Effect of high pressure processing on structural and functional properties of canned aquafaba

Abstract

Aquafaba is chickpea cooking water. It has great functional properties since it consists of starch and protein. High pressure processing (HPP) is proven to modify the functionality of starch by keeping its integrity. The objective of this study was to check if HPP can improve structural and functional properties of canned aquafaba. HPP treatments were given at pressure levels: 200, 259, 400, 542, and 600 MPa with holding time between 5 and 30 min. After HPP, part of the samples was freeze dried for crystallinity and particle size analysis and the fresh part used for rheological, functional properties, and colour. HPP enhanced functional properties, mostly foaming stability which increased from 50.5 to 67 min. Rheological properties were enhanced mainly for consistency coefficient from 0.6 to 1.4 Pa.s. Crystallinity dropped slightly compared to control sample, while the colour got brighter, from 27.5 to 49.6. Processing time and pressure intensity did not contribute in increasing particle size. The combination of high intensity and long pressurization time resulted the smallest particle size (90 µm).

Introduction

People are moving towards vegan foods in order to have healthy life, follow some religious restrictions, and due to allergies such as eggs, mainly albumin in egg white (Aslan and Ertaş, 2020). Accordingly, we have noticed huge increase in plant-based-products through food industries to have some vegan choices of cakes, mayonnaise, meringues, salad dressings, and more (He et al., 2021; Jarpa-Parra et al., 2017; Nguyen et al., 2021).

Chickpeas are the 3rd produced and processed pulse worldwide (Bashir and Aggarwal, 2017; Joshi and Parthasarathy, 2016) and from that point we can imagine how many tons are used every year for only hummus production. While producing hummus, there is a huge waste which is the water residue from cooked chickpeas that is called “aquafaba”.

Recently, aquafaba has been scientifically recognized as an egg white replacer for its great functionality and used in many vegan products such as eggless cakes and whip cream, vegan mayonnaise, chocolate mousses and meringues (Aslan and Ertaş, 2020; He et al., 2021; Mustafa et al., 2018; Nguyen et al., 2021; Raikos et al., 2020). It has been used as fresh from cooked chickpeas or from canned chickpeas. Some studies were conducted on this ingredient regarding discovering its properties and trying to use it in some applications. Only three studies tried to enhance aquafaba properties through non thermal food processing techniques, high pressure and ultrasound (Alsalman and Ramaswamy, 2021a, 2021b; Meurer et al., 2020). Enhancing functional and structural properties is important for food industries to have better desserts produced from aquafaba. Rheological properties need to be discovered and enhanced as well in order to have easy flow in the food industries pipes.

No study was conducted to enhance canned aquafaba properties, although now is the era of speed and everybody is busy to cook. People tend to use ready-to-eat-food or eat canned food. A novel non thermal processing which is high pressure processing (HPP) is used in this study since it is known of its effects to enhance many food properties including functional, rheological, and structural properties (Ahmed and Thomas, 2019; Ahmed et al., 2018; Ahmed et al., 2017; Alsalman and Ramaswamy, 2021a; Alsalman and Ramaswamy, 2021b). As a result, the objective of the study is discovering the ability to enhance functional, rheological, and structural properties of aquafaba from cans through HPP using response surface experimental design and compare the results to control sample (unprocessed).

Materials and methods

Materials and sample preparation

Kabuli chickpea cans were purchased from local market and stored at room temperature (25 ˚C) for experimental use with a time span less than one week. Aquafaba was drained and separated from chickpea cans, placed in polyethylene bags and sealed for high pressure processing (HPP).

High pressure processing (HPP)

HPP was carried out using a laboratory scale HP equipment (QFP 2 L-700 Avure Technologies, OH, USA), with a pressure vessel of 100 mm in diameter and 254 mm in height. The average pressurization rate was 20 s/100 MPa and decompression time was < 5 s. The initial temperature of water was 20 °C and reached to 26 °C at 600 MPa due to adiabatic heating. Samples were processed at pressures 200, 259, 400, 542, and 600 MPa for specific times 5, 9, 18, 26, and 30 min according to RSM central composite design. Untreated sample was considered as a control. After HPP, some samples, liquid aquafaba, were directly taken for foaming and emulsion properties, rheological properties and colour analysis and the rest were lyophilized for crystallinity and particle size analysis. All test samples were analysed in triplicate for various output parameters except when stated otherwise.

