Baking soda or baking powder is the most common carbon dioxide (CO₂) source and is used to obtain aerated cakes, for example. Mixing the batter under CO₂ pressure is an alternative to using baking powder.

Baking powder is usually made of a blend of an alkaline agent that generates CO₂ and of an acidic counterpart to neutralize the alkaline agent. The neutralization yields the release of CO₂ mainly during baking. The removal of baking powder seems to be a ‘hot topic’ for the baking industry, driven by the trend to reduce certain ingredients, including salt (clean-label).

A prototype mixer was used with air and CO₂ applied with gauge pressures of 0.3 and 0.5 bar. CO₂ pressure-mixing yielded the best results regarding cake-specific volume (2.5 mL/g or 86% of the specific volume of the reference cake with baking powder) compared to air pressure. This result was explained by the solubilization of CO₂ in the liquid phase of the batter during mixing and its release during baking.  

Bsking powder (BP) releases carbon dioxide (CO₂) during the mixing and baking process; it is made of two components, an alkaline component, which is usually sodium bicarbonate and an acidic component usually made of sodium pyrophosphate. The acidic component neutralizes the alkaline component resulting in the release of CO₂. BP acts usually at two stages, with a double-action; CO₂ is first released during mixing thanks to a partial neutralization of sodium bicarbonate, which contributes to the stabilization of the gas nuclei embedded in the batter during mixing. In the second stage, the neutralization is finalized thanks to the full availability of the acidic component. Mixing the batter while applying an overpressure in the headspace of the mixer can be considered as an alternative to BP; the use of CO₂ is relevant since the solubilization of this gas can be expected during mixing. This strategy has been mainly investigated in the case of bread dough, cookie dough and in cake or sponge cake batter. This study aimed to show the impact of the replacement of the BP by a process of mixing under pressure, on certain properties of the cake and, in particular, the sensory experience.

Materials and methods

The ingredients used in the preparation of batter were wheat flour (15.2% water content, 10.5% protein, 1.3% fat, 68.1% starch and 0.4% ash on wb; Giraudineau, France), whole liquid egg (77.5% water content, 0.8% minerals, 12.1% protein, 10.2% fat and 0.8% carbohydrates on wb; Transgourmet, France), saccharose of caster sugar type (Béghin-Say, Tereos, France), fat that was an anhydrous blend of 70% vegetable oil (rapeseed oil) and 30% anhydrous milk fat (butter) supplied by Corman (Belgium), sodium bicarbonate (Brenntag, Germany) and SAPP 10 (sodium acid pyrophosphate, Budenheim, Germany).

There were two recipes (i) with BP and (ii) without BP. The recipes are given in Table 1.

Table 1: Composition of the control cake batter (with BP) and cake batter without BP

Batter preparation was a multistage mixing method. It consists of a creaming stage where fat and sugar are first creamed together. Then, liquid egg was added followed by flour with or without BP. The gases considered for mixing were air and CO₂ at two levels of pressure (i) 0.3 bar or (ii) 0.5 bar above atmospheric pressure. The pressure levels were chosen according to the maximal pressure of the mixer.

Four types of cakes were studied:

• the reference: with BP and mixed at atmospheric pressure, “Ref”
• the negative control: without BP and mixed at atmospheric pressure, “Neg”
• Air cakes: without BP and mixed with air ovepressure at 0.3 or 0.5 bar above atmospheric pressure, “Air 300” and “Air 500”
• CO₂ cakes: without BP and mixed with air ovepressure at 0.3 or 0.5 bar above atmospheric pressure, “CO₂300” and “CO₂ 500”.

Baking molds (dimensions 170*78*80 mm) were filled with 300g of batter; they were directly baked at 180°C for 30 minutes in a deck oven (MIWE condo deck oven, Germany) to prevent batter degassing. After baking, the cakes were removed from the molds and were cooled at room temperature for two hours. Then, the cakes were placed in a sealed plastic bag until analysis tests.

Sensorial analysis

In order to evaluate the general appreciation of the product and the preferences for some of its attributes, two tests were performed: a hedonic scoring test coupled with a Just About Right (JAR) test. Only three formulations were compared: ‘Ref’ with BP, ‘Neg’ without BP and ‘CO₂ 300’ without BP and CO₂ overpressure mixing. The hedonic test consists of evaluating the appreciation of the cakes by consumers, a hedonic rating is performed using a nine-point rating scale ranging from ‘very unpleasant’ to ‘very pleasant’ and ‘neither pleasant nor unpleasant’. The maximum sum corresponds to the sum of the scores if all the judges had given the maximum score of nine.

