© The Authors, 2024, Published by the Universidad del Zulia*Corresponding author: nabila_kara2000@yahoo.com
Keywords:
Milking
Dairy
Microbiology
Physiochemical
Factors aecting global quality of milk produced in a semi-arid Algerian steppe zone
Factores que afectan la calidad global de la leche producida en una zona esteparia semiárida de
Argelia
Fatores que afetam a qualidade global do leite produzido numa zona semiárida de estepe argelina
Nabila Kara
1
*
Benalia Yabrir
2
Abbes Laoun
2
University of Zulia, Faculty of Agronomy
Bolivarian Republic of Venezuela
Abstract
The purpose of this research was to investigate the eect of the zone,
season and collecting point on the quality of milk produced in a semi-
arid steppe zone of Algeria. Throughout the four seasons of the year
and separated into ve zones, this study was done on 334 farms and 25
collectors. It involved 1336 milk samples. The obtained results showed
that the physico-chemical and microbiological quality of milk produced
in semi-arid zones is inuenced by the zone, season, and collecting point.
The collecting point behaves similarly to the season, except for pH. They
showed a highly signicant eect (p ≤ 0.01) for Staphylococcus aureus
to a very highly signicant one (p ≤ 0.001) for all other physico-chemical
characteristics (acidity, density, freezing point, wetting, fat, protein and total
solids) and microbiological parameters (thermo-tolerant coliforms, aerobic
germs at 30°C, Listeria monocytogenes and Salmonella). On the other hand,
the eect of the zone was variable. It is signicant (p ≤ 0.05) for Listeria
monocytogenes, highly signicant for freezing point and wetting, and
very highly signicant for the other parameters, except for fat content and
Salmonella which were not inuenced by the zone. Among other things, pH
was not aected by the collection point.
This variability in milk’s quality is
the result of above mentioned factors, either considered independently or in
combination. The collection point highlights the mixing eect. The season
acts directly through its temperature (condition of transport and storage of
milk) or indirectly on the feeding of the animals and the area directly by its
climate or indirectly through its plant cover.
Rev. Fac.
Agron. (LUZ). 2024, 41(1): e244103
ISSN 2477-9407
DOI: https://doi.org/10.47280/RevFacAgron(LUZ).v41.n1.03
Animal production
Associate editor: Dra.
Rosa Razz
1
Faculty
of
Natural
and
Life
Sciences,
Ferhat
Abbes
University, Setif 19000, Algeria.
2
Faculty
of
Natural
and
Life
Sciences,
Ziane
Achour
University, Djelfa 17000, Algeria.
Received: 05-09-2023
Accepted: 06-01-2024
Published: 04-02-2024
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ). 2024, 41(1): e244103. January-March. ISSN 2477-9407.
Resumen
El objetivo de esta investigación es investigar el efecto de la
zona, la estación y el punto de recolección en la calidad de la leche
producida en una zona de estepa semiárida de Argelia. Durante las
cuatro estaciones del año, separadas en cinco zonas, este estudio se
realizó en 334 ncas y 25 colectores. Involucró 1336 muestras de
leche. Nuestros resultados muestran que la calidad de la leche está
inuenciada por estos tres factores. El punto de recogida se comporta
de forma similar a la estación, excepto pH. Ellos muestran un efecto
altamente signicativo (p ≤ 0,01) para Staphylococcus aureus,
muy altamente signicativo (p ≤ 0,001) para las características
sicoquímicas (acidez, densidad, punto de congelación, humedad,
grasas, proteínas y sólidos totales) y microbiológicos (coliformes
termotolerantes, gérmenes aerobios a 30 °C, Listeria monocytogenes
y Salmonella). El efecto de la zona es signicativo (p ≤ 0,05)
para Listeria monocytogenes, altamente signicativo para punto
de congelación y humedad, y muy signicativo para los demás
parámetros, excepto el contenido de grasa y Salmonella que no fueron
inuenciados por la zona. Entre otras, el pH no se vio afectado por el
punto de recolección. Esta variabilidad en la calidad de la leche es el
resultado de los factores antes mencionados, ya sea considerado de
forma independiente o en combinación. El punto de recogida resalta
el efecto de mezcla. La estación actúa directamente a través de su
temperatura (condición de transporte y almacenamiento de la leche)
o indirectamente sobre la alimentación de los animales y la zona
directamente por su clima o indirectamente a través de su cobertura
vegetal.
