J. Food and Dairy Sci., Mansoura Univ., Vol. 9 (1): 41 – 49 , 2018
Nutraceuticals Impact on Probiotics Growth: A Challenge in Synbiotic-
Yoghurt Production
Gomaa, M. A. E. ; S. G. A. Alneamah and Eman H. A. Ayad
Food Science Department, Faculty of Agriculture (Saba Basha), Alexandria University.
m.gomaa@alexu.edu.eg
ABSTRACT
The prebiotic effect of three concentrations of thirteen crude plant extracts: eight aqueous extracts (rosemary, dill, garlic,
ginger, flaxseeds, thyme, oat, and moringa leaves); and five Dimethyl sulfoxide (DMSO) extracts (rosemary, dill, garlic, ginger
and flaxseeds) on ten different probiotic LAB was studied. Some strains (Lactobacillus brevis KP653, Lactobacillus delbrueckii
subsp. lactis KP645, and Lactobacillus acidophilus CHA2) were sensitive to the plant extracts, and relative decline in the growth
was noticed. While, Lactobacillus delbrueckii subsp. delbrueckii KT615, Bifidobacterium longum 141B, Lactobacillus
plantarum KP623, Lactobacillus delbrueckii subsp. bulgaricus YASH2, Lactobacillus johnsonii A1, Lactobacillus casei YA1,
and Streptocccus thermophilus T11 were positively influenced with the presence of some extracts. Sixteen synbiotic yoghurt
trials were prepared, which produced well-formed set-yoghurt style, similar or close to the control in appearance. Total
acceptability scores ranged between 76 and 98%. The highest value was recorded for the control, followed by yoghurt containing
rosemary, dill, flaxseeds, thyme, oat, and moringa. While the lowest overall score was recorded for yoghurt containing garlic.
Keywords: Nutraceutical, Probiotics, Prebiotics, synbiotic, yoghurt.
INTRODUCTION
Functional dairy products were recently
recognized, as aids reduction of the risk of many
diseases (Palmer, 2009; Popkin and Kenan, 2016; Ward,
2016). The dairy industry and market are already the
area of most commercial success of functional foods
(Kalamian, 2017; Torrence, 2017). Growth of the dairy
industry is set to continue with total world milk
production of 818 million tons for the year 2016 (Davis
and Hahn, 2016). such growth is a good opportunity,
since most of the consumers become more aware of the
role of nutrition in their diets. However, consumers will
not compromise on taste or product quality for healthy
products which is an real challenge in functional dairy
products development (Tamime and Thomas, 2017).
Furthermore, during functional foods designing and
manufacturing, bioactive ingredients are added to a food
carrier, which can influence acceptance of the overall
product (Bimbo et al., 2017).
The term nutraceutical was developed in 1989 by
the foundation for innovation in medicine (Kalra, 2003).
A nutraceutical is any substance that may be considered
as food or part of a food that provides medical or health
benefits including prevention and treatment of diseases
(DeFelice, 1995). Exopolysaccharides, dietary fibers,
polyunsaturated fatty acids, proteins, peptides, amino
acids, and antioxidative vitamins are examples of
nutraceuticals. Most of the nutraceuticals are well
known for their prebiotic activities (El Sohaimy, 2012).
Such activities include: Induces selective stimulation of
growth and/or activity of intestinal bacteria, potentially
associated with health and well-being (Gibson and
Roberfroid, 1995; Scott et al., 2014; Mills et al., 2015).
Probiotics are live microorganisms that, when
administrated in adequate amounts, confer nutritional
and/or therapeutic benefit to the host (Reid et al., 2003).
Prebiotic is non-digestible food ingredient that
beneficially affects the host by selectively stimulating
the growth and/or the activity of one or a limited
number of bacteria in the colon (Gibson and Roberfroid,
1995). The ingested prebiotic stimulates the whole
indigenous population of probiotic to growth, and the
larger that population, the larger is the number of new
bacterial cells. (Roberfroid, 2007).
Synbiotic is a blend of probiotics and prebiotic
that beneficially influences the host by enhancing the
survival and implantation of probiotics in
gastrointestinal tract (Collins and Gibson, 1999).
