article critique

Cheddar whey processing and source: I. Effect on

composition and functional properties of whey protein

concentrates1

T. Ji & Z. U. Haque*

Department of Food Science and Technology, Mississippi Agricultural and Forestry Experiment Station, Mississippi State

University, MS 39762, USA

(Received 8 November 2001; Accepted in revised form 30 June 2002)

Summary Cheddar whey (RW), from either a Jersey (J) or a mixed herd (M), was used to observe the

effect of source (WSr) on the composition and functionality of whey products. To observe

the effect of whey processing, J- and M-RW were dehydrated by four processes (WPr): (i)

UF and vacuum-evaporation (VE) followed by lactose crystallization (C) and spray-drying

(SD); (ii) VE followed by C and SD; (iii) UF and VE followed by SD without C and (iv)

UF followed by SD without C. Moisture, crude fat, ash, calcium and crude protein were

analysed. The emulsifying activity index (EAI), emulsion stability (ES), thermostability,

oil-holding capacity and solubility (SO) were determined. Both WPr and WSr affected

these properties of whey and whey protein concentrate (WPC). Mean EAIs of J- and

M-RW were similar but significantly increased by UFVECSD and UFVESD treatment,

respectively, to 171 and 174 m 2 g )1

for J, and to 107 and 143 m 2 g )1

for M. The ES of RW

and pasteurized whey was significantly different based on WSr. Jersey whey showed better

SO than M whey. Thermostability of WPCs was significantly increased when VE was a

component of WPr. The J-whey apparently had higher ash content, although this was

decreased by UF treatment, calcium content was significantly increased. Moisture content

of WPC was also WPr dependent, being more than twice higher for UF-treated WPC

compared to VE-treated WPC. Though both parameters influenced powder functionality,

WPr appeared to have a dominant affect in terms of SO and TS, and appeared crucial for

EAI and ES.

Keywords Dehydration, Jersey whey, thermostability, ultrafilteration, vacuum evaporation, whey quality.

Introduction

Whey, the milk serum produced during the manu-

facture of cheese, is a nutritionally superior ingre-

dient with desirable physicochemical attributes.

Whey can be processed by various methods such as

pasteurization, vacuum evaporation (VE), UF,

reverse osmosis, ion exchange, gel filtration, elec-

tro-dialysis, crystallization and spray-drying (SD)

(Kosaric & Asher, 1985; Speer, 1998). The func-

tional properties and composition of whey can be

affected by its processing method and source (Morr

et al., 1973; Schmidt et al., 1984).

The functional properties of whey proteins

encompass those physicochemical attributes of a

protein that make it useful in food products. A

number of researchers have indicated the import-

ance of structural properties on whey protein

functionality (Morr, 1984; Schmidt et al., 1984)

and have determined the relationship of structure

1 Approved for publication as Journal Article #J-9744 of the

Mississippi Agricultural and Forest Experiment Station,

Mississippi State University. Funded by National All-Jersey

and Mississippi Agricultural and Forest Experiment Station

Project No. MIS-343010.

*Correspondent: Fax: +1 662 325 8728;

e-mail: [email protected]

International Journal of Food Science and Technology 2003, 38, 453–461 453

� 2003 Blackwell Publishing Ltd

of food proteins to their activity or functionality

(de Wit & de Boer, 1975; Nakai & Li-Chan, 1985).

Morr & Foegeding (1990) studied the composi-

tion of commercial whey protein concentrates

(WPCs) and whey protein isolates. Upon further

analysis the types of minerals in the ash were

found to vary, as did the proportions of individual

proteins in the samples tested. WPCs from pro-

cessed Cheddar cheese-type whey was studied for

foaming, emulsifying and physicochemical prop-

erties, in order to understand the relationship

between structure and function (Patel & Kilara,

1990). The composition and physicochemical

characteristics such as solubility, foaming and

emulsifying properties of WPCs were related to

free fat, bound fat, ash, calcium, denaturation

enthalpy and denaturation temperature (Kilara,

1994). However, little or no work has been done to

understand the effect of commonly used whey

processing methods (WPr) on whey and WPC

functionality.

The literature abounds with reports related to

the composition of bovine milk (Ormiston et al.,

1967; McDowell, 1972; Cerbulis & Ferrell, 1976;

Barnes et al., 1989). The average composition of

milk is influenced by factors such as breed, stage

of lactation, age, feed, season and conditions of

cow, etc. It has been reported that the Jersey (J)

breed had higher amounts of total solids and less

variation of the contents than the Holstein breed.

