Efecto Del K-carragenina

8/22/2019 Efecto Del K-carragenina

1/6

Effect ofk-carrageenan on rheological properties, microstructure, texture and

oxidative stability of water-in-oil spreads

Raluca I. Alexa a,b, John S. Mounsey a,*, Brendan T. OKennedy a, Jean C. Jacquier b

a Teagasc, Moorepark Food Research Centre, Fermoy, Co. Cork, Irelandb School of Agriculture, Food Science & Veterinary Medicine, Agriculture & Food Science Centre, University College Dublin, Belfield, Dublin 4, Ireland

a r t i c l e i n f o

Article history:

Received 11 February 2009

Received in revised form

24 September 2009

Accepted 8 October 2009

Keywords:

Water-in-oil spreads

k-Carrageenan

Rheology

Microstructure

Oxidation

a b s t r a c t

The effect of k-carrageenan concentration (0-7.5 g kg1) on the rheology, microstructure, texture and

oxidative stability of water-in-oil (W/O) spreads (600 g fat kg1 emulsion) was examined over 60 days

storage time. Results showed that increasing the k-carrageenan concentration to 7.5 g kg1 significantly

increased the viscosity of the aqueous phase (to 42.7 mPa s at 60 C) resulting in gelation of the aqueous

phase on cooling. The microstructure of the spreads was disrupted by higher levels of k-carrageenan,

resulting in a less homogeneous distribution of the aqueous phase. Melt temperature (where tan d>1)

decreasedsignificantly from62 to 56.2 C withincreasingk-carrageenanconcentration from0 to 7.5 g kg1.

The firmness and the G0 at 6 C for all samples were significantly increased after 60 days storage with only

smalleffectsdue tok-carrageenanlevels.Oxidation of thefat phasewas evidentby thesignificant increases

in peroxidevaluesof all spreads on storage,with k-carrageenanexhibiting no antioxidant behaviour. While

increased k-carrageenan levels modified the microstructure of W/O spreads in terms of the droplet size of

the aqueous phase and its distribution few changes were evident in the continuous fat phase.

2009 Elsevier Ltd. All rights reserved.

1. Introduction

Spreadable fats are emulsions of the W/O type and were intro-

duced as an economical, functional and low calorie alternative of

butter (Caponio & Gomes, 2004; Laia, Ghazalia, Cho& Chong, 2000).

Replacement of the fat with water alters the rheological properties

and structural characteristics of spreads, which are mainly given by

the shape and the size of the fat crystals (Kasapis, 2000). A number

of biopolymers are used in low-fat formulations as fat mimics and

as stabilisers of the aqueous phase (Chronakis & Kasapis, 1995a;

Chronakis, 1997) through network stabilisation as well as stabili-

sation via interfacial action (Benichou, Aserin & Garti, 2002; Dick-

inson, 2003).

Polysaccharides such as k-carrageenan have been shown toenhance the sensorial properties of reduced-fat spreads (Clegg,

Moore & Jones, 1996). k-Carrageenan has the capacity to gel on

cooling through a disordered-ordered transition forming inter-

molecular double helices and subsequent aggregation and gelation

under specific conditions (Oakenfull & Scott, 1990; Heyraud,

Rinaudo, & Rochas, 1990). In a previous study by Mounsey, Sta-

thopoulos, Chockchaisawasdee, OKennedy, Gee and Doyle (2008)

on the fortification of W/O spreads containing k-carrageenan,

authors found that the increase in the gel strength of the aqueous

phase upon addition of transition metals altered the microstructure

of the W/O spreads.

The purpose of the present study was to assess the effect of

k-carrageenan on the rheology of the aqueous phase and on the

microstructure, texture, and rheology of the experimental W/O

spreads. Studies with reference to the antioxidant activities of

sulphated polysaccharides extracted from brown and red seaweeds

have been published in the literature (Sirendi, Gohtani, & Yamano,

1998; de Souza, Marques, Dore, da Silva, Rocha, & Leite, 2007;

Wang, Liu, Zhang, Zhang, Qi, & Li, 2009). In-vitro studies showed

that sulphated polysaccharides presented activity in inhibiting free

radicals. The degree of sulphation was found to be directly relatedto the radical scavenging activity, with k-carrageenan exhibiting

mild antioxidant properties (de Souza et al., 2007). The effect of

k-carrageenan on the oxidative degradation of the W/O spreads

was also investigated in the present work.

