Bio

Dr. John Wangoh

Dr. John Wangoh was born on 03/07/1955. He is married. He holds a B.Sc. (Food science and Technology) from University of Nairobi, 1978, M.Sc. (Food Science and Technology ) from University of Nairobi, 1984 and PhD (Food Science) from Swiss federal Institute of Technology-Zurich, 1997. He is currently working as a Senior Lecturer at the Depart of  Science, Nutrition and Technology. Dr. John Wangoh Joined the University of Nairobi in 1989 as a lecturer.

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Publications


2013

Njage, PMK, Dolci S, Jans C, Wangoh J, Lacroix C, Meile L.  2013.  Phenotypic and genotypic antibiotic resistance patterns of staphylococcus aureus rom raw and spontaneously fermented camel milk. British Journal of Applied Science & Technology. 3(3):87-98.
Njage, PMK, Dolci S, Jans C, Wangoh J, Lacroix C, Meile L.  2013.  Biodiversity and Enterotoxigenic Potential of Staphylococci Isolated from Raw andSpontaneously Fermented Camel Milk. British Microbiology Research Journal. 3(2):128-138.2013_biodiversity_and_enterotoxigenic_potential_of.pdf

2012

Njage, PMK, Dolci S, Jans C, Wangoh J, Lacroix C, Meile L.  2012.  Ampicillin resistance and extended spectrum β-lactamases in Enterobacteriaceae isolated from raw and spontaneously fermented camel milk. African Journal of Microbiology Research. 6(7):1446-1452.2012_ampicillin_resistance_and_extended_spectruml.pdf
Gitahi, MG, Wangoh J, Njage PMK.  2012.  Microbial Safety of Street Food in Industrial Area, Nairobi. Research Journal of Microbiology. 2012-microbial_safety_of_steet_foods.pdf
Kaindi, DWM, Schelling E, Wangoh J, Imungi JK, Farah Z, Meile L.  2012.  Risk Factors for Symptoms of Gastrointestinal Illness in Rural Town Isiolo, Kenya. Zoonoses and Public Health. 59:118-125.2012-risk_factors_diarrhoea_and_vomiting.pdf

2011

Wayua, FO.  2011.  Evaporative Cooling and Solar Pasteurization technologies for value addition of Camel (Camelus dromedaries) Milk in Marsabit and Isiolo Counties of Northern Kenya. (M. W. Okoth, J. Wangoh, Eds.).: University of Nairobi Abstract

Abstract
The potential for evaporative cooling and solar pasteurisation technologies for value addition
of camel milk in Marsabit and Isiolo counties of northern Kenya was investigated. To find
out existing postharvest handling and preservation practices, a survey was conducted using a
semi-structured questionnaire and focus group discussion on 167 came l milk producers, 50
primary and 50 secondary milk traders. Results showed that the camel milk chain was
characterised by poor milk handling infrastructure, including poor roads and lack of cooling
facilities. Camel milk was marketed raw under unhygienic conditions with minimal value
addition, and spoilage was a major problem. Milk traders occasionally boiled milk using
firewood as a means of temporary preservation during times when transport was unavailable.
Provision of appropriate cooling facilities and utilisation of renewable energy technologies
such as solar energy for milk processing were identified as possible intervention strategies to
enhance marketing.
Therefore, a low-cost charcoal evaporative cooler was developed and tested for the storage
of camel milk. The cooler, 0.75 m3 in capacity, was made of galvanised angle iron (25 mm x
25 mm x 4 mm) frame with 10 cm wide charcoal walls which were moistened through a drip
system. Temperature of camel milk inside the cooler did not significantly (p>0.05) change
after storage for 10 hours. However, temperature of control milk at ambient conditions
significantly increased (p=0.05) over the same period, from 22.6 ± 0.08°C to 28.1 ± 0.08°C.
Milk inside the cooler was also significantly cooler (p=0.05) than control milk in the
evening, with a net temperature reduction of 27.0%. Total bacterial count changed from
31.4±2.1 x 104 colony forming units per ml (cfu.ml–1) to 43.1±1.9 x 104 and 1638±81 x 104
cfu.ml–1 for milk inside the cooler and that at ambient conditions, respectively, after storage
for 10 hours. The cooler’s performance was modelled using artificial neural networks
(ANN), with inputs being ambient dry bulb temperature, wet bulb temperature, wind speed
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and temperature of drip water. The outputs were cooled milk temperature and cooling
efficiency. The ANN predictions agreed well with experimental values with mean squared
error (MSE) of 10.2, mean relative error (MRE) of 4.02% and correlation coefficients (R2) in
the range of 0.86-0.93.
The development of the solar milk pasteuriser started with thermal performance testing of
four water heating flat plate solar collectors available in Kenya with the objective of
selecting a suitable one to be used to provide process heat for batch pasteurisation. The
collectors included three commercial solar collectors purchased from local shops in Nairobi,
Kenya and one prototype collector designed and fabricated by the author. The three
commercial solar collectors had effective areas of 1.67, 1.87 and 1.83 m2 while the self-made
collector had an effective area of 1.60 m2. Thermal performance of the collectors was
determined in terms of the Hottel-Whillier-Bliss equation. The FR(ta )e values, obtained
using the effective collector areas and the inlet water temperature, were 0.76, 0.75, 0.73, and
0.82, respectively, for the commercial collectors and the self -made collector. The FRUL
values were 8.33, 12.01, 9.80 and 13.77 W.m–2.°C–1, respectively. The solar collector with
the lowest FRUL value had a black chrome selective absorber surface and was the most cost
effective for delivering temperatures of about 80°C at an efficiency of 15%. It was used to
develop a low -cost batch solar milk pasteuriser consisting of the collector and a cylindrical
milk vat. The milk vat had a 50 mm-wide hot water jacket and an outer layer of 38 mm thick
fibre glass insulation. The water jacket held approximately 30 litres of water, whereas the
milk tank had a capacity of 80 litres. The hot water produced by the collector was used for
pasteurising milk. The optimum quantity of milk which could be pasteurised by this device
under the study conditions was 40 litres, which was pasteurised in approximately 1.3±0. 5
hours at an average insolation and ambient temperature of 22.5±0.9 MJ.m–2.day–1 and
29.8±0.1°C, respectively. The average temperature difference between hot water and milk
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being pasteurised was 8.1±0.6°C. Total bacterial counts in pasteurised milk were less than 10
cfu.ml–1 while coliform counts were negative.
The solar milk pasteuriser was modelled using ANN as described for the cooler. The inputs
of the model were ambient air temperature, solar radiation, wind speed, temperature of hot
water, and water flow rate through the collector, whereas the output was temperature of milk
being pasteurised. The ANN predictions agreed well with experimental values , with MSE,
MRE and R2 of 5.22°C, 3.71% and 0.89, respectively.
It has thus been established that there is both the need and potential for evaporative cooling
and solar pasteurisation along the camel milk value chain in Kenya. The two technologies
augment each other in increasing the quantity and quality of marketed camel milk from
scattered pastoral production sites in Kenya. The devices are of low cost and can be locally
fabricated by village artisans using locally available materials , and their performance can be
successfully modelled using ANNs, which helps to design an appropriate system for any
application.