Little research has been conducted on the compo-

sition and functional properties of J whey powders

and WPCs. It would be useful to see if there were

any differences based on source (WSr); that is, if

the functionality of whey powders and WPCs

would vary based on the breed of cows.

Basic data are required to understand the

impact of variability in WPr and WSr so that

consistency in powder functionality is assured.

The objective of this study was to assess the effects

of the commonly used dehydration method of

WPr and two common whey sources, J and mixed

herd (M), on some key powder functionality.

Materials and methods

Milk sources

Two sources of milk were used: (i) Jersey cattle

herd (Rowzees Farm, Newton, MS, USA) and (ii)

mixed cattle herd (16.7% J and 83.3% Holstein)

(Mississippi State University South Dairy Farm,

Starkville, MS, USA). Milk was obtained using a

refrigerated milk truck just prior to cheese manu-

facture between April and May of 1998.

Manufacture of Cheddar cheese

Using milk form each of the above sources,

Cheddar cheese was manufactured in triplicate

1600-L batches at the Mississippi State University

Dairy Plant according to Kosikowski (1982) with

slight modifications as described earlier (Aryana &

Haque, 20011 ). Starter culture (#98) (Lactococcus

lactis and Lactococuss cremoris) and rennet (18.5

per 100 kg cheese milk) were from Chr. Hansens

Lab., Milwaukee, WI, USA. Annato color (6.2 g

per 100 kg cheese milk) was from Miles Lab., Inc.,

Elkhart, IN, USA.

Processing of Cheddar whey

Whey formed during the manufacture of Cheddar

cheese were collected (approximately 1365-L per

batch), skimmed through a de-creaming separator

and pasteurized (Mueller, Springfield, MO, USA)

at 82.2 �C for 23 s (Fig. 1). A portion of this fresh raw whey (RW) and pasteurized whey (PW) was

immediately flash-frozen in liquid nitrogen, freeze-

dried using a laboratory-scale freeze-drier (Lab-

conco, Kansas City, MO, USA) and stored at

)30 �C for use as non-heat treated controls. A 227-L aliquot of the PW was used in pilot plant

scale falling film vacuum-evaporator (VE) under

partial vacuum (APV, Sorborg, Denmark) to

obtain a solution containing 38–40% solids, as

opposed to the initial solids content of 8–9%, as

measured using a ATAGO hand-held refractom-

eter (N-4, NSG Precision Cells, Inc., Farmingdale,

NY, USA). The temperature of the whey during

VE was carefully maintained within the operating

range of 65–70 �C. The VE step was carefully accomplished within 30 ± 5 min, as preliminary

experiments using vertical slab sodium dodecyl

sulphate-polyacrylamide gel electrophoresis in the

presence of 7 m urea (Haque & Mozaffar, 1992)

indicated thermal aggregation of whey proteins

(primarily b-lactoglobulin) (Haque & Sharma, 1997, 20022 ) at times >45 min. The remainder of

the PW was ultrafiltered using a Romicon Model

Composition and functionality of Cheddar whey T. Ji & Z. U. Haque454

International Journal of Food Science and Technology 2003, 38, 453–461 � 2003 Blackwell Publishing Ltd

HF 10SSS (Romicon, Woburn, MA, USA)

through a 10k membrane to an approximate solids

content of 11%, and then vacuum-evaporated.

The concentrated whey thus obtained were

directly spray-dried using a pilot plant scale

spray-drier (APV, Sorborg, Denmark) or kept

overnight in a 4 �C cooler for lactose crystalliza- tion (C) and removal and then spray-dried. All

WPCs were stored in )30 �C until use.

Chemical analysis

pH

The pH value was measured using an Orion 210A

pH meter (Orion Research, Inc.). The pH meter

was standardized by commercial buffer solutions

(Fisher Scientific).

Titrable acidity (TA)

About 17.6 mL of the prepared sample and

0.5 mL of 1% phenolphthalein indicator were

used for titration with 0.1 n sodium hydroxide

(NaOH). The sample solution was titrated from

clear to a pink colour that had to persist for at

least 30 s. The acidity expressed, as lactic acid, was

calculated according to Case et al. (1985):

Acidity ð%Þ ¼ ðmL of 0.1 N NaOH � 0:009 � 100Þ=weight of sample

Moisture

A modified vacuum oven drying method (Marth,

1978) was used to determine the moisture content.

