J Sci Food Agric 1995,68,271-277

Effects of Protein from Different Sources on the Characteristics of Sponge Cakes, Rice Cakes (Apam), Doughnuts and Frying Batters Suhaila Mohamed,* Siti Mawar Md Lajis and Norhashimah Abdul Hamid Fakulti Sains Makanan dan Bioteknologi, Universiti Pertanian Malaysia, 43400, Serdang, Selangor, Darul Ehsan, Malaysia

(Received 3 February 1994; revised version received 19 September 1994; accepted 15 December 1994)

Abstract: Sponge cakes containing total substitution of whole egg with egg yolk had the largest volume, best texture, highest moisture, colour and flavour com- pared with all other cakes. Cakes made with total substitution of other proteins had smaller volumes than the control, while those made with egg white had the lowest moisture. Cakes made with whey powder had the tenderest texture. Doughnuts made with protein other than gluten had reduced oil absorption compared with the control. Doughnuts containing whey or skimmed milk had the most desirable flavour; this may be attributed to the presence of lactose. Gluten doughnuts were most disliked because of their hard texture and pale colour. Doughnuts made with total substitution of whole egg with egg white had good texture and low oil absorption. Skimmed milk powder was best for the expansion and texture of chemically leavened rice cakes (apam), while egg white produced the best expansion for yeast-leavened rice cakes, compared with the other proteins studied. The protein that produced the most desirable textures in yeast-leavened rice cakes in order of merit were skimmed milk powder, egg white and egg yolk.

Whey, skimmed milk powder and gluten helped improve the crispiness of frying batters. Ovalbumin did not affect the crispiness but significantly reduced the oil absorption of the frying batters. Addition of proteins other than whey and ovalbumin, increased the oil absorption of frying batters.

Key words: protein, whole egg, egg white, egg yolk, gluten, soya protein isolate, skimmed milk powder, whey powder, cakes, doughnuts, moisture, volume, texture, oil absorption, colour, rice cakes (apam), frying batters.

INTRODUCTION MATERIALS AND METHODS

The use of protein in food relies heavily on its functional Fresh eggs (1 day old) were obtained from the Uni- and sensory properties which, in turn, depend on the versity farm, and some were separated into white and chemical, physical and interactive properties of proteins yolk. The proteins, eg whole eggs (14% protein), egg with other food components such as lipids and carbo- white (12% protein), egg yolk (17% protein), skimmed hydrates. The functional properties of protein include milk powder (355 g kg-' protein; Graduate Brand water and fat binding, flavour binding, foaming, emul- from F&N dairies), gluten (750 g kg-' protein; Meilun sifying, colour and textural characteristics. Food Chemicals Co Ltd), whey (120 g kg-' protein;

We attempted to study the effect of protein from dif- Damah Trading Co Ltd) and soya protein isolate ferent sources on the volume, texture, moisture content, (963 g kg-' protein) were incorporated into the ingre- colour and oil absorbing characteristics of cakes, dients for making sponge cake, rice cakes and dough- doughnuts, rice cakes (apam), and frying batters. nuts. The amounts of protein to be added into the

sponge cake were calculated so as to contain the equiv- * To whom correspondence should be addressed. alent of 21 g protein in the cake formulation and 28 g

J Sci Food Agric 0022-5142/95/%09.00 0 1995 SCI. Printed in Great Britain 27 1

272 S Mohamed, S M M Lajis, N A Hamid

in the doughnut formulation. For rice cakes and frying batters, the contents of the protein substances were varied.

Sponge cake preparation

Whole egg (150 g, or the equivalent amount (based on protein content, with no adjustment for the moisture content of the other proton sources) of the other pro- teinaceous substances), 100 g sugar and 8 g mono- and diglyceride emulsifier (Quick 75") were weighed and mixed in a Kenwood mixer at the minimum speed for 2 min. Wheat flour (100 g) and 4 g baking powder (Royal" containing sodium acid pyrophospate and sodium bicarbonate) were added and mixed at the minimum speed for another 2 min. Water (35 g) was then added and the mixture mixed at the maximum speed for 1 min. Liquid margarine (40 g) (Tiger brand from Lever Brothers Co Ltd) was added into the batter and the mixture was baked at 180°C for 35-40 min, then cooled to room temperature.