Palabras clave: ordeño, lácteos, microbiología, sicoquímica.
Resumo
O objetivo desta pesquisa é investigar o efeito da zona, estação
do ano e ponto de coleta na qualidade do leite produzido em uma
zona de estepe semiárida da Argélia. Durante as quatro estações do
ano, separadas em cinco zonas, este estudo foi feito em 334 fazendas
e 25 coletores. Envolveu 1336 amostras de leite. Os resultados
obtidos mostraram que a qualidade global do leite é inuenciada
pela zona, estação do ano e ponto de coleta. O ponto de coleta se
comporta de maneira semelhante à estação, exceto pH. Eles mostram
um efeito altamente signicativo (p ≤ 0,01) para Staphylococcus
aureus a um efeito muito altamente signicativo (p ≤ 0,001) para
todas as outras características físico-químicas (acidez, densidade,
ponto de congelamento, umedecimento, gordura, proteína e sólidos
totais) e parâmetros microbiológicos (coliformes termotolerantes,
germes aeróbicos a 30 °C, Listeria monocytogenes e Salmonella).
Por outro lado, o efeito da zona é variável. É signicativo (p ≤ 0,05)
para Listeria monocytogenes, altamente signicativo para ponto de
congelamento e umedecimento e muito signicativo para os demais
parámetros, exceto para o teor de gordura e Salmonella que não foram
inuenciados pela zona. Entre outras coisas, o pH não foi afetado pelo
ponto de coleta. Esta variabilidade na qualidade do leite é o resultado
dos fatores acima mencionados, considerados de forma independente
ou em combinação. O ponto de coleta destaca o efeito de mistura.
A estação atua diretamente através da sua temperatura (condição de
transporte e armazenamento do leite) ou indiretamente na alimentação
dos animais e da área diretamente pelo seu clima ou indiretamente
através da sua cobertura vegetal.
Palavras-chave: ordenha, laticínio, microbiologia, sico química.
Introduction
Milk and milk products play an important role in
human nutrition throughout the world. In recent years, the
major dairy industry players include dairy farmers declared that
milk quality depend largely its safety, hygienic standers intended for
consumption and acquisition of technology skills requires dynamic
of transformation from farm procedures that distributes milk to retail
stores.
Several authors agree that assessment of bacterial levels is a
frequently used procedure to measure the microbial quality of milk.
Milk can be contaminated at several levels, at milking, on farm
storage, during transport and at delivery (Millogo et al., 2010).
Furthermore, microbial contamination of milk occurs when bacteria
found in the cow’s udder mammary, mastitis or from the cow and its
environment, milking techniques, methods of disinfection of milking
machines, storage equipment, milking utensils and storage conditions
(Gebeyehu et al., 2022), non-hygienic handling and handling
practices (Islam et al., 2018; Nyokabi et al., 2021). In addition,
physicochemical parameters inuence the quality of milk in one way
or another. Each measurement has its own specicity. For example
the pH and acidity of milk are linked to freshness, the density when
skimming, the freezing point when wetting, and the dry extract to the
richness of the milk. Fat and proteins are involved both in the milk
payment system for the quality and the cheese-ability of the latter.
Some of these factors are related to the geographical origin (sampling
area) (Lingathurai et al., 2009; Mhone et al., 2011; Gemechu and
Amene, 2016; Skeie et al., 2019), season of collection (Celano et al.,
2022; Dolango et al., 2021) and at dierent collection points from
the farm to the processing unit (Millogo et al., 2010; Islam et al.,
2018; Tobar-Delgado et al., 2020; Dolango et al., 2021; Nyokabi et
al., 2021).