Rheological measurements

Steady shear flow was carried out using a Discovery Hybrid Rheometer HR-3 (TA Instruments, New Castle, DE). Processed samples and control sample were placed in a 1000-µm gap between two stainless steel parallel plates (plate diameter 40 mm). Tests were carried out based on application of a single cycle upward ramping shear rate test in which the shear rate was increased from 0.1 s⁻¹ to 100 s⁻¹ in 14 min. Flow parameters were evaluated based on Hershel-Bulkley model and the model parameters were related to process variables. Samples were conducted in duplicates.

Foaming and emulsion properties

Foaming capacity of aquafaba was measured using the procedure detailed by Shim et al. (2018) with some modifications. 100 mL of aquafaba solution was placed in a graduated cylinder and whipped using a hand mixer at maximum speed for 2 min. Foaming capacity was expressed as percentage by using the following equation:

$$Foamingcapacity\left(\%\right)=\frac{V_f-V_i}{\mathit{Vi}}\times 100$$ 1

where V_f and V_i represented the final and initial volume.

Foam stability of aquafaba was measured by allowing the foam to stand in the graduated cylinder over time that was recorded as the bubbles broke down and the level decreased.

Emulsion capacity of aquafaba was determined as described by Rasekh and Metz (1973) with some modifications. Aquafaba samples were diluted 1:8 sample to water ratio then homogenized for 1 min using tissue tearor. 5 mL of canola oil was added to 5 mL of the homogenized liquid and homogenized again for 2 min using the same homogenizer. Then the homogenized liquid was centrifuged at 3000 rpm for 30 min and the oil was separated, and emulsion formed was measured by a pipette.

Emulsion stability was measured according to the procedure conducted by Cepeda et al. (1998). The same emulsion previously formed was warmed in a water bath at 80 °C for 30 min, cooled to room temperature, centrifuged at 3000 rpm for 30 min, and the volume of emulsion was measured the same way described previously.

Crystallinity by Fourier transform infrared (FTIR) spectroscopy

The FTIR spectra of freeze-dried samples were obtained by using a Nicolet™ iS™5 FT-IR Spectrometer (Thermo Scientific, Madison, WI, USA) over a wavelength range of 500–4000 cm⁻¹ equipped with an OMNIC operating system software (Version 9.0, Thermo Scientific, Madison, WI, USA). Samples were covered on the surface in contact with attenuated total reflectance (ATR) on a multi-bounce plate of Zn-Se crystal at 25 °C. Each spectrum was collected from an average of 32 scans with a resolution of 4 cm⁻¹ and the results were reported as mean values. Fourier self-deconvolution (FSD) was performed and the peaks were fitted in starch region (1300–800 cm⁻¹). A half-band width of 15 cm-1 and a resolution enhancement factor of 1.5 were employed (Chávez-Murillo et al., 2018). Samples were analysed to estimate the crystallinity changes based on their relative intensities of 1048 cm⁻¹/1022 cm⁻¹ (Chung et al., 2008).

Particle size analyzer using light scattering

The particle size of the lyophilized pressure-treated aquafaba samples and control sample was measured by a laser light scattering (Mastersizer 3000; Malvern Instruments Ltd, Worcestershire, UK) with Hydro EV Flexible volume wet dispersion. The refractive index values used for water was 1.33. The particle size of 90% (Dv90) of the volume distribution were calculated from the instrument software.

Color analysis (lightness “L*”)

Color was measured using a Hunter colorimeter model ColorFlex (Hunter Associates Laboratory, Reston, VA) in terms of L* (lightness), a* (redness and greenness) and b* (yellowness and blueness). The instrument (45 8/0 8 geometry, 10 8 observer) was calibrated with black and white tile standards followed by samples measurements. A transparent cup was used to place processed aquafaba samples and the control sample. It was placed above the light source and L* value was the only value added to the responses because the interest was only in the lightness of the aquafaba.

