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Foaming properties of sugar-egg mixtures with milk protein concentrates
Food Research International, Vol. 29, Nos 5-6, pp. 521-525,
ELSEVIER
PII:
1996
Copyright 0 I996 Published by Elsevier Science Ltd on behalf of the Canadian Institute of Food Science and Technology Printed in Great Britain SO963-9969(96)00048-8 0963-9969196 $15.00 + 0.00
Foaming properties of sugar-egg mixtures with milk protein concentrates Stefan Yankov & Ivan Panchev Higher
Institute of Food and Flavour
Industries,
26 “Maritza”
Blvd., Plovdiv 4002,
Bulgaria
The foaming properties of sugar-whole liquid egg mixtures using milk protein concentrates (MPC) such as bulstartprotein (BP), sour milk protein concentrate (SMPC) and whey protein concentrate (WPC) were studied. The effect of individual concentrates was found not to be equal or unidirectional. When compared with one another in terms of their effect on foam stability and foam overrun, the sequence WPC > SMPC > BP was obtained. Changes in viscosity corresponded to changes in the stability of the various mixtures, which was related to variations of the lamellar liquid viscosity and the drainage rate. Copyright 0 1996 Published by Elsevier Science Ltd on behalf of the Canadian Institute of Food Science and Technology
Keywords:
foam stability,
sugar-egg
mixtures,
bulstartprotein.
sour milk protein
concentrate, whey protein concentrate, regression models.
INTRODUCTION
MATERIALS
Proteins are widely used as functional ingredients in the production of a number of foodstuffs. Foaming properties stand out among the functional properties of proteins, arousing keen interest. Foamed sugarwhole liquid egg mixtures are the basis for the production of a variety of flour confectionery. These doughs may be defined as multicomponent, heterogeneous disperse systems consisting of foam, emulsion and suspension. After baking they may be regarded as hard foam. A number of studies have investigated the functional properties of milk proteins (Cheftel & Lorient, 1984; Mutilangi 1982; Kinsella, Morr, 1984; & Kilara, 1985; Krkoskova et al., 1985; Slack et al., 1986; Pate1 & Kilara, 1990; Lorient, 1991; Britten et al., 1993; Phillips et al., 1993), and egg proteins (Cunningham, 1976; Kitabatake & Doi, 1987; Tsuji, 1987; Trziszka, 1989; Risova et al., 1989) have also been studied. The objective of the present study was to investigate and model the effect of milk protein concentrate (MPC) on the functional and structural-mechanical properties of a foamed sugar-egg mixture.
Materials
AND METHODS
Fresh whole liquid eggs, sugar and MPC such as “bulstartprotein” (BP) and “sour milk protein concentrate” (SMPC) produced by the Department of Milk and Dairy Products Technology at the Higher Institute of Food and Flavour Industries (Plovdiv, Bulgaria), and “whey protein concentrate” (WPC) from the Membranni Tekhnologii (Plovdiv, Bulgaria) were used. Bulstartprotein is a dry biologically enriched milk protein concentrate obtained after ultrafiltration of skim cows’ milk. The lactose is partially enzyme hydrolysed with the help of the enzyme lactase (Gist, Brocades, Holland) with activity 5000 UE g-‘. Milk after hydrolysis is concentrated by ultrafiltration installation (Pasilac, Denmark). The obtained concentrate is enriched with milk-acid bacteria ingredients in Bulgarian yoghurt, Lb. bulgaricus and Str. thermophilus, and drying in a spray drier (Simov et al., 1993). SMPC is a product prepared after pasteurization of skim cows’ milk, milk-acid coagulation to obtain the gel with a low water-retaining ability and subsequent concentration after separation (Sahanikov et al., 1988). 521
522
S. Yankov, I. Panchev
Table 1. Approximate composition of protein ingredients
Protein Protein in gradient % BP SMPC WPC
Carbohydrate %
Fat %
Ash %
20.0 23.3 25.1
1.5 2.8 13.2
8.0 4.4 4.0
65.0 69.5 49.5
The approximate composition is shown in Table 1. Methods
Foam preparation The sugar-whole liquid egg mixture was homogenized by stirring to complete dissolution of sugar. The proportion of ingredients (wt. egg/wt. sugar) was according to a response surface design (Table 2). Dry milk concentrates were hydrated before being added to the sugaregg mixture. The required amount of MPC was weighed. Distilled water was added with stirring using a glass rod to form a smooth paste. The MPG/distilled water ratio (wt. MPC/wt. water) was 1:2 in the case of BP and 2:l in the case of WPC respectively. After that the sugar-eggMPC mixture was homogenized at ambient temperature for 30 min using a household-type mixer (Model E314Major, Germany) at a rotational speed of 350 rpm. Foams were formed by whipping the sugar-whole egg mixture and MPC added to it in a household-type mixer (Model E31CMajor, Germany) at ambient temperature. Foaming was developed by whipping 100 ml of mixture in a 1.0 1 vessel in two stages. The first took 5 min at a rotational speed of 350 rpm and the second lasted 10 min at a rotational speed of 1200 rpm. After foam formation was completed, the mixer was stopped and the mixer head was lifted carefully in consideration of minimal foam destruction. Samples of the foam were gently removed with a spatula and preweighed weighing boats were quickly filled to the constant volume of 100 ml for each measurement. The increase in the volume of foamed compositions, foam overrun (FO), was determined by the methods of Phillips et al. (1987, 1990). Table 2. Variables and their levels in the two-factor five-level response surface design