Kaindi, DWM, Schelling E, Wangoh J, Imungi JK, Farah Z, Meile L.  2011.  Microbial Quality of Raw Camel Milk Across the Kenyan Market Chain. Food 5. Global Science Books. ((Special Issue 1)):79-83.2011_microbial_quality_of_raw_camel.pdf
Njage, PMK, Dolci S, Jans C, Wangoh J, Lacroix C, Meile L.  2011.  Characterization of Yeasts Associated with Camel Milk using Phenotypic and Molecular Identification Techniques. Research Journal of Microbiology DOI: 10.3923/jm. 2011-characterization_of_yeasts_associated_with_camel_milk.pdf

2010

Njage, PMK;, Jans C;, Wangoh J;, Farah Z;, Lacroix C;, Meile L.  2010.  iodiversity And Genotyping Of Staphylococci Isolated In Raw And Fermented Camel Milk In East Africa..
Farah, Z;, Meyer J;, Wangoh J;, Eberhard P;, Gallmann P;, Rehberger. B.  2010.  Effect of Ultra - High - Temperature treatments on camel milk..
PMN, K, PO L, Wangoh J.  2010.  Effect of Lactoperoxidase-Thiocyanate-Hydrogen Peroxide System and Storage Temperature on Keeping Quality of Raw Camel Milk.. . African Journal of Food Agriculture Nutrition and Agriculture Online. 10(10)
Akweya, BA.  2010.  Prevalence of streptococcus agalactiae and staphylococcus aureus in camel (Camelus dromedarius) milk in Garissa and Wajir districts of Kenya, their sensitivity to antibiotics and acceptability of camel milk and its products. (J. Wangoh, P. Gitau, Eds.).: University of Nairobi Abstract

Abstract
Camel milk is commonly consumed raw by pastoralists in arid areas who may
be unaware of the risks posed by such milk. It was therefore very important to
determine the prevalence of Staphylococcus aureus and Streptococcus
agalactiae, which are some of the most common pathogens in such milk.
Camel milk samples from Garissa and Wajir were analyzed to determine the
prevalence of Staphylococcus aureus and Streptococcus agalactiae. The
antibiotic resistance of the bacteria was also studied. Milk samples (n =207)
were aseptically obtained from primary marketing agents. Samples were
analyzed for the presence of Staphylococcus aureus and Streptococcus
agalactiae. The confirmed Staphylococcus aureus and Streptococcus
agalactiae were subjected to diffusion sensitivity test. Resistance was
determined by measuring the diameter of the zone cleared by the antibacterial
and the isolates were reported as susceptible, intermediate, or resistant.
Questionnaires were administered to evaluate camel milk and milk product
acceptability.
The prevalence of Staphylococcus aureus and Streptococcus agalactiae in the
two districts differed with Garissa having higher percent incidence both for
Staphylococcus aureus (34.95%) and Streptococcus agalactiae (37.79%).
Wajir, had lower prevalence of Staphylococcus aureus (10.58%) and
Streptococcus agalactiae (7.69%). Staphylococcus aureus and Streptococcus
agalactiae were resistant to most of the antibiotics except Gentamicin.
x
Although camel milk and milk products were acceptable, each had different
quality parameters that attracted customers. The most important purchasing
criterion for raw camel milk was taste (27%, 19% and 18%) for Wajir, Garissa
and Nairobi respectively. While packaging (18%, 18% and 16%) was more
important for pasteurized milk also in the same order. For yoghurt the most
important purchasing criteria were taste (18%) and aroma (19%). The taste of
sour camel milk is the most important attribute in both Garissa (30%) and
Nairobi (24%).
The results indicate the potential health risk of consuming raw camel milk and
increasing incidences of resistance of mastitis organisms to the common
antibiotics. There is need to educate camel milk producers on hygienic milk
production as well as inform the raw camel milk consumers on dangers
involved. Marketing of camel milk and products can be enhanced using the
attributes appropriate for each product in the respective district.