Samples (3 g) were weighed into a pre-weighed

round flat-bottom metal dish, placed in vacuum

oven at 100 �C for 5 h, cooled to room tempera-

ture in a desiccator and weighed. Moisture content

was calculated as follows:

Moisture ð%Þ ¼ ðloss in weight � 100Þ =weight of sample

Crude fat

Fat content was obtained using modified Mojon-

nier (AOAC Method #989.05) and Goldfish meth-

ods (Min, 1994) for control whey and WPCs,

respectively. Crude fat in WPC samples was

calculated according to Dugan (19763 ):

CF ð%Þ on dry weight basis ¼ ðg CF in sample � 100Þ=g dried sample

Ash

Ash content was measured using AOAC method

#930.30. One gram of the samples was weighed

accurately into prepared crucibles, and then the

crucibles were put into Blue M muffle furnace

(Blue M Electric Co, Blue Island, IL, USA) at

550 �C until only white ash remained.

Ash ð%Þ on dry basis ¼ ðwt. after ashing � tare wt. of crucibleÞ

� 100=sample weight

Crude protein (CP)

Crude protein content of control whey and WPCs

was measured by estimating total nitrogen content

using a modified Kjeldahl Method (AOAC, 1990;

Method #955.04) and a conversion factor of 6.38.

The percentage of nitrogen in the samples was

calculated according to Meloan & Pomeranz

(1980):

Separator

Ultrafiltration

Spray drying Vacuum evaporation

Vacuum evaporation

Crystallizatiion tank

Crystallizatiion tank

Spray drying

Spray drying

Spray drying

Cream

HTST Pasteurization (82 °C/23 s)

Cheddar whey vat (1700–1900)

Figure 1 Flow chart for the manu-

facture of Cheddar whey protein

concentrates.

Composition and functionality of Cheddar whey T. Ji & Z. U. Haque 455

� 2003 Blackwell Publishing Ltd International Journal of Food Science and Technology 2003, 38, 453–461

Nð%Þ ¼ ½ðmL of 0.1 N H2SO4 for sample � mL of H2SO4 for blankÞ � ðnormality of H2SO4Þ � 0:014 � 100�=g of sample

Total calcium

Calcium content of control whey and WPCs was

determined by the gravimetric method of Ntailia-

nas & Whitney (1964). This method is based on

the spontaneous and tenacious binding of calcium

with EDTA. Standard curves were prepared using

standard CaCl2 solution at pH 13.0 with calcium

as an indicator.

Functional properties

Emulsifying activity index (EAI), emulsion stabi-

lity (ES), thermostability (TS), oil holding capacity

(OHC) and solubility (SO) were determined as

described by Haque & Mozaffar (1992).

Emulsion preparation

About 0.25 g of sample was dissolved in 20 mL

of 10 mm imidazole-HCl, pH 7.0, buffer by

mixing with a magnetic stirrer for 30 min. About

1.6 mL of sample was placed in a 10-mL beaker,

and 0.4 mL of peanut oil was added. This sample

and oil mixture was sonicated in a Vibra Cell

sonicator (Sonics & Materials, Inc., Danbury,

CT, USA) for 20 s at 20% of total power in the

10-mL beaker, to form an emulsion. This

emulsion in the 10-mL beaker was used for

determining ES and EAI.

Emulsifying activity index

The prepared emulsion was diluted 1000-fold using

a dilution buffer consisting of 10 mm imidazole-

HCl, pH 7.0, containing 0.1% SDS by taking 10-lL aliquots (30 lL total) from three different locations in the 10-mL beaker containing emulsion and

adding 30 mL of dilution buffer. Absorbance was

measured at 600 nm. The EAI was expressed as

surface area, m 2 g )1 , and calculated as

fð0:4606Þ � ðabsorbance at 600 nmÞ =½ðDispersed phase fraction ¼ 0:2Þ � ðdry powder concentration after dilution, in mg mL�1Þ�g

Emulsion stability

From the 10-mL beaker containing the emulsion,

a 1.0-mL aliquot of the emulsion was pipetted into

a 1.5-mL Eppendorf microtube. The emulsion was

centrifuged at 3200 g4 for 30 min in a Millipore

Personal Centrifuge. The tip of a 500-lL syringe (Hamilton #750 syringe with a 22-gauge needle)

was placed through the oil layer to the aqueous

layer, and the aqueous layer was withdrawn. The

volume of aqueous phase was determined in

millilitres and multiplied by 100 to give the

percentage of emulsion stability.