Doughnut preparation

Wheat flour (500 g), 50 g sugar, 200 g whole egg or the equivalent amount of other protein, 250 g water, 4 g salt, 10 g bread improver (100 M" which is a mixture of KBrO, , ascorbic acid, L-cysteine, fungi amylase, CaSO, and starch fillers, from Federal Flour Mills Co Ltd) and 7.5 g instant dried yeast (Mauri Fermentation Co Ltd) were mixed in a bowl mixer of 2 min. Doughfat (50 g) (Lazat Brand from Felda Refinery Corporation) were then added and the dough mixed for another 8 min. The dough was formed into a ball, proved for 30 min, rolled and cut into shape, then proved for a further 10 min before being fried at 165°C for 5 min.

Preparation of chemically leavened or yeast leavened rice cakes

Rice flour (100 g), (53.1 g) sugar, (97.34 g) water and 8.85 g leavening agents (Fresh yeast or Royal" baking powder) were mixed thoroughly with 0-15 g of the appropriate protein. When yeast was used as the leav- ening agent, the mixture was left to ferment for 3.5 h. The batter was steamed for 25 f 5 min.

Preparation of frying batters

Rice flour was mixed into batters by the addition of measured amounts of 16 g litre-' salt solution until the viscosity was approximately 2000 CP s. Firm bananas were then sliced lengthwise, dipped in the batter and fried in RBD (refined, bleached and deodorised) palm olein (Labour Brand) for 5 k 1 min at 185°C. Effects of

powdered ovalbumin (Sigma) and other proteins on the crispiness, and oil absorption of the fried batters were determined.

Volumes of sponge cakes and doughnuts were deter- mined by volume displacement of mung beans in a large container large enough to accommodate the product. Texture (firmness) was assessed by an Instron Universal testing machine (Model 1140, Germany) with a com- pression anvil attachment (diameter 3.5 mm) at a cross- head speed of 5 cm min- ' to produce 25% deformation from the height of the cake or doughnut. For rice cakes and frying batters the yield stress (maximum force required to break the product) was taken as the value for the texture. Moistures were determined by drying in a 105°C oven to constant weight (AOAC 1980). Oil absorption by doughnuts and frying batters during frying were determined by soxhlet extraction (AOAC 1980). Colour was determined using the Hunter Lab tri- stimulus colorimeter. Sensory evaluation was done by 12 panellists using Ranking test for colour, flavour, uni- formity and texture while a 1-9 hedonic scale was used to evaluate the overall acceptability (9-like extremely). Data were statistically analysed by ANOVA for signifi- cant differences at the 5% level. Bars shown in the figures indicate one standard deviation.

RESULTS AND DISCUSSION

Sponge cakes volume

In the 'all-in' sponge cake process, air stabilisation is achieved by the addition of a lipid surfactant. Aeration by egg protein/lipoprotein during whisking is no longer crucial, yet proteins may still play an interactive role with the lipid surfactants. Total substitution of whole egg with egg yolk resulted in a significant volume increase of 11.1 YO compared with the control (Table 1). Total substitution of whole egg with egg white, gluten or skimmed milk powder resulted in a 27 f 1% decrease in cake volume. Total substitution of whole egg with soya protein isolate and whey reduced the cake volume by 34 and 5 1 %, respectively. Egg yolk con- tained 420 g kg-' hydrophobic amino acids and 70- 100 g kg-' lecithin. Lecithins behaved as an emulsifier which increased the sponge cake volume and shelf-life (See1 ef a1 1935; Tamstorf et a1 1985). The beating action during cake making allows hydration of the dry components and entrainment of air. The initially large air bubbles incorporated, and stabilised by surfactants and subsequently distended by the mixing action, into an increased number of smaller bubbles. Their integrity depends upon adequate surfactant being available for surface coverage and stability (Davies 1985). Table 1 shows that the batter density of control cakes is lightest followed by that containing egg yolk, skimmed milk powder and finally soya protein. A weak correlation