Njage, PMK.  2010.  Microbial diversity, safety and role of predominant lactic acid bacteria in raw and spontaneously fermented camel milk in Kenya and Somalia. (J. Wangoh, Z. Farah, L, Meile, Eds.).: University of Nairobi Abstract

Abstract
In Eastern Africa, where 60 % of the world camel population is held, there is a long tradition
of preparing fermented camel milk known as suusac. The fermentation is spontaneous and
results in a product whose quality varies greatly, may be risky and even dangerous for
consumer health due to unpredictable microbial inhabitants. These risk factors arise not only
from unhygienic handling of camel milk but also from zoonotic bacteria usually attributed to
producing animal mastitis. Misuse of common antibiotics in treatment of camels could also
push bacteria to develop mechanisms to evade the inhibitory power of antibotics.
There is now a major change in consumer choice with shift towards good hygienic quality
camel milk and products and also readiness to pay more for the better quality. This calls for
development of formal camel dairy to address this value addition potential and also reduce
health risks leading to improved camel milk commercialisation.
It is therefore important to understand the predominant microorganisms in raw milk and
suusac and to ascertain their potential impact safety and quality of raw camel milk and
suusac. The diversity of pathogens and yeasts in raw and spontaneously fermented camel
milk in Kenya and Somalia was studied using phenotypic and molecular techniques.
Potential pathogenic microorganisms were studied for their virulence and antibiotic
resistance profiles. Technological properties of predominant lactic acid bacteria were studied
as prerequisite to the introduction of an adapted starter culture for suusac fermentation.
A total of 235 presumptive staphylococci isolated from 105 camel milk and related samples
from five locations in Kenya and two locations in Somalia were identified and characterized
phenotypically and genotypically. PCR amplification of the genes encoding antiphagocytic
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capsular polysaccharides cap5 and cap8, and staphylococcal enterotoxins SEA to SEE and
SEG to SEJ was also carried out. Secondly, the antibiotic resistance patterns of 47
Staphylococcus aureus isolates was studied using microdilution assays to determine minimal
inhibitory concentrations and disc diffusion tests. Genotyping was then done using
microarray hybridization and confirmation of antibiotic resistance genes by PCR.
Escherichia coli, Klebsiella pneumoniae Pneumomia and Enterobacter cloacae which have
been implicated worldwide as producers of Extended Spectrum β-lactamases (ESBLs) were
the predominant Enterobacteriaceae in raw milk and suusac. Antibiotic resistance risk posed
by these bacterial pathogens was characterized for 95 isolates both phenotypically and
genotypically. Escherichia coli isolates were also evaluated for presence of virulence factors.
The prevalence and epidemiology of E. coli O157 and non-O157 shigatoxigenic E. coli
(STEC) along the raw and fermented camel milk marketing chain was studied in 70 samples.
Serotypes and associated virulence factors in the isolated strains were also determined.
Various selective media and immunomagnetic separation were used followed by multiplex
PCR for virulence genes stx1, stx2 and eae and for positive samples a second multiplex PCR
to type for the serotypes O157, O113 and O111. PCR-RFLP of the fliC gene also carried out
on the O157, O113 and O111STEC to elucidate the epidemiology of the serotypes.
Yeasts were identified using combination of both phenotypic and genotypic techniques.
Identification was done using API 20C AUX followed by Restriction Fragment Length
Polymorphism (RFLP) of intergenic spacers ITS1 and ITS2 using restriction endonucleases
HhaI, HinfI and HaeIII. RAPD was performed with (GTG)5, (GAC)5, (GACA)4
microsatellite primers and M13 core sequence (5'-GAG GGT GGC GGT TCT-3'). Sequence
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analysis of either ITS1 and ITS2 or the 26S rRNA encoding gene was performed on selected
isolates.
Finally, 95 lactic acid bacteria (LAB) consisting of Lb. helveticus, Lb. fermentum, Lc. lactis
subsp. Lactis and Str. thermophilus isolated from various camel milk and associated sources
from main camel milk production points in Kenya and Somalia were studied for acidification
and metabolic properties. Str. infantarius which is a putative human pathogen was also
studied due to its predominance amongst presumed streptococci isolated to ascertain its role
in the spontaneous fermentation. Initial screening was carried out in a microtiter assay and
LAB were then selected for fermentation in batch culture experiments using a CINAC
system which allowed continuous follow-up of pH changes during fermentation in camel
milk during incubation at 30, 35 and 40oC for 36 h. Parameters including maximal
acidification rate (Vmax), time and pH at which Vmax occurred (tmax and pHmax), lag phase (ta),
time during which the acidification rate was equal to or higher than Vmax/2 (dt50), time to
reach pH 5.0 (tpH5), final pH (pHF) and time to reach final pH (tpHF) were calculated.