In Algeria, milk production is no exception to this rule, in most
subjects, variations across the area and sampling point was documented
(Kaouche, 2018; Meklati et al., 2023). In addition, avoiding or
limiting the presence and subsequent growth of microorganisms in
milk is an ongoing obstacle for those involved in milk production
(Tobar-Delgado et al., 2020). In this order of idea and, to verify or
disprove this hypothesis, our study ts. Therefore, physicochemical
properties (pH, density, freezing point, added water, fat, protein, total
dry solids, and titratable acidity) and microbiological quality (aerobic
germs, thermotolerant coliform, Staphylococcus aureus, Salmonella,
and Listeria monocytogenes) of milk produced in a semi-arid Algerian
steppe zone were described with emphasis on some variation’s factors
(zone, season and collecting point).
Materials and methods
Study area and feeding system
This study was conducted in Sétif area located in high plains of
eastern Algeria (latitude: 35.0 - 36.5 °N and longitude: 5 - 6 °E)
at 1300 m above sea level. This region is characterized by a semi-
arid continental climate, with dry and hot summer and cold and wet
winter. Three agro-ecological zones characterize the region: North
with black and deep vertic soils and an annual rainfall of 600 mm,
Center with brown calcareous soils and annual rainfall which does
not exceed 300 mm, and South with common stony soils and some
saline soils in depression and annual rainfall less than 200 mm.
The main annual temperature is 14.3 °C with signicant variation’s
2-7
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This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Kara
et al.
Rev. Fac. Agron. (LUZ). 2024 40(1): e244103
3-7 |
seasonal (with a maximum in July 25.5 °C, a minimum in January
of 5 °C) (Rouabhi et al., 2019). Cows fed beneting mixed ration ad
libitum based on hay, straw during all the year plus supplementation
with concentrate and for all animals, traditional management in the
area consists of a winter housing period and access to pastures during
spring and summer seasons.
Sampling proceedings
Table 1 summarizes the distribution of sampling protocol. A total
of 1336 raw milk were collected from dairy producers from dierent
collectors and geographical area. Each farm was visited once time in
dierent seasons (autumn, winter, spring and summer). Four levels of
sampling were carried out: at the farm, at the collector tank (before
and after refrigeration), and at the dairy. All farms have mechanical
milking equipment (milking trolley).
Samples were collected in sterilized bottles and immediately
refrigerated in a portable isothermal glacier and transferred to the
laboratory of the Dairy unit of Sétif for analysis. The analysis was
carried out in less than 3h.
Physicochemical and microbiological analyses
Analyses were carried out according Beerns and Luquet (1987)
protocols. Physicochemical analysis of milk samples was carried
using the Lactoscan Milk Analyzer of the Alpes Industries Services
brand (Serial 24936; Supply 12-14V DC 50W). It included pH,
density (DEN) (kg.cm
-3
), freezing point (FP) (°C), added water
rate (AW) (%), fat content (FC) (g.L
-1
), protein content (PC) (g.L
-1
)
and total dry solids (TDS) (g.L
-1
). Titratable acidity (TA) (°D) was
evaluated in presence of 0.5 % phenolphthalein indicator and sample
was titrated with Dornic sodium (N/9).
Microbiological determination included aerobic germs count
(FAMT), Count of Thermotolerant Coliform (CTT), Staphylococcus
aureus (SA), Salmonella, and Listeria monocytogenes (LM). A serially
diluted from 10
-1
to 10
-6
from the mother solution, were prepared with
a tryptone salt solution (TSE) and employed to determine the quantity
of microbiota in milk. Colony forming units per mL (UFC.mL
-1
) were
used to express count for each germ.