Randomized central composite RSM design and statistical analysis

Randomized central composite RSM design was used to investigate the effect of pressure level and pressurization holding time on ten responses. Eleven combinations of the variables were selected by experimental design shown in Table 1. A separate experiment of untreated aquafaba was used as control sample to compare the results. No optimization step was conducted, because the goal of the study was to check the possibility of HPP to enhance canned aquafaba. If there were enhancement, the only goal was to see what the best run parameters are.

Table 1.

Randomized central composite RSM design matrix with un-coded values of the factors

Run	A: Pressure	B: Time	Consistency coefficient (K)	Flow Behavior Index (n)	Yield stress	Foaming capacity	Foaming stability	Emulsion capacity	Emulsion stability	Crystallinity 1048/1022	Particle size	Lightness (L*)
	MPa	min	Pa.s		Pa (E-07)	%	min	mL	mL	Ratio (× 10−1)	µm
1	401	18	1.08 ± 0.2	0.51 ± 0.1	8.9 ± 0.0	68.3 ± 3.1	50.5 ± 5.0	5.0 ± 0.0	4.3 ± 0.2	6.9 ± 0.0	139 ± 13.4	33.4 ± 0.1
2	542	26	0.90 ± 0.0	0.60 ± 0.0	2.2 ± 0.0	82.5 ± 2.0	14.5 ± 1.5	5.2 ± 0.2	4.8 ± 0.6	7.7 ± 0.1	90 ± 5.0	28.9 ± 0.0
3	401	30	1.35 ± 0.7	0.45 ± 0.1	1.9 ± 0.0	75.8 ± 4.2	48.0 ± 5.0	4.8 ± 0.2	4.5 ± 0.4	7.7 ± 0.1	187 ± 21.6	31.8 ± 0.0
4	200	18	0.43 ± 0.1	0.65 ± 0.0	2.5 ± 0.0	69.2 ± 2.4	46.0 ± 1.6	5.7 ± 0.5	5.3 ± 0.6	8.0 ± 0.1	224 ± 27.0	33.3 ± 0.1
5	401	18	1.08 ± 0.2	0.51 ± 0.1	8.9 ± 0.0	68.3 ± 3.1	50.5 ± 5.0	5.0 ± 0.0	4.3 ± 0.2	6.9 ± 0.0	139 ± 13.4	33.4 ± 0.1
6	259	26	0.25 ± 0.1	0.65 ± 0.0	2.8 ± 0.0	80.8 ± 5.0	24.7 ± 1.7	5.2 ± 0.5	4.7 ± 0.5	8.0 ± 0.1	190 ± 4.0	29.9 ± 0.0
7	542	9	0.30 ± 0.0	0.71 ± 0.0	8.7 ± 0.0	72.5 ± 2.5	61.5 ± 9.5	5.5 ± 0.7	5.3 ± 0.5	7.8 ± 0.3	320 ± 2.1	40.4 ± 0.2
8	259	9	0.12 ± 0.0	0.70 ± 0.0	1.1 ± 0.0	78.3 ± 5.0	67.0 ± 2.0	5.0 ± 0.4	4.3 ± 0.5	7.8 ± 0.1	143 ± 6.6	49.4 ± 0.6
9	401	5	0.25 ± 0.1	0.66 ± 0.0	1.2 ± 0.0	72.5 ± 2.0	39.5 ± 2.5	5.2 ± 0.2	4.7 ± 0.2	7.3 ± 0.1	150 ± 14.8	49.6 ± 0.2
10	401	18	1.08 ± 0.2	0.51 ± 0.1	8.9 ± 0.0	68.3 ± 3.1	50.5 ± 5.0	5.0 ± 0.0	4.3 ± 0.2	6.9 ± 0.0	139 ± 13.4	33.4 ± 0.1
11	601	18	0.45 ± 0.1	0.64 ± 0.0	1.9 ± 0.0	78.8 ± 3.8	53.5 ± 1.5	5.7 ± 0.2	5.5 ± 0.4	7.7 ± 0.3	120 ± 2.2	27.0 ± 0.0
Control	–	–	0.65 ± 0.1	0.51 ± 0.1	2.9 ± 0.0	79.2 ± 3.1	50.5 ± 1.5	4.8 ± 0.2	4.8 ± 0.7	9.3 ± 0.0	24.1 ± 3.5	27.5 ± 0.1