Independent
Levels
Symbol Coded
Uncoded
Coded
Uncoded
Sugar cont. (g gg)
X1
CS
Protein cont. (%)
X2
c,
-1.414 -1 0 1 1.414 -1.414 -1 0 1 1.414
1.0 1.3 2.0 2.1 3.0 0.1 0.8 2.5 4.2 4.9
variables
FO,(wt.lOO
ml composition)-(wt.100 (wt. 100 ml foam)
ml foam) x 1oo (1)
Foam stability Foam stability of the foamed composition was evaluated by a modified method based on the work of Phillips et al. (1987, 1990). Samples of foam with the constant volume of 100 ml for each measurement were carefully taken and put in a 120 ml glass vessel. The 2 mm hole drilled in the bottom of the vessel was sealed before filling. The vessel was placed over an electric balance (E 12OOS,Sartorius, Austria) on which another vessel had been fixed. The tape was removed and the drained liquid collected in the second vessel was continuously measured. The initial drainage rate, &, expressed as a relation between the maximum volume of drained serum, V, and the time, B, needed to drain one-half of the maximum amount of liquid, V/2, was adopted as a quantitative criterion to describe the foam stability (Elizalde et al., 1991). Viscosity The viscosity of the model compositions was studied on a coaxial rotational viscosimeter (Model Rheotest 2.1, VEB MLW, Freital, Germany) connected with a PC and was determined with bob N, by a shear rate of 82 s-l at a temperature of 20°C. Experimental design and statistical analysis The regression analysis was applied to process and assay the experimental results obtained (Draper & Smith, 1981). The response surface methodology was used to develop models (Vuchkov & Stojanov, 1986). An experimental design of five levels and two factors with five replicates at the center point was used. It was assumed that three functions fk (k = 1, 2, 3) exist for each response variable Yk (foam overrun (FO), Y,; foam stability (Ro), Y,; viscosity (q), Y,) in terms of two independent variables. Yk =fk(& t X2)
(2)
where X1 designates sugar concentration, C,, expressed as a relation between weight of eggs and sugar, C, = (wt. eggs)/(wt. sugar) and X2 designates concentration of milk protein concentrates C,. Due to the unknown form of the functionsfk, secondorder polynomial equations were used to approximate the true functions of eqn 2. Yk = bko + CbkiXi + XbkiiXf + XXbkvXiXj
(3)
where bko, bki, bkii, bkg are constant coefficients and Xi, Xj are the coded independent variables, linearly related to the uncoded variables C, and C,,.
Foaming properties of sugar-egg mixtures
The results presented in this study are the means of three independent replicates. A total of 13 treatments were performed in random order. The independent variables, the coded variables and their levels are presented in Table 2 (Vuchkov & Stojanov, 1986). The experimental data obtained for the response function are given in Table 3. The software MLRG compiled by System 1360 (1970) was used to analyze the data and fit the second-order polynomial of eqn 3 to the experimental results shown in Table 3.
RESULTS
This was probably due to the dependence of the air volume involved on the geometry of the whipping vessel as suggested by Britten & Lavoie (1992). The analysis of the influence of separate Xi factors on the Y(F0) function led to some conclusions. Milk protein concentrates had an unequal effect in the X1 variation range. So, for SMPC the maximum FO value was obtained in the C, variation range tested, and it occurred at C, =O.l and 4.9 with changes in the value of sugar concentration within the limits of I1.5 and 2-3, respectively. In general, a minimum FO value was observed at a value of protein concentration 2.5. In the case of WPC, a trend to suppress foaming with increasing C, was noted. In the case of BP, the maximum FO values were obtained at C, = 2.5 and 0.1 for C, < 2 and C, > 2, respectively. It is evident that a trend of raising FO with increasing C, was present for SMPC, while this was reciprocal in the case of BP and WPC. The differences in the composition of the proteins involved were determinant of their behaviour. Sugar decreased the foaming ability of the model compositions studied. By increasing the C, value in the range tested, decreases in FO of 2.04, 1.87 and 1.96 times for BP, SMPC and WPC, respectively, were noted. The maximum FO values obtained with C, and C, are given in Table 4. The comparison of the protein concentrates as regards foam ability showed the following sequence: WPC > SMPC > BP.
AND DISCUSSION
Foam overrun
The foaming ability of the compositions under study was defined by foam overrun. The quadratic models for FO of BP (Yi ,), MPC (Yiz) and WPC ( Yi3) were: Y,, = 370 + 54.6X, - 19.6X2 - 18.5X,X2 - 15.0X: - 7.5X;
r2 = 0.967
(4)
P 5 0.05
Y,2 = 318 + 68.3X, f 4.5X2 + 7.5X,X2 + 5.4X: + 17.2X;
r2 = 0.986
(5)
P 5 0.05
Y,3 = 267 + 17.3X, - 73.5X2 -47.1X,X2 - 5.8X: f 17.8X;
r2 = 0.971
(6)
P 5 0.05
523
The FO values ranged within the limits of 18&440% and were in some disagreement with to the higher ones reported for foamed protein mixtures by some authors.
