Influence of production processes in quality of fermented milk

doi:10.4236/health.2010.24057

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Vol.2, No.4, 381-389 (2010) Health

doi:10.4236/health.2010.24057

Influence of production processes in quality of

fermented milk “Laban” in Lebanon

Zeineddine Mayssoun1, Nassif Nadine2

1National Beverage Company, Quality Department, Choueifat, Lebanon; misso_zd@hotmail.com

2Lebanese University, Faculty of Agricultural Sciences, Environmental Department, Dekwaneh, Lebanon; nadinenassif3@hotmail.com

Received 6 December 2009; revised 20 January 2010; accepted 25 January 2010.

ABSTRACT

Yoghurt (Laban) is one of the most consumed

food products in Lebanon. Thus its quality has

given a concern. In this study, the sensory,

chemical and rheological properties of com-

mercial and traditional samples were investi-

gated in order to characterize this fermented

milk. Hence, Laban samples were collected from

14 areas in Lebanon; especially from moun-

tainous regions and from the capital Beirut.

Forty-two samples were prov ided by processing

industry whether at small, medium, or large

scale. A statistical analysis was carried out, and

thus sensory and physicochemical properties

were subjected to two approaches of variance

analysis. Pearson correlation coefficients be-

tween attributes were also calculated. Both, the

analyses of variance and correlations were

conducted using SPSS 3. The physicochemical

analysis and the microbiological analysis ex-

hibit a significant effect of the date, and the

manufacturing process. Also, the instrumental

data showed no significant correlation between

physicochemical and microbiological parame-

ters, which indicates that they are completely

independent. Moreover, the general apprecia-

tion of descriptive sensory analysis of products

display that this appreciation is not dependant

on the production process. It is also noticed

that some sensory characteristics can be dread

by instrumental measures. This research en-

dorses the essential role of quality control for

the manufacturing of yoghurt in Lebanon.

Keywords: Laban; Rheology; Manufacturing

Process; Sensory Analysis; Lebanon

1. INTRODUCTION

Yoghurt (Laban) is one of the most consumed prod-

ucts in Lebanon. It is obtained through lactic acid fer-

mentation of heat-treated milk by Streptococcus ther-

mophillus and Lactobacillus bulgaricus at 40-45℃ [1].

The annual consumption of Laban is approximately 20

Kg per capita in Lebanon [2]. Laban may be prepared

from full fat milk or low fat milk, but it must conform

to the different standards set by the government re-

garding its fat and total solids content [3].

The possibility of using some artisanal strains as

starter for the development of fermented milks with

characteristics similar to traditional products, at an in-

dustrial scale, is very promising. However their potential

use depends on further assessment of their aptitude to be

reproduced by fermentation and preserved by freezing

and/or by freeze drying. Moreover, these strains should

first be tested in mixed cultures, in order to obtain fer-

mented milks with rheological and flavor characteristics

similar to those of artisanal products.

In Lebanon, Laban is manufactured by both industrial

and small traditional producers. Lately in Lebanon, a

number of yoghurt factories have been developed. There

is an obvious competition between these factories con-

sidering mainly, in addition to production rate, the qual-

ity control. Quality and reproducibility of fermented

milks and processes are ensured by using industrial

starters. Nevertheless, consumers prefer traditional fer-

mented milks since artisanal starters give these products

more typical flavors [4], where small producers inocu-

late the milk with an artisanal starter obtained from the

previous day’s preparation.

The production of yoghurt is a very classical proce-

dure that does not necessitate variations. However, post

fermentation handling is a very critical to induce desir-

able properties to the product. Indeed, the Laban, being a

highly consumed product in Lebanon, its need to have

produced under hygienic conditions to be more widely

available to the consumer, prior to becoming too acidic

and to avoid any texture modification.

