the community, who was
believed to have more experience and in-depth knowledge of
the fruit and area, was identified for each focus group. The
focus group dynamics facilitated the generation of forgotten
information. Ages of respondents ranged from 20 to above
70 years. In each locality, information was gathered by
answering questions based on the following parameters: (1) fruit
harvesting and gathering, (2) processing methods, (3)
consumption patterns, (4) storage practices of fruit and fruit
products, and (5) processing and storage constraints. Specific
questions were developed for each actor and were subdivided
At the collector’s level: Fruit species, collection period,
distance covered for fruit collection, fruit quality
characteristics (colour, taste, maturity and size), method of
collection, fruit storage and ripening, collection constraints,
customers for fruits, selling price, end uses of fruit.
At the processor level: Processed products, quality of
processed products (colour, taste, odour), frequency of
processing, end consumer (household use or trade),
quantity and price of products and customer preferences.
At the consumer level: Procurement of product, quality
characteristics, storage of product, consumption time
and quantities, quality perception of consumed product
(colour, taste, odour), further processing including the
use of product as an ingredient.
Focus group discussions were centred on obtaining
information about harvesting methods, product processing and
quality constraints, processing steps and the uses of product
as an ingredient. Observations during the harvesting and
processing steps were conducted as a follow up to the information
obtained from the farming respondents.
The data were analysed using SPSS 22.0 for Windows
(Apache Software Foundation, USA) and Microsoft Excel
2013. Data were subjected to descriptive statistics from coded
questions asked in the individual interviews.
Results and discussion
Figure 2 shows photographs of the pulp of fruits from three
Strychnos species found in Zimbabwe. Data collection for
Fig. 2 Pulp of a Strychnos
spinosa, b Strychnos cocculoides
and c Strychnos innocua
fruits of the same species may be imprecise (Termote et al.
2010). BUnder-differentiation^ of a species is encountered
when a single vernacular name can be used for species of
morphological similarity, or Bover-differentiation^ when
several names are used for one species (Rampedi and Olivier
2013). Thus, to gather reliable and reproducible
information, the species were grouped into two major groups:
group A (comprising S. cocculoides and S. spinosa) and
group B (S. innocua and S. madagascariensis). Within
either group, the species’ phenotypic and sensory
characteristics are similar and hence traditionally similar vernacular
names are used (Table 2).
In all the areas visited, Strychnos spp. are harvested from
September to December, i.e. the warm summer period
marking the end of the dry season and the beginning of the rainy
season. Citation of fruit species in the localities we visited is
illustrated in Table 2. The most frequently cited species in
Lower Gwelo and Marondera were S. cocculoides and
S. spinosa, while Bikita and Chimanimani respondents cited
mainly S. innocua and S. madagascariensis. S. pungens is not
included in the description of the processing results because
respondents did not process fruits of this species due to its
limited availability. Each informant cited on average three
species known to them and identified two species found in
Gathering and fruit selection are principally activities
conducted by women during their daily chores when they tend the
field or collect firewood, and by children going to and from
school or as they herd cattle. Females made up the majority of
the respondents (83%) (Table 1). Females are usually
identified as the majority of respondents in studies such as ours
because they are regarded as the custodians of traditional
knowledge (Dovie et al. 2008) (Table 2).
In this study we found that Strychnos spp. trees were often
confined to another individual’s homestead or field and
respondents freely collect the fruits without seeking authority
since monkey orange trees and fruits continue to be regarded
as communally-owned in all areas visited. Because the fruits
are found within walking distance from homesteads and are
communally owned, they are accessible and free to harvest,
and available in times of seasonal imbalances, especially for
the rural poor. In Zimbabwe, indigenous fruit trees are
Table 1 Demographic profile of respondents in the districts visited during a survey for indigenous knowledge of Strychnos spp. fruit collection and
product processing in Zimbabwe
generally located in forests, cropped fields, grazing parks and
around homesteads (Akinnifesi et al. 2002).
