Impact of fermented whey protein concentrate on texture of Iranian white cheese
Department of Food Science and Technology, Ramin Agricultural and Natural Resources University, Ahvaz, Iran
The influence of fermented whey protein concentrate (FWPC) added before and after formation of cheese curd on the textural
characteristics of Iranian white cheese was studied. The FWPC, prepared from whey obtained during cheese making, was added
at different levels 5, 10, 15, and 20% (v/v) after (A) or before (B) cheese curdling. It was found that both incorporation level and
time of addition of FWPC (A and B) caused significant effects on texture profile analysis (TPA) of cheeses. In B cheeses,
increasing the level of FWPC, except at B10%, lead to considerable decrease in hardness and chewiness while adhesiveness and
cohesiveness was significantly increased. All experimental cheeses exhibited a decline in values for each rheological parameter
during ripening. However, statistical analysis of data revealed that only hardness, fracturability, adhesiveness and cohesiveness
were significantly affected by ripening.
Keywords: Iranian white cheese, fermented whey protein concentrate, texture, TPA
Whey proteins are highly susceptible to heat-induced denaturation, irreversibly denature and coagulate
when exposed to high temperatures. The partial unfolding of the protein by heat exposes additional water
binding sites that are unavailable in the native unheated proteins (Jayaprakasha and Brueckner 1999).
Several researchers (Santoro 1994, El-Sheikh et al 2001, Lobato-Calleros et al 2001) have investigated
use of heat particulated/precipitated whey protein concentrates (WPC) in the manufacture of different
kinds of cheeses to increase cheese quantity, i.e. yield or/and cheese quality as a fat replacer to improve
cheese texture and flavour.
According to McMahon and Oberg (1998), the most important method to produce a cheese with a soft
texture is to increase the moisture content and create a moisture to protein ratio equal to or greater than
that observed in full fat cheese. The use of whey protein in the form of WPC or other whey products as a
fat replacer in different cheeses such as Mozzarella (Rudan et al 1998), Domiati (El-Sheikh et al 2001),
Havarti (Lo and Bastion 1998) and Manchego (Lobato-Calleros et al 2001) has been shown to increase
the moisture content of cheeses.
Calcium also plays a significant role in cheese functionality and texture by cross-linking protein
(Metzger et al 2000). By removing some of the bound calcium from casein micelles to reduce the cross-
linking of caseins by preacidification through the addition of FWPC to the milk prior to enzymatic
coagulation, it is possible to manufacture a cheese with softer texture.
On the other hand, the extent of proteolysis in cheese is directly related to the concentration of starter
and the bacterial population of cheese. Khosrowshahi et al (2006) confirmed that as the concentration of
starter inoculated to milk increased, the value of fracture stress at a given ripening time significantly
decreased, leading to a less resistant body against applied stress. Katsiari et al (2002) also reported that
low-fat Feta-type cheese with higher moisture, lower hardness and a flavour similar to that of full-fat
versions could be made by adding adjunct cultures to cheesemilk.
The effects of combining the technique of preacidification, starter culture concentration and the use of
whey protein as a fat replacer by using FWPC on texture quality of soft-brined Iranian white cheese are
not known. Hence, the aim of this study was to investigate the combining effects of FWPC added before
and after formation of cheese curd on TPA characteristics of Iranian white cheese.
Materials and methods
Preparation of FWPC: After collection of whey during preparation of Iranaian-white cheese, the whey
was heated at 84ºC for 15 min. Then it was cooled to 35ºC and inoculated with 1-2% of the same mixed
starter cultures mesophile and thermophile (1:1) used in preparation of cheese. After about 8 hrs
fermentation at 35ºC, the pH of fermented whey reduced to 4.5 and fermented whey protein concentrate
was separated from the whey permeate. This precipitate usually contained about 10 to 11% total solids and
it was used in cheese making after adjustment of its total solids to 10%. The FWPC at different levels 5,
10, 15, and 20% (v/v) was added after (A) or before (B) formation of cheese curd.
Starter Cultures: The lyophilized mesophile and thermophile starter cultures were used for Feta cheese
making. The mesophilic culture (CHOOZIT 230, Bulk cultures, Danisco, Germany) contained two
organisms Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris and thermophilic
cultures (YO-MIX 532, Bulk cultures, Danisco, Germany) was yoghurt cultures containing Streptococcus
thermophilus and Lactobacillus delbruckii subsp. bulgaricus.
Preparation of Iranian white cheese: Cheeses were manufactured according to the method used in
Iranian cheese making plants (Azarnia et al 1997, Madadlou et al. 2005).
Sample Preparation and Collection: Cheese Sampling and preparation were carried out according to
AOAC (2000). The cheese blocks selected as test samples were homogenized with mixer to obtain
homogenous mixture. The final temperature was ?25°C and for this, mixer was frequently stopped after
channeling and spooning cheese back into blades.