Milk testing and quality control is an essential com-

ponent of any milk processing industry whether small,

medium or large scale. Milk being made up of 87% wa-

ter is prone to adulteration by unscrupulous middlemen

Z. Mayssoun et al. / Health 2 (2010) 381-389

382

and unfaithful farm workers. Moreover, its high nutritive

value makes it an ideal medium for the rapid multiplica-

tion of bacteria, particularly under unhygienic produc-

tion and storage at ambient temperatures. We know that,

in order for any processor to make good dairy products,

good quality raw materials are essential “Quality, it

starts at the farm”. Different technological and microbi-

ological parameters have been reported to influence yo-

ghurt quality: composition, heat treatment of milk, con-

ditions of incubation (temperature and pH) and storage

(temperature and duration) [5-7].

Yoghourt is a very prominent media for yeast. Even

though pasteurization eliminates them from raw milk,

they appear again when they are subjected to handling

and manufacture. Heat treatment of yoghurt was effi-

cient in improving its shelf life and its microbial count.

In September 1971, the milk committee had agreed that

the future standard on yoghurt should not be considered

as “yoghurt” even with a qualifying term. The excuse for

this that the appellation “yoghurt” must denote a product

with specific bacteria in viable form and in abundance

this did not conform to the heated yoghurt [8]. In this

way the Lebanese standard precise that these bacteria

should be stay alive in finished product.

The addition of stabilizers was shown to be necessary.

Regarding preservation alone, different yeasts had differ-

ent reactions to sodium benzoate and potassium sorbate.

For instance Trichosporon cutaneum was most sensitive to

potassium sorbate. Indeed 100 mg/Kg was enough to en-

sure less than 105 cfu g-1 for a 14 days storage period,

whereas 200 mg/Kg limited the count to less than 105 cfu

g-1 for a 21 days storage period [9]. Potassium sorbate was

shown to be more effective than sodium benzoate. Thus,

as we see, preservation of yoghurt requires more than 100

mg/Kg of preservatives. The latter could have an identical

effect than heat treatment at 65℃. Indeed, the yeast and

mold count was limited to less than 10 cfu g-1 after 12

months of storage at 20℃. This showed the efficiency of

the preservatives and their very delicate usage. Indeed if

extra amounts were used some off-flavors, health prob-

lems and extra costs might occur [9]. According to Leba-

nese standard [10], the maximal content in sorbic acid and

its salts must be never exceed 50 mg/Kg and the use of

benzoic acid are forbidden.

The efficient production of milk under good hygienic

conditions is the key to successful dairying. The princi-

pal constraints in Lebanese smallholder systems are in-

adequate feeding, low genetic potential in animals and

the major farms don’t have a milking room. If milking

doesn’t take place manually, mostly, it takes places with

movable milking machine for larger herds with the pos-

sibility of transmission of many germs leading the prod-

uct to spoilage before reaching the market. The trans-

portation of milk from the producer to the processor and

finally to the consumer take place by the producer itself

or through a conveyor. Generally, milk was collected in

plastic or aluminum containers and transported to the

processor via refrigerating car or no according to the

distance covered [11].

Therefore, The objective of the current study is to

compare the quality of Laban sample collected from 2

representative regions (Mount Lebanon and Beirut) in

Lebanon with the International Standards in order to as-

sess the suitability of this nutritious material for health.

2. MATERIALS AND METHOD

2.1. Laban samples

Laban samples were collected from 14 areas distributed

throughout the Lebanese territory especially from Mount

Lebanon and Beirut regions (see Table 1). Forty-two

samples were provided by processing industry whether

small, medium or large scale. Samples were collected

during 3 periods for 1 month. A replication of the de-

scriptive sensory evaluation, coupled with instrumental

measurements, was done for each sample.

2.2. Physicochemical An alysis

Titratable acidity was determined by titrating Laban

samples with 0,1N NaOH using phenolphthalein as an

indicator as outlined by AFNOR [12]. Results were ex-

pressed in g of lactic acid per Kg of sample. The fat con-

tent was determined by Gerber method [13]. The dry

solids content by drying method as outlined by the As-

sociation of Official Analytical Chemists (AOAC) [14].