Statistical analysis
The data collected was entered in Excel version 2010 and
were analyzed using IBM SPSS (Statistical software Package for
Analysis for window 7, Chicago, version 21). Descriptive statistics
were established to report the variability of the dierent parameters
involved in the evaluation of the milk quality. Results of the analysis
were expressed as means ± SD (standard deviation). The signicant
dierences between means were evaluated by one-way ANOVA
using Turkey range test, where sampling point, zone and season are
the factors of variation. Statistical signicance was determined at the
95 % condence interval and p<0.05.
Result and discussion
General quality
The present work revealed milk fat content of approximately
32.72 ± 3.38 g.L
-1
; protein level around 30.90 ± 1.91 g.L
-1
; and total
dray solid 104.67 ± 34.52 g.L
-1
.
Table 1. Distribution of number cow’s milk samples per farms, area and collector.
Zone Northen Central Estern Western Southern Total
Number of Collectors
5 5 5 5 5 25
Number of farms
*
67(15-10-10-16-16) 52 (12-10-9-11-10) 62 (14-8-13-14-13) 73 (13-18-12-14-16) 80 (15-13-11-18-23) 334
Number of sample milk
268 208 248 292 320 1336
*In parentheses: number of farms per collector
These values were slightly lower than those reported for common
milk. It is well recognized that that fat level of milk is unquestionably
the most valuable constituent of milk; although current consumers
prefer skimmed milk. In Algeria, fat content is an incentive criterion
for quality payment of the milk.
As regards the physical characteristics of milk, expressed by
pH, acidity, density, freezing point and added water, these have the
following respective mean values 6.67 ± 0.09; 16.67 ± 0.34 °D;
1.0309 ± 0.003 at 20 °C; -0.51 ± 0.16 °C and 3.13 ± 1.81 %. These
values generally agree with Algerian and European standards. The
values observed for the freezing point may suggest an addition of
water, which could be due to residual water after washing milk
recipients (Nyokabi et al., 2021).
It is well admitted that the count total mesophilic aerobic ora is
carried out for the payment of the milk to the quality, among other
things, this ora is seen as a general indicator of overall quality
related to the conditions of hygiene, collection and keeping of the
product (Dolango et al., 2021). The data showed in table 2 indicate
an average microbial load of 6.25 ± 3.04.10
6
UFC.mL
-1
which was
higher than standard permissible limits of Algeria xed at 3.10
5
(JORADP N°39, 2017) and the European standards established at
10
5
UFC.mL
-1
for raw cow’s milk (Anonyme, 1992). The presence
of coliforms in milk indicates a recent fecal contamination, as these
bacteria cannot survive outside the gut for a long time (Beerns and
Luquet, 1987). In current study, the average contamination of milk
samples by coliforms was 5.48 ± 0.37.10
3
UFC.mL
-1
which exceeding
the Algerian standards (JORADP N°39, 2017). These results may
reect a poor state of freshness of raw milk, and an indicator of poor
hygienic and sanitary practices during milking and further handling,
as transport and storage conditions (Islam et al., 2018). S. aureus was
detected with an average rate of 0.83 ± 1.38.10
2
UFC.mL
-1
witch is
not conform to the national standard (JORADP N°39, 2017) xed
at 10
2
of the minimum threshold value, is commonly associated
with intoxications of food through its capacity to produce dierent
kinds of potent enterotoxins (Islam et al., 2018). Contamination of
milk by Salmonella at the average rate equal to 0.21 ± 0.69 UFC.
mL
-1
not meets the Algerian standards which require total absence of
Salmonella in milk (JORADP N°39, 2017). This contamination may
be the origin of infected cattle feces, infected udders, contaminated
milking equipment, air, feed and water, and milkers (Gebeyehu et
al., 2022). The presence of L. monocytogenes at the level of 0.35 ±
0.98.10
1
UFC.mL
-1
is lower than the Algerian standard. This species
excreted by livestock can contaminate milk and food production
chain and among pathogen in human health (Šteingolde et al., 2021).
Factors aecting milk quality
Several factors have been described to assess variation in milk
composition. Some are linked to the surrounding environment, others
linked to the animal (Nyokabi et al., 2021). Among these factors,
area, season and collection points are reviewed in this study.
