Assessment of Ultra Filtration and Vacuum Evaporation on Whey Protein Concentration

2nd Mercosur Congress on Chemical Engineering

4th Mercosur Congress on Process Systems Engineering

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ASSESSMENT OF ULTRAFILTRATION AND VACUUM

EVAPORATION ON WHEY PROTEIN CONCENTRATION L. Serpa1, F.F. Rauber1, A.J. Cichoski1 and M. Di Luccio1*

1Programa de Mestrado em Engenharia de Alimentos – Universidade Regional Integrada do Alto Uruguai e das Missões

Abstract. In Brazil, unlike the rest of the world, cheese whey is still considered a residue of low importance on the nutritional point of view, and is often directed to animal feeding, to wastewater treatment of dairy plants or simply discharged in the environment. In the USA, 90% of cheese production residue is used in manufacturing of ingredients destined to human nutrition, which meant more than 500,000 tons of whey in 2001. From 1998 to 2001, Brazil imported more than 140,000 tons of dry whey, due to the lack of internal production. Low pressure evaporation can minimize drastically operation costs of the concentration process, since cheese whey contains more than 93% of water. Many protein fractions of milk are thermally sensitive and the increase in temperature may also favor reactions of proteins with sugars present in the whey. Therefore, vacuum evaporation can reduce protein losses caused by long exposure of whey to high temperatures. Ultrafiltration has also been used in many applications in the dairy industry. Such separation process presents an additional advantage over vacuum evaporation because it allows whey proteins to be concentrated without concentrating lactose that permeates ultrafiltration membranes. The recovery of proteins from whey would help to reduce the organic load discharged by dairy industry in the environment and also to obtain a high value product that can be fractioned and used as ingredient in special food products. In this context, the present work aimed to compare the concentration and recovery of cheese whey albumin by ultrafiltration and vacuum evaporation processes, evaluating the effect of process operation parameters on the quality of the protein concentrate obtained.

Keywords: whey protein, vacuum evaporation, ultrafiltration.

1. Introduction In cheese manufacturing usually a large amount of whey is produced. This byproduct contains low amount of

fat, minerals, hydrosoluble vitamins and proteins. The whey proteins include �-lactoalbumin and globulins, which

show molar mass around 17,000 Daltons and 170,000 Daltons, respectively. These proteins are highly digestible

and thus adequate for human nutrition during early age and for patients with digestion disturbances (Sgarbieri,

1996).

Currently approximately 50% of cheese whey in the world is applied in production of fermented beverages,

juices, bakery, used in animal nutrition and is usually dehydrated e commercialized as energy and nutritive

supplement (Almeida et al, 2001).

Unlike the rest of the world, cheese whey still is considered as waste in Brazil. In USA a large amount of

dairy industry wastewaters are recovered and 90% cheese production residues are used in manufacturing of

products for human nutrition, reaching more than 500,000 tons in 2001 (USDEC, 2004). From 1998 to 2001,

Brazil imported more than 140,000 tons of dry cheese whey, due to the lack of internal production (Almeida et

al., 2001; Pinheiro et al., 1993). Evaporation at low pressure can minimize operation costs, since cheese whey

contains more than 93% of water (Linden, 1996). Besides, some proteins fractions may be damaged by exposure

to high temperatures and can also react with the sugars present in the whey. In the case of cheese whey, protein

* To whom all correspondence should be addressed. Address: Av. Sete de Setembro 1621, Erechim, RS – Brazil



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fractions may present different stabilities to temperature. The most thermally resistant is �-lactoglobulin,

followed by �-lactoglobulin and immunoglobulins.

Ultrafiltration has also been used in many applications in the dairy industry (Bassetti, 2003). Like other

membrane separation processes it offers many advantages over conventional technologies. Its application in food

industry is particularly interesting since membrane processes can operate at mild temperatures, avoiding damages

caused by thermal processes, thus, maintaining the original characteristics of the processed products (Bronstein,

1998). Ultrafiltration presents an additional advantage over vacuum evaporation because it allows whey proteins

to be concentrated without concentrating lactose that permeates ultrafiltration membranes.