All analyses were performed in duplicate. Apparent vis-

cosity (η), expressed in Pa.s, was determined by using a

Brookfield viscosimeter mod DV-II (Brookfield Eng.

Lab., Middleborro, MA, U.S.A.), operating at 20℃. A

LV4 spindle was used at different shear rates: 2, 5, 10,

20, 50 and 100 rpm.e.

2.3. Microbiological Analyses

The Total and Faecal coliform bacteria were isolated by

plating the diluted samples (dilution of 1 g of sample in

sterile distilled water with 0,8% NaCl) on Maconkey

Agar incubated for 24 h at 37℃ for Total coliform [15],

and at 44℃ for Faecal coliform [16]. Salmonella spp.

was isolated after enrichment in selenit broth at 37℃ for

24 h, than plating on SS Agar incubated at 37℃ for

24-48 h [17]. Staphylococcus aureus were isolated by

plating the diluted samples on Chapman Agar at 37℃

for 24 h [18]. Yeasts and molds are also isolated using

“Chloramphenical yeast Agar” at 30℃ for 5 days [19].

Bacteria counts were expressed as colony-forming units

(cfu) per 1 g of sample. All tests were duplicated for

each isolate.

Z. Mayssoun et al. / Health 2 (2010) 381-389

383

Table 1. Distribution of Laban samples throughout the Lebanese territory.

N° Code Date of fondation origin Scale

1 LMO 1961 ELGHOBEIRI (Mount Lebanon) ٍSmall

2 ER 2000 ELJAHLIEH (Mount Lebanon) Small

3 LKA 2005 ELCHOUWEIFAT (Mount Lebanon ) Small

4 LW 2002 KABER CHMOUN (Mount Lebanon ) Small

5 LR 1992 ALLAY (Mount Lebanon ) Small

6 LD 1992 BORJ EL BARAJNI (Beirut) Medium

7 GD 1994 ELAMROUSAYEH (Mount Lebanon ) Medium

8 LG 1960 HARET HREIK (Mount Lebanon ) Medium

9 LK 1990 JISER EL BACHA (Beirut) Medium

10 ES 1976 DMIT (Mount Lebanon ) Medium

11 LM 2005 DEKWANEH (Mount Lebanon ) Medium

12 PR 1991 SIN EL FIL (Beirut) Medium

13 DD 1857 KFARCHIMA (Mount Lebanon ) Large

14 Dk 1978 AIN EL SINDIYANA (Mount Lebanon ) Large

2.4. Descriptive Sensory Analysis

Sensory analysis was carried out in Lebanon with the

collaboration of a panel of 16 volunteer members. Two

hours were conducted to train the panelists in the good

use of the intensity scale and to compare their perception.

The 4 characteristics tested are given in Figure 1. Sam-

ples were classified for each descriptor according to a

5-category intensity scale (scale 1 denoting an absence

of the considered perception and scale 5 denoting a very

intense perception).

Each product was coded randomly by 1 letter and 2

digits. Samples, stored at 4℃ for 4 days, were presented

in a simultaneous way. Extrinsic factors such as tem-

perature, quantity presented, and container were homo-

geneous for all the products. Spring water was provided

for mouth rinsing between samples. In order to control

the sort out of samples, the distribution of samples to

panelists is realized according to “latin square plane of

williams”.

3. STATISTICAL ANALYSIS

Sensory and physicochemical properties were subjected

to two-way analysis of variance. It allowed studying the

variability between samples, by taking into account the

variability between subjects. Pearson correlation coeffi-

cients between attributes were also calculated. Analyses

of variance and correlations were conducted using Soft-

ware Statgraphics Plus version 3,0 (Stastical Graphics

Corp., Rockville, MD, U.S.A.).

