Combination of high-pressure homogenization and ultrasound improves physiochemical, interfacial and gelation properties of whey protein isolate

https://doi.org/10.1016/j.ifset.2020.102450Get rights and content

Highlights

  • HPH-US combined treatment effectively enhanced foaming properties of WPI.

  • Emulsifying ability index of WPI was enhanced by 13.97% at 120 MPa and 600 W of treatment.

  • Hardness of WPI gel was increased by 170.45% at 120 MPa and 600 W of treatment.

Abstract

The main purpose of this work was to investigate the influence of high-pressure homogenization (HPH, 60, 90, and 120 MPa, three cycles) combined with ultrasound (US, 120, 360, and 600 W, 30 min) on the physiochemical, interfacial, and gelation properties of whey protein isolate (WPI). Compared with an individual application of HPH or US, a combined HPH-US treatment can further reduce average particle size (D4,3) and turbidity of WPI, while significantly ameliorating its surface hydrophobicity, fluorescence intensity, and free sulfhydryl content. Compared with that of an untreated WPI, the emulsifying ability index (EAI) of WPI was increased by 8.54% after a 120 MPa HPH and by 7.63% after a 600 W US, whereas it increased by 13.97% after a combined treatment of 120 MPa and 600 W HPH-US. Accordingly, the foaming ability (FA) and the foaming stability (FS) were enhanced by 26.10% and 118.18% at 120 MPa and 600 W, respectively. The hardness of WPI gel was also increased by 170.45% at 120 MPa and 600 W compared to the untreated WPI. Therefore, the combination of HPH and US could make a remarkable improvement in the physicochemical functional characteristics of WPI, providing basic data support for the food industry to obtain excellent novel WPI ingredients.

Introduction

High-pressure homogenization (HPH) is an innovative non-thermal physical technology with intensive disruptive forces, such as strong shear stress, a cavitation effect, and turbulence (Bot et al., 2017; Calligaris et al., 2018; Villay et al., 2012). It has been widely applied in food processing to improve foaming properties of proteins (Martínez et al., 2011), enhance the rheological and emulsifying properties of fluid foods (Kielczewska et al., 2003), and prepare nanoemulsions (O'Sullivan et al., 2017). Specifically, it has been found that an increase in the HPH pressure could reduce the particle size of a soy protein isolate (SPI) (Song et al., 2013). In addition, the solubility of myofibrillar protein solutions was significantly increased at 103 MPa of the HPH pressure (Chen et al., 2016). Furthermore, HPH treatment is used to increase the antioxidant activity (reducing power) of the peanut protein isolate hydrolysates (Dong et al., 2011). In general, HPH can be considered an effective method for improving the functional properties of food proteins.

Ultrasound (US) technology has been implemented in food processing to alter the physicochemical and functional properties of proteins, such as soybean protein (Hu et al., 2015), black bean protein (Jiang et al., 2014) and rice protein (Li et al., 2016). Cavitation occurs when the ultrasonic waves pass through a fluid (Bot et al., 2017; Li et al., 2020). Although the principle of HPH cavitation vs. the ultrasonic cavitation is different, the cavitation effects that HPH or US induce are similar. Compared with the HPH cavitation, US cavitation has a microfluidic beam effect (Polat et al., 2011) and mechanical action (Jambrak et al., 2008; Shi et al., 2018) to generate a thermal effect and a highly reactive free radical (Dubinsky et al., 2008). In recent years, it has been reported that ultrasonic treatment could improve foaming properties of alpha-lactalbumin at 20 and 40 kHZ (Jambrak et al., 2010), enhance the emulsifying ability of the egg protein (Xiong et al., 2016), and decrease the turbidity of the myofibril protein at 193 W/cm2 for 15 min (Zhang et al., 2017). In addition to the above-mentioned benefits, ultrasonic technology is environmentally, friendly and less time consuming (Jiang et al., 2019).