The fruits are harvested by picking fallen fruits, or by
climbing trees and plucking fruit from branches. Other
harvesting practices such as shaking trees, or hitting them with
stones or tree branches are also used. These modes of
harvesting may cause damage to the hard shell of the fruit, which is a
protective barrier to insect infestation and microbial
contamination, thus potentially causing loss of sensory, nutritional and
physical properties of the fruit.
For all species, major attributes for fruit maturity and
harvesting were colour (89% of respondents), liquefaction (72%)
and taste (49%). Fruit colour changes from green to bright
yellow or orange (colour intensity depending on species) at
the onset of ripening. Specifically, for S. cocculoides and
S. spinosa liquefaction is a common maturity indicator used
by respondents, identified by holding the fruit to the ear and
shaking to listen for the sound of sloshing pulp and loose
seeds. The best tasting fruits are known from past experience
and respondents know the location of the trees that bear the
most delicious fruits. These results concur with those of
Akinnifesi et al. (2007), where they concluded that
traditionally in Southern Africa the harvesting of indigenous fruits
Inventory of Strychnos spp. identified and collected in Zimbabwe
depends largely on past knowledge and observations within
We noted that in all areas there is variation in taste between
species and within species, from bitter, astringent to sweet.
Taste and flesh consistency are also used to distinguish
between species’ groups. S. cocculoides and S. spinosa were
described as sweet or sweet and sour, with a brown juicy flesh
when ripe. The sweet taste of fruit from S. cocculoides
explains why it is the most preferred of the monkey orange
species (Mwamba 2006). Citric, malic and succinic acids
found in S. spinosa species may contribute to the sourness
percei ve d b y consumers. S. madagasc ar iensis and
S. innocua fruits were described as containing bright yellow
firm flesh, with a sweet to bitter taste, which has been
attributed to the presence of tannins in S. innocua flesh (Bello et al.
2008). Fruit colour, liquefaction and taste superseded other
collection and selection criteria such as fruit size (21%) and
Fruit storage practices and constraints
Of the four monkey orange species, S. cocculoides was the
only species that was picked unripe and stored for ripening;
Citation in locality (%)
Chimanimani Marondera Lower
the other three species were only picked when ripe. In total,
from all the regions surveyed for S. cocculoides, 89% percent
of the respondents picked fallen ripe fruits, and 70% picked
mature fruits from the tree. Twenty seven percent of
respondents picked light green mature fruit for ripening during
storage. According to respondents, the degree of maturity was not
a constraint as through experience they know the ideal stage of
maturity that allows the fruit to ripen in storage. Because of
their hard shell and acidic nature with a pH of around 3.5
(Saka et al. 2007), Strychnos spp. can tolerate relatively high
temperatures and long storage times before deteriorating in
quality. Ripening could be either accelerated or reduced by
different storage methods. Methods used to accelerate
ripening are the mimicking of dark, air tight conditions, such as by
burying fruits underground in sand, in sacks with dry hay, dry
chicken manure, mealie meal or fine wood ash. Thus, the
fruits are kept in the buried environments in order to control
the atmospheric conditions that allow the concentration of the
ethylene plant hormone that consequently hastens the ripening
period, signifying the climacteric nature of the fruit (Barry and
Giovannoni 2007; Sitrit et al. 2003). Respondents indicated
the storage treatment and estimated the storage time of the
fruit based on their experience. They indicated that picking
of mature unripe fruits for storage in burial places also reduces
competition from other fruit collectors, especially of a
wellknown, sweet tasting variety, which is in line with findings of
Motlhanka et al. (2008) and Rampedi and Olivier (2013).
Unripe mature fruits can be stored in this manner for more
Fig. 3 Overview of processing methods of Strychnos spp. fruit in Zimbabwe
than two months (according to 18% of the respondents). To
delay ripening, mature fruits are kept cool by storing them in
ventilated grain sacks, under (or in) granaries and in closed
clay pots. Ripe fruits can be stored for one month (59% of the
respondents), two months (9% of respondents) and more than
two months (1% of respondents), before they rot. Thirty
percent of respondents said they immediately consumed or
processed the fruit and did not store the fruit at any stage of
collection. The constraints identified by the respondents were a
shortage of fruits of the sweet tasting variety, and seasonality,
where respondents desired a longer storage time and extended
availability of fruits throughout the year.