Oil-holding capacity

One millilitre of peanut oil was mixed with 50 mg

WPCs. The mixture was centrifuged in a Techno-

spin Centrifuge at 4000 r.p.m. (32 000 g) for 30 s

after vortexing for 30 s. The oil layer was carefully

separated from the top of the tube using a syringe.

The difference between the weight of oil added and

the weight of oil separated at the top of the tube

was calculated as a percentage to give OHC.

Thermostability

Whey protein concentrates were dissolved in

10 mm imidazole buffer, pH 7.0, to prepare a

1% (w/v) solution. This 1% sample solution was

heated in a boiling water bath for 10 min and then

cooled to 25 �C. Transmittance of visible light (600 nm) through the heated samples was com-

pared with that of the unheated samples. The

change in absorbance was used to determine the

thermostability of the sample.

Solubility

About 0.5 g of WPC was dissolved in a tube

containing 5 mL of 10 mm imidazole-HCl buffer.

After vortexing for 10 s, the tube containing the

sample solution was left undisturbed for 5 min.

Then, the tube was centrifuged in a Technospin

Centrifuge at 4000 rpm (32 000 g) for 10 min at

20 �C. Next, the liquid phase with the components solubilized in it was removed with a syringe. The

sampletubewas dried ina microwaveovenfor 3 min

and weighed. Solubility was determined as follows:

Insolubility ð%Þ ¼ ðweight of insoluble sample � 100Þ=sample weight

Solubility ð%Þ ¼ 100 � insolubility %

Composition and functionality of Cheddar whey T. Ji & Z. U. Haque456

International Journal of Food Science and Technology 2003, 38, 453–461 � 2003 Blackwell Publishing Ltd

Statistical analysis

The experiment was designed by using the one-

way completely randomized block method. Data

were analysed by anova using the General Linear

Models procedure of the Statistical Analysis

System (SAS Institute, 1998). Means were com-

pared by the least significant difference test at

P < 0.05.

Results and discussion

Although there was no significant difference in the

initial pH of the J and M controls, WPr caused

these to change significantly (Table 1). Both J and

M VECSD showed the lowest pH values indica-

ting a WPr related effect on pH. As expected, TA

value was the highest in VECSD (Table 1). This

experiment indicated that VE alone, without UF,

increased pH and TA of both J-WPCs and

M-WPCs.

Organic acids exist in many foods and influence

flavour, colour, stability and quality (Sadler, 1994).

Titrable acidity indicates the amount of acids present

in a product and varies from 0.1 to 0.28% (as lactic

acid) in fresh Holstein and J milk (Caulfield &

Riddell, 1936). Whey differs widely in composition

according to the composition of the original milk,

method of curd coagulation and type of cheese.

The pH of sweet whey samples is only slightly less

than that of fresh milk (Bassette & Acosta, 1988),

which is 6.6–6.8 at 20 �C (Walstra & Jenness, 1984). On the other hand, acid whey in which lactose is

converted to lactic acid by lactose fermenting

bacteria, has a pH of approximately 4.7 (Bassette

& Acosta, 1988).

The moisture content of WPCs varied from 4.15

to 0.83% and appeared dependent on WPr. Whey

powders concentrated by UF showed significantly

higher moisture content compared to when VE was

used (Table 1). Nickerson (1978) reported that the

moisture content of dried, sweet whey was 4.5%.

Anderson & Berlin (1974) reported a comparative

study of the moisture analysis methods for

Cheddar and cottage cheese whey powders. The

moisture analysis methods compared in the study

included toluene distillation, vacuum dehydration

and Karl Fischer titration. They mentioned that

free moisture, exclusive of water of hydration of

lactose crystals, might be measured by drying in

vacuum at 65 �C at 100 torr for 6 h. This implies tenacious binding of the water molecules to the

WPC and our data indicated that this was

decreased when VE was used. The VE process

involves evaporation under partial vacuum in the

temperature range of 60–80 �C (Fig. 1). The CP was significantly higher in J controls,

i.e. freeze-dried RW and PW, compared to those

Table 1 Effect of whey processing

method and source of whey on the

pH, TA and moisture of whey

protein concentrates*

pH TA (%) Moisture (%)