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ). 2024, 41(1): e244103. January-March. ISSN 2477-9407.
Eect of zone on milk quality
The physicochemical and microbiological variables were aected
by sampling area, except for the fat level and Salmonella count
(table 2). Milk obtained from dairy farms in northern was more
acidic, with greater water added and a higher protein concentration
compared with all other regions. In fact, the milk samples collected
from eastern province was lower added water. Samples taken from
central zone was more dense and richer in TDS content. Similar level
in density, Dornic acidity and added water was recorded in Southern
and Western zone. The eect of zone (region) on milk quality varies
according literature. Lingathurai et al. (2009) states that total solids,
fat, and crude protein of southern cow milk sample were signicantly
inuenced by regions; pH was slightly inuenced. For Gemechu
and Amene (2016), there was no signicant dierence in fat and
protein content observed among the study areas; however titratable
acidity, specic gravity and pH value were signicantly inuenced
by collection area. According Meklati et al. (2022), titratable acidity,
density, fat level, total dry extract were signicantly aected by
region but not pH.
Table 2. Eect of zone on milk quality.
Northern Central Eastern Western Southern Mean±SD p
pH 6.65±0.09
b
6.66±0.13
b
6.68±0.10
a
6.68±0.06
a
6.68±0.06
a
6.67±0.09 ***
Acidity 16.86±0.49
b
16.96±0.41
a
16.99±0.38
a
17.00±0.38
a
17.00±0.38
a
16.67±0.34 ***
Density 1.0312±0.002
ab
1.0314±0.003
a
1.0312±0.003
ab
1.0308±0,003
bc
1.0308±0,003
bc
1.0309±0.003 ***
FP 0.51±0.01
ab
0.51±0.02
c
0.51±0.01
ab
0.51±0.14
bc
0.51±0.14
bc
0.51±0.16 **
% AW 3.41±1.68
a
3.20±1.87
ab
2.96±1.64
b
3.36±1.99
a
3.36±1.99
a
3.13±1.81 **
FC 32.72±3.10
a
32.99±3.55
a
32.68±3.56
a
32.69±3.30
a
32.62±3.45
a
32.72±3.38 NS
PC 31.59±2.50
a
30.61±1.52
bC
30,90±1.92
b
30.56±1.60
C
30,81±1.68
bc
30,90±1.91 ***
TDS 107.23±30.76
ab
110.87±26.20
a
106.72±32.82
ab
104.17±34.45
b
96.77±41.56
c
104.67±34.52 ***
CTT
(x10
2
)
37.72±26.29
C
53.94±31.46
b
54.49±36.38
ab
62.11±33.15
a
59.56±34.12
ab
54.67±3.65 ***
FAMT
(x10
5
)
52.85±30.55
c
59.89±28.63
b
72.09±28.01
a
64.06±28.68
b
63.25±32.59
b
62.46±30.49 ***
SA
(x10
2
)
0.51±0.92
c
0.75±0.93
bc
1.05±1.61
a
0.91±1.68
ab
0.89±1.40
ab
0.83±1.38 ***
LM
(x10
1
)
0.22±0.60
b
0.37±0.67
ab
0.35±0.95
ab
0.49±1.29
a
0.29±1.09
b
0.35±0.98 *
Salmonella
0.17±0.45
a
0.24±0.67
a
0.25±0.90
a
0.20±0.70
a
0.21±0.67
a
0.21±0.69 NS
abc
: from same line, the Value from dierent letters are signicantly dierent at p<0.05
Concerning microbiological quality, a higher count of CTT was
observed in Western zone, FAMT in Estern region. S. aureus was
most present in Estern zone and L. monocytogene in Western area.
However, area sampling did not aect Salmonella count. The eect
of area in TBC, CTT was reported (Mhone et al., 2011). A signicant
eect of area in total count of S. aureus is similar to the nding
reported by Lingathurai et al. (2009), Mhone et al. (2011) and Skeie
et al. (2019). No signication variation in Salmonella charge between
the farms was obtained by Gebeyehu et al. (2022).