Chemical and microbial analysis of FWPC: Fat content was determined by Gerber’s method. Total
solids content was determined by drying 10 g sample at 100°C for 4h (AOAC 2000). Protein content was
determined by macro-kjeldahl method (AOAC 2000). The percentage of proteins was obtained by
multiplying the percentage of total nitrogen by a factor of 6.38. The pH of the sample was determined
using the digital pH meter (Electronics India, Model JIIE) and titrable acidity was determined according
to AOAC (2000). For ash content, 10 grams of sample was accurately weighed in a crucible and dried in
hot air oven at 105ºC. The sample was then ignited on a flame and finally ashed in a furnace at 550±20 ºC
to a constant weight till white ash was left (AOAC 2000). Lactose was determined according to Ranganna
(1986) by employing Lane-Eynon method. The count of lactic acid bacteria (LAB) was enumerated by
MRS agar using pour plating technique of the APHA (Vanderzant and Splittstoesser 1992). FWPC (1.0
mL) was decimally diluted in sterile peptone water (Merck, Germany) (0.1%) and 0.1 ml aliquot dilutions
were incubated in 37 ºC for 3 days (Vinerola and Reinhemir 1999). After 3 days Colony Forming Units
(CFU) were counted by a colony counter.
Texture evaluation: Texture analysis of Feta cheese samples were measured by TA-HDi Texture
Analyzer (Stable Micro Systems, Godalming, UK), a new version of TA- XT2 Texture Analyzer.
Penetration test was carried out on cheese blocks (5.0 cm × 5.0 cm × 3.5 cm) before and after ripening period.
The test on matured samples was performed immediately after removed from brine at 11°C. Two 0.5 cm slices
were cut from each side of the blocks.
Testing conditions for analysis of cheeses were selected according to instrument adjustment applied
for measuring of softness of soft cheeses. A 5 mm aluminum cylindrical probe (No. P/5R), a pretest speed
2.0 mm/s and a test speed 1.0 mm/s were used. The probe was penetrated in the samples to a depth of
10mm by adjusting a 3 g surface trigger. At this point, the probe was returned to original position at constant
speed (i.e. post speed 1.0 mm/s). A force versus time plot was generated with data acquisition of 200 pps.
Statistical analysis: Statistical analysis: Analysis of variance (ANOVA) was carried out using SAS
program (Version 8.2) to determine significant differences within the main factors and interactions.
Duncan’s multiple-comparison test was used as a guide for pair comparisons of the treatment means at
Results and discussion
Characteristics of FWPC: The physico-chemical composition of FWPC was as follow: protein 4.34%,
fat 1.21%, ash 0.05%, lactose 3.91%, Acidity 0.63 g per cent lactic acid, and pH 4.5. In addition, the
mean count of LAB of FWPC was about 8.83 log cfu/g.
TPA characteristics: The changes in rheological parameters of Iranian white cheeses were determined
by the texture profile analyzer TA-HDi in terms of hardness, fracturability, adhesiveness, cohesiveness,
springiness, and chewiness before and after one month ripening of experimental cheeses. Table 1 shows
the effect of addition of FWPC added before and after formation of cheese curd on the various TPA of the
fresh and ripened Feta cheeses. It can be observed from the table that the TPA characteristics of all the
fresh Feta cheeses were significantly different. Analysis of variance also revealed that place of addition
(except on springiness), concentration of FWPC, and the interaction of theses two factors had significant
effects on the TPA characteristics of fresh Iranian white cheeses.
In B cheeses, increasing the level of FWPC, except at B10%, lead to considerable decrease in hardness
and chewiness while adhesiveness and cohesiveness were significantly increased (Table 1). The lower
firmness and chewability was probably due to higher moisture content and proteolysis (data are not
shown). The higher moisture content in the B group is in agreement with results obtained by Downes et al
(1981), Santoro (1994) and Zisu and Shah (2005) who reported higher moisture content of cheeses made
with added whey protein concentrate. B10% showed contradictory texture profile due to adverse effect of
FWPC on this trial. As it mentioned before, FWPC contains denatured whey proteins which has high
potential to increase water holding capacity (WHC) of the cheese curd. Furthermore, slightly decrease in
pH of the cheese milk reduces calcium ion concentration and increases moisture retention in the curd
(Zisu and Shah 2005). However, the decrease in the PH of the final curd by means of acidification
(Roginski et al 2003), addition of starter culture (Hayaloglu et al 2005) or addition of FWPC cause a
higher syneresis of the curd and result in a denser protein matrix possibly due to increased coalescence of
casein strands (Zisu and Shah 2005). The lower degree of protein hydration in B samples with 10%
FWPC was probably due to predominant effect of reduction of pH of the cheese milk rather than
increasing effect of whey proteins on the WHC. The highest hardness and chewiness in B group were
related to B10% with 5.32 N and 25.13 N.mm, while the lowest were related to B20% as 1.56 N and 9.9
N.mm, respectively. The values for TPA hardness and chewiness on the day of manufacture were in the
order A > control > B. The results revealed that incorporation of increasing amount of FWPC
significantly increased adhesiveness in A and B samples; in which the highest value was recorded for
B20%. However, there was no major difference between B20%, A15% and A20% and the values for
adhesiveness was in the order A > B > control. B samples had a softer texture than A samples and no
fracturability in B cheeses was observed. Among A cheeses, increasing the level of incorporation up to
15% notably increased the fracturability and thereafter slightly decreased. Although A cheeses were
harder than B cheeses and control, they were more brittle. A group had also lower cohesiveness than other
cheeses and the values were in the order B > control > A. Similar to the results obtained for B cheeses,
Bonczar et al (2002) reported that soft cheeses produced from ultrafiltrated milk were characterized by
significantly lower hardness and higher cohesiveness than cheese obtained from non-concentrated milk,
which was probably connected with higher water capacity and higher amount of nitrogen compounds in
cheese manufactured from retentate.
