Enhancing chicken breast meat quality through ultrasonication: Physicochemical, palatability, and amino acid profiles

Highlights

• •Ultrasonication (US) reveals potential in altering meat physicochemical properties.
• •US reduces pH, cooking loss, and redness, while increasing lightness and yellowness.
• •The hardness and chewiness of chicken breast meat decreased following US.
• •Amino acid content of US-meat reveals its potential effect on flavor profile.
• •SEM of US-meat displayed a rougher and less smooth surface than untreated sample.

Abstract

Ultrasonication, a technology that employs high-frequency sound waves, has demonstrated potential for modifying the properties of various food items. However, the effect of ultrasonication on chicken meat, particularly concerning amino acid composition and flavor enhancement, has not been sufficiently investigated. The objective of this research was to bridge the gap in the literature by exploring the impact of various ultrasonic treatments at varying power levels (300, 500, and 800 W) and durations (10 and 30 min) on the physicochemical characteristics, texture, and amino acid profile of chicken breast meat, with a focus on improving its palatability and flavor. The results indicated that ultrasonication reduced the pH and cooking loss, as well as hardness and chewiness while simultaneously increasing lightness and yellowness values of chicken breast meat. Moreover, ultrasonication enhanced the amounts of essential amino acids, including glutamic acid, alanine, and glycine as well as the free amino acid content, which gives meat its savory and umami flavor. Furthermore, the results demonstrated significant changes in the texture and structure, as demonstrated by the scanning electron microscopy (SEM) images, and in chemical makeup of chicken breast meat, as indicated by the FTIR spectra. These modifications in the molecular and microstructural characteristics of meat, as induced by ultrasonication, may contribute to the enhancement of tenderness, juiciness, and overall palatability.

1. Introduction

Since chicken is a staple item in many diets around the world, the chicken meat industry is crucial to satisfying the demand for premium meat on a global scale [1]. The goal of enhancing the quality and sensory attributes has long been directed toward the chicken breast, a popular and extensively used source of protein [2], [3]. A variety of factors, such as genetics, nutrition, processing methods, and consumers preferences, all have an impact on meat quality [4], [5]. The search for higher-quality products has prompted researchers to investigate a number of techniques, such as ultrasonication, that may improve meat quality.

Ultrasonication creates various physical and chemical effects, including cavitation, acoustic streaming, microstreaming, shear forces, and thermal effects, which can alter the structural characteristics of meat [6]. For instance, ultrasonication improved functional properties of meat products by accelerating the maturation process, reducing the energy for cooking, extending shelf life, and enhancing tenderness [7], [8], [9], [10]. Additionally, ultrasound treatments altered the microstructure and water-holding capacity, modified the collagen, connective tissue, and softness of the meat [11], [12]. Studies have indicated that processed meat products can benefit from a number of high-frequency focused ultrasonic treatments which enhance cooking, lessens the need for salt, and deactivates dangerous microbes in meat [13]. Furthermore, ultrasonication increased the tenderness of meat by rupturing muscle fibers and improved membrane permeability by facilitating the absorption of marinades and flavorings [12], [14].

While extensive research has been conducted on the use of ultrasound technology in bovine and porcine meat, it has primarily overlooked the impact of this technology in chicken meat [15]. Given the demand for premium products and the importance of customer preferences, it is crucial for the industry to enhance the quality of chicken products [4], especially with regard to its color, texture, and cooking loss [16]. Furthermore, increasing the free amino acid (FAA) content in meat could contribute to offering improved flavor and overall sensory experience for consumers [17], [18]. Considering the advantages of using ultrasonication to enhance meat quality, it is essential to explore the impact of ultrasound treatment on chicken breast meat. This study aims to address the knowledge gap and contribute to the understanding of how ultrasonication can be utilized to enhance the quality of chicken meat, meet consumer expectations, and support the sustainability of the poultry industry.

2. Materials and methods

2.1. Sample collection and determinations of ultrasound power and time

The samples were obtained from the Pectoralis major (chicken breast muscle) of 12 broilers from an e-commerce platform in Foshan, China. The chicken breasts were cooled to 4 °C ± 1 and subsequently weighed before being vacuum-packed in low-density polyethylene bags [18].

A laboratory-scale ultrasound equipment (THC-1000SF, Jining Tianhua Ultrasonic Electronic Instrument Co., Ltd., Jining, China) with a frequency of 24.5 kHz was used. The unpackaged sample was positioned at the bottom of the ultrasonic bath, and distilled cold water served as the medium for transmitting acoustic waves. The samples were exposed to ultrasound at power levels of 300 W, 500 W, and 800 W for 10 min and 30 min each (based on preliminary tests), resulting in six different treatment combinations. Following each treatment, the distilled water was removed, and the samples were stored at 4 °C for further analysis. The control samples consisted of untreated meat samples.

2.2. Determination of pH

A calibrated pH meter (PHS-3C, INESA Scientific Instrument Ltd. Co., Shanghai, China) was used to evaluate the pH of control and ultrasonicated samples following a slurry method as described by Wu et al. [19]. One gram of chicken meat samples was mixed with 10 mL of distilled water and homogenized for about 30 s at high speed before pH analysis.

2.3. Identification and quantification of free amino acids (FAAs)

The concentration of FAAs in control and ultrasonicated samples was evaluated according to the method described by Shimamura et al. [20]. Ten grams of ground samples were mixed in 40 mL of sulfosalicylic acid solution (2 % w/v), which was subsequently centrifuged (TG16-WS, Xiangyi Inc, China) at 3000 rpm for 10 min. the inner layer was centrifuged again at 10,000 rpm for another 10 min. The supernatant was then pass through a filter (0.45 µm), and the concentration of amino acids (ng/20 µL) was determined using a fully automated analyzer (Hitachi L-8800, Hitachi Co., Ltd., Tokyo, Japan).