2. Materials and methods

2.1. Materials

A commercial source ofk-carrageenan (Grindsted Carrageenan

CL 107, Danisco, Denmark) was used without further purification.* Corresponding author. Tel.: 353 2542443.

E-mail address: [email protected] (J.S. Mounsey).

Contents lists available at ScienceDirect

LWT - Food Science and Technology

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / l w t

0023-6438/$ see front matter 2009 Elsevier Ltd. All rights reserved.

doi:10.1016/j.lwt.2009.10.003

LWT - Food Science and Technology 43 (2010) 843848
mailto:[email protected]://www.sciencedirect.com/science/journal/00236438http://www.elsevier.com/locate/lwthttp://www.elsevier.com/locate/lwthttp://www.sciencedirect.com/science/journal/00236438mailto:[email protected]


2/6

The vegetable oil blend was obtained from DairyGold (Mitchels-

town, Ireland). The fatty acid composition of the oil blend was

480 g kg1 monounsaturated, 320 g kg1 saturated, 190 g kg1

polyunsaturated and 10 g kg1 trans fatty acids. The monoglyceride

emulsifier (Paalsgaard 0291) was supplied by Grinstead A/S, Bra-

band, Denmark. All other solvents and chemicals used were of

analytical grade and purchased from SigmaAldrich, St. Louis, MO

63103, USA. Deionised water was used for the aqueous phase.

2.2. Manufacture of W/O spreads

Water-in-oil spreads (batches of 10 kg) were prepared in

duplicate following margarine production technology using a Per-

fector scraped surface heat exchanger (Gerstenberg and Agger,

Copenhagen, Denmark) as described previously (Mounsey et al.,

2008). A control spread was prepared by mixing an aqueous phase

(water; 400 g kg1 of the final product) and the fat (or oil) phase

contained the oil blend and the emulsifier (600 g kg1 of the final

product) at approximately 55 C. The preliminary mixing of the oil

and aqueous phase was performed for 1 min at 1500 rpm using

a Silverson mixer (model AX3, Silverson Machines Ltd., Waterside,

Chesham, Bucks, UK). The formed W/O emulsion was transferred to

the jacketed tank connected to the Perfector and pasteurized at75 C for 1520 s and immediately cooled down to 65 C. The

emulsion (w55 C) was pumped through two scraped-surface

coolers (at 432 rpm) bringing the temperature to 12 C before the

spread was filled into 454 g plastic tubs and stored at 4.5 C prior to

testing. The spreads containing k-carrageenan (1.56, 3.12, 6.25, 12.5

or 18.8 g L1 in the aqueous phase) were produced in order to give

a final k-carrageenan concentration of 0.625, 1.25, 2.5, 5, and

7.5 g kg1 reported to the total quantity.

2.3. Rheology of the aqueous phase

Small-scale deformation measurements were carried out on the

aqueous phase of the spreads using cup and bob systems in an AR

2000 Rheometer (TA Instruments, UK). All measurements weremade at a frequency of 1 Hz and a maximum strain of 0.500%.

Parameters such as the storage modulus (G0), loss modulus (G00) and

tan d (G0/G0) were monitored during cooling from 60 C to 6 C at

a rate of 1 C min1 using a Peltier heating element, followed by re-

heating to 60 C at the same ramp rate. The samples (15 g) were

loaded at 60 C and covered with n-Tetradecane (Sigma Chemica,

Co., St. Louis, MO, USA) to minimise evaporation.

Viscosity of the aqueous phase of the spreads was measured

using the same geometry of the AR 2000 Rheometer as above. A

shear rate sweep from 0.1 to 500 s1 was applied for 5 min. The

apparent viscosity (mPa s) was taken at 60 C and a shear rate of

100 s1.