The JAR test evaluates the degree of satisfaction with several product attributes. In our case, the attributes evaluated were (i) the browning of the crust, (ii) the porosity of the crumb, (iii) the hardness of the crumb, (iv) the sweetness, (v) grilled aroma and (vi) the overall aromatic intensity. The evaluation was based on five degrees of satisfaction ranging from ‘not really enough’ to ‘just right’ to ‘really too much’. The tests took place over two consecutive days in the ONIRIS school sensory analysis rooms which meet the NF EN ISO 8589 (2010) standard. The room contains 30 individual boxes, the temperature and luminosity are controlled. The 60 judges (standard NF EN ISO 11136 -2017) performed the tests in one session. The judges were recruited from within the ONIRIS staff voluntarily and were mostly ONIRIS students. For both tests, the samples were presented in identical cardboard boxes. The sample numbers were determined by the FIZZ sensory analysis software (Biosystèmes, France). Each formulation had a distinct number and these numbers were different between the two tests. The order of the sample presentation for each judge was determined with the FIZZ software in order to ensure a balanced order of presentation of the samples. A questionnaire in a paper format combining the two tests was given to each judge at the beginning of the session with the information sheet and the consent form.

Results

The specific volume of the cakes was compared between the different formulations.

As in our previous study, Palier et al. (2022), the reference cake ‘Ref’, with BP exhibited the greatest specific volume (2.9 ± 0.1 mL/g). The ‘Air 300’ and ‘Air 500’ cakes were similar to the ‘Neg’ one (2.1. ± 0.1 mL/g). However, mixing under CO₂ pressure improved the specific volume of the cake by 19% compared to the ‘Neg’ cake without BP (2.5 mL/g), or corresponded to 86% of the specific volume of Ref’ cake with baking powder. There was no significant difference (p> 0.05) between the two pressure levels (0.3 or 0.5 bar). In Palier et al. (2022) the hypothesis formulated was that the release of CO₂ during baking improved the volume. Moreover, CO₂ might be kept in batter until baking and released at the right time during baking, just before the stiffening of the structure (Hesso, 2014; Godefroidt et al., 2021). In conclusion, overpressure mixing with CO₂ allows to increase the specific volume of the cakes without BP. However, their specific volume corresponded to 86% of one of the ‘Ref’ cake with baking powder.

Pictures of the top and of a slice of the cakes have been taken in order to compare visually the crust and the crumb of each cake.

The cake ‘Ref’ with BP was flat on the top and ‘Air’ ones had a concave shape. Both experienced a collapsing phenomenon.  On the contrary, the ‘CO₂’ and ‘Neg’ cakes were well bombed on the top. Donovan (1977) showed that to reach an optimal volume and a homogeneous texture and structure, the maximum CO₂ release must take place in the same time interval as the starch gelatinization and protein denaturation corresponding to the stiffening of the structure, also called batter-crumb transition. Indeed, the rapid stabilization of the bubbles during the rigidification avoids the collapse of the structure. Moreover, during cake cooling the gases contract or condense. The degree of starch gelatinization and protein aggregation and particularly proteins determine the strength of the crumb structure and thus the cake’s ability to collapse (Gough et al., 1978; Guy and Pithawala, 1981) by contributing to stronger cell walls (Wilderjans et al., 2008).

In the case of cakes mixed with air overpressure, there was no CO₂ released and the crumb was not completely bakd as can be seen in figure 3. Thus, there was less expansion and the breakdown could be explained by undercooking which resulted in a weaker crumb structure. The flat shape of the top of the cake ‘Ref’ could be due to the kinetics of CO₂ release during baking. The maximum of CO₂ release might be released after the stiffening of the structure and therefore, this additional gas could not be retained in the structure and thus led to a breakdown of the structure. The crust of the cakes without BP and especially ‘Neg’ and ‘Air’ ones was lighter than the crust of the ‘Ref’ cake with BP. In our previous study (Palier & al., 2022), we have explained this difference in lightness by batter pH. In fact, Maillard reactions are influenced by pH; the more acidic the pH, the less Maillard reactions occur and vice versa (Fox & al., 1983; Raville, 1987;  Susan Mathew & al., 2019). Cakes with BP ‘Ref’ were more basic than the others, most certainly because of an incomplete neutralization reaction. Even if they had the same pH, the crust of ‘CO₂’ cakes was darker than the other cakes without BP, probably because they were completely baked, and thus had a higher water activity that diluted the Maillard reaction (Fox & al., 1983).