In this context, the objective of this work was to evaluate the concentration of protein of mozzarella cheese

whey by vacuum evaporation and ultrafiltration, aiming to recover high value products from this dairy industry

residue and reduce its discharge in receiving bodies.

2. Materials and Methods

2.1. Cheese whey Mozzarella cheese whey was obtained from a local dairy industry. The whey was collected diary and kept at

4°C until use. Each sample was analyzed for pH, titrable acidity (°Dornic), total and soluble (°Brix) solids,

lactose, protein and color.

2.2. Vacuum evaporation

A vacuum evaporator (“Stephan Geiger” 3678, model UMMSK-12), consisting in a 8 Liter chamber with

temperature control through a partial vapor jacket with manual valve for controlling temperature and pressure.

The stirring system was equipped with two stirrer blades at 2 and 4 cm from the bottom of the chamber and a

digital control.

For evaluation of the effect of temperature, pressure and agitation a complete 23 factorial design was

performed. The range of the investigated variables was determined after some preliminary experiments and is

presented in Table 1. Each evaporation experiment was carried out for 30 minutes. The responses were analyzed

the concentration factor, protein, lactose, total solids in function of the factors in Table 1. Central points were

performed in triplicate to evaluate non-linearity and experimental error (Chang et al., 2002). The data were

treated with the aid of Statistica 5.0 (Statsoft Inc., Tulsa, OK, USA). All analyses were performed considering a

level of 95% of confidence (p<0.05).

After the experiment a sample of 100 mL of the concentrate was taken and used in physico-chemical

determinations. Of each sample were analyzed: pH, acidity (Tronco, 1997), density (Behmer, 1996), °Brix, total

solids (Tronco, 1997), lactose (Silva, 1997), protein by Kjedahl method (AOAC, 1975) and colorimetric

(Bradford, 1976) and color using a Minolta CR 400 colorimeter.

E-mail: [email protected]



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Table 1. Values of coded levels and real values used in the complete factorial design (23) used to evaluate cheese whey

concentration by vacuum evaporation

Coded Levels Independent Variables -1 +1 0*

Temperature (°C) 40 50 45 Manometric Pressure

(kgf.cm-2) -0.4 -0.8 -0.6

Stirring rate (rpm) 170 230 200 * Central Point

2.3. Ultrafiltration

Ultrafiltration experiments were carried out in a 100 L pilot plant at Senai-Chapecó (SC, Brazil). The plant

consists in a tangential hollow fiber ultrafiltration module with area 4.4 m2 and molecular weight cut-off

(MWCO) of 10,000 Daltons. The UF unit is equipped with temperature, pressure and flow rate controllers.

The effect of temperature, pressure and flow rate on permeate flux and physico-chemical characteristics of

permeate were evaluated using a 23 complete factorial experimental design. Central points were here also

performed in triplicate to evaluate non-linearity and experimental error (Chang et al., 2002). The range of the

factors investigated in this experimental design was chosen based on limitations of the equipment and are

presented in Table 2.

Each experimental run began and ended with a 60 min. clean water permeation with total recycle of permeate

stream. The flux was followed during regular time intervals. After clean water permeation the system was purged

and then fed with cheese whey. 60 min permeation with total recycle was carried out, followed by a 6-fold

concentration. Flux was also followed in whey permeation and samples were collected for physico-chemical

analyses.

Module cleaning was carried out right after each experiment using a CIP system. The CIP consisted in a triple

flush with clean water for 10 min each, followed by recirculation of a 6 wt% aqueous NaOH solution during 60

min. A new triple water rinsing was carried out, followed by recirculation with a 0.01 wt% aqueous solution of

H3PO4.