Metabolites of sugars, lactose, glucose and galactose and flavour compounds, citrate, acetate,
acetaldehyde, diacetyl and ethanol, were also quantified using High Performance Liquid
Chromatography (HPLC). L(+)-/D(-)-lactic acid production was studied using an enzymatic
assay. Potential cultures were selected based on the number of desirable acidification kinetic
values for fast acidification and also flavor metabolites when compared to the other cultures.
Presumptive staphylococci increased along the market chain. There were 146 (62 %)
confirmed staphylococci isolates of which, 66 (45 %) were Staphylococcus aureus.
Coagulase positive staphylococci were predominant in raw camel milk directly obtained
from the camel (25 %), at the market level (23 %) and fermented milk (suusac) (21 %). S.
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epidermidis accounted for 29 % of coagulase negative Staphyolococci (CNS) studied. The
remaining CNS were distributed among S. simulans (18 %), S. saprophyticus (11 %), S.
haemolyticus (2 %), S. hyicus (2 %), S. xylosus (2 %), S. lentus (1 %), S. carnosus (1 %) and
S. microti (1 %). Aerococcus viridans (1 %), Macrococcus caseolyticus (1 %) and M.
nishinomiyaensis (1 %) were also identified. The gene cap5 encoding antiphagocytic
capsular polysaccharide was observed for 9 (14 %) and cap8 for 16 (24 %) of the isolates.
Enterotoxin genes were observed in 47 % of the isolates with sej in 34 %, seb in 6 %, sed in
5 % and seg in 3 % of the isolates. Amongst the species enterotoxin genes were detected in
90 %, 65 %, 38 % and 22 % of the S. simulans, S. epidermidis, S. sapropyticus and S. aureus
respectively. Rep-PCR genotyping revealed diversity of the isolates though with close
similarities irrespective of the level along the market chain and sampling location indicating
ubiquity of the isolates in primary and secondary environments.
There were 11 (23 %), 12 (26 %), 5 (11 %), 6 (13 %), 3 (6 %) and 18 (38 %) isolates
resistant to ampicillin, gentamicin, streptomycin, tetracycline, trimethoprim, fusidic acid
respectively. Amongst the multi-resistant isolates 2 were resistant to 2 antibiotics, 7 to 3
antibiotics and 6 to 4 or more antibiotics. Based on microarray, all 3 isolates tested were
positive for the β-lactamase resistant genes (blaZ), tetracycline resistance with gene tet38 and
the Panton-Valentine leukocidin gene pvl. Additionally, 2 isolates harboured streptomycin
resistance gene and tetracycline resistance through the gene tet(K). PCR targeting these
genes was performed for all isolates and 6 were positive for tetK, 9 for blaZ and 2 isolates
harboured both tet(K) and blaZ genes.
Enterobacteriaceae were not detected at milking and first collection point but were present at
104- 106 CFU/ml in final market raw camel milk and 103-107 CFU/ml in suusac. The
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Enterobacteriaceae belonged to 14 species and 10 genera. Predominant isolates were
Escherichia coli 1 (47), Klebsiella pneumoniae Pneumoniae (35) and Enterobacter sakazakii
(18). Salmonella arizonae, Serratia odorifera 1, Enterobacter cloacae and Escherichia coli 1
occurred at mean cell counts greater than 8 log cfu/ml. Enterotoxin genes stx1 and stx2 were
not detected in any of the E. coli isolates with only one isolate with sequence coding for
intimin (eae) was detected.
Of the isolates, 61 (63 %) were resistant to ampicillin, of which 46 (48 %) were E. coli, 45
(46%) K. pneumoniae Pneumoniae and 16 (7%) E. cloacae. ESBLs were not phenotypically
detected in any of the isolates by double disc diffusion test. However, PCR revealed
prevalence of blaSHV, blaCTX-M-3-like and blaCTX-M-14-like genes in 37 (60 %), 25 (40 %) and
11 (18 %) of the isolates respectively. K. pneumoniae Pneumoniae not only harbored
majority of the genes (74 % of K. pneumoniae Pneumoniae), but a strain of K. pneumoniae
Pneumoniae possessed all 3 genes and 13 harbored both blaSHV and blaCTX-M-3-like genes.
Thirty six percent of the isolates harbored either single or combinations of factors stx1, stx2
and eae with 78 % being stx1 positive, 18.6 % eae positive, 3.9 % stx1 and stx2 positive and
0.78 % stx2 and eae positive. Prevalence of isolates positive for the virulence factors stx1,
stx2 and eae increased from 32.6 % at herd level to 34.2 % in first collection point and 44.3
% in the final market. Though highest percentage of presumptive E. coli isolates (57 %) were
isolated using EMB agar while the rest were from CHROMagar (23 %) and CT-SMAC (21
%), amongst the isolates harboring virulence genes, 100 %, 12 % and 39 % were isolated
from CT-SMAC, EMB agar and CHROMagar respectively. Serotypes O157, O111 and O113
represented 94 %, 2 % and 4 % of the STEC respectively. Thirty nine different restriction
XXIII
endonuclease digestion profiles were revealed by the RFLP of the flic gene with O157 having
29 profiles bearing 7 clusters with common profiles.
There were low numbers of yeasts in milk at herd level but 4.4±1.4 log cfu/ml and 5 ±1.5 log
cfu/ml at the first collection point and final market respectively. Counts of up to 7.5 ± 2.5 log
cfu/ml were found in laboratory fermented suusac. Amongst the identified isolates, API
enabled the identification of 80 (47%) and resulted in either incorrect identification or