Indigenous processing knowledge
According to our survey, fruits of Strychnos spp. are harvested
for a period of between three and four months and in excess of
what is consumable during the harvest season; and thus some
fruits are processed. Strychnos spp. products were broadly
classified as products for either future use or immediate use, for the
purposes of this survey. For all processed products of Strychnos
spp. the first step was to wash fruits with clean water to remove
dirt and dust particles. The flesh is exposed by pounding and
cracking the shell on a hard surface or with a stone, after which
specific processing is done. An outline of the processing
methods used is shown in Fig. 3 and details of the processing
of each product are given in the following sections.
Food products for prolonged storage
Drying of S. innocua and S. madagascariensis In Bikita
district, high temperatures and low rainfall often result in poor
harvests of staple food crops and fresh vegetables. This has led
to reliance on the processing of indigenous fruit, particularly
drying of S. innocua and S. madagascariensis (typical to dry
regions in Zimbabwe such as Bikita), so as to reduce fruit
moisture content for prolonged preservation. All respondents
in Bikita district use alternate sun and fire drying due to a lack
of electricity for refrigeration and mechanized equipment. The
alternate use of the two drying methods was done primarily to
reduce drying time as the sugar content of S. innocua
necessitates prolonged drying. In contrast, there was no
drying practised with the species in Chimanimani district, a
wetter area in Zimbabwe. It was observed that though
abundant in Chimanimani district during the fruiting
season, S. innocua and S. madagascariensis fruits were
heavily littered, indicating underutilization even for
consumption as fresh fruits. This was attributed to the fact
that the region’s high rainfall and fertile soils are
appropriate for other agricultural cropping practices, and
hence other food sources are available and affordable.
Prior to drying, fruit flesh is pre-treated with either fine salt,
crystalline sugar or both, depending on consumer preference.
The flesh/seed is spread and pressed to stick to the surface of
hand-plaited reeds interlocked with strips of palm leaves. By
midmorning, the rack is exposed to the sun on a traditional
dish rack (called dara) or on bundles of firewood. The rack’s
position is changed throughout the day for maximum
exposure to the sun. At dawn of the following day, the rack is
firedried with wood as the fire source, or (when wood is
unavailable) corn cobs or stalks (Fig. 4). Fire drying is done for at
least four hours, and thereafter the product is left uncovered on
the kitchen floor overnight. A layer of fresh fruit flesh is added
the next morning and the consecutive sun and fire drying steps
follow as the previous day. The alternate sun and fire drying
steps are continued for five to seven consecutive days, where
the length of processing depends on the desired thickness of
product, household size and consumer preference. The
Fig. 4 Drying process of
S. innocua and
S. madagascariensis in Bikita
product obtained can be stored for more than three months
according to 75% of respondents, while 25% of respondents
said they consumed the product soon after processing and did
not store for later consumption. Most consumers of the
product said they had a sensory preference for the smoky flavour of
the product. Wood smoke and fire-charred wood produce
chemical components such as lactones, alcohols, carbonyls,
esters, furans, and phenols, which exhibit several flavours,
including pungent, bitter, spicy, burnt sugary, or smoky
flavours (Maga 1987). Without the smoky flavour the product
was reported as not well accepted by consumers.
Sun drying of S. cocculoides and S. spinosa Solar drying of
S. cocculoides and S. spinosa was commonly done in Lower
Gwelo (68%) district. During hot summer days, monkey
orange flesh is either spread over a flat surface with maximum
heat absorbance or in traditionally-made solar driers covered
with transparent or black plastic. The solar dryers use
convective air for heat that subsequently dries the product. Drying
takes between five days and two weeks, depending on
prevailing weather conditions and whether the desired moisture
content is reached. The determination of the moisture content is
subjective, and physical tests, such as stickiness of the
product, are reported often to be used to evaluate if the product is
dry enough. When dried sufficiently, the product is stored at
room temperature in perforated sacks. The dried product is the
starting material to prepare sweet and snack products or for
inclusion as an ingredient in different preparations such as
juice, porridge or beverages.