Dietary antioxidants and polyphenols can act as
prebiotics, they are present in plants, herbs, roots and
plants leaves and vary considerably from one plant to
another. They are considered nutraceuticals which help
in combating some of the major health problems such
as, cardiovascular diseases, cancer, osteoporosis,
arthritis, diabetes, cholesterol etc. Antioxidants and
polyphenols play a major protective role by preventing
oxidative reactions and working as free radicals
scavengers. This has led to a new era, in which the food
industry has become a research-oriented sector
(Halliwell, 1994; Das et al., 2012). The objective of the
present study was to evaluate the effect of some crude
plant extracts on the growth of some probiotic strains
and the production of synbiotic-yoghurt.
MATERIALS AND METHODS
Strains source
Ten probiotic lactic acid bacteria (LAB) used in
this study (Lactobacillus delbrueckii subsp. delbrueckii
KT615, Lactobacillus brevis KP653, Lactobacillus
delbrueckii subsp. lactis KP645), were obtained from
the Faculty of Agriculture, Saba Bacha, Alexandria
University culture collection (FASBAU). Culture of
Bifidobacterium longum 141B was obtained from
Faculty of Agriculture, Shatby, Alexandria University.
Cultures of Lactobacillus plantarum KP623,
Lactobacillus acidophilus CHA2, Lactobacillus
delbrueckii subsp. bulgaricus YASH2, Lactobacillus
johnsonii A1, Lactobacillus casei YA1, and
Streptocccus thermophilus T11 were provided from the
Faculty of Agriculture, Al -Basra University, Iraq.
These ten strains were considered potentially probiotics
since they tolerate bile salts and low pH, comparable to
the human digestive system and they show antagonistic
activity against some enteropathogenic strains as an
indicator.
Gomaa, M. A. E. et al.
42
Culturing conditions
MRS broth medium (De Man et al., 1960)
(Biolife, Italy) was used for reactivating and growing
the selected LAB being used in the present study. All
strains were maintained for long preservation on MRS
slant agar for further study. Bacterial growth from slant
culture was reactivated in 10 ml broth medium at 37 °С
for 24 h at anaerobic conditions.
Plants samples
Plants samples mentioned in Table (1) were
purchased from markets of Alexandria Governorate,
Egypt. All plants samples were collected in clean sterile
plastic bags and transported to the lab in ice box. Plants
were washed using cold water (4 °C, pH 7), and airdried
at 25 °C for 1 h. Chosen parts of each examined
plant were prepared according to the proper
methodology.
Milk
Fresh full fat buffalo’s milk was purchased from
the local market in Alexandria Governorate. Analysis of
milk, was carried out using milk analyzer (3510
Laktostar, Funke Gerber, Berlin, Germany).
Preparation of crude plant extracts
Aqueous extraction of eight plants (rosemary,
dill, garlic, ginger, flaxseeds, thyme, oat, and moringa
leaves) were prepared as previously described by
Schinella et al., 2002 and Wojdyło et al., (2007). Plant
samples (25 g) were ground to a fine paste using a food
processor mill (National, Egypt). The samples were
extracted with 100 ml distilled water for 1 h using a
Magnetic Stirrer (HANNA, Romania). The crude plant
extracts were centrifuged at 3500 rpm for 10 min
(Electrocenterfuge, EC415, Italy). The extract was then
filtered through Whatman paper (Cat. No. 1004, 110
mm). All crude plant extracts sterilized using Millipore
filter (0.22 μm micro-filters, GVS, USA) into 15 ml
sterile Falcone tubes and then stored at -18 °C until use.
DMSO crude extract from rosemary, dill, garlic, ginger
and flaxseeds were prepared as described by Romo-
Vaquero et al. (2014).
Yield of the extracted bioactive compounds, was
calculated using the following equation:
V
D D
V X
X E
Y g ml
×
− ×
=
( ) 1000
(μ / )
Where Y= Yield of crude plant extract (μg/ml); XD =
Extract density (g/ml); ED = density of eluent (g/ml);
V= Eluent volume (ml); XV = Extract volume (ml)
Determination of antioxidant capacity (AOC) and
total phenolic compounds (TPC) in crude plant
extracts
The DPPH assay (Moo-Huchin et al., 2014) was
employed to estimate the AOC, where inhibition (%) of
DPPH was calculated according to the following
equation:
Where A0 is the control absorbance, A1 is the sample
absorbance measured at 517 nm.