It is necessary to remember that weather and climate are directly
related to geographic zone. According to Leiber et al. (2006),
variations in milk quality are the result of complex interactions of many
environmental factors, as well as geographic origin, photoperiod,
and altitude which comprises hypoxia, climatic conditions including
ambient temperature and humidity, solar radiation and topographic
challenges along with grazing. Coppa et al. (2014) showed dierences
in milk fat acid composition according to dierent geographical
region. Many authors use milk fatty acids composition to discriminate
and authenticate the area origin of bulk milk. The results of these
predicting models remains uncertain whether the results were due to
the direct eect of altitude or more likely to the cow-feeding system
(Coppa et al., 2014).
The eects of photoperiod on milk composition were highlighted
but studies about it are fuzzy. Dahl et al. (2000) consider that milk
composition is generally unaected by photoperiod while other
authors plead in favor of its act, positively by increasing milk fat
content as well as milk yield (Espinoza and Oba, 2017) or negatively
by reducing milk fat percentage for animals exposed to long period
compared to short one (Phillips and Schoeld, 1989). But the act of
photoperiod can be masked when changing management practices
(Espinoza and Oba, 2017).
Likewise, several studies discussed the eect of altitude on milk
quality, and results are disparate and sometimes contradictory. Leiber
et al. (2006) found a clear inuence of high altitude grazing on major
milk constituents and on SCC; but according to Correddu et al.
(2021), the contents of protein and lactose and the pH value of the
milk were not aected by altitude, except fat concentration but not
FA prole. Alrhmoun et al. (2023) found two type of relation between
altitude and milk quality; positive relationship for milk fat, protein,
free fatty acid, and somatic cell count and negative one for lactose
content, milk urea nitrogen, and pH-value, and attribute the impact of
altitude on milk composition to its eect on dairy cow physiology by
direct parameters (atmospheric pressure, temperature, and turbidity)
or indirect factors (solar radiation, moisture, wind, season length, feed
quantity and quality, and geology). For example, at high altitudes, a
higher body fat mobilization was induced when feed intake is limited,
then somatic cell count tends to increase due to management and
housing factors, also it cause pulmonary hypertension, which results
in an increased susceptibility against some pathogen related diseases
like mammary infections (Alrhmoun et al., 2023).
4-7
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This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Kara
et al.
Rev. Fac. Agron. (LUZ). 2024 40(1): e244103
5-7 |
Eect of season on milk quality
The season has a signicant eect on all physico-chemical and
microbiological parameters. This variation diers in each parameter
by season sampling (table 3).
Milk from cold periods (autumn and winter) was lower acid and
had higher pH values than milk collected in hot period (spring and
summer). Only, the milk collected in winter was showed a higher
milk density. The highest fat level were recorded in winter, spring and
summer, the lowest fat means was obtained in autumn; and the higher
in protein content was noted in winter/spring while the poorest were
found in summer and autumn. Milk collected in winter was richer
in dry matter compared to other season sampling. Autumn milk was
higher added water followed by spring and summer. Winter milk was
less wet.
Table 3. Eect of season on milk quality.