Table 3. Experimental data for the two-factor five-level response surface analysis
Treatment
Sugar
Protein
No.~
cont. (CA
cont. (C,)
1 2 3 4 5 6 7 8 9 IO II 12 13
-1 -1
I 1 -1.414 1.414 0 0 0 0 0 0 0
-1
1 -1 I 0 0 -1.414 1.414 0 0 0 0 0
FOh
RoC
rid
BP’
SMPCf
WPCg
299 298 425 350 253 436 388 331 383 364 364 363 376
278 261 394 407 234 435 344 372 319 311 314 310 318
301 253 428 191 215 267 396 181 255 265 261 280 275
“Experimental treatments were performed in random hFoam overrun (FO) in %. cFoam stability (Ro)in g min-‘. dViscosity (q) in mPa s. ‘MPC is “bulstartprotein” (BP). fMPC is “sour milk protein concentrate” (SMPC). “MPC is “whey protein concentrate” (WPC).
order.
--
BP
SMPC
WPC
BP
12.57 21.05 42.00 23.53 5.05 19.56 34.96 23.66 14.16 14.06 16.48 21.23 18.83
-15.77 17.99 56.75 41.06 15.87 43.73 26.4 38.79 31.13 25.12 26.77 22.66 29.18
14.82 43.47 42.43 101.66 12.52 61.32 36.05 139.53 17.82 26.82 18.21 18.81 22.38
51 65 24 20 76 24 31 26 35 27 34 33 33
SMPC ..____ 44 59 31 31 86 20 30 34 29 33 35 36 30
WPC 69 76 21 23 98 19 32 37 36 28 34 30 28
S. Yankov, I. Panchev
524
Table 4. Maximum of FO and the corresponding values of C, and C,,
Maximum FO c, c,
BP”
SMPCb
WPCC
469 3.0
480 3.0 4.9
522 3.0
0.1
Minimum R0 G C,
0.1
aMPC is “bulstarprotein” (BP). bMPC is “sour milk protein concentrate” (SMPC). CMPCis “whey protein concentrate” (WPC).
WPCC
13.1 1.3 2.5
8.7 1.0 0.6
3.7 1.0 2.5
Y32= 32.6 - 16.8X1 +2.6X2 - 3.7X1X2
Y2,/7 = 16.95 +6.55X1 - 3.24x2 - 6.74X1X2 - 11.33X: + 7.17X:
r* = 0.967
P 5 0.05
(7)
Y22 = 26.97 + 12.93X1 +0.51X2 - 4.48X1X2 ? = 0.878
P ( 0.05
(8)
Y23 = 20.8 + 19.4X1 +29.28X2 + 7.65X1X2
3 = 0.949
P 5 0.05
(9)
The analysis of the models for the effect of factors tested on the foam stability determined that the influence of MPC concentration on the R. values is in the following sequence: WPC > SMPC > BP. The minimum value of Re obtained at the ends of the interval tested were always higher than those at the center. Higher foam stability at the low-point area of the C, interval tested was observed, i.e. C, > 2.5%. The effect of BP was similar to WPC while different for SMPC. When C, was changed in the interval from C, = 1 to 2, increasing C, caused increasing Re values, while changing C, from C,=2 to 3 had the opposite effect. The strong effect of sugar on foam stability was confirmed. Table 5 shows the minimum R. values obtained for X1 and _X,levels. When compared with one another in terms of their revealed the stability, the different compositions sequence WPC > SMPC > BP. Viscosity
Based on the analysis of the viscosity and the rheograms, the following quadratic equations for viscosity r] of BP ( Y3i), SMPC ( Y32)and WPC ( YJ~)were derived: Y3, = 32.4 - 18.2X, + 0.4X2 - 4.5x1x2 + 9X: - 1.8X:
SMPCb
“MPC is “whey protein concentrate” (WPC)
Models revealing the dependence of the stability of foamed compositions expressed by the initial drainage rate R. for BP (Yzt), SMPC (Y& and WPC (Y23) were as follows:
+ 5.11x; + 30.55x;
BPa
“MPC is “bulstarprotein” (BP). bMPC is “sour milk protein concentrate” (SMPC).
Foam stability
+ 1.84X; + 3.23X;
Table 5. Minimum of & and the corresponding values of C, and CP
r2 = 0.988
P 5 0.05
(10)
+ 9.9X: - 0.6X:
r2 = 0.890
P 5 0.05
(11)
Y33= 31.2 - 26.6X1 + 2.0X2 + 1.3X,X2 + 13.8X: + 1.8X;
r2 = 0.874
P I 0.05
(12)
The behaviour of viscosity changes corresponded to that of the stability of foamed compositions expressed through Ro. This was observed for all three protein concentrates. These findings supported the conclusions drawn by Hailing (1981) and Richard (1979) concerning the relation between the changes in the viscosity of lamellar serum and the drainage rate. By increasing the protein concentration, the forming interfacial film became thicker and more rigid. This accounted for the apparent increase in viscosity at lower concentrations. Increasing the concentration reduced the drainage rate and enhanced the involvement of more water in foam matrices. This was especially characteristic of foams obtained with milk proteins. Viscosity was inversely proportional to the volume of liquid fraction. Increasing the thickness of the liquid film dividing adjacent air bubbles increased foam fluidity and this accounted for the decrease in the viscosity at higher concentration levels. CONCLUSIONS The influence of different milk protein concentrates on foaming properties of sugar-whole liquid egg mixtures was not equal and unidirectional. In terms of their effect on foam overrun and foam stability, the sequence WPC > SMPC > BP was obtained. Changes in viscosity of sugar-egg mixtures with added MPC corresponded to changes in the stability of foamed mixtures. The models allowed one to determine the influence of milk protein concentrates, WPC, SMPC and BP, on the foaming properties of sugar-egg mixtures. ACKNOWLEDGEMENTS The Ministry of Science and Education and the National Research Fund, the Republic of Bulgaria, provided financial assistance to this work.