TPC of ethanol extracts were prepared as
previously described by González‐Aguilar et al. (2007)
with minor modifications. Total phenol and flavonoid
compounds were extracted from 10 g of sample
previously homogenized in a 15ml of ethanol (80%) and
distilled water. The homogenate was incubated at 60 °C
for 60 min and filtered using SELECTA, Nr. 595, 11
cm, (Germany). The volume of pooled solution was
brought up to 50 ml. Concentrations of total phenols
was measured as described by Singleton and Rossi
(1965) with some modifications. Extracts (50 μl) were
mixed with 3ml of H2O, 250 μl of Folin and Ciocalteus
phenol reagent 1 N. After 8 min of equilibrium time,
750 μl of Na2CO3 (20%) and 950 μl of H2O were added
to the extracts, previous incubated at room temperature
for 120 min. The absorbance was measured at 760 nm
with an UV-Vis Spectrophotometer (Cary, model 50
Bio, Varian, Italy).
TPC in all samples was determined as described
by Khalil and Frank (2010). The amount of TPC was
expressed as milligram(s) of Gallic acid equivalents
(GAE) per gram of initial weight (IW) according to the
following equation (Francisco and Resurreccion, 2009).
g
mg
IW g
yedm mg
m
A b
IW g
mg
GAE
1000μ
1
( )
( ) ( )
( )
760 × ×
−
=
Where A is the absorbance at 760 nm, b is the yintercept
of the standard curve, and m is slope of
standard curve and yedm is yield of the extracted dry
matter.
Biomass production development
Strains inoculums (200 μl), from active
subcultures, were added to 9 ml MRS broth medium.
Where, plant extracts were added at levels of 200 μl,
400 μl, and 600 μl in addition to 600 μl, 400 μl and 200
μl distilled water, respectively, to reach a final volume
of 10 ml. Bacterial growth was monitored by measuring
the optical density at 600 nm (OD600) using a
Spectrophotometer (APEI PD 303, Japan) for 24h.
Afterwards, a growth curve was created for each trial.
Data analysis
The average change rate in OD readings were
calculated across the growth curve and the values were
expressed as O OD at 600 nm in Parito chart.
Synbiotic-yoghurt production
Synbiotic yoghurt was prepared using
pasteurized (5s/ 80°C) buffalo milk and yoghurt starter
bacteria (Lactobacillus delbrueckii subsp. bulgaricus
and Streptococcus thermophilus). Starter culture was
added at 42 ºC and mixed. In addition, one probiotic
culture (Bifidobacterium longum 141B, 0.33% (w/v)
∼107 cfu/ml) was separately added. Afterwards, 1.5% or
2.0% (w/v) of eight prebiotics were added to make
sixteen different combinations. The inoculated milk was
poured in cups, incubated at 42 ºC for 3 h until the pH
4.6 reached, and was followed by rapid cooling.
pH determination
pH values of the crude extracts, milk, and yogurt
samples were measured using a pH meter (Jenway
3505, England)
Sensory evaluation
This was carried out by ten panelists. Flavour,
appearance, and texture of yoghurt samples were
evaluated. A predetermined list of 21 sensory attributes
100
0
0 1 ×
−
A
A A
J. Food and Dairy Sci., Mansoura Univ., Vol. 9 (1), January, 2018
43
was used to describe the sensory characteristics of
yogurts (Stone et al., 2012).
RESULTS AND DISCUSSION
Crude Plants extracts
Yield of aqueous extracts of rosemary, dill,
garlic, ginger, flaxseeds, thyme, oat, and moringa leaves
and five DMSO extracts of rosemary, dill, garlic, ginger
and flaxseeds is shown in Table (1). It was noticed that,
when DMSO was used, either 10% or 99%, more yield
was achieved in contrast with aqueous extract of the
same plant. DMSO did not affect the bacterial growth.
Similar observation was proofed by Wadhwani et al.
(2009); Gomaa (2010).
Data also revealed that garlic gave the highest
yield when DMSO of 99% was used as an eluent (72.0
μg/ml). While water extract of ginger gave the lowest
yield (1.0 μg/ml). Concerning water extraction, the
highest concentration was observed in case of oat (6.7
μg/ml), followed by rosemary, dill, moringa, thyme, and
flaxseed, since the values were 5.7, 5.5, 3.3, 1.3, and 1.2
μg/ml, respectively. Extracts yield of rosemary, dill, and
flaxseeds using DMSO 10% were 54.0, 29.0, and 13.7
μg/ml, correspondingly. Ginger showed more than
twelve folds the yield when DMSO 99% was used as an
eluent (12.8 μg/ml), compared with water extraction.