Figure 1. Attributes used in the sensory evaluation of Laban.

4. RESULTS AND DISCUSSIONS

4.1. Physicochemical Analyses

Results of physicochemical analyses are shown in Fig-

ure 2. Significant differences (α < 0,05) in titratable

acidity (see Table 2), total solid content, and fat content

were found between samples collected from different

origins. In plus, a significant effect of date was observed.

A typical yoghurt sample was described by the Lebanese

Institut of Normalisation (LIBNOR) [10], should contain

3% milk fat and, not less than 8,5% milk solids non-fat

with a titrable acidity of no high than 1,5%. The total

solid content of Laban samples varied between 6,78 and

13,25%.

Therefore, almost 31% of samples were conformed to

Lebanese Standard. However Toufeili and others [20],

showed that the composition varied according of feeding,

milk production period, and the race. Concerning fat

content, the mean value obtained deviate widely with

minimum of 2,3% and maximum of 8,4%. Results

showed that 86% are conformed to Lebanese standard.

Two industries are under standard (GD “medium scale”

Z. Mayssoun et al. / Health 2 (2010) 381-389

384

and DD “large scale”). These lower values can result

from 2 causes: milk in its original composition, is poor

in fat content or due to fraud practice on behalf of indus-

trialist be possible during the moment of reception of

milk or during obtaining finished product.

% o f total s olid

content

LMOLKALR GD LKLM DD

selected laban samples

(a)

Date1

Date 2

Date 3

% of fat c onten t

LMOLKALR GD LK LMDD

Selected laban samples

(b)

Date 1

Date 2

Date 3

0.2

0.4

0.6

0.8

1.2

1.4

1.6

Titra ble acid it

g / l

LMOLKALR GD LK LM DD

Selected laban samples

(c)

Date 1

Date 2

Date 3

Figure 2. Physicochemical characteristics of selected Laban

samples. (a) percentage of total solid content during 3 dates in

the 2 regions, (b) percentage of fat content during 3 dates in the

2 regions, and titratable acidity (g/l) (c).

Table 2. Two way analysis of variance for titratable acidity.

Test of Between-Subjects Effects

Dependent Variable: RDT

Source

Type III

Sum of

Squares

df Mean

Square F Sig.

Corrected

Model 1.758a 15 .117 11.915 .000

Intercept 43.513 1 43.513 4423.361.000

DATE .166 2 8.295E-02 8.432 .002

USINE 1.592 13 .122 12.451 .000

Error .256 26 9.837E-03

Total 45.527 42

Corrected

Total 2.014 41

aR Squared= .873 (Adjusted R Squared = 800)

Finally, lactic acid content varied between 0,63% for

PR industry (medium scale) and 1,37% for DD industry

(large scale). Consequently, the values of lactic acid con-

tent obtained for the Laban samples were in agreement

with those described by Lebanese Standard. In previous

researches, fresh yoghurts had lower titratable acidity.

The apparent viscosities of traditional samples (see

Figure 3) were lower than that of the commercial product

Z. Mayssoun et al. / Health 2 (2010) 381-389

385

Figure 3. Evolution of cisaillement speed according to the

applicated constrainte during the second date in the 2 regions.

(DD and DK). These observations are in agreement with

the results of Guizani and others [21], who found that

commercial fermented milk samples had higher viscosi-

ties than home made products. Owning to additional

solids in the formulation of the commercial products. In

lack for any reference that described the normal viscos-

ity of yoghurt, these higher values probably explained by

homogenization of milk with milk powder or casein

without proportional addition of water content.

4.2. Microbiological Analyses

Considering the microbiological part of the study,

Analysis of variance showed significant differences (α

<0,05) between industries for those of 6 parameters (see

Table 3). As described by the Lebanese and French

Standards, the Total and Faecal coliform count must be

lower than 100 cfu per 1 g of Yoghurt [15,16, 22] the

absence of salmonella in 25 g of sample and not higher

than 10 cfu g-1 of Saphylococcus aureus [23]. Indeed, the

yeast and mold count must be lower than 103 cfu g-1

[19-23].