Foaming properties of sugar-egg mixtures REFERENCES
Phillips,
L. G., Haque,
for the measurement Britten, M., Bastrah, S., Fortin, J. & Fichtali, J. (1993). Emulsifying and foaming properties of sodium caseinate obtained from extrussion process. Milchwissenschat, 48, 303-306. Britten, M. & Lavoie, L. (1992). Foaming properties of proteins as affected by concentration. J. Food Sci., 57, 12191222. Cheftel, J. & Lorient, D. (1982). The functional properties of milk proteins and their improvement. Laif, 62, 435-483. Cunningham, F. (1976). Properties of egg white foam drainage. Poultry Sci., 55, 738-745. Draper, N. & Smith, H. (1981). Applied Regresion Analysis. Wiley, New York. Elizalde, B. E., Giaccaglia, D., Pilosof, A. M. R. & Bartholomai, G. B. (1991). Kinetics of liquid drainage from protein stabilized foams. J. Food Sci., 56, 2426. Halling, P. (1981). Protein stabilized foams and emulsions, CRC Crit. Rev. Food Sci. Nutr., 15, 1.5-203. Kinsella, J. (1984). Milk proteins physicochemical and functional properties. CRC Crit. Rev. Food Sci. Nutr., 21, 1977 204. Kitabatake, N. & Doi, E. (1987). Conformational change of hen egg ovalbumin during foam formation. J. Agric. Food Chem.. 35, 953-957. Krkoskova, D., Buzinkayova, D. & Romanova, J. (1985). The foaming properties of milk proteins. Potravinarske VedyUVTIZ, 3, 287-294. Lee, Sh.Y., Charles, M. & Ewan, Y. (1992). Structural and functional properties of caseinate and whey protein isolate as affected by temperature and pH. J. Food Sci., 57, l2lO1213. Lorient, D. (1991). Recent knowledge on the functional properties of milk proteins and related products, Lait, 71, 141. Morr, C. (1984). Production and use of milk proteins in food. Food Technol., 38, 3943. Morr, C. & Foegeding, E. A. (1990). Composition and functionality of commersial whey and milk protein concentrates and isolates. Food Technol., 44, lOCLlO4. Mutilangi, W. & Kilara, A. (1985). Functional properties of heat denaturated whey proteines of heat denatured whey proteins. II. Emulsifying and foaming properties. Milkwissenschuft, 40, 391-393. Patel, M. & Kilara, A. (1990). Studies on WPC 2. Foaming and emulsifying properties and their relationships with physicochemical properties. J. Dairy Sci., 73, 273 I-2740.
525 Z. & Kinsella,
J. E. (1987). A method
of foam formation
and stability. J.
Food Sci., 52, 1074-1077. Phillips, L., Yang, S., Schulman, W. & Kinsella, J. (1989). Effects of lisozime clupeine and sucrose on the foaming properties of WPI and P-lactoglobulin. J. Food Sci., 54, 743-746. Phillips, L. G., German, J. B., O’Neill, T. E., Foegeding, E. A., Harwalkar, V. R., Kilara, A., Lewis, B. A., Mangino, M. E., Morr, S. V., Regenstein, J. M., Smith, D. M. & Kinsella, J. E. (1990). A standardized procedure for measuring foaming properties of three proteins. J. Food Sci., 55, 1441-1444. Phillips, L., Schulman, W. & Kinsella, J. (1993). pH and heat treatment effects on foaming of WPI. J. Food Sci., 55, I I lb 1119. Richard, S. (I 979). Physicalchemical properties of whey protein foams. J. Agric. Food Chem., 27, 665-668. Risova, J., Vavreinovw, S., Vonchikova, 0. & Simunek, Z. (1989). The influence of some additives on the foaming properties of egg white. Potruvinarske Vedy-UVTIZ., 7, 183-191. Sahanekov, H., Panajotov, P., Kashkavalov, P., Stojanov, D. & Craleva, N. (1988). Razrabotvane na technologia za proizvodstvo na kiselo mleko s povisheno suho vestesrvo. Nuuch. Sesiu, 35, 15-20. Simov, J. (1993). Izuchavane na sastava i svoistvata na visokoproteinov preparat na mlechna osnova “Bulstartprotein”. Hranitelnu Promishlenost, 8, I l-l 3. Slack, A., Amundson, C. & Hill, C. (1986). Foaming and emulsifying characteristics of fractionated whey protein. J. Food Process Preservation, 10, 8 l-88. System 1360 (1970). Scientific subroutine package (360A-CM03X) Version III, IBM Technical Publications Department, New York. Trziszka, T. (1988). Physicochemical and technological characteristics of egg white foam, Dissertation, ZNAR, Wroclaw, No. 69, p. 78. Trziszka, T. (1989). The quality of egg foam depending on technological conditions. Proc. Hohenheimer Gefuige Symp., Stuttgart, Scholtgssev S., pp. 30431 I. Tsuji, S. (1987). Investigations on the physical properties of whipped egg white foams. J. Jpn. Sot. Food Sci. Technol., 34, 1377142. Vuchkov. I. & Stojanov, St. (1986). Mutemutichesko Modelirune i Optimizirane nu Technologicheski Ohekti. Tehnika, Sofia, pp. 131ll54.