These findings are in agreement with Zhang et al.
(2014).
Some review articles compared the extractability
of the prebiotic arabinoxylans from cereal using
different techniques. It was concluded that the yield
achieved by water extraction was always lower than that
achieved by chemical and enzyme methods (Zhang et
al., 2014; Mensink et al., 2015; Ruthes et al., 2015).
Therefore, using solvents such as DMSO is suggested as
a mean to increase prebiotic yield from different plants.
Table 1. Yield of bioactive compounds in crude plants extracts.
Plant Eluent
Common name Species source Distilled Water DMSO 10% DMSO 99%
Rosemary Rosmarinus officinalis Leaves 5.7 μg/ml 54.0 μg/ml N.D
Dill Anethum graveolens Leaves 5.5 μg/ml 29.0 μg/ml N.D
Garlic Allium sativum Cloves 1.25 μg/ml N.D 72.0 μg/ml
Ginger Zingiber officinale Rhizome 1.0 μg/ml N.D 12.8 μg/ml
Flaxseeds Linum usitatissimum Seeds 1.2 μg/ml 13.7 μg/ml N.D
Thyme Thymus vulgaris Leaves 1.3 μg/ml N.D N.D
Oat Avena sativa Seeds 6.7 μg/ml N.D N.D
Moringa Moringa oleifera Leaves 3.3 μg/ml N.D N.D
N.D = not determined; DMSO = Dimethyl sulfoxide
Total phenolic compounds (TPC)
Average of the TPC in ethanolic extracts of all
plants extracts ranged from 10.70 to 205.23 mg GAE/g
(Table 2). The highest TPC value among all plant
extracts was observed in moringa leaves, whereas the
lowest TPC in oat. The other six plants (ginger, thyme,
rosemary, garlic, flaxseeds and dill) recorded values of
123.56, 112.61, 104.99, 61.89, 57.85, and 49.28 mg
GAE/g, respectively, in water extracts. In contrast,
plants extracts using DMSO showed lower TPC than
aqueous extracts (Table 2). Overall, TPC data provide
convincing evidence that all trials have high TPC levels
detected in ethanolic extracts. These results are in
agreement with the previous work (Khalil and Gomaa,
2016).
Antioxidants capacity (AOC)
Data in Table 2 show that the highest AOC value
among all extracts was observed in rosemary, dill, and
moringa (99% inhibition). The lowest value was
observed in oat (56% inhibition). Ginger, garlic, and
flaxseeds recorded values ranged between 71 and 98%
inhibition. Generally, DMSO extracts showed higher
proportion of antioxidants than aqueous extracts.
All trials in this study contained TPC and AOC
among other preferred characteristics, which make most
of them very promising when added to any dairy
product with positive impact on human health. In
general, high consumption of vegetables, fruits and
herbs with their antioxidants has been associated with a
lowered incidence of degenerative diseases including
cancer, heart disease, inflammation, arthritis and
immune system decline etc. (Langseth, 1995; Leong and
Shui, 2002).
Table 2. Total phenolic compounds (TPC), antioxidants
capacity (AOC), and pH of water and DMSO
extracts of eight plants.
Plant Solvent
TPC
(mg GAE/g
extract)
AOC
(DPPH %
inhibition)
pH
Rosemary
Water 104.99 79 4.18
10% DMSO 46.89 99 6.96
Dill
Water 49.28 83 4.36
10% DMSO 37.37 99 6.13
Ginger
Water 123.56 80 6.02
99% DMSO 51.66 98 ND
Garlic
Water 61.89 90 5.80
99% DMSO 18.56 94 ND
Flaxseeds
Water 57.85 71 4.85
10% DMSO 45.94 90 5.75
Thyme Water 112.61 81 3.45
Oat Water 10.70 56 3.39
Moringa Water 205.23 99 4.18
pH
pH values of all samples ranged between 3.39 and
6.96 as shown in Table (2). The lowest pH among all
treatments was of 3.39 in water extract of oat, followed by
the water extracts of thyme, rosemary, moringa, dill, garlic,
and ginger they recorded 3.45, 4.18, 4.18, 4.36, 5.80, 6.02
pH values respectively. Concerning 10% DMSO extracts,
the highest value was recorded in case of rosemary (6.96),
while flaxseeds was of the lowest (5.75) and dill recorded
6.13. When 99% DMSO was used as solvent pH was not
determined.