inability to identify the others. RFLP, RAPD and sequence analysis enabled complete
identification to species and some differentiation at strain level with RAPD allowing more
discrimination within species. There were 21 yeast species belonging to the genera
Rhodotorula, Cryptococcus, Candida, Saccharomyces, Trichosporon, Geotrichum and
Issatchenkia. The most frequently isolated yeasts were Saccharomyces cerevisiae (19 % of
the identified isolates), Candida inconspicua (12 %), Trichosporon mucoides (11 %),
Candida famata (11 %), Rhodotorula mucilaginosa (8 %), Candida lusitaniae (6 %),
Cryptococcus laurentii (5 %), Cryptococcus albidus (5 %), Candida guilliermondii (5 %),
and Trichosporon cutaneum (5 %). Lowest viable counts for the identified yeasts were 2.4
cfu/ml for C. tropicalis and highest were 7.6 cfu/ml (range; 2.4-8.5 cfu/ml) for C. famata and
8.0 cfu/ml (range; 2.6-8.5 cfu/ml) for C. guilliermondii.
When LAB were ranked in the increasing order of mean pH from the microtiter acidification
assay, the strains were Str. infantarius (5.32 ±0.36), Lb. helveticus (5.33±0.09), Lc. lactis
subsp. lactis (5.5±0.49), Lb. fermentum (5.67±0.53) and Str. thermophilus (5.7±0.15). Lc.
lactis subsp. lactis had a short ta (145 min), tmax (424.5 min) tpH5 (535 min) and tpHF (30h),
and low pHF (4.10) during incubation at 30 oC. Moreover, at 35oC, the Vmax increased from
0.00531 to 0.006805 pH units min-1, tmax decreased from 424 to 271 min and tpHF decreased
XXIV
from 30.75 to 19.00 min. Even though Str. thermophilus 150A3.1 showed short ta (183 min),
tmax (378 min) and low pHF (4.4) at 30oC, at 35oC Str. thermophilus was in the grouped with
slowest acidifiers. Str. thermophilus 150A3.1 however, produced the highest quantity of
galactose (3.8 g/l) and glucose (3.56 g/l) at 37oC. Str. thermophilus 221A11.3 performed
better at 35 than 30oC with increased Vmax (from 0.00169- 0.0063 pH units min-1) together
with shorter ta ( from 279 to 82.5 min) and tpHF (from 43 to 19.0 h). Str. thermophilus
221A11.3 also produced highest formate (2072 mg/l) at 35oC. Lb. helveticus showed second
highest Vmax (0.00937 pH units min-1), had a low pHmax (5.17), short tpH5 (705 min) and low
pHF (4.23) at 30oC. Lb. helveticus also produced highest amounts of acetaldehyde (106.7
mg/l at 37oC), ethanol (1590 mg/l at 37oC) and acetate (1540 mg/l at 35oC). However highest
quantities of D(-) lactate (1.338 g/l at 37oC) were also produced by Lb. helveticus. Mixed
cultures Lc. Lactis subsp. lactis + Str. thermophilus 150A3.1, acidifed at highest overall Vmax
(0.07999 pH units min-1) and Lc. lactis subsp. lactis + Lb. helveticus to lowest pHF (3.9). By
combining Lb. helveticus with either of Str. thermophilus 221A 11.3 and Str. thermophilus
150A3.1, they produced lactate at highest (7.62 g/l) and second highest (7 g/l) quantities
respectively at 35oC. Lb. helveticus + Str. thermophilus 221A 11.3 also reached pH 4.1
within 33.5 h at 30oC. Even though Str. infantarius had short relatively short tmax at 30oC, at
35oC it reached a lower pHmax (5.29) and acidified at a longer dt50 (1202 min) when
compared with other strains. The range in time it took to reach maximum acidification for all
the strains or their combinations was was however high (9-1204 min at 40oC incubation).
The high prevalence of toxin-producing staphylococci requires consideration for food
hygiene and safety especially regarding the aspect that the milk is consumed raw or as
fermented raw milk.
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Controlled antibiotic therapy in Kenyan and Somali camels should be introduced to prevent
the increase of antibiotic resistant bacteria. Pastoralists should also be instructed on the use
for rapid detection mastitis tests and the best single antibiotic or their combinations that
minimize development of resistances.
Molecular methods remain the most reliable methods of choice for identification of ESBLproducing
enterobacteria isolates. The finding of a high diversity of enterobacteria in camel
milk especially at market level and suusac calls for measures to improve handling of camel
milk.
The higher prevalence of STEC in camel milk than in cases with milk from other species
indicates that this milk could be an important vehicle for transmission of STEC to humans.
Possibility of a continuous contamination with different STEC strains then distribution of
these strains during handling and storage of milk at this point was also revealed. This calls
for interventions on hygienic factors and animal health at all levels in the marketing chain.
A combination of phenotypic and molecular methods for proper yeast identification is
recommended. The high diversity and numbers of yeasts indicate their role in the
fermentation of camel milk and potential for inclusion as starter cultures.
In order to further select and adapt the starter cultures, sensory analysis, antibiotic
susceptibility tests and also survival of the cultures under different preservation methods
should be studied in order to optimize their application. The robust nature of Str. infantarius
calls for challenge tests including Str. infantarius as a contaminant to further select starter
combinations that would show competitive advantage over this predominant but potentially
pathogenic bacterium.