(Received
25 July 1995; accepted
30 August
1996)
ELSEVIER
PII:
1996
Copyright 0 I996 Published by Elsevier Science Ltd on behalf of the Canadian Institute of Food Science and Technology Printed in Great Britain SO963-9969(96)00048-8 0963-9969196 $15.00 + 0.00
Foaming properties of sugar-egg mixtures with milk protein concentrates Stefan Yankov & Ivan Panchev Higher
Institute of Food and Flavour
Industries,
26 “Maritza”
Blvd., Plovdiv 4002,
Bulgaria
The foaming properties of sugar-whole liquid egg mixtures using milk protein concentrates (MPC) such as bulstartprotein (BP), sour milk protein concentrate (SMPC) and whey protein concentrate (WPC) were studied. The effect of individual concentrates was found not to be equal or unidirectional. When compared with one another in terms of their effect on foam stability and foam overrun, the sequence WPC > SMPC > BP was obtained. Changes in viscosity corresponded to changes in the stability of the various mixtures, which was related to variations of the lamellar liquid viscosity and the drainage rate. Copyright 0 1996 Published by Elsevier Science Ltd on behalf of the Canadian Institute of Food Science and Technology
Keywords:
foam stability,
sugar-egg
mixtures,
bulstartprotein.
sour milk protein
concentrate, whey protein concentrate, regression models.
INTRODUCTION
MATERIALS
Proteins are widely used as functional ingredients in the production of a number of foodstuffs. Foaming properties stand out among the functional properties of proteins, arousing keen interest. Foamed sugarwhole liquid egg mixtures are the basis for the production of a variety of flour confectionery. These doughs may be defined as multicomponent, heterogeneous disperse systems consisting of foam, emulsion and suspension. After baking they may be regarded as hard foam. A number of studies have investigated the functional properties of milk proteins (Cheftel & Lorient, 1984; Mutilangi 1982; Kinsella, Morr, 1984; & Kilara, 1985; Krkoskova et al., 1985; Slack et al., 1986; Pate1 & Kilara, 1990; Lorient, 1991; Britten et al., 1993; Phillips et al., 1993), and egg proteins (Cunningham, 1976; Kitabatake & Doi, 1987; Tsuji, 1987; Trziszka, 1989; Risova et al., 1989) have also been studied. The objective of the present study was to investigate and model the effect of milk protein concentrate (MPC) on the functional and structural-mechanical properties of a foamed sugar-egg mixture.
Materials
AND METHODS
Fresh whole liquid eggs, sugar and MPC such as “bulstartprotein” (BP) and “sour milk protein concentrate” (SMPC) produced by the Department of Milk and Dairy Products Technology at the Higher Institute of Food and Flavour Industries (Plovdiv, Bulgaria), and “whey protein concentrate” (WPC) from the Membranni Tekhnologii (Plovdiv, Bulgaria) were used. Bulstartprotein is a dry biologically enriched milk protein concentrate obtained after ultrafiltration of skim cows’ milk. The lactose is partially enzyme hydrolysed with the help of the enzyme lactase (Gist, Brocades, Holland) with activity 5000 UE g-‘. Milk after hydrolysis is concentrated by ultrafiltration installation (Pasilac, Denmark). The obtained concentrate is enriched with milk-acid bacteria ingredients in Bulgarian yoghurt, Lb. bulgaricus and Str. thermophilus, and drying in a spray drier (Simov et al., 1993). SMPC is a product prepared after pasteurization of skim cows’ milk, milk-acid coagulation to obtain the gel with a low water-retaining ability and subsequent concentration after separation (Sahanikov et al., 1988). 521
522
S. Yankov, I. Panchev
Table 1. Approximate composition of protein ingredients
Protein Protein in gradient % BP SMPC WPC
Carbohydrate %
Fat %
Ash %
20.0 23.3 25.1
1.5 2.8 13.2
8.0 4.4 4.0
65.0 69.5 49.5
The approximate composition is shown in Table 1. Methods
Foam preparation The sugar-whole liquid egg mixture was homogenized by stirring to complete dissolution of sugar. The proportion of ingredients (wt. egg/wt. sugar) was according to a response surface design (Table 2). Dry milk concentrates were hydrated before being added to the sugaregg mixture. The required amount of MPC was weighed. Distilled water was added with stirring using a glass rod to form a smooth paste. The MPG/distilled water ratio (wt. MPC/wt. water) was 1:2 in the case of BP and 2:l in the case of WPC respectively. After that the sugar-eggMPC mixture was homogenized at ambient temperature for 30 min using a household-type mixer (Model E314Major, Germany) at a rotational speed of 350 rpm. Foams were formed by whipping the sugar-whole egg mixture and MPC added to it in a household-type mixer (Model E31CMajor, Germany) at ambient temperature. Foaming was developed by whipping 100 ml of mixture in a 1.0 1 vessel in two stages. The first took 5 min at a rotational speed of 350 rpm and the second lasted 10 min at a rotational speed of 1200 rpm. After foam formation was completed, the mixer was stopped and the mixer head was lifted carefully in consideration of minimal foam destruction. Samples of the foam were gently removed with a spatula and preweighed weighing boats were quickly filled to the constant volume of 100 ml for each measurement. The increase in the volume of foamed compositions, foam overrun (FO), was determined by the methods of Phillips et al. (1987, 1990). Table 2. Variables and their levels in the two-factor five-level response surface design