Gomaa, M. A. E. et al.
44
Biomass production development
Biomass production development was studied for
the ten strains, where plant extracts were added in three
concentrations (200 μl, 400 μl, and 600 μl) in 10 ml
MRS broth medium. Bacterial growth was monitored
and the biomass production data were analysed. The
average change rate in OD readings were calculated,
values were expressed as O OD600 nm.
Lactobacillus delbrueckii subsp. delbrueckii KT615
Figure (1) shows the effect of different plant
extracts on the growth of Lactobacillus delbrueckii
subsp. delbrueckii KT615 probiotic strain during 24 h of
incubation. Limited growth was noted, since the highest
recorded O OD600 was 0.115 for control. Thyme,
moringa, garlic, rosemary, dill, and oat aqueous extracts
and ginger DMSO extract showed stimulative effect in
this respect.
Concerning garlic, dill, rosemary, and flaxseeds
DMSO extracts, they showed O OD600 less than the
control. All DMSO extracts suppressed the bacterial
growth as compared with the control. This is not due to
the presence of DMSO itself since it did not affect the
bacterial growth (Wadhwani et al., 2009) and ginger
DMSO extract gave O OD600 value higher than the
control.
Lactobacillus brevis KP653
Data in Figure (1) show that the probiotic strain
Lactobacillus brevis KP653 grew well in the broth
media containing different plant extracts, except two
concentrations of moringa aqueous extract (200 and 400
μl), since the control recorded 0.316 O OD600. As
regards to moringa, the highest O OD600 value was
0.343 unit for the concentration of 400 μl, followed by
the lower concentration (200 μl) which recorded very
close value to the control (0.319 unit). In contrast the
highest concentration (600 μl) showed O OD600 value
lower than the control (0.271).
Lactobacillus delbrueckii subsp. lactis KP645
Although all plant extracts negatively affected
the growth of probiotic strain Lactobacillus delbrueckii
subsp. lactis KP645, compared to the control, the
bacterial growth in most extracts was relatively high.
All trials showed O OD600 lower than control, with
range of 0.304 and 0.045 (Figure 1).
Bifidobacterium longum 141B
Probiotic culture of Bifidobacterium longum
141B grown in the presence of different plants extracts
showed limited growth, since the O OD600 of control
was 0.144 unit (Figure 2). The data also indicate that
most plant extracts, enhanced the bacterial growth.
Generally low variation was observed between
treatments, since all O OD600 values ranged between
0.214 to 0.103. Relatively high O OD600 was observed in
case of rosemary and moringa aqueous extracts (200 μl)
as compared to the control.
Lactobacillus plantarum KP623
Data in Figure (2) indicate that, this strain
performed in all trials similarly, or even better than the
control. O OD600 values ranged between 0.443 and
0.169. Better growth was found in case of thyme, oat,
and moringa aqueous extracts at all concentrations (200,
400, and 600 μl), compared to the control, except for oat
aqueous extracts at 600 μl, which nearly matched the
control. The lowest O OD600 was detected in case of
garlic DMSO extract at all three concentrations.
Lactobacillus acidophilus CHA2
The growth performance of the probiotic strain
Lactobacillus acidophilus CHA2 was affected by
different plants extracts, where the growth slightly
decreased, compared to the control (0.313 O OD600). Its
growth ranged between 0.307 and 0.112 O OD600 as
shown in Figure (2).
Lactobacillus delbrueckii subsp. bulgaricus YASH2
Results (Figure 3) revealed that, bacterial growth
of this strain in all trials was affected with various
degrees, O OD600 values ranged between 0.665 and
0.177. The control achieved 0.452 O OD600 as average.
Higher O OD600 values were observed in case of thyme,
oat, moringa and rosemary aqueous extracts at all
concentrations (200, 400, and 600 μl) except for
rosemary aqueous extracts at 600 μl which recorded O
OD600 values of 0.376 unit.
Lactobacillus johnsonii A1
Probiotic culture of Lactobacillus johnsonii A1
showed very good growth, whereas the control achieved
0.452 O OD600 as average (Figure 3). Generally, the
culture maintained viability and good growth at all trials
and concentrations. O OD600 values ranged between
0.459 and 0.122. It exhibited better growth in trials
containing thyme aqueous extracts at all concentrations
(200, 400, and 600 μl), moringa, oat, and rosemary
aqueous extracts at only two concentrations 200, and
400 μl and flaxseeds aqueous extracts at 200 μl as
compared to control.