Samples Jersey Mixed Jersey Mixed Jersey Mixed

RW 6.41a 6.46a 0.096ab 0.090ab 93.22a 93.20a

PW 6.36abb 6.48aA 0.099abA 0.080abB 93.28a 93.34a

UFSD 6.42aB 6.57aA 0.090bA 0.070bB 4.00b 4.15b

UFVECSD 6.35ab 6.44a 0.095ab 0.087ab 1.83bc 0.83c

VECSD 6.23b 6.18b 0.133a 0.108a 1.87bc 2.26bc

UFVESD 6.31abB 6.46aA 0.105ab 0.085ab 1.22c 0.95c

*Raw whey and pasteurized whey were liquid samples and the remaining items were

powders. Each value represents a mean of three replications. RW, raw whey; PW,

pasteurized whey; UFSD, ultrafiltered and spray-dried WPC without lactose separation;

UFVECSD, ultrafiltered, vacuum-evaporated and spray-dried WPC after lactose separ-

ation; VECSD, vacuum-evaporated and spray-dried WPC after lactose separation;

UFVESD, ultrafiltered, vacuum-evaporated and spray-dried WPC without lactose

separation. a,bMean values within the same column with different superscripts are significantly

different (P < 0.05). A,BMean values within the same row with different superscripts are significantly

different (P < 0.05). Shown only where there was significant difference.

Composition and functionality of Cheddar whey T. Ji & Z. U. Haque 457

� 2003 Blackwell Publishing Ltd International Journal of Food Science and Technology 2003, 38, 453–461

of M. This was consistent with significantly higher

CP of fresh raw J (3.38%) and M milk (2.96%).

The parameter was also affected by WPr. The CP

of UF samples was significantly higher than that

of samples that were subjected to VE alone (Table

2). Composition of whey can be modified by

removal of lactose and minerals to make whey

products with 15–40% protein (Matthews, 1984).

Partially delactosed whey powder contains

16–24% protein (Modler, 1985).

Total ash content and calcium was apparently

higher in the J controls compared to M whey

although the difference was not significant (Table2).

Again, this correlated with the significantly differ-

ent ash content of 8.41 and 7.79% for J and M,

respectively, for fresh raw milk. The WPr signifi-

cantly affected total ash content of the WPCs. Ash

content of WPCs following UF was significantly

lower than RW (Table 2) and this is to be expected

due to the intrinsic nature of the process that

allows removal of micromolecules. On the other

hand, VE removes only moisture and thus con-

centrates all solutes and colloids. This premise was

substantiated by our J-related data that showed

that VECSD treatment gave a mean ash content of

9.37% that was significantly higher than all other

treatments. Though the M-VECSD did not show

significant difference, the trend was apparent

(Table 2). According to Hargrove & Alford

(1974), typical dried, sweet and acid whey have

10.8 and 8.3% ash content, respectively. Mavrop-

oulou & Kosikowski (1973) reported that ash

content of commercial whey powder varied from

7.3 to 11.8%.

Total calcium content of different WPCs signi-

ficantly varied based on WPr and WS (Table 2). It

was much higher than the value obtained by

Mavropoulou & Kosikowski (1973). These differ-

ences may be due to the relative accuracy of the

EDTA chelation based gravimetric method that

we used. An important observation was that

unlike in the case of total ash, the UF appeared

to preferentially concentrate calcium content even

though total ash comparatively decreased (Table

2). This implied that calcium-rich proteins or

peptides did not escape in permeation during UF

processing and were concentrated. This had been

speculated earlier (Haque, 1993).

Data related to fat content of the whey was

complicated by the commercial Cheddar cheese

manufacturing process used so as to mimic

pragmatic conditions that exist in the cheese

manufacturing industry. Part of the Cheddar

manufacturing process entailed initial standardi-

zation of fat content between 3.7 and 3.8% to

maintain consistency in texture and flavour of full

fat Cheddar. Therefore, our results gave similar

CF content for J and M whey (Table 2). Highest

Table 2 Effect of whey processing method and source of raw milk and whey on the composition of whey protein concentrates*

Crude protein† (%) Ash† (%) Fat (%) Calcium (mg g)1)