2.4. Rheology of W/O spreads

A controlled strain AR-2000 rheometer (TA Instruments, New

Castle, Delaware) was used in the dynamic mode for small-scale

deformation measurements. Disc-shaped samples of spread

(25 mm diameter, 2.5 mm in thickness) were prepared using

a 25 mm diameter cork borer. A 25 mm diameter serrated parallel

plate geometry was used with a serrated lower plate. Samples

were placed on the lower plate and compressed with a normal

force of 0.5 N to prevent slippage, with 3 min for temperature

equilibration and stress relaxation prior to testing. Measurements

were taken at a frequency of 1 Hz and a strain of 0.2 %. Samples

were loaded at 6 C before n-Tetradecane (Sigma Chemical Co., St.

Louis, MO, USA) was added to the side in order to avoid evapo-

ration. The change in G0

, G

00

and tan d were measured during

heating from 6 to 60 C at a rate of 1 Cmin1. Tests were carried

out in triplicate.

2.5. Texture Profile Analysis (TPA)

Compression tests were performed using a TA-XT2 Texture

Analyser from Stable Microsystems (UK). Cylinders of spreads of

25 25 mm were cut and allowed to equilibrate at 4.5 C for 4 h.

Samples were compressed to 50% of their initial height (12.5 mm)

at a crosshead speed of 1 mm s1 using a 5 kgload cell and a 75 mm

diameter plate. Six samples were analysed from each spread tub.

The hardness values, expressed in Newtons (N) were measured at

the point of fracture.

2.6. Scanning Electron Microscopy (SEM)

Samples were prepared for cryo-SEM by mounting them into

copper rivets and plunged into nitrogen slush (207 C). Samples

were then transferred under vacuum into the preparation chamber,

freeze fractured with a cold blade, etched at 88 C for 5 min and

then sputtered coated with gold (10 mA for 60 s). Samples were

then transferred under vacuum onto the cold stage which was

maintained at 125 C and imaged using FE-SEM (Zeiss Supra

Gemini, Darmstadt, Germany). Images were acquired at 2.00 kV

with 200020,000 magnification.

2.7. Determination of the peroxide values (PV)

The PV test of melted fat (mEq O2.kg1) was derived from the

International Dairy Federation (IDF) Standard 74:1974. The W/O

spread sample was melted at 62C and 0.1 mL of melted fat was

dissolved into 10 mL of chloroform/methanol (70:30) mixture,

followed by addition of ammonium thiocyanate and ferrous

chloride, respectively. Using glass stoppers, the tubes were

inverted and placed in dark cupboard for 10 min. Simultaneously,

a blank test with only reagents and no sample was carried out.

The absorbance of the samples was read at 505 nm on a Varian

Cary Scan 1 instrument. After calibration, the blank value was

subtracted from the sample values (1) and the PVs were

calculated.

OD[ AbssampleLAbsstandard (1)

where OD is the optical density.

Samples were analysed after 1, 5, 7, 15, and 31 days of storage.

2.8. Statistical analysis

The rheology, texture and oxidative stability data of W/O

spreads containing k-carrageenan were statistically tested by

analysis of variance (ANOVA) using SigmaStat (version 3.0; JandelScientific, Corte Madera, CA, USA). Differences among treatments

were determined by StudentNewmanKeuls pairwise-compar-

ison test. Treatment means were considered significantly different

at *P< 0.05.

3. Results and discussion

3.1. Rheology of the aqueous phase of W/O spreads

3.1.1. Viscosity at 60 C

The effect of k-carrageenan concentration on the apparent

viscosity of the aqueous phase of W/O spreads is presented in Fig.1.

The sample containing 1.56 g kg1 k-carrageenan (in the aqueous

phase) had a low viscosity (4.31 mPas) whereas the apparent

R.I. Alexa et al. / LWT - Food Science and Technology 43 (2010) 843848844


3/6

viscosity increased significantly (***P< 0.001) to 42.7 mPas for

sample containing 18.8 g kg1 k-carrageenan. At low concentra-

tions the coils of k-carrageenan are free to move in the solutionwhile the apparent viscosity proportionally increases with the

concentration (Morris, 1984; Mounsey et al., 2008). Nonetheless, k-

carrageenan remained on a non-gelled state at 60 C, even at

concentrations as high as 18.8 g kg1.