Food products for immediate consumption
S. cocculoides and S. spinosa pulp is combined with other
ingredients to make porridge, alcoholic and non- alcoholic
beverages and, less frequently, jam and confectionary for
immediate consumption as in Table 3. Immediate consumption
in this context implies consumption from the time of
processing until no more than two to three days later.
Sundrying (a so - called
process kurovera) 5-7 h
Table 3 Meal times of specific
monkey orange-based products in
S. innocua and S. madagascariensis
S. cocculoides and S. spinosa
Meal timesa (N)
a Respondents answered to meal times for all the products consumed in the household, where each respondent
may have answered consumption times for more than one product
Porridge Two variations of cereal-based porridge meals made
with S. cocculoides or S. spinosa (group A) pulp were
encountered in the survey. The first porridge variant was a
maizebased porridge (called mutandabota) prepared in 15% of the
households in Bikita, 30% of those in Chimanimani, 55% in
Marondera and 82% of households in Lower Gwelo. Maize
porridge is the most commonly processed product using group
A spp. The second porridge variant was a sorghum-based
porridge (called umcaba), as identified by a focus group in
Lower Gwelo area.
For the maize-based porridge, pulp is macerated in water
for 30 min. to 2 h, either standing or with whisking using a
wooden spoon to detach flesh material from the seeds. The
resulting juice or pulp is subjected to heat, and upon boiling,
white maize meal (Zea mays) to water 1:4 (w/v) is added with
stirring until a lump free, gelatinized and a uniform slurry is
obtained; the maize-based porridge. For the sorghum-based
variant, untreated monkey orange pulp or juice is mixed with
boiled, solar-dried ground sorghum, and then consumed
immediately. In both processing methods, the porridge
products are generally thin, flavoured with peanut butter
or sweetened with crystalline sugar. Texture of the
maize meal variant depends on the weight to volume
ratio of maize meal flour to monkey orange pulp. The
maize porridge is usually consumed immediately while
slightly hot or warm as a breakfast food or snack. It can
also be stored in closed clay pots and in cool conditions
for a maximum of two days for re-warming prior to
Fermented beverage Thirty five percent of the households
interviewed in Marondera and 41% of respondents in Lower
Gwelo fermented S. cocculoides and S. spinosa pulp to make
mahewu, a sweet sour cereal-based fermented non-alcoholic
beverage containing fresh monkey orange pulp. Two
variations were encountered in the preparation of a fermented
beverage. In processing method I, the pulp was mashed with cool
stiff maize meal porridge (sadza) (Fig. 3). Either maize,
sorghum or millet flour was added to the mashed product as the
fermentation substrate. In processing method II (Fig. 3),
sorghum or millet flour was added to the fruit pulp without
mashed stiff maize porridge as an initial ingredient. For either
variant, the resultant mixture is incubated for 12–24 h to
facilitate fermentation at ambient temperatures and both are
referred to as mahewu. Saccharomyces yeasts, inherent to the
cereals, contribute to flavour development of mahewu
(Blandino et al. 2003).
Respondents in Marondera (10%) and Lower Gwelo
(14%) added yeast and prolonged the fermentation time
to produce an alcoholic brewed beer. When an alcoholic
beverage is to be prepared, yeast is added to the
product of process I, set near a cooking fire (to maintain
temperatures above 30 °C) and allowed to ferment
naturally over a period of three to four days.
Unfermented beverage The whole fruit pulp or sieved
monkey orange juice may be used to prepare juice. Pulp is sieved
or strained with a mesh sieve substituted traditionally with a
woven high-density polyethylene (HDPE) fruit sack. Water is
added in a 1:1 ratio and lemon fruit juice or citric acid
(depending on availability) is added as a preservative for the
juice. The juice is boiled and crystalline sugar added, again
depending on consumer preference and intended storage time.
The product was consumed within three days. This type of
juice was prepared by 5% of the households in Chimanimani,
15% in Marondera and 41% in Lower Gwelo.