Samples Mixed Mixed Jersey Mixed Jersey Jersey Jersey Mixed

RW 6.40c 5.88c 8.41ab 7.79ab 7.38c 6.73b 14.60cA 14.41eB

PW 6.56c 9.01b 7.89abc 7.81a 10.42b 6.91b 15.48bA 14.26eB

UFSD 15.11aA 14.67a 5.92c 5.57ab 15.34a 9.06aB 31.34aA 29.73aB

UFVECSD 9.28bA 14.38a 6.13bc 5.48b 15.41a 4.10cB 31.55aA 28.05bB

VECSD 1.58d 14.59a 9.37a 7.67ab 15.97a 1.81d 14.59cB 18.94dA

UFVESD 7.82bA 13.79a 5.90c 5.50b 15.27a 3.38cB 31.44aA 27.31cB

*All results integrated to 0% moisture content. Each value represents a mean of three replications.

†Ash and crude protein content of raw Jersey and mixed milk were 6.9 and 5.7%, and 29.6 and 23.6%, respectively, on a dry

weight basis.

Raw whey and pasteurized whey were dehydrated by freeze-drying as used for controls (low-temperature treatment).

RW, raw whey; PW, pasteurized whey; UFSD, ultrafiltered and spray-dried WPC without lactose separation; UFVECSD,

ultrafiltered, vacuum-evaporated and spray-dried WPC after lactose separation; VECSD, vacuum-evaporated and spray-dried WPC

after lactose separation; UFVESD, ultrafiltered, vacuum-evaporated and spray-dried WPC without lactose separation. a,bMean values within the same column with different superscripts are significantly different (P < 0.05). A,BMean values within the same row with different superscripts are significantly different (P < 0.05). Shown only where there was

significant difference.

Composition and functionality of Cheddar whey T. Ji & Z. U. Haque458

International Journal of Food Science and Technology 2003, 38, 453–461 � 2003 Blackwell Publishing Ltd

and lowest CF content was seen for UFSD and

VECSD, respectively. Data show a significant

decrease in the amount of free fat when VE was

used as the only dehydration step prior to SD

(Table 2). When UF was used to concentrate the

whey prior to VE, CF content was significantly

higher (Table 2). This was primarily due to the fat

concentrating effect of UF and may also be due to

tenacious hydrophobic interactions between fats

and proteins. Data indicated significant WPr

related influence on the CF content of WPCs.

The comparatively low fat content of WPCs

when only VE was used conceivably reflects

formation of hydrophobic complexes that resisted

the organic solvent extraction method used in this

study. In a separate study, such VE-induced

hydrophobic complexes were detected by electron

microscopy (Aryana & Haque, 20015 ). As UF,

which reduces peptides (Haque, 1993) and ash

from the whey concentrate, significantly reduced

this effect of VE on CF (Table 2), it is postulated

that tenacious lipid–peptide–ash complexes are

formed during the heated vacuum recycling of

whey during VE. We have earlier reported the

formation of casein–peptide based complexes or

�plasteins� (Haque & Mozaffar, 1992) that were highly hydrophobic.

Although there was no significant difference in

the EAI of J and M controls, WPr markedly

enhanced it. This was particularly so when UF

and VE were combined (UFVECSD and UF-

VESD) and more so when J was the source (Table

3). The EAI of the WPCs varied dramatically from

69 to 174 m 2 g )1 . Data indicated an apparent

synergistic relationship that enhanced this import-

ant functional attribute. We have reported earlier

(Haque, 1993) that the level of UF concentration

influenced emulsifying properties of whey. The

significantly greater enhancement of the attribute

in J-WPCs compared to the controls and the

M-WPCs was conceivably due to higher protein

and calcium content (Table 2).

The WPr did not affect the ES of WPCs

significantly but there were significant differences

based on WSr. An inverse relationship between

EAI and ES has been reported earlier (Haque,

1991) and this has to do with the fact that the

forces that enhance emulsion formation may

actually thwart its subsequent stability (Haque,

1993).

Interestingly, pasteurization dramatically

reduced TS of the RW regardless of WSr causing

about a 50% reduction in this attribute (Table 3).

Whey processing played a significant role in

reviving this attribute of commercial importance.

The UF step alone appeared to be unable to revive

this attribute. On the other hand, TS was revived

and significantly enhanced when VE was used

alone or in conjunction with UF (Table 3).

Thermostability is a desirable attribute for food

proteins, especially for high-protein beverages that

need heat treatments (Haque, 1993).