Independent
Levels
Symbol Coded
Uncoded
Coded
Uncoded
Sugar cont. (g gg)
X1
CS
Protein cont. (%)
X2
c,
-1.414 -1 0 1 1.414 -1.414 -1 0 1 1.414
1.0 1.3 2.0 2.1 3.0 0.1 0.8 2.5 4.2 4.9
variables
FO,(wt.lOO
ml composition)-(wt.100 (wt. 100 ml foam)
ml foam) x 1oo (1)
Foam stability Foam stability of the foamed composition was evaluated by a modified method based on the work of Phillips et al. (1987, 1990). Samples of foam with the constant volume of 100 ml for each measurement were carefully taken and put in a 120 ml glass vessel. The 2 mm hole drilled in the bottom of the vessel was sealed before filling. The vessel was placed over an electric balance (E 12OOS,Sartorius, Austria) on which another vessel had been fixed. The tape was removed and the drained liquid collected in the second vessel was continuously measured. The initial drainage rate, &, expressed as a relation between the maximum volume of drained serum, V, and the time, B, needed to drain one-half of the maximum amount of liquid, V/2, was adopted as a quantitative criterion to describe the foam stability (Elizalde et al., 1991). Viscosity The viscosity of the model compositions was studied on a coaxial rotational viscosimeter (Model Rheotest 2.1, VEB MLW, Freital, Germany) connected with a PC and was determined with bob N, by a shear rate of 82 s-l at a temperature of 20°C. Experimental design and statistical analysis The regression analysis was applied to process and assay the experimental results obtained (Draper & Smith, 1981). The response surface methodology was used to develop models (Vuchkov & Stojanov, 1986). An experimental design of five levels and two factors with five replicates at the center point was used. It was assumed that three functions fk (k = 1, 2, 3) exist for each response variable Yk (foam overrun (FO), Y,; foam stability (Ro), Y,; viscosity (q), Y,) in terms of two independent variables. Yk =fk(& t X2)
(2)
where X1 designates sugar concentration, C,, expressed as a relation between weight of eggs and sugar, C, = (wt. eggs)/(wt. sugar) and X2 designates concentration of milk protein concentrates C,. Due to the unknown form of the functionsfk, secondorder polynomial equations were used to approximate the true functions of eqn 2. Yk = bko + CbkiXi + XbkiiXf + XXbkvXiXj
(3)
where bko, bki, bkii, bkg are constant coefficients and Xi, Xj are the coded independent variables, linearly related to the uncoded variables C, and C,,.
Foaming properties of sugar-egg mixtures
The results presented in this study are the means of three independent replicates. A total of 13 treatments were performed in random order. The independent variables, the coded variables and their levels are presented in Table 2 (Vuchkov & Stojanov, 1986). The experimental data obtained for the response function are given in Table 3. The software MLRG compiled by System 1360 (1970) was used to analyze the data and fit the second-order polynomial of eqn 3 to the experimental results shown in Table 3.
RESULTS
This was probably due to the dependence of the air volume involved on the geometry of the whipping vessel as suggested by Britten & Lavoie (1992). The analysis of the influence of separate Xi factors on the Y(F0) function led to some conclusions. Milk protein concentrates had an unequal effect in the X1 variation range. So, for SMPC the maximum FO value was obtained in the C, variation range tested, and it occurred at C, =O.l and 4.9 with changes in the value of sugar concentration within the limits of I1.5 and 2-3, respectively. In general, a minimum FO value was observed at a value of protein concentration 2.5. In the case of WPC, a trend to suppress foaming with increasing C, was noted. In the case of BP, the maximum FO values were obtained at C, = 2.5 and 0.1 for C, < 2 and C, > 2, respectively. It is evident that a trend of raising FO with increasing C, was present for SMPC, while this was reciprocal in the case of BP and WPC. The differences in the composition of the proteins involved were determinant of their behaviour. Sugar decreased the foaming ability of the model compositions studied. By increasing the C, value in the range tested, decreases in FO of 2.04, 1.87 and 1.96 times for BP, SMPC and WPC, respectively, were noted. The maximum FO values obtained with C, and C, are given in Table 4. The comparison of the protein concentrates as regards foam ability showed the following sequence: WPC > SMPC > BP.
AND DISCUSSION
Foam overrun
The foaming ability of the compositions under study was defined by foam overrun. The quadratic models for FO of BP (Yi ,), MPC (Yiz) and WPC ( Yi3) were: Y,, = 370 + 54.6X, - 19.6X2 - 18.5X,X2 - 15.0X: - 7.5X;
r2 = 0.967
(4)
P 5 0.05
Y,2 = 318 + 68.3X, f 4.5X2 + 7.5X,X2 + 5.4X: + 17.2X;
r2 = 0.986
(5)
P 5 0.05
Y,3 = 267 + 17.3X, - 73.5X2 -47.1X,X2 - 5.8X: f 17.8X;
r2 = 0.971
(6)
P 5 0.05
523
The FO values ranged within the limits of 18&440% and were in some disagreement with to the higher ones reported for foamed protein mixtures by some authors.