2009

Kaindi, MDW.  2009.  Microbiological quality of camel milk along the market chain and its correlation with foodborne illness among children and young adults in Isiolo, Kenya. (J. Wangoh, E. Schelling, J. K. Imungi, Eds.).: University of Nairobi Abstract

General Abstract
The study was done to determine the microbiological quality of raw camel milk along the
informal market chain and to assess risk factors in symptoms of food-borne illnesses and the
role of camel milk in the diet of camel pastoralists. Camel milk samples were collected from
the milking point, camel milk first collection point (primary collectors) in the local market
center and at the final market in Nairobi. Microbiological assessment involved enumeration
of total bacterial count (TBC), presumptive Streptococcal/ Enterococcal count (PSEC), Yeast
and Mold count (YMC), Enterobacteriaceae count (EBC) , and presumptive Staphylococcal
count (PSC). Deterrn ination of the shelf Iife of pasteurized camel milk stored at 4-7°C, 2SoC,
and at 30°C was also investigated. Raw camel milk was pasteurized at 6SoC for 30 minutes in
a water bath. Further, a cross sectional study was carried out by interviewing 993 randomly
selected households in peri-urban zone of Isiolo town to assess risk factors in symptoms of
food-borne illnesses with special attention given to the consumption of camel milk, cow milk
and goat milk.
Results indicate that microbial counts were increasing along the marketing chain. Camels'
milk milked in aseptic manner from the udder had TBC 2.1 x 101-4. 7x 104 cfuml', PSEC
1.8xI01-2.4xI04 cfumrl. Bulked milk at the herd level had TBC 9.2xl02-1.7xl04 cfuml",
I PSEC 3.7x10 I-3.4x.I0- ~ cfuml -I, YMC 2.lx10 I-?2.7xI0- cfurnl -I,EBC I.lxlO I-8.lxI0 2 cfuml -I
and PSC 3.Sxl02-8.3xl03 cfumrl. Bulked camel milk at the primary collector at the local
market center had TBC I.lxl03-S.6xl05 cfuml", PSEC 3.1xlOI-2.7xl04 cfuml', YMC
bulked milk at the final market in Nairobi had TBC 4.7xl05-107 cfuml", PSEC 2.0xl02-
9.lxI04-2.8xl05 cfumrl.Milk at the milking level had TBCs not exceeding microbiological
XIV
limit of 105 cfumri and thus a grade I quality milk. At primary collectors 25% had EBC
exceeding 103 cfuml' indicating grade Il quality of milk. 75% of bulked milk at the final
market exceeded the TBC acceptable limits of 106 cfuml' and EBC of 5.0xl 04 cfumri which
is in grade III and IV quality of raw milk which per the Kenya bureau of Standards 2006,
indicates poor quality milk and a threat to human health.
The Kenya Bureau of Standards specifications for pasteurized cow milk were applied as
criteria to establish the shelf life of camel milk. The shelf life was considered ended when the
Total bacteria counts exceeded 3.0x 104 cfurnl', Enterobacteriaceae count was> 10 cfum!"i
or alcohol test positive. Raw milk used had Total Bacteria Count 5.7x 105 cfuml',
Enterobacteriaceae Count l.4x 104 cfuml", Presumptive Streptococcal/ Enterococcal Count
1.2xl04 cfuml', Presumptive Staphylococcal Count 6.7x103 cfuml', Yeast and mold Count
9.5xlOi cfuml', acidity 0.16%, pH 6.64, antibiotic residue free, hydrogen peroxide free and
alcohol test negative. The residue TBC after pasteurization process was less than 10 cfuml i
while EBC, PSEC, PSC and YMC were completely destroyed. TBC of pasteurized camel
milk stored at 4-7°C exceeded the KEBS specifications in 49-54 days while TBCs of camel
milk stored at 25°C and at 30°C exceeded the limit in less than 24 hours. Thus with
appropriate refrigeration, pasteurized camel milk keeps for longer periods than when exposed
to high ambient temperatures.
Results of the cross-sectional survey indicate raw camel milk as highly significant to foodborne
illnesses. Raw camel milk had odds ratio (OR) 2.1; 95% confidence interval (CI) 1.38-
3.22, and p-value of 0.001 for cases with diarrhoea and/or vomiting either with or without
fever. Raw camel milk was also found to have OR 3.4; 95% CI= 1.52-7.80; p= 0.003 for
cases with diarrhoea and/or vomiting without fever and was not significant for cases with
xv
vomiting without fever (OR 2.9; 95% CI 0.91- 8.97; p=0.071). Backward selection
multivariate logistic regression indicates raw camel milk as a risk factor to food-borne
poisoning with OR 2.6; 95% CI=1.61-4.31, p=O.OOO; Log likelihood value (P (LRX2)) =
8.0002; raw cow milk emerged as a protective factor with OR 0.5; 95% CI=0.33-0.89,
p=0.015, P (LRX2) = 0.0145. Washing of hands with soap, treating drinking water, boiling of
milk, presence of proper drainage system and improved pit latrine emerged as significant
protective factors to symptoms of food-borne poisoning. Since unhygienically handled raw
camel milk was associated with food-borne illnesses, consumers of camel milk should be
sensitized either to boil or consume processed camel milk. This study recommends for urgent
development and adaptation of feasible and sustainable interventions to improve the camel
milk hygiene and safety in Kenya and to mitigate food-borne related diseases in the agropastoral
ist regions.

2008

2007

undefined.  2007.  Effects of lactoperoxidase system in camel milk for preservation and fermentation purposes. (J. Wangoh, Lamuka, P.O., Eds.).: University of Nairobi Abstract