Table 3 Effect of whey processing method and source of whey on the functional properties of whey protein concentrates*

EAI (m 2

g )1

) ES (%) Thermostability (%) Solubility (%)

Samples Jersey Mixed Jersey Mixed Jersey Mixed Jersey Mixed

RW 94.50d 90.75bc 79.00bB 84.33aA 83.21b 83.82c 94.25b 90.33ab

PW 68.64e 72.29c 85.66aA 80.83bcB 40.07c 41.74e 96.84aA 93.36aB

UFSD 157.23bcA 92.48bcB 78.33b 79.33c 41.11cB 53.93dA 85.46b 87.76bc

UFVECSD 170.57abA 107.09bB 71.67cB 82.33bA 100.00a 99.32a 77.94cA 65.78dB

VECSD 148.92cA 108.08bB 77.00bc 80.67bc 98.78aA 94.92bB 83.82bc 87.95bc

UFVESD 173.91a 143.34a 77.33bB 81.00bcA 99.73aA 95.22bB 87.57b 83.59c

*Each value represents a mean of three replications.

Raw whey and pasteurized whey were dehydrated by freeze-drying as used for controls (low-temperature treatment).

RW, raw whey; PW, pasteurized whey; UFSD, ultrafiltered and spray-dried WPC without lactose separation; UFVECSD,

ultrafiltered, vacuum-evaporated and spray-dried WPC after lactose separation; VECSD, vacuum-evaporated and spray-dried WPC

after lactose separation; UFVESD, ultrafiltered, vacuum-evaporated and spray-dried WPC without lactose separation. a–eMean values within the same column with different superscripts are significantly different (P < 0.05). A,BMean values within the same row with different superscripts are significantly different (P < 0.05). Shown only where there was

significant difference.

Composition and functionality of Cheddar whey T. Ji & Z. U. Haque 459

� 2003 Blackwell Publishing Ltd International Journal of Food Science and Technology 2003, 38, 453–461

Pasteurization and the associated agitation

conceivably dispersed clusters of whey proteins,

thus bringing about an overall increase in surface

area and enhancing potential for interaction with

micro-molecules. Grappin & Beuvier (1997)

reported up to 7% denaturation of whey proteins

during pasteurization. Haque and Kinsella (1987)

used calcium ionophores to conclude that

b-lactoglobulin, the major whey protein, exposes specific calcium binding sites during short expo-

sure to heat akin to the thermal exposure of

pasteurization. Such binding should result in

further increase in protein surface area due to

charge repulsion and thus make them less ther-

mostable. On the other hand, VE tended to

increase the level of thermal aggregation of the

whey proteins (Aryana & Haque, 2002) and thus

decreased hydrocarbon–aqueous interface, a phe-

nomenon that probably resulted in the observed

increase in TS. This work is substantiated by the

observations of Fujino et al. (1995) who used

differential scanning calorimetry to show that

vacuum preheating (as in VE) increased the

thermal stability of whey proteins.

The OHC of the controls, RW and PW, were,

respectively, 24.57 and 21.23 for J, and 21.71 and

20.15 for M. Data reflected similarly lower OHC

values for M at all process steps. However, these

differences were not significant based on WSr and

WPr (data not shown).

Solubility of the WPCs was WSr dependent.

Jersey whey samples showed better overall SO than

M whey samples for all treatments except VECSD

where M whey samples were better (Table 3). The

higher calcium content of J whey conceivably

resulted in higher degree of aggregation, denatur-

ation and insolubilization during processing.

Haggett (1976) reported that ultrafiltered WPCs

had a range of 88–100% protein solubility.

Conclusions

In terms of composition, WSr had a significant

impact in CP of the WPCs. The ash and calcium

contents appeared to be modulated by both WSr

and WPr. Whereas WPr impacted moisture con-

tent; VE gave significantly drier WPCs. Interest-

ingly, UF appeared to specifically enhance calcium

content in spite of decreasing overall ash content.

Of the five functional attributes studied, two (TS

and SO) were significantly affected by WPr, two

(EAI and ES) were affected by both WPr and

WSr, and one (OHC) was not significantly impac-

ted by either. Although both parameters seemed

equally important, WPr appeared to have a

dominant impact on powder attributes of func-

tional importance. The following article in this

series discusses the effect of WPr and WSr on ice

cream and yoghurt quality (Haque & Ji, 2003).

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