Whey protein isolate (WPI) plays a significant role in the dairy industry, and it is viewed as an excellent source of high-quality natural proteins due to its easy digestion and many essential branched-chain amino acids, including leucine, isoleucine, and valine (Devries & Phillips, 2015; Graf et al., 2011). In recent years, various modification methods have been applied to improve its functionality, including physical methods (HPH (Chen et al., 2016) and US (Li et al., 2016)), chemical methods (Jiang et al., 2019), and enzymatic methods (Fu & Zhao, 2017). In our previous work, it has been verified that US pretreatment combined with pH (Gao et al., 2019) or transglutaminase (Jiang et al., 2019) could improve the functional properties of WPI through alteration of its spatial structure. Recently, the combined process of HPH-US led to nanoemulsions at energy density levels which were approximately half of those required by single HPH or US to obtain the same emulsification performances (Calligaris et al., 2016; Calligaris et al., 2018). Based on this, a combined HPH-US process became a possible way to reduce energy and cost to obtain the same objective results. Also, it is well known that HPH and US treatments can unfold the spatial structure of proteins to expose some reactive groups, such as free sulfhydryl and hydrophobic groups, thus further enhancing the functionality of proteins. However, it has not yet been clarified whether the combined HPH-US treatment would further ameliorate functionality of proteins compared with the individual HPH and US treatments. Therefore, the objective of the current work was to investigate the effects of a combined HPH-US treatment on the particle size, surface hydrophobicity, content of free sulfhydryl, interfacial properties (including emulsifying and foaming), and gelation properties of WPI. This research can provide basic data support for the food industry as it develops WPI ingredients with excellent functionalities.

Section snippets

Materials

Whey protein isolate powder (WPI, 93.5%) was purchased from Mullins Whey Co., Ltd. (Mosinee, WI, USA). Sodium dodecyl sulfate (SDS), 8-anilino-1-naphthalenesulfonic acid (ANS), β-mercaptoethanol and 5,5′-Dithiobis-(2-nitrobenzoic acid) (DTNB) were purchased from Sigma Co., Ltd. Trimethylolaminomethane was purchased from Solarbio Co., Ltd.

HPH treatment of WPI

WPI solution (12%, w/v) was prepared using distilled water until WPI was completely dissolved, and its pH value was adjusted to 7.0 with 4 mol/L NaOH.

Particle size distribution

The effect of HPH (0, 60, 90 and 120 MPa) combined with US (0, 120, 360 and 600 W) on the particle size distribution of WPI was shown in Fig. 1. Fig. 1a shows that after the HPH treatment, the particle size distribution of the WPI suspension became narrower, and the distribution range became more concentrated. The average particle size (D43) of WPI was significantly reduced (p < 0.05) when the HPH pressure ranged from 0 to 120 MPa. At 120 MPa of HPH pressure, D43 of WPI decreased by 35.97%

Conclusion

This paper presented that a combined HPH-US treatment can ameliorate the physicochemical and functional properties of WPI more effectively than the separate HPH and US treatments. Compared to the separate HPH and US treatments, a combined HPH-US treatment reduced D43 and turbidity of WPI, while increasing its surface hydrophobicity and free sulfhydryl. In fact, after a combined HPH-US treatment at 120 MPa and 600 W, D43, and turbidity reached the minimum, whereas the surface hydrophobicity and

Acknowledgment

This study was supported by project for the National Key Research and Development Program of China (No.2016YFD0400605), Natural Science Foundation of Heilongjiang Province of China (No.C2017029) and Key Program of Heilongjiang Province of China (No. 2019ZX07B02-04).

Author contributions

Ruijie Shi: Conceptualization, Methodology, Software, Investigation, Writing - Original Draft.

Yue Liu: Validation, Formal analysis, Visualization, Software.

Jialun Hu: Validation, Formal analysis, Visualization.

Hao Gao: Writing - Review & Editing, Data Curation.

Abdul Qayum: Writing - Review & Editing, Data Curation.

Akhunzada Bilawal: Writing- Review & Editing.

G.Munkh-Amgalan: Writing- Review & Editing.

Zhanmei Jiang: Writing- Review & Editing, Supervision, Funding acquisition.

Juncai Hou: Writing-

Declaration of competing interest

We declare that we have no financial and personal relationships with other people or organizations, there is no professional or other personal interest of any nature or kind in any product, service or company in the manuscript entitled, “Combination of high-pressure homogenization and ultrasound improves physiochemical, interfacial and gelation properties of whey protein isolate”.

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