Efects of protein from diferent sources on foodstuffs 273

TABLE 1 Characteristics of cakes and doughnuts made of proteins from different sources"

Source Volume moisture Firmness Batter density Colour Sensory evaluation (4 ( g k g - ' ) (kgforce) ( g litre-') hedonic source

L a b

Cakes Control 1005 b

(Total (100%) substitution Egg white 739 e Egg Yolk 1113 a Gluten 735 e Soya protein 664 f Skimmed milk 715 e Whey 485 h

Partial (50%) substitution Egg white 704 e Egg Yolk 936 c Gluten 915 c Soya protein 915 c Skimmed milk 837 d Whey 575 g

Doughnuts Control 143 a Total (100%) substitution Egg white 40 b Egg Yolk 28 b Gluten 38 b Soya protein 60 b Skimmed milk 46 b Whey 29 b

Partial (50%) substitution Egg white 40 b Egg Yolk 60 b Gluten 34 b Soya protein 39 b Skimmed milk 36 b Whey 50 b

690 bc 0.76 ab 511 a 51.8 ab 11.1 ab

600 f 1.15 a 760a 0.81 ab 690bc 1.21 a 680cd 1.09 ab 730 ab 0.90ab 660cde 0.69 ab

643 cd 55.9 ab 13-1 ab 570 b 60.6 a 6-3 a N D ~ 62.0 a 8.5 a 853 e 624 a 8-0 a

n.d 22.2 e 7.5 e 680 d 35.8 cd 8-4 cd

630 ef 0.46 b 750a 0.43 b 670 cde 0.59 b 640 def 0.46 b 670 cde 0.45 b 700 bc 0.47 b

663 d 54.9 ab 12.2 ab 550 ab 56.0 ab 9.6 abcd ND 55.9 ab 12.2 ab 674 d 544 ab 12.2 ab

n.d 24.6 de 6.4 d 614 c 43.9 bc 8.0 cd

Oil absorption (%)

6 5 0 e 0.98 de 15.3 ab 57.2 g 11.7 ab

650 e 1.17 cd 700 abc 2.62 ab 670 cde 3.01 a 670 de 1.56 c 670de 2.33 b 700ab 2.48 b

11.2 d 58.5 d 11.0 cd 12.9 bcd 53.5 k 11.5 bc

11.3 d 66.2 c 8.8 f 15.8 a 56.6 h 9.7 ef

11.0 d 58.3 e 8.9 f 12.0 cd 47.1 1 13.3 a

710 ab 0.98 de 680 bcde 0.62 ef 660 de 0.89 def 670 de 0.51 f 680 bcd 0.71 ef 720 a 0.78 def

14.5 abc 57.9 f 10.8 cde 13.5 abcd 66.2 b 10.1 de 13.8 abcd 70.1 a 1.7 g 14.4 abc 55.6 j 11.6 bc 14.4 abc 56.4 i 12.4 ab 14.4 abc 60.2 c 11.0 cd

18.8 b 7.25 abc

25.0 a 6.00 cd 22-0 ab 8.00 a 25.9 a 4.50 ef 24.2 ab 3.25 f

21.9 ab 6.6 c 6.50 bcd

21.9 ab 5.75 de 18.8 b 7.58 ab 23.6 ab 6.25 cd 22.3 ab 6.42 bcd 9.1 c 6.33 bcd 8.8 c 3.58 f

20.7 e 6.08 bc

21.9 d 7.42 ab 19.7 g 5.25 cd 19.9 g 3.17 e 21.8 d 4.42 de 26.5 f 6.00 bc 16.8 h 6.00 bc

22.5 c 4.92 cd 23.4 b 6.25 bc 15.9 j 3.17 e 21.2 e 5.42 cd 22.4 c 7.17 ab 24.6 a 7.83 a

~~

Values followed by the same letters are not significantly different at 5% level for each product. ND, not determined.