All data was analysed using the Stat ease Design Expert 10.0.5 statistical software (Stat Ease Inc., Minneapolis, USA). The software was used to analyse the test data obtained through experiments by least square multiple regression analysis. Different models, interactions tested, and their suitability was evaluated based on the analysis of variance (ANOVA) and associated F-values. The significance was tested at 5% probability level. The generated statistical parameters were used to assess the validity of generated models.

Results and discussion

Rheological properties

Steady shear flow

Apparent (App.) viscosity of high pressure (HP) treated canned aquafaba did not have a significant change with higher shear rates. Almost all of the samples ended up with 0.1 Pa.s at 100 s⁻¹ shear rate, but the beginning was different at 0.1 s⁻¹ shear rate as demonstrated in Fig. 1a. In the figure it is shown that changing one variable which is the pressure intensity had an effect on App. viscosity with keeping the pressurization time constant. On the other hand, when checking the effect of the time on App. viscosity with keeping the pressure at 400 MPa, it was found that it made a change. The interesting result was that middle pressure intensity at 400 MPa for 18 min had the highest App. viscosity (3.7 Pa.s). The reason might be due to carbohydrates gelatinization and protein dehydration and aggregation that increased the viscosity which is in agreement with Alsalman and Ramaswamy (2021a, b); Floury et al. (2002); Machacon et al. (2018). While higher intensities decreased viscosity because the particles became aligned as a result the friction between the molecules decreased (Koocheki et al., 2013). Control sample’s App. viscosity was 2.2 ± 0.3 (data not shown) where it was decreased and increased with different pressure intensities and timings. Alsalman et al. (2020) found that canned aquafaba App. viscosity was 0.2 Pa.s and attributed the difference of results with other studies to the presence of EDTA and salt.

Fig. 1.

a Comparison of apparent viscosity at shear rate 0.1 s⁻¹ with different pressurization levels and times. b Comparison of apparent viscosities between high pressure treated canned aquafaba at 542 and 259 MPa for 9 and 26 min. c 3-D graphs corresponding to models fitted for consistency coefficient (K), flow behavior index (n), and yield stress (σ_y)

In general, aquafaba samples showed a shear thinning behavior which is a characteristic of a non newtonian fluids as illustrated by Fig. 1b. This figure illustrates that 259 MPa has lower viscosity than 542 MPa no matter the holding time if it was 9 min or 26 min which is in agreement with Alsalman and Hosahalli (2021). Fluids with shear thinning behavior are analyzed by power-law or Herschel-bulkley models. These models are used to observe the flow behavior through the interaction between viscosity and shear rate by three parameters which are consistency coefficient, flow behavior index, and yield stress.

In this study, Herschel-bulkley model fitted better than power law model with low standard error (< 20). Herschel-Bulkley model is as follows:

$$\sigma ={\sigma }_y+K{\gamma }^n$$ 2

where σ is shear stress (Pa), σ_y is yield stress (Pa), K is consistency coefficient (Pa.sⁿ), γ˙ is shear rate (s⁻¹), and n is flow behavior index (dimensionless).