For years, Total and Faecal coliforms (FC) were

widely thought to be meaningful indicators. FC, also

called Thermotolerant coliforms, have been used

throughout this study as fecal indicators to evaluate the

levels and sources of microbiological contamination of

yoghurt produced in Mount Lebanon and Beirut re-

gions. Table 4 shows that Total coliforms concentra-

tions exceeded the Lebanese and French standards in

GD and LG industry (medium scale) and FC concen-

trations in GD and LK (medium scale). Therefore 14%

are none conforms. These Higher values can be results

from the non respect of good hygienic practices (GHPs)

in farms, insufficient heat treatment of milk during

manufacturing, and keeping out the milk without re-

frigeration.

As can be seen in Table 4, they are 2 traditional fac-

tory (ER and LKA), who that exceed the standard of

Staphylococcus aureus count. The importance of

Staphylococcus aureus in yoghurt may be result from

bad hygiene or high contamination of dairy product

[24]. Taken the hygienic quality of containers into ac-

count [25,26], and the absence of refrigeration, Staphy-

lococcus aureus is responsible for alimentary intoxica-

tion.

Concerning salmonella count, the mean values var-

ied between 40 and 95 cfu g-1 for these 4 industry: LKA,

GD, LG and LK (See Figure 4). But these suspected

germs are present only in 1 date among the 3 dates.

It’s prove that it is necessary to be a casual contamina-

tion and may be result from poor hygiene of farms,

personnel, utensils, the starter used, and insufficient

heat treatment. Further tests should be done to confirm

the presence of salmonella species other than plating.

There is also possible examination of pathogenic or-

ganisms, but what is more significant is the examina-

tion of yeasts and molds as these are capable of spoil-

ing yoghurt well within an anticipated sell-by-date [1].

They reproduce by “budding”. Indeed no growth of

yeast was observed in commercial fermented milk

samples (DD and DK). However, a higher count was

observed in the others Laban samples were manufac-

turing according to traditional methods (inoculation

with an artisanal starter culture obtained from the pre-

vious day’s preparation). Therefore 71% are none con-

forms (see Table 4). This high count can be influenced

moreover by the age of product than the containers

used and the method of transformations [27]. These

lower values can be explained by usage of preserva-

tives such sorbic acid who have a anti-fungic effect. It

has been suggested that a limitation in the count to less

than 100 viable yeast cell/ml should be put. Indeed a

count of 1000 cells/ml could imply a serious risk of

deterioration [1]. Low fat yoghurts appear to be less

suitable as a growth medium than full fat but the reason

is not known yet. Oxidative yeasts are also important

spoilage organisms. They could be limited by the

availability of oxygen. They may develop moist flat

colonies. They usually grow on the walls of the con-

tainer whereas the fermentative yeasts dominate in the

middle.

4.3. Correlation between Technological

Parameters

As can be seen in Table 5, the high correlation was ob-

served between Total coliforms and Faecal coliforms

(r=0,995). Fat content was correlated to total solids con

tent (r=0,635). Significant but poor correlations were

observed between yeasts and the presence of salmonella

Z. Mayssoun et al. / Health 2 (2010) 381-389

386

Table 3. Two way analysis for Faecal coliforms.

Test of Between-Subjects Effects

Dependent Variable: RDT

Source

Type III Sum

of Squares df Mean Square F Sig.

Intercept Hypothesis 3221458.333 1 3221458.333 12026.778 .006

Error 267.857 1 267.857a

REP Hypothesis 267.857 1 267.857 .001 .976

Error 19868660.7 67 296547.175b

USINE Hypothesis 35425625.0 13 2725048.077 9.189 .000

Error 19868660.7 67 296547.175b

DATE Hypothesis 1046488.095 2 523244.048 1.764 .179

Error 19868660.7 67 296547.175b

a. MS(REP)

b. MS(Error)

Table 4. Microbiological characteristics of selected Laban samples.