3.1.2. Gelling properties at 6C

The effect of increasing k-carrageenan concentration on the

gelation properties of the aqueous phase of the W/O spreads was

monitored on cooling from 60 to 6 C. The G0 values of samples at

6 C are shown in Fig. 1. The aqueous phases containing 3.12 and

6.25 g kg1 k-carrageenan showed no gelation on cooling. By

increasing the concentration of k-carrageenan to 12.5 g kg1 the

aqueous phase had a gelling temperature (Tg) of 23C and

a relatively weak gel was obtained at 6

C (53 Pa). Furtherincreasing k-carrageenan concentration of the aqueous phase to

18.8 g kg1, Tg increased to 28.3C and a strong gel of 1.49 kPa was

obtained at 6 C.

3.2. Small scale deformation of W/O spreads

3.2.1. Rheology at 6C

Small-scale rheological assessment was performed in order to

investigate the structure of the experimental W/O spreads under

non-destructive conditions. The effect of k-carrageenan concen-

tration as well as the length of storage on the elastic modulus (G0) of

the W/O spread is presented in Fig. 2. Statistical interpretation

showed that the G0 values did not change significantly (*P> 0.05)

with increased levels ofk-carrageenan. On the other hand, the G0

ofthe control at 6 C had substantially greater values (*P< 0.05) after

60 days of storage, as well as the G0 of the k-carrageenan containing

samples. The increase in the G0 over time may be due tothe increase

in the amount of crystallinity in the oil phase, thus increasing the

solidness of the spreads at 6 C. Borwankar, Frye, Blaurock &

Sasevich (1992) found that the rheology of W/O spreads is strongly

associated with the degree of fat crystallisation.

An additional rheological parameter used to describe the

viscoelastic profile of a material is the tangent of the phase angle

(tan d (G00/G0)). The effect ofk-carrageenan on tan d (measured as

a function of storage is presented in Fig. 3). The tan d values of the

W/O spreads showed little change with the addition of k-carra-

geenan (*P> 0.05), butincreased sharply with the storage. Thetan d

values of the control significantly increased (*P 1 or the temperature at

which the total solidfat content is zero (Himawan, Starov & Stapley,

2006) of all samples increased over time (Table 1), possibly due to

modification in the structure of fat crystals (a, b0, and b polymorph

types) found in the network. It was shown by Ojijo et al. (2004)

using polarized light microscopy that the fat crystal network of an

olive oil/monoglyceride mixture suffered a progressive growth in

crystal clusters during storage, due to a more compact geometry of

hydrocarbon chains.

The melting temperature of the spreads significantly decreased

(*P< 0.05) with k-carrageenan concentration from 62.4 C

(control) to 55.9 C (sample containing 7.5 g kg1 k-carrageenan).

This may be probably due to the variation in the emulsion prop-

erties, with k-carrageenan having a destabilisation effect. After 60

days of storage the spreads didnot melt in the range of temperature

examined. The melting profile of the experimental W/O spreads

was comparable to that observed by Borwankar et al. (1992) in

a study on melting characterisation of margarine and table spreads

containing gelatine, which gelled in the aqueous phase at low

1

10

100

0 5 10 15 20

-carrageenan (g.kg-1

)

Apparentviscosityat60C

(mPa.s

)

0.1

1

10

100

1000

10000

G'at6C(

Pa)

Fig. 1. The effect ofk-carrageenan on the apparent viscosity of the aqueous phase of

W/O spreads at 60 C and 100 s1 shear rate ( ) and the storage modulus (G0) at 6 C

( ). Note: 18.8 g kg1 in the aqueous phase corresponds to 7.5 gkg1 in the final

spread. Each point on the curve represents the mean of triplicate trials. Vertical bars

show standard deviation of the means.