Table 2. Values of coded levels and real values used in the complete factorial design (23) for evaluation of UF

concentration of cheese whey

Coded Levels Independent Variables -1 +1 0*

Temperature (°C) 40 50 45 Manometric Pressure

(kgf.cm-2) -0.4 -0.8 -0.6

Stirring rate (rpm) 170 230 200 * Central Point



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3. Results and Discussion

3.1. Concentration by vacuum evaporation Table 3 presents the matrix of the experimental design with the real and coded variables and the respective

responses. The responses that were analyzed statistically were the concentration factor and protein content. Table

4 shows the results of lactose and color of each experimental run. In concentration by vacuum evaporation both

protein and lactose are concentrated and little change could be observed in the ratio protein/lactose.

The concentrated samples also showed color variation in relation to the raw whey. It was not possible to

correlate the color variation (∆E) with lactose or protein content. However, when the color parameter is

separately compared with protein content in the concentrates, a correlation of color with protein could be

observed.

Table 3. Matrix of the complete 23 factorial design (real and coded variables)

Run T(a) (°C) P(b) (kgf/cm2) SR(c) (rpm) CF(d) Proteína(e) (%) Ratio Ptn/Lactose

01 40 (-1) -0.4 (-1) 170 (-1) 1.0059 12.30 0.15 02 40 (-1) -0.4 (-1) 230 (+1) 1.1877 11.83 0.16 03 40 (-1) -0.8 (+1) 170 (-1) 1.0018 12.76 0.15 04 40 (-1) -0.8 (+1) 230 (+1) 1.2121 12.21 0.15 05 50 (+1) -0.4 (-1) 170 (-1) 1.0032 12.58 0.15 06 50 (+1) -0.4 (-1) 230 (+1) 1.0874 12.71 0.14 07 50 (+1) -0.8 (+1) 170 (-1) 1.0482 7.52 0.14 08 50 (+1) -0.8 (+1) 230 (+1) 1.2240 12.26 0.15

09(a) 45 (0) -0.6 (0) 200 (0) 1.0125 11.90 0.16 09(b) 45 (0) -0.6 (0) 200 (0) 1.0813 11.86 0.14 09(c) 45 (0) -0.6 (0) 200 (0) 1.0668 12.62 0.14

Note: atemperature, bpressure, cstirring rate, dconcentration factor, eKjedahl

Table 4. Lactose and color results of each concentrate obtained in experimental design.

Run Lactose (%) ∆L*(a) ∆a*(b) ∆b*(c)

∆E(d)

01 5.34 -4.81 0.43 -1.73 5.13 02 5.08 -2.71 0.59 -0.31 2.79 03 5.62 -1.19 -0.08 -0.59 1.33 04 5.79 -4.36 0.38 -0.65 4.42 05 5.68 -1.06 -0.28 -0.22 1.12 06 5.75 -0.16 -1.29 -1.09 1.69 07 6.55 -0.68 -0.36 -0.17 0.79 08 6.06 -1.02 -1.68 -1.03 2.22

09(a) 5.24 -0.54 -0.35 0.15 0.66 09(b) 5.52 0.98 -0.46 -0.30 1.12 09(c) 5.72 0.90 -0.67 -0.17 1.13

Nota: (a) lightness difference; (b)red-green difference, (c) yellow-blue difference, (d) total color variation 222 baLE ∆+∆+∆=∆



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Figure 1 shows the Pareto chart of effects of the factor on concentration factor. It may be observed that stirring

rate presented significant (p<0.05) positive effect. Operating pressure and temperature did not show significant

effects on concentration factor, possibly due to high experimental error observed (Table 3).

Effect (absolute value)

-1,53267

6,922293

22,36251

p=,05

(1)TEMP

(2)Pressure

(3)Stirring ratl

-5 0 5 10 15 20 25

Figure 1. Pareto chart of effects of manipulated variables on concentration factor.