Summary
This study was conducted to investigate preservative effect of the LPsystem
on both raw and pasteurized camel milk. The effect of the LPsystem
on selected starter cultures in the raw and pasteurized camel
milk was also investigated. Experiments were therefore conducted to:
 evaluate the effect of LP-system activation on shelf-life of raw
camel milk with the underlying activities being to:
o determine the duration of antibacterial effect in camel milk
stored at different temperatures after activation of its LPsystem
and
o monitor effect on keeping quality of increasing
concentrations of sodium thiocyanate and hydrogen
peroxide within physiological limits.
 determine the effect of the LP-system on keeping quality in
pasteurised camel milk
 determine the effect of the LP-system on starter culture activity in
camel heat treated and raw camel milk.
The concentration of thiocyanate occurring naturally in the milk used in
the present investigations ranged from 9.7 to 36.4 mg/l. No addition of
thiocyanate was therefore necessary to activate the LP-system. The
average thiocyanate values of camel milk from different sites were
2
15.8, 32.9 and 9.74 mg/l and were significantly different (p<0.001)
across the three sampling sites in this study.
Changes in total viable counts between LP-activated and LPinactivated
camel milk were determined during storage at 10, 20 and
30°C. Viable counts increased with storage temperature. Microbial
growth was halted for 15, 17 and 76 hours at 30, 20 and 10°C
respectively by activation of the LP-system in raw camel milk. At 30°C
the effect was mainly bacteriostatic and at 20°C, there was an initial
bactericidal effect in the first 15 hours. At 10°C, the bactericidal effect
was noted throughout the period of 76 hours.
The titratable acidity between LP-activated and LP-inactivated camel
milk was determined during storage at 10, 20 and 30°C. There lag in
acid production of 14, 23, and 10 hours at 10, 20 and 30°C
respectively as compared to the controls and was significantly different
(p>0.05) across the three incubation temperatures. Shelf life difference
between LP-system activated samples and their respective controls
was 19 hours at both 10 and 20°C and 4 hours at 30°C.
The differences in mean acid produced between the control samples
and the activated samples, however, were 0.12, 0.61 and 0.49 for 10,
20 and 30°C respectively. Inhibition of acid production by the LPsystem
increased from significant (p<0.05) during storage at 10°C to
highly significant (p<0.01) during storage at 20 and 30°C. The present
investigation therefore shows that by activating the LP-system it is
3
possible to extend the storage period of raw camel milk and that the
effect of the LP-system on the microbes present varies with
temperature of storage.
The effect of increasing levels of thiocyanate and hydrogen peroxide
on antibacterial activity of LP-system in raw camel milk at 30ºC was
investigated. Changes in total viable counts and lactic acid
development in raw camel milk at concentrations of 0, 10:10, 20:20,
30:30 and 40:40ppms, NaSCN
-
:H2O2 were monitored. The delay in
multiplication of bacteria increased significantly with an increase in the
LP-system components from no lag phase in the control to 4, 6, 11.5
and 9.5 hours in the 10:10, 20:20, 30:30 and 40:40 ppm levels of
NaSCN/H2O2 respectively.. The lag in acid production was 0, 4.8, 6, 12
and 8 hours for 0, 10:10, 20:20, 30:30 and 40:40 ppm dose of
NaSCN:H2O2, respectively. The shelf life of the camel milk was 4, 6,
12, 16 and 16 hours, respectively, for 0, 10:10, 20:20, 30:30 and 40:40
ppm dose of NaSCN:H2O2.
Lactoperoxidase system (LPS) was activated in camel milk followed by
pasteurization after 0, 4, and 8 hours after of storage.
This resulted in a shelf life of 15, 32, 17 and 17 days for the nonactivated
control and those activated after 0, 4, and 8 hours of storage
respectively during storage of samples at 10ºC. At 20°C, the shelf life
was 6, 13, 9 and 7 days for non-activated control and those activated
after 0, 4, and 8 hours of storage respectively. These results showed
4
a significant effect of storage time prior to pasteurisation on the effect
of the LP-system on the surviving microflora between the control and
activated samples at all the 3 times of storage prior to pasteurisation
(p<0.001). The number of viable bacteria in untreated sample reached
108 after 45 days compared to 105-107 in treated samples during
storage at 10ºC and 108 after 15 days in untreated compared to 107-
106 in treated samples under storage at 20ºC. The mean specific
growth rates at 10ºC storage temperature were 0.51, 0.2, 0.41 and 0.5
for the inactivated control, activated and pasteurized after 0, 4, and 8
hours respectively and were significantly lower in the LP-treated camel
milk samples than in the control (p<0.001). At 20ºC storage
temperature, the mean specific growth rates were 1,46, 0.27, 0.69 and
1 for the inactivated control, activated and pasteurized after 0, 4, and 8
hours respectively. These were also significantly lower in the LPtreated
camel milk samples than in the control (p<0.001)
Sensitivity of lactic starter cultures to LP-system was investigated by
monitoring acid production by mesophillic, thermophillic and Suusac
starter cultures in both LP-system treated and untreated camel milk.
Inoculation with starter was done after zero, 4 and 8 hours of storage
of LP-activated samples.
In all the three starters, LP-system activation resulted in a significant
slow down in acid development in raw camel milk activated and
inoculated immediately. For the thermophillic starter mean lactic acid
5
was 0.41, 0.32, 0.35 and 0.36 for the inactivated control sample and
those activated then inoculated with starter after 0, 4, and 8 hours
respectively. The differences in means between the control and the
activated samples were very highly significant (p<0.001), highly
significant (p<0.01) and not significant (p>0.05) at the inoculation times
o, 4 and 8 respectively. For the Suusac starter, mean lactic acid was
0.67, 0.62, 0.67 and 0.52 for the inactivated control sample and those
activated then inoculated with starter after 0, 4, and 8 hours
respectively. The differences in means between the control and
activated samples were highly significant (p<0.01) at all the inoculation
times after activation. However, for mesophillic starter culture the mean
values of lactic acid produced were 0.53, 0.48, 0.42 and 0.54 for the
inactivated control and activated then inoculated with starter after 0, 4,
and 8 hours respectively. The differences in means between the
control and activated samples were significant (p<0.01) at 0 and 4
hours and non-significant (p>0.05) at 8 hours. This implied that camel
milk preserved using this method could support satisfactory mesophillic
and thermophillic starter culture activity if the milk is held prior to
processing.
The investigation on the effect of the LP-system on starter activity in
camel milk heat-treated prior to inoculation showed that heat treatment
reduced starter inhibition by the LP-system for the mesophillic and
thermophillic starter cultures for samples LP-system activated, heat
6
treated and inoculated at immediately. For the mesophillic starter mean
lactic acid values for the inactivated control sample, activated and then
inoculated after 0, 4 and 8 hours were 0.52, 0.52, 0.54 and 0.40
respectively. The differences in mean lactic acid values between the
control and activated samples showed that a non-significant effect of
inoculation time at time 0 (p>0.05), a significant effect after 4 hours
(p<0.05), and a very highly significant effect (p<0.001) after 8 hours.
Mean lactic acid values for the thermophillic starter for the inactivated
control sample and those activated and then inoculated after 0, 4 and 8
hours were 0.52, 0.52, 0.54 and 0.40 respectively. The inhibition
changed from insignificant (p>0.05) on inoculation at time 0 and 4
hours (p<0.05) and was highly significant (p<0.01) on inoculation after
8 hours. Thus the inhibitory effect of the LP-system on mesophillic
and thermophillic starter culture activity in heat treated camel milk
apparently is reactivated and increases with time of preservation of raw
milk by LP-system. However with suusac starter, the mean lactic acid
values inactivated control sample and those activated and then
inoculated after 0, 4 and 8 hours respectively were 0.69, 0.58, 0.64
and 0.71. At zero and four hours after activation inhibition was
significant (p<0.05) compared to a non-significantly different inhibition
(p>0.05) on inoculation after 8 hours of storage.
The use of the LP-system might therefore have a significant influence
on the time taken to reach the desired pH in the vat, which is a critical
7
factor for the manufacturer of fermented camel milk and this influence
is dependent on the time of preservation of raw camel milk prior to
processing of fermented products.