Quadratic model was fitted for the three responses (R² > 0.85) as shown in Table 2. K, n, and σ_y were affected significantly by processing time (P < 0.05), but insignificantly by pressure intensity. Figure 1c demonstrated the RSM plots of those responses. Consistency coefficient (K) showed the viscosity over specific part of the curve that is included in the model. The range of K was from 0.25 Pa.s (401 MPa for 30 min) to 1.4 Pa.s (401 MPa for 5 min). K was high at 401 MPa because proteins got aggregated with pressure which increased the friction between molecules (Ahmed and Ramaswamy, 2003). With long holding time until 30 min, the bonds between molecules were disrupted which led to more uniform surface. As a result, the friction decreased and K decreased (Koocheki et al., 2013; Machacon et al., 2018). The mathematical equations are shown in Table 3 for rheological responses (K, n, and σ_y). Pressure intensity increased K and decreased n and σ_y, while the pressurization time increased K and σ_y and decreased n. This is concluded from the positive and negative effects on the response when changing the variables (pressure intensity and pressurization time).

Table 2.

Model statistics and adequacy of the models for all responses

Response	Model	P-value (time)	P-value (pressure)	R2	SD
Consistency coefficient	Quadratic	0.0178	0.2513	0.86	0.23
Flow behaviour index	Quadratic	0.0177	0.7413	0.86	0.05
Yield stress	Quadratic	0.0080	0.1525	0.99	0.00
Foaming capacity	Quadratic	0.2043	0.4623	0.70	4.17
Foaming stability	Linear	0.0845	0.9000	0.33	13.9
Emulsion capacity	Quadratic	0.1231	0.2062	0.91	0.12
Emulsion stability	Quadratic	0.4704	0.0578	0.90	0.20
Crystallinity 1048/1022	Quadratic	0.1059	0.2293	0.95	0.14
Particle size	Quadratic	0.4175	0.6557	0.65	52.3
Lightness (L*)	Quadratic	< 0.0001	0.0059	0.98	1.45

Table 3.

Polynomial mathematical models with interaction terms obtained in terms of coded factors for different responses

Response	Equation
Consistency coefficient	1.08 + 0.11 * A + 0.29 * B + 0.12 * AB − 0.38 * A2 − 0.20 * B2
Flow behaviour index	0.51 − 0.01 * A − 0.06 * B − 0.02 * AB + 0.08 * A2 + 0.04 * B2
Yield stress	8.900 e-007 − 1.997 e-008 * A + 5.043 e-008 * B − 8.498 e-009 * AB − 3.387 e-007 * A2 − 3.708 e-007 * B2
Foaming capacity	68.33 + 1.17 * A + 2.15 * B + 1.88 * AB + 3.93 * A2 + 4.04 * B2
Foaming stability	46.02 − 0.64 * A − 9.66 * B
Emulsion capacity	5.00 + 0.06 * A − 0.08 * B − 0.13 * AB + 0.30 * A2 − 0.03 * B2
Emulsion stability	4.33 + 0.17* A − 0.05 * B − 0.22 * AB + 0.49 * A2 + 0.07 * B2
Crystallinity 1048/1022	6.902 − 0.07 * A + 0.10 * B − 0.07 * AB + 0.50 * A2 + 0.35 * B2
Particle size	139.00 − 8.76 * A − 16.33 * B − 69.25 * AB + 20.38 * A2 + 18.63 * B2
Lightness (L*)	33.38 − 2.35 * A − 7.00 * B + 2.00 * AB − 1.190 * A2 + 4.09 * B2

A  pressure leve, B pressurization time

When the flow is equal to 1, the sample is Newtonian. Values less than 1 are samples with shear-thinning behavior. As a result, n is the opposite of K as shown in Fig. 1c. When K is high, n is low and vice versa. Flow index ranged from 0.45 to 0.71. The lowest value for the sample treated at 401 MPa for 30 min. and the highest value for the sample treated at 542 MPa for 9 min. The processing time and pressure for the former gave the highest value of K and the latter gave the lowest. Many other studies got similar trends of K and n and attributed the results to protein aggregation where weak bonds such as hydrogen bonds increased (Ahmed et al., 2003; Alsalman and Ramaswamy, 2021a). Yield stress σ_y is the force needed to initiate the sample flow. In this study σ_y ranged from 8.9 E−7 Pa (401 MPa for 18 min) to 1.1 E−7 Pa (259 MPa for 9 min) which is in agreement with Ahmed et al. (2005) where σ_y increased with pressure. Results showed low σ_y values for all the runs since canned aquafaba is more liquid than the aquafaba obtained from cooking (Alsalman et al., 2020).