Monkey orange products and their consumption patterns
among respondents are shown in Table 3. Dried S. innocua
and S. cocculoides were mainly consumed as a sweet snack at
lunch time or between meals during time of chores by women
and children. Fermented beverage (mahewu) was consumed
fresh, though some respondents stored the product for a
maximum of two days in a cool environment. Beer was consumed
fresh and up to two to three days after preparation as a leisure
drink during traditional ceremonies and social gatherings.
In the dry region, consumption of monkey orange fruits was
100% for group B spp. and 74% for group A spp. In the wet
region consumption was 82% for group A. The high values
obtained were because the fruit was consumed in its
unprocessed fresh state, hence the high general use for both groups
of species as a pulp. Fruits from the species groups were used
to process the same products, though S. innocua and
S. madagascariensis fruits were not used as a dried product
in the wet region. The proportion in which a particular product
was used only significantly varied (p < 0.05) between the two
regions for both groups of species for the dried product of
group A and for fresh pulp of group B (Fig. 5).
There was a marked difference in uses between the two
groups of Strychnos spp. Group A species had more uses
and were processed into more products than group B species
in both regions. Uses for group B species was higher in the dry
region than in the wet region. Respondents from the wet
region only consumed the fresh fruit of S. innocua or
S. madagascariensis. These findings and observations suggest
that the poorest of the resource limited communities (in the
dry region) better utilize their indigenous fruit by processing
than rural communities that are better off. Communities,
however, do not have proper preservation techniques to allow for
long term use and storage when fruits are out of season,
leading to loss of product by rotting and underutilization.
We found in this study that, in addition of their food value,
monkey orange fruits and products are marketable. In general,
selling was done in the drier and poorer regions, indicating the
possibility of supplementing income in these marginal areas.
Dried S. innocua or S. madagascariensis was mainly sold
informally at rural growth points (small business centres in
rural communities where basic essential services and markets
are concentrated) and from home-to-home. A stack of dried
fruits about 100 g in weight was sold for US $1 with its price
doubling as the fruit drew out of season. Juice was sold at US
$1 for 750 ml at gatherings. None of the products was
reportedly sold in the formal markets at the time of the survey,
demonstrating underutilization of monkey orange despite its
potential for trade as has been indicated in other studies where
monkey oranges are traded between Southern African
countries (Mkonda et al. 2002; Ruffo et al. 2002; Southampton
Centre for Underutilised Crops 2006). Women, being the
custodians of neglected and underutilized fruits, may be
empowered by a change in this situation.
Product processing constraints and quality criteria
Figure 6 presents an overview of processing operations,
constraints and sensory quality characteristics of products from
Strychnos spp. in the study areas.
Solar drying of S. cocculoides and S. spinosa is highly
dependent on environmental temperatures and conditions.
Fruits are harvested in the rainy season, a period when drying
conditions are indefinite, usually resulting in extended drying
times and added demand for labour. The dried products are
also highly hygroscopic, and require storage in dry conditions.
To prevent the loss of quality by an ingress of moisture, the
processed product was stored in plastic sacks or tins with tight
closing lids and re-dried to extend its shelf life. The absence of
efficient drying and storage facilities for monkey oranges was
identified as a prominent difficulty, especially when the rainy
season begins. These processing and quality constraints were
highlighted as highly problematic in the focus group
discussion. Other quality constraints observed during drying were
dust, and animal and mould contamination, especially during
humid weather. When solar driers were used, poor hygienic
standards were also noted as a factor of equal importance
through the inclusion of seeds and vegetables from previous
drying processes. This may also account for the degradation of
Fig. 6 Process constraints and
quality criteria identified by
respondents in study regions
to disease for
young and old
Important quality characteristics of dried S. innocua and
S. madagascariensis product are colour, a smoky flavour
and low moisture content, though they vary from one
processor to another and from time to time. Respondents appreciated
a golden to brown colour; a darker colour than this was
perceived as charred and likely to have a characteristic burnt taste
and flavour. Though fruit is spread uniformly on the drying
rack, the desired colour is difficult to achieve due to variation
in fire and solar temperatures because heat and air flow are not
controlled or uniformly distributed on the drying rack during
the drying period. Therefore processors have to continuously
change the rack position during both fire and solar drying.