(r2 < 0-6) was found between cake batter density (which can be used as an indication of air incorporated) and the final cake volume in these cake formulations. Amongst the proteins studied, egg white is known to have the best foaming ability (Halling 1981; Cheftel et a1 1985) due to the presence of basic proteins, ie lysozymes, ovoglobulins E, and E, (Davies 1985; Hart 1986). Aqueous solutions of egg white proteins reduce the surface tension of water, but their ability to form/ stabilise foams differed considerably under different conditions (Davies 1985). High-density lipoprotein (HDL) granule of yolk alone; yolk lipids alone or in combination with yolk protein and a mixture of

lipovitellin + livetins, gave no air incorporation into cake batter. Yolk protein or yolk plasma (low-density lipoprotein (LDL)) alone gave air incorporation to cake batter but a low cake volume due to cake collapse. Yolk plasma and egg white proteins play a major role in the formation of foams, whereas the H D L granules inhibit aeration (even by egg white) but assist in stabilising and retaining the air during baking (Davies 1985). This study confirms that the final cake volume was more affected by the emulsifying capacity and foam stabilising ability of egg yolk than the foaming ability of the egg white. Amongst the milk proteins, p-casein has detergent-type properties due to the asymmetrical

274 S Mohamed, S M M Lajis, N A Hamid

arrangement of hydrophobic and hydrophilic residues. 8-Casein had good foamability by reducing surface tension, whereas globular whey proteins were relatively resistant to surface denaturation and gave poor yet stable foams (Davies 1985). Omission of gluten (use of wheat starch instead of wheat flour) resulted in a high volume cake that never collapsed (Davies 1985).

Partial (50%) substitution of the whole egg with other proteins reduced the volume decrease of the cakes as shown in Table 1.

Sponge cake moisture

Cakes containing 50-100% substitution of whole egg with egg yolk had the highest moisture content (significant 5% increase) even when compared with the control, while cakes containing 100% substitution with egg white had the lowest moisture content (Table 1). Substitution of 100% with skimmed milk also produced high-moisture cakes. Again it appears that the emulsify- ing capacity of egg yolk plays a very important role in keeping the cake moist. This study indicated that the use of egg yolk is recommended for high-moisture cakes, while the use of egg white is recommended for products that require a low-moisture content for extended storage life, eg fat-free sponge cakes and biscuits. The effect of partial (50%) substitution of the whole egg with other proteins on cake moisture are shown in Table 1.

Sponge cake texture

The texture of cakes prepared using different proteins was not significantly different from the control. The firmest cakes were made using egg white and gluten while the tenderest cake was made from whey powder (Table 1). The tenderness of cakes made with whey powder could be due to its high lactose content since the texture of cakes was related to its sugar and mois- ture content (Brown 1984). Texture is also likely to be related to the cake volume and crumb density. Kamat et a1 (1976) suggested that the tenderness of cakes in the presence of egg yolk are due to the stabilising and binding effect of the lipoproteins on the fat which ensured their even distribution in the cakes during baking. Partial substitution of whole eggs with other proteins seemed to result in tender cakes insignificantly different from the control.

Cakes made with egg yolk and whey had significantly higher ‘a’ values indicating a reddish or more orange colour tone. Cakes made with 100% egg white and gluten had a significantly higher ‘b’ value, due to the yellowness or paler tone than the control, while cakes made with skimmed milk powder had significantly lower ‘b‘ values.