Mean of 6 repetitions (cfu g-1)

Codea Total

coliforms

Faecal coli-

forms

Staphylococcus

aureus

Salmonella

Shigella Yeasts Molds

1 LM 0 0 0 0 1100 48

2 ER 0 0 50 0 467 12

3 LKA 50 0 33 40 1147 0

4 LW 0 0 0 0 350 0

5 LR 0 0 0 0 46 0

6 LD 0 0 0 0 275 2

7 GD 1733 2533 0 42 1008 18

8 LG 150 75 0 67 1400 5

9 LK 0 133 0 95 7833 0

10 ES 0 0 0 0 6667 148

11 LM 0 0 0 0 1267 2

12 PR 83 0 0 0 78 2

13 DD 67 0 0 0 75 0

14 DK 18 0 0 0 33 2

(r= 0,547). This result are in according to the study carry

out in Bekaa region [28]. It’s proving that there are no

correlations between physicochemical parameters and

microbiological parameters and that they are completely

independent.

4.4. Descriptive Sensory Analysis

ANOVA univarietes results, taking into account the effects

of both laban samples and subjects, showed no significant

difference (α <0,05) between the 14 laban samples tested

Z. Mayssoun et al. / Health 2 (2010) 381-389

387

100

200

300

ufc / g

LMO LKALRGDLKLMDD

Date 1

Date 3

selected industr y

Date 1

Date 2

Date 3

Figure 4. Salmonella count during the 3 dates in the 2 regions.

for the 4 characteristics: texture, taste, acidity and, general

appreciation. As an illustration, Figure 5 shows the score

obtained for 4 selected attributes.

A general appreciation of descriptive sensory analysis

of products display that this appreciation does not de-

pend on the production process. In Table 6, general ap-

preciation of products were correlated with taste (r = 1),

and acidity (r = 0,901). Correlation results revealed that

there were 2 groups of attributes for the flavor of Laban.

No correlation was observed between general apprecia-

tion and texture in our study. Pearson correlation coeffi-

cients were highly significant between acidity and taste

(r = 0,904), it’s indicate that these criteria are very im-

portant in the evaluation of Laban.

4.5. Relationships between Sensory Data

and Physicochemical Measurements

The statistical relationship between sensory and instru-

mental data was examinated using Pearson’s correlation

procedure. Some sensory characteristics can be dread by

instrumental measures (see Table 6). The sensory values

for viscosity were correlated with the viscosity measured

with a viscosimeter type Brookfield (r = 0,789).

These correlations were also observed by Marshall

and Rawson [29], indicated that texture measurement

were correlated with sensory evaluation of viscosity. In

the same way, fat content was negatively correlated with

the acidity (r = –0,855).

Table 5. Correlation analysis between instrumental parameters of Laban samples for 3 dates.

TC FC Staph. Salmo. Yeast Molds T.S.C. Fat C. Acidity

TC 1 0,995b. –0,118 0,258 –0,012 –0,084 –0,377 –0,34 –0,447

FC 0,995 1 –0,12 0,277 0,001 –0,026 –0,428 –0,355 –0,418

Staph. –0,118 –0,12 1 –0,018 –0,103 –0,136 –0,075 0,03 0,041

Salmo. 0,258 0,277 –0,018 1 –0,188

0,547 –0,152 –0,198 0,072

Yeast –0,012 0,001 –0,0103 –0,188 1 0,55 –0,28 –0,199 0,002

Molds –0,084 –0,026 –0,136 0,547 0,55 1 –0,387 –0,118 0,159

T.S.C. –0,377 –0,428 –0,075 –0,152 –0,28 –0,387 1 0,635 –0,221

Fat C. –0,34 –0,355 0,03 –0,198 –0,199 –0,118 0,635 1 –0,508

Acidity –0,447 –0,418 0,041 0,072 0,002 0,159 –0,221 –0,508 1

bIn bold, significant values at the level of significance alpha= 0,05 (two-tailed test). Abbreviations: Total coliform (TC), Faecal coliform (FC),

Staphylococcus aureus (Staph.), Salmonella (Salmo.), Total solid Content (T.S.C.), and Fat content (Fat C.).