Table 3. Experimental data for the two-factor five-level response surface analysis
Treatment
Sugar
Protein
No.~
cont. (CA
cont. (C,)
1 2 3 4 5 6 7 8 9 IO II 12 13
-1 -1
I 1 -1.414 1.414 0 0 0 0 0 0 0
-1
1 -1 I 0 0 -1.414 1.414 0 0 0 0 0
FOh
RoC
rid
BP’
SMPCf
WPCg
299 298 425 350 253 436 388 331 383 364 364 363 376
278 261 394 407 234 435 344 372 319 311 314 310 318
301 253 428 191 215 267 396 181 255 265 261 280 275
“Experimental treatments were performed in random hFoam overrun (FO) in %. cFoam stability (Ro)in g min-‘. dViscosity (q) in mPa s. ‘MPC is “bulstartprotein” (BP). fMPC is “sour milk protein concentrate” (SMPC). “MPC is “whey protein concentrate” (WPC).
order.
--
BP
SMPC
WPC
BP
12.57 21.05 42.00 23.53 5.05 19.56 34.96 23.66 14.16 14.06 16.48 21.23 18.83
-15.77 17.99 56.75 41.06 15.87 43.73 26.4 38.79 31.13 25.12 26.77 22.66 29.18
14.82 43.47 42.43 101.66 12.52 61.32 36.05 139.53 17.82 26.82 18.21 18.81 22.38
51 65 24 20 76 24 31 26 35 27 34 33 33
SMPC ..____ 44 59 31 31 86 20 30 34 29 33 35 36 30
WPC 69 76 21 23 98 19 32 37 36 28 34 30 28
S. Yankov, I. Panchev
524
Table 4. Maximum of FO and the corresponding values of C, and C,,
Maximum FO c, c,
BP”
SMPCb
WPCC
469 3.0
480 3.0 4.9
522 3.0
0.1
Minimum R0 G C,
0.1
aMPC is “bulstarprotein” (BP). bMPC is “sour milk protein concentrate” (SMPC). CMPCis “whey protein concentrate” (WPC).
WPCC
13.1 1.3 2.5
8.7 1.0 0.6
3.7 1.0 2.5
Y32= 32.6 - 16.8X1 +2.6X2 - 3.7X1X2
Y2,/7 = 16.95 +6.55X1 - 3.24x2 - 6.74X1X2 - 11.33X: + 7.17X:
r* = 0.967
P 5 0.05
(7)
Y22 = 26.97 + 12.93X1 +0.51X2 - 4.48X1X2 ? = 0.878
P ( 0.05
(8)
Y23 = 20.8 + 19.4X1 +29.28X2 + 7.65X1X2
3 = 0.949
P 5 0.05
(9)
The analysis of the models for the effect of factors tested on the foam stability determined that the influence of MPC concentration on the R. values is in the following sequence: WPC > SMPC > BP. The minimum value of Re obtained at the ends of the interval tested were always higher than those at the center. Higher foam stability at the low-point area of the C, interval tested was observed, i.e. C, > 2.5%. The effect of BP was similar to WPC while different for SMPC. When C, was changed in the interval from C, = 1 to 2, increasing C, caused increasing Re values, while changing C, from C,=2 to 3 had the opposite effect. The strong effect of sugar on foam stability was confirmed. Table 5 shows the minimum R. values obtained for X1 and _X,levels. When compared with one another in terms of their revealed the stability, the different compositions sequence WPC > SMPC > BP. Viscosity
Based on the analysis of the viscosity and the rheograms, the following quadratic equations for viscosity r] of BP ( Y3i), SMPC ( Y32)and WPC ( YJ~)were derived: Y3, = 32.4 - 18.2X, + 0.4X2 - 4.5x1x2 + 9X: - 1.8X:
SMPCb
“MPC is “whey protein concentrate” (WPC)
Models revealing the dependence of the stability of foamed compositions expressed by the initial drainage rate R. for BP (Yzt), SMPC (Y& and WPC (Y23) were as follows:
+ 5.11x; + 30.55x;
BPa
“MPC is “bulstarprotein” (BP). bMPC is “sour milk protein concentrate” (SMPC).
Foam stability
+ 1.84X; + 3.23X;
Table 5. Minimum of & and the corresponding values of C, and CP
r2 = 0.988
P 5 0.05
(10)
+ 9.9X: - 0.6X:
r2 = 0.890
P 5 0.05
(11)
Y33= 31.2 - 26.6X1 + 2.0X2 + 1.3X,X2 + 13.8X: + 1.8X;
r2 = 0.874
P I 0.05
(12)
The behaviour of viscosity changes corresponded to that of the stability of foamed compositions expressed through Ro. This was observed for all three protein concentrates. These findings supported the conclusions drawn by Hailing (1981) and Richard (1979) concerning the relation between the changes in the viscosity of lamellar serum and the drainage rate. By increasing the protein concentration, the forming interfacial film became thicker and more rigid. This accounted for the apparent increase in viscosity at lower concentrations. Increasing the concentration reduced the drainage rate and enhanced the involvement of more water in foam matrices. This was especially characteristic of foams obtained with milk proteins. Viscosity was inversely proportional to the volume of liquid fraction. Increasing the thickness of the liquid film dividing adjacent air bubbles increased foam fluidity and this accounted for the decrease in the viscosity at higher concentration levels. CONCLUSIONS The influence of different milk protein concentrates on foaming properties of sugar-whole liquid egg mixtures was not equal and unidirectional. In terms of their effect on foam overrun and foam stability, the sequence WPC > SMPC > BP was obtained. Changes in viscosity of sugar-egg mixtures with added MPC corresponded to changes in the stability of foamed mixtures. The models allowed one to determine the influence of milk protein concentrates, WPC, SMPC and BP, on the foaming properties of sugar-egg mixtures. ACKNOWLEDGEMENTS The Ministry of Science and Education and the National Research Fund, the Republic of Bulgaria, provided financial assistance to this work.