0

50

100

150

200

250

300

0 0.62 1.25 2.5 5 7.5

-carrageenan (g.kg-1)

xa

b

b

xa

bb

xa

aa

xa

abb

xa

b b

xa

b

b

G(kPa)

Fig. 2. Effect of k-carrageenan concentration on the G0 (at 6 C) of W/O spreads as

a function of storage time after 2 ( ), 15 ( ), and 60 ( ) days. Letters a, b, c represent

significant differences within treatment means between 2, 15 and 60 days. Letters x, y,

z represent significant differences between treatment means after 2 days. Means with

the same letter do not differ significantly at *P< 0.05.

0

0.05

0.1

0.15

0.2

0.25

0.3

0 0.625 1.25 2.5 5 7.5


Tan

x

a

b

c c

b c

x

a

x

a

x

a x

a

x

a

b b b

b b

c

c

Fig. 3. Effect ofk-carrageenan on tan d (at 6 C) of W/O spreads as a function of storage

time after 2 ( ), 15 ( ), and 60 ( ) days. Letters a, b, c represent significant differences

within treatment means between 2, 15 and 60 days. Letters x, y, z represent significant

differences between treatment means after 2 days. Means with the same letter do not

differ significantly at *P 1) of

W/O spreads as a function of storage time.

k-Carrageenan [g kg1] Melt t

2 Days 15 Days 60 Days

0 56a 62.4a

0.625 54.5ab 62.3ab

1.25 53.7ab 58.8bc

2.5 53.8ab 55.9cd 5 54.5ab 56.3ce

7.5 52.8bc 55.9cf

For each column, means with the same letter do not differ significantly at *P< 0.05.

Fig. 4. Scanning electron images of control W/O spread at (a) low magnification, (b) high magnification and sample containing 7.5 g kg1 k-carrageenan at (c) low magnification and

(d) high magnification.

R.I. Alexa et al. / LWT - Food Science and Technology 43 (2010) 843848846


5/6

addition of 7.5 g kg1 k-carrageenan in the overall product resulted

in a less homogeneous aqueous phase distribution, with slightly

larger and clustered aqueous phase droplets (Fig. 4d). k-Carra-

geenan increased the viscosity of the aqueous phase and most

likely induced gelation of the droplets during spread manufacture,

as previously shown by Mounsey et al. (2008). Similar results were

obtained by Clegg et al. (1996) in spreads containing 40 g kg1

gelatine.

3.6. Oxidative stability of W/O spreads

Lipid oxidation significantly affects the quality characteristics of

spreadable fats due to formation of rancid flavours and secondary

oxidised compounds which are detrimental for the health

(Frankel, 1998). Chaiyasit, Elias, McClements & Decker (2007)

showed that the concentration of peroxides is directly associated

with the oxidative stability of fats. The effect of k-carrageenan on

the oxidative stability of W/O spreads, as measured by the PV test,

was monitored during 31 days and presented in Fig. 6. The PV is

a measure of the hydroperoxide concentration in the early stages

of oxidation (Kochhar, 20 03). In all tests, PV increased in time. The

PV of the control increased noticeably (*P< 0.05) from 0.72 to

2.33 mEq O2 kg1 during storage time, although the spreads were

resistant against oxidation for 5 days. Samples containing levels of

up to 2.5 gkg1 k-carrageenan were not significantly (*P> 0.05)

more oxidised after 7 days of storage compared to the control.

These results indicate that all samples became rancid during

storage and the oxidation proceeded more rapidly in samples

containing high levels of k-carrageenan. It was anticipated that

k-carrageenan would have potential lipid antioxidation effect,

such as other polysaccharides (Matsumura et al., 2003; de Souza

et al., 2007). As k-carrageenan increased the viscosity of the

aqueous phase, forming gel droplets upon cooling (Mounsey et al.,

2008), it was hoped that the oxidation would be delayed by

decelerating the activity of reactants. Basaran, Coupland and

McClements (1999) showed that the viscosity of the aqueous

phase had no effect in delaying the motion of small molecules

through the polysaccharide gel network. Polysaccharides may

have a possible antioxidant effect through a metal ion chelation

mechanism or hydrogen donation (McClements & Decker, 2000).

In our study, k-carrageenan did not retard the oxidation of W/O

spreads. It is possible that the oxidation was promoted by the trace

amounts of metallic cations contained by k-carrageenan source

and implicit, higher levels present in samples prepared with

increased concentration ofk-carrageenan in the aqueous phase; or

due to incorporation of air and commencement of oxidation of the

oil-blend during emulsification process.