Sensory evaluation of sponge cake

Hedonic scores showed that cakes made with egg white, egg yolk, and skimmed milk powder were acceptable to the panellists, the cakes made with egg yolk getting the highest scores. Cakes made with gluten, soya protein isolate or whey were unacceptable to the panellists either due to their taste, colour, texture or combinations of these three factors. Hedonic scores for overall accept- ability were positively correlated to cake volume (rZ = 0.72).

Doughnut volume

All the doughnuts made with partial or total substitut- ion of whole egg with other protein had less than half the volume of the control. This may indicate that whole egg is an excellent protein/amino acid source for the growth and reproduction of the yeast, which produces the carbon dioxide to leaven the dough. This conclusion was made based on the fact that chemically leavened cakes made with total substitution with egg yolk had bigger volumes than cakes made with whole eggs, while cakes made with partial substitution with egg yolk, gluten or soya protein had almost the same volume as cakes made with whole eggs (Table 1).

Doughnut moisture

Doughnuts made with egg yolk and whey had a signifi- cantly higher moisture content than the control. The high moisture content in the egg yolk doughnuts was probably due to the emulsifying capacity of the yolk as in cake products. The high moisture content in whey doughnuts was probably due to their high lactose content, which may induce the metabolic breakdown of the lactose by the yeast to produce a lot of ethanol in the dough which, in turn, evaporated during the mois- ture determination and was included as ‘moisture’.

Doughnut texture Sponge cake colour (L, a and b values)

Only cakes made with whey powder and skimmed milk powder were significantly darker than the control and this was most probably due to the high lactose contents of these products resulting in more Maillard browning.

All the doughnuts which were made with other proteins in place of whole egg had a significantly firmer texture than the control, the firmest being those made with gluten and egg yolk. The firmness of gluten doughnuts was to be expected since it results in dense gluten

Eflects of protein from diferent sources on foodstufs 275

protein network in the dough. The firmness of the other protein doughnuts are related to the decreased volume of the doughnuts. Partial (50%) substitution of whole egg with other proteins resulted in doughnuts having textures equivalent to or softer than that of the control.

Doughnut oil absorption

The use of egg white, soya protein isolate, skimmed milk powder or whey powder instead of whole egg, resulted in fried doughnuts with reduced fat content. This can partly be due to the low (if any) fat content of these proteins and partly due to low oil absorption during frying. Excess oil absorption will reduce the acceptability as well as the storage life (oxidative rancidity) of the product. The decrease in oil absorption may be related to the rate of denaturation of the protein which will inhibit the oil from entering the rest of the dough.

Doughnut colour

Total substitution of whole egg with whey, gluten or egg yolk resulted in a darker coloured doughnut than the control. Partial substitution of these proteins or total substitution with egg white, soya protein isolate, or skimmed milk resulted in a lighter product. Gluten, soya protein isolate and skimmed milk powder dough- nuts had a lower 'a' value (redness) than the control. All the protein-substituted doughnuts had higher 'b' value (yellowness) than the control except for egg yolk, gluten and whey doughnuts.

Sensory evaluation of the doughnuts

All doughnuts made using total and partial substitution with other proteins had acceptable colour, except for partially substituted gluten doughnuts which were too pale in colour. The colour of whole egg and egg white doughnuts were especially attractive. The texture of whole egg doughnuts and whey doughnuts were uniform and preferred over the other doughnuts. Doughnuts containing added gluten were least liked because of their taste and texture. All the other types of doughnuts had acceptable taste and flavour, and those containing skimmed milk powder or whey were espe- cially preferred, probably due to the presence of lactose in these products.

Many studies on the inclusion of milk proteins in bread formulations, revealed that whey protein can have dramatic effects on dough rheology and bread volume/crumb texture. The cysteine and cystine resi- dues of whey proteins can take part in thiol-disulphide rearrangements and result in dough softening and weakening arising from the effects on the gluten (Davies 1985).