Typical wood smoke flavour is caused by factors such as
wood moisture content, air temperature, intermediate or stable
volatile compounds and chemical reactions with other food
components (Maga 1987). These are not controllable at a
household level. The type of wood used in fire-drying is based
on availability, therefore differences in sensory quality of the
product are encountered. The fruit may be pre-treated with
sugar or salt before drying. Respondents indicated that
crystalline sugar facilitates rapid drying, prevents the compacting
of the dried product on the rack and eases separation on
handling and consumption, while salt maintains colour and
texture of the fruit. Pre-treatment with sugars (i.e. osmotic
dehydration) has been used in the preservation of other fruit
to hasten drying, reduce browning, increase retention of
volatiles and reinforce a sweet taste (Osorio et al. 2007). In some
cases in the areas visited, pre-treatment was immediately
followed by sun drying with no incubation leading to the
assumption that some of the pre-treatment effects may not
reach the maximum due to limited exposure to the osmotic
agents, i.e. the sugar or salt.
Respondents mentioned increased flavour, sweetness,
clarity and low viscosity as good quality indicators of monkey
orange juice. Colloids such as polysaccharides are known to
be responsible for the viscosity of fruit juice and cloudiness in
other fruit juices such as lemon juice (Uçan et al. 2014).
S. cocculoides and S. spinosa juice is viscous and the viscosity
affects the appearance of the product and its overall
acceptance. Processors add a significant amount of water until the
juice is sufficiently liquefied. The dilution and resultant
consistency depend on consumer preference, as found in the study
of Bille et al. (2013), where panellists also preferred diluted
juice. However, on the contrary, respondents did agree that
although viscosity is reduced by dilution, the major drawback
was a reduced Strychnos spp. flavour. During processing the
separation of seed and flesh is low, giving low juice yield
Porridge is mainly prepared for and consumed by the
whole family and usually introduced as a complementary food
to infants from as early as four to six months. Porridge that had
simmered longer lost the characteristic monkey orange
flavour. Thermal treatments can inactivate enzymes that catalyse
the production of volatiles as well as cause the loss of
precursors of the volatile compounds (Nijhuis et al. 1998). Cooking
time and ratios of addition of monkey orange juice or pulp
also may have a bearing on the resultant flavour.
The most important sensory quality determinants of
monkey orange fruits were colour and taste (sweetness). Fruits are
picked before maturity for ripening during storage.
Respondents used external visual attributes such as colour,
size and surface structure to predict the taste of the fruit.
Selection of this nature is, however, a subjective method
(Reid 2002). There are currently no objective minimum
indices for the determination of maturation at the household level
in rural areas, which results in variation in fruit selection. All
in all, fruit harvesting and processing conditions, and
parameters, are not standardized and therefore variation in product
quality are prominent for all the products we identified.
Conclusion and recommendations
Collection, processing and consumption of the monkey
orange fruit are common activites in the dry and wet regions
we assessed in Zimbabwe. Health benefits, value addition,
market access, and education about propagation and
cultivation of monkey orange fruit have an effect on proper
utilization of the fruit in both regions for food and nutrition security.
Respondents in farming communities believe the fruit
products, particularly porridge, have health benefits. The chemical
compounds involved and mechanisms for nutritional and health
benefits are unknown, as these appear to be new findings that
require further scientific studies for substantiation. Exploration
of strategies through scientific research for value addition and
market access by small-scale fruit processing units through
community cooperatives are an important contribution to
curbing the challenge of food and nutrition security for households
and individuals in Zimbabwe. Increasing education on the
cultivation and propagation of monkey orange trees through
information and planting material available at different centres in
Southern Africa, such as Veld Products Research and
Development, Botswana, and World Agroforestry Centre,
Zimbabwe (Southampton Centre for Underutilised Crops
2006), are also important for sustainability of these indigenous
fruits. We recommend putting in place a research and
development program targeted at monkey orange and other
underutilised fruits under the custodianship of stakeholders
from government, research institutes and processors. The results
of improved technologies and know-how, which will benefit
women cooperatives and small-scale processors by expanding
what they sell and promote and therefore their incomes, can be
transferred by government extension services and NGO’s.