Autumn Winter Spring Summer p
pH 6.72±0.09
a
6.71±0.05
a
6.63±0.11
b
6.63±0.05
b
***
Acidity 16.96±0.39
a
16.97±0.29
a
16.89±0.39
b
17.01±0.28
a
***
Density 1.0305±0.003
a
1.0319±0.003
b
1.0308±0.002
a
1.0306±0.002
a
***
FP 0.50±0.12
c
0.51±0.02
a
0.51±0.01
ab
0.51±0,14
b
***
% AW 3.41±1.76
a
2.75±1.86
c
3.25±1.94
ab
3.04±1.63
bc
***
FC 31.33±2.93
a
33.94±3.57
b
32.86±3.36
c
32.72±3.14
c
***
PC 30.12±1.16
a
32.37±2.25
b
31.16±1.67
b
29.89±1.24
a
***
TDS 96.50±40.10
a
112.58±27.33
b
104.82±34.73
c
104.43±32.99
c
***
CTT 51.60±43,55
b
40.85±30.11
c
54.54±27.25
b
71.66±22.46
a
***
FAMT 51.42±43.80
c
61.08±21.53
b
61.07±24.32
b
72.26±20.86
a
***
SA
0.95±2.06
a
0.63±1.00
b
0.99±1.21
a
0.73±0.91
b
**
LM
0.58±1.64
a
0.25±0.69
bc
0.36±0.64
b
0.19±0.45
c
***
Salmonella
0.33±1.10
a
0.14±0.42
b
0.26±0.59
a
0.11±0.36
b
***
abc
: from same line, the Value from dierent letters are signicantly dierent at p<0.05
Millogo et al. (2010) did not show any dierence between pH,
FC and PC taken during the rainy and dry seasons. Seasonality did
not aect protein and total solids at the two sampling periods (winter
vs summer). In contrast, fat and pH were higher in summer than in
winter (Celano et al., 2022). Dierences in the mean milk composition
were observed seasonally in total solids levels but not in density,
protein and fat content (Nateghi et al., 2014). These variations can
be attributed mainly to the feeding (Larsen et al., 2014). In summer,
animals are grazing on natural pastures, and in winter, animals feed
on dry forage; so summer milk is higher quality when compared to
winter milk (Nateghi et al., 2014).
Concerning microbiological quality, milk collected in summer
reported a highest count for FAMT and CTT, the lowest one
were recorded in cold period: autumn and winter respectively. A
contamination by S. aureus and Salmonella was a similar prole in
autumn and spring with lowest level recorded in winter and summer.
Total number of colonies from LM is the most variable among
seasons, and decreases from autumn to summer. It was found to be
higher in autumn and lower in summer. These trends were observed
by Petróczki et al. (2020) who assigned the highest values to heat
stress of cows during the summer because of higher temperatures and
humidity and lowest values to the inhibition of growth of mesophilic
microorganisms at low temperature. On contrary, Celano et al. (2022)
consider that water and medium-low temperatures could favor the
growth of these microorganisms. Also, Nateghi et al. (2014) state that
animals are less frequently transferred to outside because of feeding
on dry forage so contamination is developed in closed farms aecting
milk microbial load, in winter season. Gebeyehu et al. (2022) in
southern of Ethiopia were demonstrated that, though the overall
isolation rate of Salmonella was higher during the wet season than
the dry season; the dierence was not statistically signicant.
Eect of sampling point on milk quality
Milk samples were collected from farm, collector container before
cooling (tank end collection), after cooling (cold tank) and upon
arrival at the processing dairy unit (delivery tank). Results of variance
analysis indicated a signicant dierence on physicochemical and
microbiological parameters between sampling point, except for pH
(table 4).
There is no eect of sampling point of milk in pH value, which
agrees with Millogo et al. (2010). Findings of the present study for
density agree with Nyokabi et al. (2021), and disagree with previously
research when concerning FP. The present work revealed that fat,
protein and total dray sec were aected by collection point; while
Millogo et al. (2010), Tobar-Delgado et al. (2020) and Nyokabi et al.
(2021) didn’t nd any. PC varied between farm level/delivery unit,
while the fat level and TDS revealed signicant variation between
farm, tank before and after cooling and tank dairy unit. It seems that
milk fat level highly susceptible to time of transport and storage
conditions. According to Nyokabi et al. (2021), the absence of
signicant dierences in milk composition (protein and TDS levels)
may be due to similarities in agricultural practices, the use of a similar
breed of cattle, and similar food management strategies.
In this research, the type and bacterial load has been used as a
determinant of the acceptance of the microbiological quality of
milk provides information on the sanitary and hygienic designed
for milk handling technique associated with storage condition and
transport. Bacterial enumeration at the nal stage of the chain can
reveal the hygienic conditions of previous milk handling (cleanliness
of equipment and storage and transport conditions “refrigeration”.