4. Conclusions

This study showed that increased levels of k-carrageenan

resulted in increased viscosity at 60 C as well as gelation on

cooling of the aqueous phase of model W/O spreads. The textural

hardness and dynamic rheological parameters (G0 and tan d at 6 C)

were not significantly modified by increased k-carrageenan addi-

tion. A less homogeneous structure was associated to an improved

meltability of the spreads containing increased levels of k-carra-

geenan. Nonetheless, k-carrageenan did not inhibit oxidation of the

W/O spreads. k-Carrageenan has application in controlling the

rheology of the aqueous phase of W/O spreads during spread

formation, storage and subsequent re-heating.

Acknowledgements

This research has been funded by Department of Agriculture and

Food under the Food Institutional Research Measure (National

Development Plan). The authors thank J. Roche for his help in the

preparation of W/O spreads. Vivian Gee of the National Food

Imaging Centre is gratefully acknowledged for help with collection

of the SEM images presented.

References

Basaran, T. K., Coupland, J. N., & McClements, D. J. (1999). Monitoring molecular

diffusion of sucrose in Xanthan solutions using ultrasonic velocity measure-ments. Journal of Food Science, 64, 125128.

Benichou, A., Aserin, A., & Garti, N. (2002). Protein-polysaccharide interactions forstabilization of food emulsions. Journal of Dispersion Science and Technology, 23,93123.

de Bruijne, D. W., & Bot, A. (1999). Fabricated fat-based foods. In A. J. Rosenthal (Ed.),Food texture: Measurement and perception. Gaithersburg: Aspen Publishers(pp. 185227).

Borwankar, R. P., Frye, L. A., Blaurock, A. E., & Sasevich, F. J. (1992). Rheologicalcharacterization of melting of margarines and tablespreads. Journal of FoodEngineering, 16, 5574.

Bot, A., & Vervoort, S. (2006). Hydrocolloid functionality in spreads and relatedproducts. In P. A. Williams, & G. O. Phillips (Eds.), Gums and stabilisers for the

food industry 13. Cambridge: RSC Publishing (pp. 381394).Caponio, F., & Gomes, T. (2004). Examination of lipid fraction quality of margarine.

Journal of Food Science, 69, 6366.Chaiyasit, W., Elias, R., McClements, D. J., & Decker, E. A. (2007). Role of physical

structures in bulk oils on lipid oxidation. Critical Reviews in Food Science and

Nutrition, 47, 299317.

0

5

10

15

20

0 0.625 1.25 2.5 5 7.5

Hardness(N)


va ab

cc

vwa

abcabc

c

xw aa

a

ayb

a ab w

a

aa a

vwa

ab ab

b

Fig. 5. Effect ofk-carrageenan on the hardness of W/O spreads at time 6 ( ),15 ( ), 30

( ), and 60 ( ) days of storage at 4.5 C. Each bar represents the mean of duplicate

trials. Vertical bars show standard deviation of the means. Letters a, b, c represent

significant differences within treatment means between 6, 15, 30, and 60 days. Letters

v, w, x, y represent significant differences between treatment means at day 6. Means

with the same letter do not differ significantly at *P< 0.05.

0

2

4

6

8

10

0 0.625 1.25 2.5 5 7.5


Peroxidevalue(mEq

O2.kg

-1)

v

a abc d

e

va

bc d

e

va b

c d

e

wa

bc

d

e

wx

a

bc

d

e

wya

abab

d

e

Fig. 6. Effect ofk-carrageenan on the oxidative stability of W/O spreads after 1 ( ) 5

( ), 7 ( ), 15 ( ), and 31 ( ) days storage at 4.5C. Each bar represents the mean of

duplicate trials. Vertical bars show standard deviation of the means. Letters a, b, c, d, e

represent significant differences within treatment means between 1, 5, 7, 15 and 31

days. Letters v, w, x, y represent significant differences between treatment means at

day 1. Means with the same letter do not differ significantly at *P

Documents

Efecto Del K-carragenina