Constraints for Strychnos spp. processing (i.e. drying rate,
product splitting, flesh/seed separation, juice yield, phase
separation), shelf life and sensory quality characteristics (colour,
flavour, and viscosity) were increased by mainly
unstandardized processing conditions and treatments. These
constraints illustrate how generic some food technological
problems and solutions can be, and yet how product-specific some
problems and solutions are in relation to the different fruits of
the same species; a concept that can be translated to various
types of indigenous fruits in Southern African countries.
In scientific literature, Strychnos spp. have been labelled
(amongst other indigenous fruits) as Blost fruit^ (National
Research Council 2008) and as neglected and underutilized
species that are being lost at an extraordinary rate before they
can be completely characterized, researched and promoted
(Padulosi et al. 2013). Food and nutrition security is
multifaceted due to its interrelated complex dimensions. To facilitate
the achievement of food and nutrition security, every
contribution from all disciplines is worthwhile. Therefore, as a
followup to this survey, it is paramount from a food quality and
design perspective to conduct experimental research to assess
product quality characteristics and the contribution to nutrition
of traditionally-processed products from Strychnos spp.
Acknowledgements We thank the Netherlands Fellowship Programme
for financial support (grant award CF9151/2013). Also we are grateful for
the assistance given by Mrs. Beauty Katsenga, Ever going Association
(Mahusekwa, Marondera), Fambidzanai Permaculture, Mr. Bornface
Matimba, Mr. Goodwill Moyo, community leaders, and participants in
the interviews and focus groups in the study areas (Marondera, Bikita,
Chimanimani and Lower Gwelo, Zimbabwe).
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Ruud Verkerk obtained his BSc
on general microbiology and
received his PhD in food
technology from Wageningen University,
The Netherlands. He has worked
his whole career in different
positions at Wageningen University,
where he is now an associate
professor in the Food Quality and
Design group. His main research
focus is on secondary plant
metabolites (phytochemicals) in food
supply chains with specific
emphasis on processing. He
specializes in the role of the food matrix
in the behaviour of nutrients and phytochemicals in relation to processing
of fruits and vegetables.
Loveness K. Nyanga is a senior
lecturer and researcher at the
Institute of Food, Nutrition and
Family Sciences, University of
Zimbabwe. She is the chairperson
of Nutrition Action Zimbabwe, a
local NGO in Zimbabwe. She
holds a PhD in Food Science from
Wa g e n i n g e n U n i v e r s i t y ,
The Netherlands. Her research
areas include traditional and
indigenous foods, food safety, food and
nutrition security and small scale
Vincenzo Fogliano graduated in
Chemistry at the University of
Rome and received a PhD in
F o o d S c i e n c e a t C o r v i n u s
University of Budapest. He held
various positions in Biochemistry
and Food Chemistry at the
universities of Rome and Naples. In 2013
he became Professor and chair of
the Food Quality Design Group at
the University of Wageningen,
The Netherlands. His activity is
on the Maillard reaction, the design
of functional food containing
dietary fibre, proteins and
phytochemicals from different sources. He acted as coordinator of FP7 EU projects,
COST action and strategic national cluster projects. Vincenzo was President
of the International Maillard Reaction Society up to 2012 and is a member of
the advisory board of ILSI Europe. He is the author of more than 250
publications (h index of 46), being among the world's highly cited scientists
according to the ISI Thompson list (www.highlycited.com).
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Anita Linnemann obtained a double Masters degree from Wa g e n i n g e n U n i v e r s i t y i n Tropical Agriculture and Food Technology . She completed her P h D t h e s i s , e n t i t l e d E c o p h y s i o l o g y o f b a m b a r a groundnut (Vigna subterranea (L.) Verdc.), and has been a staff member of the Food Quality and Design group of Wageningen University since 1995. Her expertise is in consumer-orientated food product development with special attention to sustainability