Foaming andemulsion properties

Foaming capacity (FC) and stability (FS)

The range of FC and FS of pressurized canned aquafaba samples was 68.3–82.5% and 14.5–67.0 min, respectively (Table 1). Models fitted for the responses were quadratic for FC and linear for FS (Fig. 2). Both variables, pressure intensity and pressurization time, had insignificant effect on FC and FS (P > 0.05). From Table 3, the effect of pressure intensity and pressurization time is positive for FC and negative for FS. In another words, the higher the pressure variables were, the higher FC value and lower FS would be. For better understanding, pressure at 542 MPa for 26 min gave the highest FC and lowest FS values. Control sample had a value of 79.2% and 50.5 min for FC and FS, respectively. When comparing control sample to pressurized ones, a conclusion could be drawn that pressure could improve foaming properties.

Fig. 2.

3-D graphs corresponding to models fitted for emulsion and foaming properties

A study conducted by Mustafa et al. (2018) showed that FC and FS for canned aquafaba was 182–476% and 77–92%, respectively. Their results of FC were way higher than results from this study, but FS in this study is higher than theirs. In this study foaming stability was measured through the time the bubble breaks because almost all the runs (10 runs) took more than 30 min to break not as Mustafa et al. (2018) where they calculated it as the volume ratio after 30 min volume based on initial volume. So, compared to that methodology these results will have 100% FS. For bubble break in this study, it was a very small break which might be 10% or less since the foam was so stable. Other studies who used cooked aquafaba had higher FC as well (Aslan and Ertas, 2020; Nguyen et al., 2021). Results may differ from one study to another depending on chickpea mass in the can, aquafaba density and viscosity, chickpea varieties and composition, processing conditions, and salt addition or other additives (Mustafa et al., 2018; Shim et al., 2018).

Emulsion capacity (EC) and stability (ES)

Regarding emulsion properties, it did not improve significantly with pressure (4.8–5.7 mL) but there was little enhancement compared to control sample (4.8 mL) (Table 1). Quadratic model fitted for both properties, EC and ES (Fig. 2). Also, pressure intensity and pressurization time were insignificant for both variables (P > 0.05) (Table 2). Pressure intensity affected emulsion properties positively, while the pressurization time had a negative effect on EC and ES (Table 3). 600 MPa for 18 min resulted the highest values of emulsion properties.

A study conducted by Alsalman et al. (2020) found that EC and ES of canned aquafaba was 7.0 mL and 6.0 mL, respectively. They compared aquafaba obtained from different cooking times and water to chickpea ratios. Higher chickpea proportions which yielded the least aquafaba and cooked for the longest time resulted the best emulsion properties (7.3 mL EC and 6.9 mL ES). Studies attributed better emulsion properties to higher protein and carbohydrates content. The reason is that proteins act as surfactants since they have hydrophilic and lipophilic parts which enhances emulsion capacity, while carbohydrates stabilize emulsions (Echeverria-Jaramillo et al., 2021; Lafarga et al., 2019). Also, emulsifying agent concentration, mixing time, and the whole homogenization process play a significant role in emulsion properties (Shim et al., 2021). Another study concluded that saponins are like surfactants, too so they gave better emulsion ability and stability (Damian et al., 2018).