Bacteria numbers will decrease with cleaner equipment and faster milk
cooling. In this regard, our ndings on the microbiological raw milk
quality should be interpreted from the levels of primary producers
(farms) and development in later stage of point dairy value chain.
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Kara
et al.
Rev. Fac. Agron. (LUZ). 2024 40(1): e244103
6-7 |
Table 4. Eect of collection point on milk quality.
Farms Tank collection Cold Tank Delivery tank p
pH 6.67±0.09
a
6.67±0,05
a b
6.66±0,11
b
6.67±0.05
a
NS
Acidity 16.67±0.34
c
16.99±0,09
b
16.99±0,09
b
17.02±0.18
a
***
Density 1.0317±0.003
a
1.0313±0.009
a
1.0307±0.001
ab
1.0298±0.001
b
***
FP 0.51±0.01
c
0.51±0.009
b
0.52±0.01
a
0.52±0.01
a
***
% AW 3.16±1.84
a
2.02±1.37
b
2,02±1.37
b
2.02±1.37
b
***
FC 32.70±3.84
a
32.79±1.53
a
31.49±1.45
b
30.37±1.10
c
***
PC 30.85±2.19
a
30,87±1,26
a
30.78±1,23
a
30.65±1.22
b
***
TDS 116.60±40.10
a
109.56±22.24
b
107.90±21.61
c
107.89±21.61
c
***
CTT 54.67±33.65
d
57.11±21.65
c
60.42±21,09
b
65.35±19.99
a
***
FAMT 62.46±30.49
d
66,99±23,56
c
68.63±21,33
b
74.34 ± 21.21
a
***
SA 0.83±1.38
b
1.06±0,97
a
1.10±0.94
a
1.10 ± 0.95
a
**
LM 0.35±0.98
b
0.75±0,88
a
0.73±0.85
a
0.74±0.89
a
***
Salmonella
0.21±0.69
b
0.48±0,63
a
0.47±0.63
a
0.46±0.62
a
***
abc
: from same line, the Value from dierent letters are signicantly dierent at p<0.05
Our data showed that the prole level of CTT and FAMT increase
by sampling levels. Similarly data was found by Islam et al. (2018)
and Tobar-Delgado et al. (2020). Likewise, a signicant interaction
for this germ was observed between the area and sample collection
chain in raw and pasteurized milk samples (Mengstu et al., 2023).
Previous studies revealed that the microbial contamination of raw
milk increase between farms and sampling times (Skeie et al., 2019).
Moreover, Mengstu et al. (2023) showed that dierences in estimated
levels of thermotolerant bacteria at dierent points in the milk chain
were specic to each region and diered signicantly across the daily
value.
S. aureus is commonly associated with intoxications of food
through its capacity to produce dierent kinds of potent enterotoxins
(Islam et al., 2018). The evolution of this germ between the collection
points follows the same pace as that found by another authors
(Kaouche, 2018; Skeie et al., 2019; Nyokabi et al., 2021). Data prole
variation of L. monocytogenes showed highly signicant dierence
among farm and other collect points. This result was consistent with
nding report by Kaouche (2018) and Šteingolde et al. (2021). These
latter authors reported that highlighted feeding of silage and indoor
keeping as the main factors which could promote the overall mean
count of Listeriosis onset during winter and spring.
Conclusion
The ndings of this paper state that all parameters (both
physicochemical and microbiological) were aected by the zone,
season, and collecting point; except that fat content and Salmonella
were not inuenced by the zone and pH by the collection point.
These variations could be the direct or indirect eect of the above
factors. Season act directly on climate (winter milk is more dense
than summer milk/ condition of transport and storage of milk) or
indirectly through the vegetation (pastures during spring and summer
seasons/ winter housing); collection point by mixing eect and more
milk is handled, more it is contaminated; and area by its relief and
climate (north rainier than the south). Also, hygienic practices during
milk collection (from farm to dairy) and animal health must be taken
in consideration.
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