2005

Lore, TA, Mbugua SK, Wangoh J.  2005.  Enumeration and identification of micro flora in suusac, a Kenyan traditional fermented camel milk product. Lebensmittel-Wissenschaft und-Technologie . 38(2):125-130.

2004

Lore, T.  2004.  Studies on the microflora in suusac, a Kenyan traditional fermented camel milk product. (Mbugua S. K., Wangoh J., Eds.).: University of Nairobi Abstract

The purpose of the study was to determine the lactic acid bacteria (LAB)and yeasts
associated with the traditional fermented camel milk product (suusac) of the Somali
community in Kenya. The traditional method of suusac production was studied by use
of questionnaire and documented. The microbial content profile and changes during
fermentation were then determined.
From 15 samples of traditionally fermented suusac, 45 LABand 30 yeast strains were
isolated ~d identified using API 50 CHL and API 20C AUXidentification systems,
respectively. The total viable microorganisms, LAB,coliforms, and yeasts and molds
were enumerated. The isolates were investigated for their functional roles in the
fermentation process, namely, acidification, flavour/aroma production and proteolytic
activity. Fermentation trials with single and mixed strain cultures were investigated to
assess their acidification and flavour-producing properties.
The traditional production of suusac involves spontaneous fermentation of camel milk
in smoked gourds at ambient temperature for 1-2 days. The milk is not subjected to
heat treatment prior to fermentation. The isolated LAB species were identified as
Lactobacillus curvatus (8% of total isolates), Lactobacillus plantarum (16%), Lactobacillus
soliuarius (8%), Lactococcus raffinolactis (4%) and Leuconostoc mesenteroides subsp.
mesenteroides (24%). The isolated yeasts were Candida krusei (20%), Geotrichum
penicillatum (12%) and Rhodotorula mucilaginosa (8%). In traditional suusac, LAB
counts averaged 6.77 logrocfu Zml, while yeast counts were relatively lower (2.05
log.ocfuZml]. Low coliform numbers were encountered « 1 log cfu /rnl].
The LAB produced considerable acidity and majority (60%) were homofermentative.
The primary functional role of the LAB was fermentation of lactose to lactic acid,
resulting in acidity levels ranging from 0.46-0.67% lactic acid equivalent. All the LAB
isolates recorded high proteolytic activity, except for L. raffinolactis, which did not
exhibit any proteolytic activity. The LAB showed varying degrees of diacetyl
production. Of the LAB, L. curvatus recorded the highest diacetyl flavour score,
corresponding to >30 mg diacetyl/ 100 ml of milk.
The yeast isolates showed limited carbohydrate-assimilating capabilities, but played a
role in flavour development and proteolysis. G. penicillatum produced diacetyl (3.1-10
mg/lOO ml), although it did not exhibit any proteolytic activity. C. krusei exhibited
some proteolytic activity, although its diacetyl-producing capacity in camel milk was
minimal (0.5-3 mg/ 100 ml).
C. krusei also played a role in mixed starter fermentation of camel milk by increasing
the activity of the LAB cultures and improving product flavour. The use of C. krusei +
1. plantarum (1: 1) and C. krusei + L. curvatus (1: 1) reduced the fermentation time by
half as compared to the use of the cultures individually.

J., W.  2004.  Equipment for small-scale milk plants.. The camel (C. dromedarius) as a meat and milk animal: Handbook and product development. , Zurich: Vdf Hochschulverlag ETHZ
J., W.  2004.  Methods of Quality Control.. The camel (C. dromedarius) as a meat and milk animal: Handbook and product development. , Zurich: Vdf Hochschulverlag ETHZ

2003

2001

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