Structural properties

Crystallinity

The absorbance at 1048/1022 cm⁻¹ reflected crystallinity since 1048 cm⁻¹ represents the crystalline region and 1022 cm⁻¹ represents amorphous region. As shown in Table 1, crystallinity ranged from 6.9 × 10^–1 to 8.0 × 10^–1 for pressurized samples and 9.3 × 10^–1 for control sample. Results from this study for HP treated samples are in agreement with Alsalman and Ramaswamy (2021a); Chung et al. (2008); Xu et al. (2019). The variation was insignificant and the effect of HP factors (pressure intensity and pressurization time) were insignificant, too (Table 2). Quadratic model fitted for the results where the lowest crystallinity at 400 MPa and highest one at 200 MPa and 260 MPa (Fig. 3). The decrease in crystallinity for HP treated samples might be due to the destruction of hydrogen bonds connecting helices (Xu et al., 2019). If the samples were denser, they would have affected rheological properties as well (Alsalman and Ramaswamy, 2021a), but because the solid content for canned aquafaba is low (≈ 5%) (Alsalman et al., 2020), rheological properties were not affected. Solid content which contains carbohydrates and proteins would have affected aquafaba crystallinity when protein denaturation and carbohydrate gelatinization take place during HPP.

Fig. 3.

3-D graphs corresponding to models fitted for crystallinity, particle size, and lightness (L*)

Particle size

There was a significant difference between HP treated aquafaba samples’ sizes (90 -320 µm) and a huge increase compared to control sample (24 µm) (Table 1). Model fitted for the results was Quadratic model where the smallest particle size was for sample treated at 542 MPa for 26 min and the biggest particle size for the sample treated at 542 MPa for 9 min (Fig. 3). Both pressurization intensity and time had a negative effect on particle size (Table 3). The highest intensity (600 MPa) resulted one of the smallest particle sizes 120 µm (Run 11) and the combination of high intensity and long pressurization time resulted the smallest particle size (Run 2) (Table 1). There is only one study that discussed aquafaba particle size, but particle size of mayonnaise produced from freeze-dried aquafaba. The average was ≈ 225 µm that is in the range of the current study (He et al., 2021). Protein aggregation and swelling of starch granules due to water absorption is a clarification for the increase of particle size in HP treated samples (Ahmed et al., 2018). A comparison of samples sizes treated at 200, 400, and 600 MPa for 18 min processing time was 224, 139, and 120 µm, respectively. The reason of the size decrease might be particles disruption due to collapse of the voids created by HP (Ahmed et al., 2017).

Color analysis (lightness L*)

Lightness is the most important color parameter for aquafaba applications since it is used in whip cream, mayonnaise, and meringues. As a result, other parameters; a* (“ + “ redness and “-” greenness) and b* (“+“ yellowness and “-” blueness); were noted but not a point of focus like L* in the discussion. Results of color parameters were L* (27.0–49.6), a* (− 2.2 to 0.1), and b* (8.2–23.1) for HP treated samples and L* (27.5), a* (− 2.17), and b* (15.2) for control samples. From the previous results, canned aquafaba lightness was the predominant parameter, while there was a slight yellowness as well because the samples were obtained from chickpeas. HP samples became brighter after processing where quadratic model fitted the results. Processing time and pressure intensity had a significant effect on lightness (P < 0.05) (Table 2) and both affected brightness negatively (Table 3). The brightest value was for sample treated at 260 MPa for 9 min and the darkest value for the sample treated at 600 MPa for 18 min (Fig. 3). Results of this study are in agreement with Shim et al. (2021), brighter than the results conducted by Alsalman et al. (2020), and darker than results from Shim et al. (2018). Many studies attributed the differences in physical properties including color to the cultivar and production process including soaking, heat, pressure, processing time, and storage conditions.

In conclusion, high pressure processing (HPP) was able to enhance rheological properties by increasing consistency coefficient (K) from 0.65 Pa.s to 1.35 Pa.s and decreasing flow behavior index (n). It also increased functional properties; better effect on foaming than emulsion properties; in addition to lightness. Optimum condition when maximizing functional properties and the lightness was 600 MPa for 5 min with a desirability of 0.87. As a result, HP is a good processing technique to promote aquafaba properties allowing better results in application wise like spongier cake, smoother and brighter whip cream, a stable viscous salad dressing and mayonnaise, and thicker mousse. Further studies on other properties can give wider range of applications for aquafaba to be used in.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declarations

Conflict of interest

The authors declare no conflict of interest.