Foaming properties of sugar-egg mixtures REFERENCES
Phillips,
L. G., Haque,
for the measurement Britten, M., Bastrah, S., Fortin, J. & Fichtali, J. (1993). Emulsifying and foaming properties of sodium caseinate obtained from extrussion process. Milchwissenschat, 48, 303-306. Britten, M. & Lavoie, L. (1992). Foaming properties of proteins as affected by concentration. J. Food Sci., 57, 12191222. Cheftel, J. & Lorient, D. (1982). The functional properties of milk proteins and their improvement. Laif, 62, 435-483. Cunningham, F. (1976). Properties of egg white foam drainage. Poultry Sci., 55, 738-745. Draper, N. & Smith, H. (1981). Applied Regresion Analysis. Wiley, New York. Elizalde, B. E., Giaccaglia, D., Pilosof, A. M. R. & Bartholomai, G. B. (1991). Kinetics of liquid drainage from protein stabilized foams. J. Food Sci., 56, 2426. Halling, P. (1981). Protein stabilized foams and emulsions, CRC Crit. Rev. Food Sci. Nutr., 15, 1.5-203. Kinsella, J. (1984). Milk proteins physicochemical and functional properties. CRC Crit. Rev. Food Sci. Nutr., 21, 1977 204. Kitabatake, N. & Doi, E. (1987). Conformational change of hen egg ovalbumin during foam formation. J. Agric. Food Chem.. 35, 953-957. Krkoskova, D., Buzinkayova, D. & Romanova, J. (1985). The foaming properties of milk proteins. Potravinarske VedyUVTIZ, 3, 287-294. Lee, Sh.Y., Charles, M. & Ewan, Y. (1992). Structural and functional properties of caseinate and whey protein isolate as affected by temperature and pH. J. Food Sci., 57, l2lO1213. Lorient, D. (1991). Recent knowledge on the functional properties of milk proteins and related products, Lait, 71, 141. Morr, C. (1984). Production and use of milk proteins in food. Food Technol., 38, 3943. Morr, C. & Foegeding, E. A. (1990). Composition and functionality of commersial whey and milk protein concentrates and isolates. Food Technol., 44, lOCLlO4. Mutilangi, W. & Kilara, A. (1985). Functional properties of heat denaturated whey proteines of heat denatured whey proteins. II. Emulsifying and foaming properties. Milkwissenschuft, 40, 391-393. Patel, M. & Kilara, A. (1990). Studies on WPC 2. Foaming and emulsifying properties and their relationships with physicochemical properties. J. Dairy Sci., 73, 273 I-2740.
525 Z. & Kinsella,
J. E. (1987). A method
of foam formation
and stability. J.
Food Sci., 52, 1074-1077. Phillips, L., Yang, S., Schulman, W. & Kinsella, J. (1989). Effects of lisozime clupeine and sucrose on the foaming properties of WPI and P-lactoglobulin. J. Food Sci., 54, 743-746. Phillips, L. G., German, J. B., O’Neill, T. E., Foegeding, E. A., Harwalkar, V. R., Kilara, A., Lewis, B. A., Mangino, M. E., Morr, S. V., Regenstein, J. M., Smith, D. M. & Kinsella, J. E. (1990). A standardized procedure for measuring foaming properties of three proteins. J. Food Sci., 55, 1441-1444. Phillips, L., Schulman, W. & Kinsella, J. (1993). pH and heat treatment effects on foaming of WPI. J. Food Sci., 55, I I lb 1119. Richard, S. (I 979). Physicalchemical properties of whey protein foams. J. Agric. Food Chem., 27, 665-668. Risova, J., Vavreinovw, S., Vonchikova, 0. & Simunek, Z. (1989). The influence of some additives on the foaming properties of egg white. Potruvinarske Vedy-UVTIZ., 7, 183-191. Sahanekov, H., Panajotov, P., Kashkavalov, P., Stojanov, D. & Craleva, N. (1988). Razrabotvane na technologia za proizvodstvo na kiselo mleko s povisheno suho vestesrvo. Nuuch. Sesiu, 35, 15-20. Simov, J. (1993). Izuchavane na sastava i svoistvata na visokoproteinov preparat na mlechna osnova “Bulstartprotein”. Hranitelnu Promishlenost, 8, I l-l 3. Slack, A., Amundson, C. & Hill, C. (1986). Foaming and emulsifying characteristics of fractionated whey protein. J. Food Process Preservation, 10, 8 l-88. System 1360 (1970). Scientific subroutine package (360A-CM03X) Version III, IBM Technical Publications Department, New York. Trziszka, T. (1988). Physicochemical and technological characteristics of egg white foam, Dissertation, ZNAR, Wroclaw, No. 69, p. 78. Trziszka, T. (1989). The quality of egg foam depending on technological conditions. Proc. Hohenheimer Gefuige Symp., Stuttgart, Scholtgssev S., pp. 30431 I. Tsuji, S. (1987). Investigations on the physical properties of whipped egg white foams. J. Jpn. Sot. Food Sci. Technol., 34, 1377142. Vuchkov. I. & Stojanov, St. (1986). Mutemutichesko Modelirune i Optimizirane nu Technologicheski Ohekti. Tehnika, Sofia, pp. 131ll54.
(Received
25 July 1995; accepted
30 August
1996)