Variability of the raw whey

Each experimental run used a different batch of whey collected at the local dairy industry. This way, it was

necessary the monitoring of physico-chemical characteristics of each whey sample. Table 5 presents the results

obtained in this characterization, showing also the means and standard deviations of the raw material used in this

step of the study.

In the present study the water content varied from 93.1 to 94.3%, total solids between 6.0 to 6.1%, lactose

between 4.82 and 5.43% and protein between 0.77 to 0.91 (Table 6). This values are in same the range of the

characterizations performed by Veisseyre (1988), Linden (1996), Tronco (1997) and Farro (2003). It is worth to

note that the variations between the different samples were mostly below 10%.

Table 5. Physico-chemical evaluation of raw whey samples used in each evaporation experiment.

Run Water (%)

TS (%) pH º D Lactose

(%) º

Brix Density Protein1 Protein2 Ratio

Ptn(NKT) /Lactose

1 93.5 6.5 6.58 12.0 4.8 8.90 1.02 0.81 0.21 0.17 2 94.3 5.7 6.87 11.0 5.4 9.00 1.02 0.80 0.21 0.15 3 93.5 6.5 6.58 12.0 4.8 8.90 1.02 0.83 0.25 0.17 4 94.3 5.7 6.87 11.0 5.4 9.00 1.03 0.84 0.25 0.16 5 93.1 6.9 6.85 14.0 4.9 9.40 1.03 0.88 0.22 0.18 6 94.0 6.0 6.92 12.0 4.9 9.20 1.03 0.83 0.22 0.17 7 93.1 6.9 6.71 12.5 4.8 9.50 1.03 0.91 0.34 0.19 8 94.0 6.0 6.92 12.0 4.9 9.20 1.03 0.90 0.31 0.18

9(a) 93.1 6.9 6.85 14.0 4.9 9.40 1.03 0.84 0.16 0.17 9(b) 94.0 6.0 6.92 12.0 4.9 9.20 1.03 0.77 0.21 0.16 9(c) 94.0 6.0 6.92 12.0 4.9 9.20 1.03 0.81 0.20 0.16

Average 93.7 6.3 6.82 12.2 5.0 9.17 1027 0.84 0.24 0.17 Std. Dev. 0.5 0.5 0.13 1 0.2 0.21 1.21 0.04 0.05 0.01 % Std. Dev. 0.5 7.8 1.9 8.0 4.4 2.29 0.12 4.76 20.83 5.88 Note: 1NKT (%), 2Bradford (%)

3.2. Concentration by ultrafiltration



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Table 6 presents the results of the factorial experimental design carried out to evaluate the effects of process

variables on permeate flux with and without recycle and the time required to concentrate the feed 6-fold. The

experimental condition that presented the higher flux with recycle was the one operated at higher pressure and

higher flow rate, while for concentration the best condition was run 4, carried out at lower temperature. A

statistical analysis of the results of the experimental design will be presented further in this paper.

Table 6. Matrix of the complete 23 factorial design (real and coded variables) and the response in term of stabilized

permeate flux

Run T (°C) P (kgf/cm2) Flow Rate (L/min)

Flux with recycle**

Concentration time (min)

Flux w/o recycle**

01 25 (-1) 0.5 (-1) 45 (-1) 9.95 93.0 6.14 02 25 (-1) 0.5 (-1) 65 (+1) 6.65 90.0 4.77 03 25 (-1) 1.5 (+1) 45 (-1) 14.45 43.2 11.86 04 25 (-1) 1.5 (+1) 65 (+1) 18.08 31.5 15.59 05 45 (+1) 0.5 (-1) 45 (-1) 9.52 68.1 8.59 06 45 (+1) 0.5 (-1) 65 (+1) 9.95 66.1 6.14 07 45 (+1) 1.5 (+1) 45 (-1) 13.25 46.1 12.55 08 45 (+1) 1.5 (+1) 65 (+1) 19.80 38.5 11.73 09* 35 (0) 1.0 (0) 55 (0) 13.55 45.3 11.36

*Central point performed in triplicate. **Stabilized flux. L/h/m2.