Lactobacillus casei YA1
Figure (3) shows the growth performance of the
probiotic strain of Lactobacillus casei YA1.Very good
growth could be detected in all treatments, O OD600
ranged between 0.391 and 0.163. The control recorded
0.344 O OD600. Moringa, oat, and thyme aqueous
extracts at concentrations 200, and 400 μl showed
higher O OD600 values than control. No trial suppressed
the growth of Lactobacillus casei YA1. However, the
lowest O OD600 value among all trials recorded in case
of the highest concentration of flaxseeds DMSO extract.
Streptocccus thermophilus T11
Probiotic culture of Streptocccus thermophilus
T11 grew well in all treatments, O OD600 ranged
between 0.513 and 0.197. The control recorded 0.431 O
OD600 in average. Moringa and oat at all concentrations
and thyme at 400 μl aqueous extracts enhanced the
growth where O OD600 values were higher than the
control. The lowest O OD600 value among all trials
recorded in case of the highest concentration of garlic
DMSO extract (Figure 3).
Generally, all data proved that, not any extract
suites every strain, each strain was affected differently
than the others. Some strains were sensitive to the
presence of plant extracts in the medium (Lactobacillus
brevis KP653, Lactobacillus delbrueckii subsp. Lactis
KP645, and Lactobacillus acidophilus CHA2), which
led to relative decline in growth, while others were
positively influenced in the presence of some extracts.
These results can be used to design new synbiotics
functional dairy products.
J. Food and Dairy Sci., Mansoura Univ., Vol. 9 (1), January, 2018
45
Figure 1. Parito chart where the average change rate in OD at 600 nm (A OD600), during 24 h at 37 °C, were
represented in descending order for eight aqueous extracts: rosemary (RW), dill (DW), garlic
(GrW), ginger (GW), flaxseeds (FW), oat (OW), thyme (TW) and moringa leaves (MW); and five
DMSO extracts: dill (DD), garlic (GrD), ginger (GD) and flaxseeds (FD) at three concentration each
(200, 400, and 600 μl/10 ml medium) in addition to control.
Δ OD at 600 nm Δ OD at 600 nm Δ OD at 600 nm
Gomaa, M. A. E. et al.
46
Figure 2. Parito chart where the average change rate in OD at 600 nm (A OD600), during 24 h at 37 °C, were
represented in descending order for eight aqueous extracts: rosemary (RW), dill (DW), garlic
(GrW), ginger (GW), flaxseeds (FW), oat (OW), thyme (TW) and moringa leaves (MW); and five
DMSO extracts: dill (DD), garlic (GrD), ginger (GD) and flaxseeds (FD) at three concentration each
(200, 400, and 600 μl/10 ml medium) in addition to control
J. Food and Dairy Sci., Mansoura Univ., Vol. 9 (1), January, 2018
47
Figure 3. Parito chart where the average change rate in OD at 600 nm (A OD600), during 24 h at 37 °C, were
represented in descending order for eight aqueous extracts: rosemary (RW), dill (DW), garlic (GrW),
ginger (GW), flaxseeds (FW), oat (OW), thyme (TW) and moringa leaves (MW); and five DMSO
extracts: dill (DD), garlic (GrD), ginger (GD) and flaxseeds (FD) at three concentration each (200, 400,
and 600 μl/10 ml medium) in addition to control.
Δ OD at 600 nm Δ OD at 600 nm Δ OD at 600 nm Δ OD at 600 nm
Gomaa, M. A. E. et al.
48
Sensory evaluation of the prepared synbiotic yoghurt
Table (3) demonstrates the scores for sensory
attributes of yoghurt samples. Evaluating the flavour
scores of samples showed that samples containing oat
gained the highest scores that was close to the control.