Table 6. Relationships between sensory data and physicochemical measurements.

T.S.C Fat C. Acidity Visco. S.Acidity Taste Texture G.A.

T.S.C 1 0.628 –0.695 0.515 –0.522 –0.394 0.361 –0.392

Fat C. 0.628 1 –0.855 c 0.728 –0.514 –0.456 0.4 –0.45

Acidity –0.695

–0.855 1 –0.535 0.74 0.533 –0.17 0.525

Visco. 0.515 0.728 –0.535 1 –0.057 –0.041

0.789 –0.046

S.Acidity –0.522 –0.514 0.74 –0.057 1 0.904 0.445 0.901

Taste –0.394 –0.456 0.533 –0.041 0.904 1 0.525 1

Texture 0.361 0.4 –0.17 0.789 0.445 0.525 1 0.522

G.A. –0.392 –0.45 0.525 –0.046 0.901 1

0.522 1

Z. Mayssoun et al. / Health 2 (2010) 381-389

388

(a)

0.0

1.0

2.0

3.0

4.0

5.0

LMO

LKA

samples

M e a n o f scores / 5

(b)

LMOER LKA LWLRLDGDLGLKESLMPRDD

samples

Mean of scores / 5

(c)

0.0

1.0

2.0

3.0

4.0

5.0

LKA

Samples

Mean of scores / 5

(d)

0.0

1.0

2.0

3.0

4.0

5.0

LMO

LKA

Samples

M ean of scores /

Figure 5. (a) Determination of viscosity, (b) Determination of

taste, (c) Determination of acidity, and (d) General appreciation

of products during the second date.

5. CONCLUSIONS

Both instrumental and sensory data distinguished large

differences between laban samples collected from Mount

Lebanon and Beirut. Faecal coliforms have been used

throughout this study as fecal indicators to evaluate the

levels and sources of microbiological contamination of

yoghurt produced in Mount Lebanon and Beirut regions.

Significant differences in titratable acidity, total solid

content, and fat content were found between samples

collected from different origins. In plus, a significant

effect of date was observed. The instrumental data

showed no significant correlation between physico-

chemical and microbiological parameters. It’s proving

that they are completely independent.

A general appreciation of descriptive sensory analysis

of products display that this appreciation does not de-

pend on the production process. Pearson correlation co-

efficients were highly significant between acidity and

taste, it’s indicate that these criteria are very important in

the evaluation of Laban. Some sensory characteristics

can be dread by instrumental measures. The texture

measurement was correlated with sensory evaluation of

viscosity.

Nevertheless, results were based on a limited number

of industries, and further testing with larger numbers

may be necessary to confirm current results. However,

over the coming years other stabilizers must be tried in a

quest for having an even more desirable body and tex-

ture as well as taste. The possibility of using some ar-

tisanal strains as starter for the development of fer-

mented milks with characteristics similar to traditional

products, at an industrial scale, is very promising. A fu-

ture identification of the different yeast species con-

taminating yoghurt over the time from different com-

mercial sources could be done. This is to help in in-

crimination of the final products once contaminated by a

tolerant yeast organism.

6. ACKNOWLEDGEMENT

The authors gratefully acknowledge the financial support of the Lebanese

University, Faculty of agricultural sciences. We wish to express our ap-

preciation for the panelists for their participation in the sensory assess-

ments.

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