In respect to ripened cheeses, results indicated that place of addition of FWPC had significant impact
on the hardness, fracturability, cohesiveness and chewiness, but this effect on springiness was not
considerable. Furthermore, hardness, fracturability and chewiness were significantly affected by addition
of FWPC, while other texture characteristics were not significantly affected. Similar to fresh cheeses, B
cheeses at the higher level of substitution (15 and 20%) considerably had softer texture and lower
fracturability than control and A cheeses. The minimum hardness was recorded for B20% as 0.61 N and
similar to fresh status no fracturability was observed. The maximum hardness and fracturability were
recorded for A15% (5.19 N) and A10% (2.78 N), respectively. One-month-old control cheese showed
significantly higher values for hardness and chewiness than B cheeses at higher levels of substitution but
lower than A cheeses. Analysis variance of data on texture characteristics of ripened Feta cheeses
revealed that A cheeses were more firm, brittle and adhesive but less cohesive and springy compared with
B cheeses. All experimental cheeses exhibited a decline in values for each rheological parameter during
ripening. However, statistical analysis of data revealed that only hardness, fracturability, adhesiveness and
cohesiveness were significantly affected by ripening.
As it is shown in Table 1, the hardness and chewiness of all cheeses was significantly decreased during
ripening likely due to increased proteolysis (Johnson 2003). The initial mean values of hardness for
control, A and B cheeses as 3.59, 6.35 and 3.25 N decreased to 2.04, 4.17, 1.95N, respectively. For
chewiness, the initial mean values for control, A and B cheeses as 16.19, 23.24 and 16.12 N.mm
decreased to 8.24, 14.17 and 8.20 N.mm, respectively. Similar to hardness and chewiness, all A cheeses
showed lower fracturability after one month ripening. In B cheeses, although on the day of manufacture
no fracturability was observed, after ripening small fracturability at the levels 5, 10, and 15% FWPC were
determined. This was probably because of decreasing adhesiveness, cohesiveness and springiness during
ripening as earlier reported by many workers (Bonczar et al 2002, Dabour et al 2006).
The adhesiveness and cohesiveness values for all cheeses decreased during the ripening period.
Maximum adhesiveness was recorded for A20% as 1.60 N.mm while maximum cohesiveness was
recorded for B20% as 0.49. The significant reduction in cohesiveness values reported for all cheeses as
ripening progressed could be attributed to increased proteolysis. Cheese cohesiveness is inversely related
to cheese proteolysis, with a trend of decreasing with increasing proteolysis (Dabour et al 2006). In
addition, the lower pH of cheese may cause further reductions in TPA-cohesiveness values. Decreases in
the pH of the cheese curd are correlated with gradual dissociation of the casein micelles into small
aggregates (Roginski et al 2003). At low pH, casein micelles lose their integrity and cohesion.
With respect to springiness, all cheeses showed a lower springiness after ripening, though these
differences were small in magnitude. The decrease in cheese springiness during ripening has been
reported previously for Cheddar and other cheeses, and is attributed to the release of calcium ions from
monocalcium and dicalcium para -caseinate molecules and to the hydrolysis of these molecules during
ripening (Dabour et al 2006).
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Table 1. Effect of different levels of fermented whey protein concentrate (FWPC) added before (B) and after (A) formation of cheese curd on TPA1
characteristics of fresh and ripened Iranian white cheeses.
5% 10% 15% 20%
5% 10% 15% 20%
5.32 ±0.20c 2.77 ±0.26d
5.76 ±0.65bc 8.35 ±1.11a 6.59 ±0.69b
4.06 ±0.17bc 1.14 ±0.34de
5.19 ±1.09a 3.91 ±0.52bc
5.33 ±1.35a 4.06 ±1.06b
2.05 ±0.48bcde 1.43 ±0.36ef
1.89 ±0.22cd 1.75 ±0.20cd
2.21 ±0.22bc 2.59 ±0.38ab
1.22 ± 0.29a
0.43 ±0.02bc 0.41 ±0.08bc
0.40 ±0.02ab 0.42 ±0.08ab
Ripened 10.24 ±1.31b
23.64 ±2.84abc 26.42 ±2.74a 20.61 ±3.52c
15.06 ±2.35ab 18.11 ±4.62a 12.14 ±3.33bc
a,b,c Means in the same row having different letters are significantly different (P<0.05); 1Texture profile analysis