Samples containing rosemary, ginger, flaxseeds, and
thyme achieved higher scores than the samples
containing dill, garlic and moringa
Table 3. Sensory evaluation of synbiotic yoghurt made with two concentrations of eight plants aqueous extracts
Overall
score 100%
concentra Flavour (smell and taste) Appearance Texture
tion (%)
Aqueous
extracts Score a Description Score a Description Score a Description
Control 0.0 5 Creamy, Sweet 5 Thick 5 Homogeneous, Light 98
Rosemary 1.5 4 Creamy, Sweet 4 Thick 4 Homogeneous, Light 95
2.0 4 Creamy, Sweet 4 Thick 4 Homogeneous, Light 94
Dill 1.5 3 Creamy, Sweet 4 Thick 5 Homogeneous, Light 93
2.0 3 Creamy, Sweet 4 Thick 3 Homogeneous, Light 95
Garlic 1.5 3 Creamy, Sweet 4 Thick 3 Homogeneous, Light 79
2.0 3 Creamy, Sweet 4 Thick 3 Homogeneous, Light 76
Ginger 1.5 4 Creamy, Sweet 4 Thick 4 Homogeneous, Light 90
2.0 4 Creamy, Sweet 4 Thick 4 Homogeneous, Light 92
Flaxseeds 1.5 4 Creamy, Sweet 5 Thick 4 Homogeneous, Light 93
2.0 4 Creamy, Sweet 5 Thick 4 Homogeneous, Light 91
Thyme 1.5 4 Creamy, Sweet 4 Thick 4 Homogeneous, Light 90
2.0 4 Creamy, Sweet 4 Thick 4 Homogeneous, Light 94
Oat 1.5 5 Creamy, Acidic 5 Thick 3 Homogeneous, Light 88
2.0 4 Creamy, Acidic 5 Thick 3 Homogeneous, Light 86
Moringa 1.5 3 Creamy, Acidic 5 Thick 4 Homogeneous, Light 95
2.0 3 Creamy, Acidic 4 Thick 4 Homogeneous, Light 96
Score a: 1=bad; 2= fair, 3= good; 4=very good; 5=excellent
All sixteen-trials produced well-formed setyoghurt
style, similar or close to the control in
appearance. Appearance scores of yoghurt samples
containing oat, flaxseeds in both concentrations (1.5 and
2.0%) and moringa in its lower concentration (1.5%)
were similar to the control. Slightly lower score (4) was
given in case of rosemary, dill, ginger, and garlic in
addition to moringa in its higher concentration (2.0%).
Comparing texture scores of samples revealed
that the highest score was recorded for the sample
containing 1.5% dill aqueous extract, while the sample
containing rosemary, ginger, flaxseeds, thyme, and
moringa ranked lower in score than the control. Texture
scores of yoghurt samples containing garlic, oat, and dill
2.0% were less.
Total acceptability scores of all samples ranged
between 76 and 98%. The highest value was recorded
for control, while yoghurt samples containing rosemary,
dill, flaxseeds, thyme, and oat aqueous extracts showed
excellent overall score (>90%). However, moringa gave
very good overall score (85 and 86%) for trials
containing 1.5 and 2.0% aqueous extract respectively.
The lowest overall score was recorded for trials
containing garlic (79 and 76%) for trials containing 1.5
and 2.0% aqueous extract respectively. It should be
mentioned that the scores of all samples were higher
than unacceptable limit (60%).
Acetaldehyde, the main factor of yoghurt
flavour, which is majorly made from conversion of
threonine to acetaldehyde catalyzed by threonine
aldolase of L. delbrueckii subsp. bulgaricus, is
converted to ethanol by probiotics that produce alcohol
dehydrogenase. Therefore, probiotic yoghurts do not
have the typical yoghurt flavour (Ranathunga and
Rathnayaka, 2013). This could be the reason for the
above results. However, it is clear that, all plant extracts
used in this study were acceptable and can be used in
dairy products.
CONCLUSION
Concerning the extraction process, the data
revealed that garlic gave the highest yield when DMSO
99% was used as an eluent (72.0 μg/ml). While water
extract of ginger gave the lowest yield (1.0 μg/ml). TPC
data showed that, all trials had high TPC levels that
detected in ethanolic extracts. AOC value of all extracts
ranged between 56 and 99% inhibition. The lowest
value was observed in oat. Generally, DMSO extracts
showed higher proportion of antioxidants than aqueous
extracts. Some strains were sensitive to the presence of
plant extracts (Lactobacillus brevis KP653,
Lactobacillus delbrueckii subsp. lactis KP645, and
Lactobacillus acidophilus CHA2), which led to a
relative decline in growth, while others were activated
in the presence of some extracts in comparison with the
control. The results also indicated that the yoghurt may
be a good carrier for developing synbiotic yoghurt.
Further research should be carried out in this respect.
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