The image above shows the pictures of the central slice of the different cakes studied. In these pictures, it is possible to differentiate the height of the cakes and the alveolar structure of the crumb of the different cake formulations. The ‘Ref’ cake with BP was the highest and had a coarser crumb, compared with the cakes without BP. The crumb of cakes without BP was denser and more compact. As mentioned before, the crumb of the ‘Air’ and ‘Neg’ cakes had a problem with underbaking. They were also smaller than ‘Ref’ and ‘CO₂’ cakes. In terms of height, the ‘CO₂’ cakes were closer to the ‘Ref’ cake with BP. As a conclusion, cakes without BP were smaller than the ones with BP. They were also undercooked. However, the height of ‘CO₂’ cakes was close to the ‘Ref’ cake with BP. ‘CO₂’ cakes had also a better shape: they were well bombed on the top while the others were flat or collapsed.

Sensorial analysis

The total score is the addition of each score for each cake from all panelists. It corresponds to a linking score. Thus, the higher the score, the more the cake was appreciated by the panel. Overall, the cakes were all liked: the total score value for each cake was above half the maximum total sum (60 judges*9 max note= 540; 540/2= 270). The cake ‘CO₂ 300’ was the most liked by the panelists, followed by the ‘Neg’ cake (negative control) and finally, the ‘Ref’ cake (positive control).

In order to understand the optimal degree of preference for several criteria regarding this cake, a criteria analysis on a JAR scale was performed. The cakes were divided into two distinct groups for crust browning (a). The BP and NBP cakes were too light for more than half of the panelists (60% of ‘not enough’ and ‘really not enough’). The CO₂ 300 cake got the most ‘JAR = just right’ (57%). For the ‘Neg’ cakes, the result was in agreement with the instrumental measurement of crust color (part 3.2.- figure 2), but not for ‘Ref’ cake. The grilled aroma (b) was perceived in a similar way for all cakes: almost half of the panel found it just right and the other half, not pronounced enough. Overall, the texture (d) of the cakes was appreciated by at least half of the panelists for all cakes except the ‘Neg’ cake; more than half of the panel (58%) found it too hard or not soft enough. These results are confirmed by instrumental measurement (TPA double compression test), where the NBP cake is the hardest (Palier et al., 2022).

Texture was also linked to the result of crumb porosity. The majority of the panel (80%) rated the ‘Neg’ cake had not enough aerated. The sweetness (e) was considered ‘just right’ by the majority of the panel for ‘Ref’ cakes. On the contrary, the ‘Neg’ and ‘CO₂ 300’ cakes were considered too sweet by almost half of the consumers. The perception of sweetness seems to be correlated with the compactness of the crumb: the less porosity the cake is, the more intense the sweetness is. The overall aromatic intensity of the ‘Neg’ cakes was too intense for 20% of the pane,l while for half of the panel, the ‘Ref’ cake was not intense enough. This was certainly due to the baking of the cake and the porosity of the crumb: the crumb was not completely baked (figure 4) and the cake was denser than the others (figure 1). Moreover, this cake was considered too sweet by almost half of the panel. On the other hand, the ‘CO₂ 300’ cake, which was also perceived as too sweet, was the one that had an overall aromatic intensity that was the most appreciated (58% of ‘just right’).  As a conclusion, the removal of BP did not decrease the overall appreciation of the cakes. The cakes were all globally appreciated. Thus, it is possible to reduce the sodium by mixing in CO₂ overpressure without negatively impacting the appreciation. It seems that it is the whole of the attributes related to the texture, the porosity, the color, or the taste, which play on the appreciation of the cakes. 

Conclusion

The aim of this study was to show the impact of the replacement of the baking powder by a process of mixing under pressure, on certain properties of the cake and, in particular, on the sensory experience. In our previous study (Palier & al., 2022), we have highlighted that overpressure mixing with CO₂ allows for replacing the BP action and obtaining more voluminous cakes. In this study, we have shown that the removal of BP modified crust lightness and cake alveolar structure. However, on the contrary, these differences did not impact sensory appreciation. Cakes without BP were more compact and thus sweetness was higher. They were more appreciated than cake with baking powder which was more voluminous and with a coarser cake.

Authors :

Juliette Palier ^{a, b, c}, Catherine Loisel ^{b, c}, Luc Guihard ^b,c, Cécile Rannou ^{b, c}, Alain Le- Bail ^{b, c}, Patricia Le-Bail ^{a, *}

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^a UR1268, Biopolymères, Interactions, Assemblages, INRAE, F-44300 Nantes, France

^b Oniris, UMR 6144 GEPEA CNRS, Nantes, F-44307, France 

^c CNRS, Nantes, F-44307, France

*Corresponding author at: INRAE, UR 1268, Impasse Thérèse Bertrand-Fontaine, BP 71627, F- 44316 Nantes Cedex 3, France. E-mail adress : patricia.le-bail@inrae.fr (P. Le-Bail)

The full article, including references, was published in Baking+Biscuit International, issue 3 – 2022.

Lead photo: Caramelle Gastronomia (Pexels)