Rice cakes (aparn)

Amongst the proteins studied skimmed milk powder was best for the expansion and texture of chemically leavened rice cakes (Fig l a and lb). Soya protein decreased the expansion and softness of both the chemi- cal and yeast leavened rice cakes. Addition of less than 20 g kg-' wheat gluten to the rice cake improved the expansion of chemically leavened rice cake but decreased their softness (Fig lc and Id). Gluten decreased the expansion and softness of yeast leavened rice cakes. Whey powder drastically decreased the expansion and softness of yeast leavened rice cakes, although it had little effect on the expansion and texture of chemically leavened ones. Egg yolk had little effect on the expansion and texture of both chemically leav- ened or yeast leavened rice cakes. Egg white produced the best expansion for yeast leavened rice cakes com- pared with the other proteins studied. This was prob- ably because yeast thrived best on egg white protein. The proteins that produced the most desirable textures in yeast-leavened rice cakes in order of merit were as follows: skimmed milk powder, egg white and egg yolk. Soya protein, whey powder and wheat gluten decreased the desirable properties of both types of rice cakes, hence are considered unsuitable ingredients for addition in rice cakes.

Frying batters

The lower the force required to break the batter the more crispy/brittle was the batter. Since the fried batters were brittle and had almost similar compositions, the differences the strain were very small compared with the stress (force). A hardness value of much below or above the range of 0.9-1.9 was undesirable because it indi- cates that the fried batter was no longer crispy and brittle but was either too soft or too tough.

Protein in general has the ability to hydrate and hold water, whilst many proteins have both hydrophilic and lipophilic side chains that can reduce the oil/water surface tension. Addition of ovalbumin up to 40 g kg- ' improved crispiness, colour and also reduced oil absorption of the fried batter. Addition of certain pro- teins like gluten, milk and whey, improved crispiness. The addition of protein may reduce the polysaccharide- polysaccharide interaction and improve crispiness. Skimmed milk, whey and gluten improved crispiness but did not increase oil absorption tremendously. Addi- tion of egg yolk increased both the oil absorption and hardness (toughness) of the fried batter. Egg yolk con- tains about 330 g kg-' lipid, 480 g kg-' water, 10 g kg- ' carbohydrate and 160 g kg-' protein (Parkinson 1966) whereby most of the protein are in the form of lipoproteins (lipovitellins) and phosphoproteins

276 S Mohamed, S M M Lajis, N A Hamid

0 0 2 4 0 8

9b protein added

a: E x p r n t l o n o f c h r r n l c r l l y I r r v r n r d r l c r crker

c: T r x t u r e o f a h r m l c r l l y I r r v e n r d r l o r crker

hrrdnrrr (KO)

2 4 0 0

% protein added

11L rxpanrion 140r I 1

1 0 2 4 0 8

96 protein added

b: r x p r n r l o n 0 1 y r r r t I r r v r n r d r l c r c r k r r

d: Texturr 0 1 y e a r t - l e a v e n e d r l c r crker

hardners (KO) 20

0 2 4 0 8

% protein added

Fig 1. Effect of various proteins on the texture and volume of steamed rice cakes.

(phosvitin) which can reduce the surface tension the frying batters, The decrease in oil absorption of between oil and water and result in greater oil absorp- ovalbumin containing batters is probably because of the tion. Addition of excess protein of any kind will reduce hydrophilic or lipophobic nature of ovalbumin (Kato the crispiness because more oil was emulsified into the and Nakai 1980). In the presence of protein, browning fried batter resulting in an oily and soft product. Figure of the fried dough occurs faster because of the presence 2a shows that addition of the other proteins (except or more amine groups to undergo the Maillard reac- probably whey powder) increased the oil absorption of tion.

S M o h a m e d , S M M Laj i s , N A Hamid 277

1 -

0 ' I I I I I

0 2 4 8 8 10 15

% protein added

(b) l b oil abrorbrd

10' - egg yolk + glutan * rklmmed milk

-0. whey * ovrlbumln % protein added

Fig 2. Effect of various proteins on the crispness and oil absorption of fried batters.

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