Figure 2 presents the evolution of permeate flux with time of permeation for the 11 runs carried out with total

recycle of permeate stream. It could be noted the reduction of permeate flux, possibly due to membrane fouling.

It is worth to note that in such cases the feed concentration remained constant and the effect of this factor does

not influence the results. In most of the runs flux is rather stable after 20 minutes of permeation. The most critical

conditions for flux decrease were the ones operated at higher pressures, when the effect concentration

polarization (accumulation of solids at membrane surface) is stronger.

The results of statistical analysis of Table 6 can be found in Figure 3. The Pareto chart shows that pressure,

flow rate and their interaction presented a significant (p<0.05) positive effect on permeate flux, while

temperature did not significantly influenced the response. This result confirm the expected since flux is directly

proportional to pressure, which is the driving force to the process, and a high flow rate can decrease the

polarization layer, decreasing mass transfer resistance.

Figure 4 shows the permeate flux during concentration runs at the central point. A further decrease in flux

could be observed when compared to the experiment runs carried out with total recycle, due to the increase in

feed concentration that causes higher polarization concentration effect.



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0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Time (min)

Per

mea

te fl

ux

(L/h

/m2 )

Run 1

Run 2

Run 3

Run 4

0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Time (min)

Per

mea

te fl

ux (L

/h/m

2)

Run 5Run 6Run 7Run 8

(a) (b)

0

5

10

15

20

25

-10 10 30 50 70

Time (min)

Per

mea

te f

lux

(L/h

/m2)

Run 9Run 10Run 11

Figure 2. Permeate flux of cheese whey with complete recycle of permeate: (a) 25°C, (b) 45°C and (c) 35°C.

Efeitos absolutos

-,975805

1,40765

2,761319

3,035375

5,41883

12,25361

p=,05

1by2

(1)TEMP

1by3

(3)VAZÃO_AL

2by3

(2)PRES

-2 0 2 4 6 8 10 12 14

Figure 3. Pareto chart of effects of factors on cheese whey permeate flux.

0

2

4

6

8

10

12

14

16

0 10 20 30 40 50 60

Time (min)

Per

mea

te fl

ux (L

/h/m

2)

Run 9Run 10Run 11Run 12Run 13



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Figure 4. Permeate flux of cheese whey during concentration at 35°C. Table 7 presents the ratio protein/lactose in the raw whey and UF-concentrated whey (mean value of all

experiments). While in vacuum concentration this ratio became almost constant after concentration, here it

increases more than 3 times. This results is in accordance to Farro (2003) that also describes na increase in this

ratio in membrane concentration using UF.

Table 7. Ratio protein/lactose for UF concentration of whey

Raw whey UF Concentrated whey Permeate Ratio Pt/Lact 0.14 0.63 0.04 % Variation 341

4. Conclusions Cheese whey concentration was evaluated using two different processes. In vacuum evaporation the condition

that achieved higher concentrate factor was at 50°C, -0.8 kgf/cm2 and 230 rpm, i.e., upper level of temperature,

stirring rate and vacuum.

In ultrafiltration of whey the condition that yielded higher concentration in a short time and highest permeate

flux was at room temperature, 65 L/min and 1.5 kgf/cm2.

The results show that vacuum evaporation presented a lower performance than UF in concentration of the

whey. Depending on the operating conditions ultrafiltration is able to concentrate whey 6-fold in 30 minutes,

while.

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Acknowledgments

The authors acknowledge CAPES, Escola Agrotécnica Federal de Concórdia, URI-Campus de Erechim,

FAPERGS for financial support to this work; COCEL and TIROL for supplying cheese whey samples and

SENAI-Chapecó, SC for allowing the realization of experimental activities at its pilot UF plant.

Documents

Assessment of Ultra Filtration and Vacuum Evaporation on Whey Protein Concentration