2.4. Colorimetric analysis

The L*, a*, and b* color values were measured using a calibrated colorimeter (Ci 7600 X-Rite, MI, USA) following the method of Baldi et al. [21]. L* values indicate the range from darkness to lightness, with larger values corresponding to lighter colors. a* values measure redness (redder/greener) while b* values measure yellowness (yellow/blue).

2.5. Determination of textural profile

Two batches of control and ultrasonicated samples subjected to texture profile analysis (TPA) using Texture Analyzer (TA-XT plus 12835, Stable Micro Systems, Surrey, UK). The measurements were carried out with a cylindrical probe by placing subsamples (1.0 × 1.0 × 1.0 cm) positioned parallel on a flat metal plate (muscle fiber axis perpendicular to the movement of the probe). The determining variables were meat hardness, adhesiveness, springiness, cohesiveness, gumminess, chewiness, and resilience [22].

2.6. Determination of cooking loss

The water bath at 80 °C was used to cook the samples until their internal temperature reached 75 °C. The samples were then cooled, dried with paper towels, weighed, and cut vertically. The weight difference was calculated to determine the cooking loss (%) [18].

2.7. Fourier transform infrared spectroscopy (FT-IR)

Spectra of the control and ultrasonicated samples were recorded in the wavelength range of 4000–400 cm⁻¹ by FTIR (Vertex 33 spectrometer, Bruker, Germany).

2.8. Scanning electron microscopy (SEM)

The morphology of both control and ultrasonicated samples were analyzed using Thermo Scientific Quatro S SEM. The cross-sectional images were recorded at 500× magnification.

2.9. Statistical analysis

All experiments were performed three times, except for FAAs, which were calculated as the average of the two samples. The general linear model was selected in Minitab (version 16.2.4), and Tukey’s test was used to evaluate the differences among individual group means [23]. The outcomes of all analyses were presented in the form of mean values, and standard deviations, and a p-value of less than 0.05 was considered statistically significant.

3. Results and discussion

3.1. Effect of US treatments on pH

pH is a crucial parameter in the meat industry that is directly linked to color changes resulting from redox reactions with myoglobin [24]. Nevertheless, not all research has found that ultrasonic treatment significantly affects the pH of meat [25], especially chicken breast meat. Numerous investigations found no statistically significant difference in meat pH immediately after ultrasonication or at various time intervals post-mortem [12], [26], [27]. Table 1 shows the nonsignificant impact of sonication time and strength on pH levels. At 300 W of ultrasound treatment, the initial pH of the sample decreased after 10 min and then began to rise as the duration of exposure was extended to 30 min. However, samples treated with higher power levels (500 W and 800 W) showed a slight decrease in pH compared to the control and 300 W-treated samples, regardless of the duration of treatment.

Table 1.

Effect of different US treatments on pH and cooking loss (%) of chicken meat samples. Different letters on the column indicate significant differences (p < 0.05).

Treatment Code	Ultrasound Power (W)	Treatment Time (min)	pH	Cooking loss (%)
Control	–	–	6.04 ± 0.03a	34.88 ± 0.76a
300 W/10	300	10	5.97 ± 0.02 abc	26.1 ± 0.47b
300 W/30	300	30	5.99 ± 0.05 abc	26.78 ± 0.1b
500 W/10	500	10	5.95 ± 0.03c	34.53 ± 1.72a
500 W/30	500	30	5.96 ± 0.03bc	35.08 ± 0.78a
800 W/10	800	10	5.93 ± 0.02c	36 ± 2.32a
800 W/30	800	30	6.03 ± 0.03ab	37.35 ± 2.44a

High-power ultrasonication was found to lower the pH of bovine muscle from 5.51 to 5.35 [28]. However, when the treatment duration increased from 60 to 90 min, the pH rose from 5.35 to 5.4, suggesting that ultrasound might have an acidifying effect at higher intensities. The difference in pH levels between the ultrasonicated samples and the control samples could be attributed to two possible explanations: the unfolding of proteins and the release of organic acids. It is possible that the high-intensity ultrasound causes the muscle proteins to unwind, thereby exposing more acidic amino acid residues and decreasing the pH [29], [30]. The ultrasonic cavitation may disrupt cellular structures and release organic acids from muscle tissue, which can result in a slight pH reduction [31].

The sonication process consists of three stages: the formation, growth, and collapse of microbubbles, which ultimately lead to the creation of acoustic cavitation. The rapid collapse of these microbubbles can result in the production of •OH and •OOH radicals after the dissociation of oxygen and water [32]. The breakdown of •OOH into O2− and H+ provides protons for pH reduction. The power intensity influences the size of the cavitation bubbles, the time and the internal pressure of bubble collapse [29]. Therefore, the dissimilar results obtained at 300 and 800 W may be attributed to the impact of the ultra-power on the intensity of the cavitation process.

In comparison to power level, treatment duration had a less noticeable impact on pH. The rapid initial increase in pH observed in the present study with prolonged sonication time may be attributed to several mechanisms, such as the concealment of acidic groups in proteins, which increased pH [33]. Despite this, the pH of the samples insignificantly increase with a longer duration of ultrasound treatment (30 min), as shown in Table1. According to earlier studies by Got et al. [33], pre-rigor sonication of bovine semitendinosus muscle at 10 Wcm⁻² resulted in a 0.2 unit increase in pH following 2–4 h after treatment. This was attributed to the modification in ionic groups within the protein structure. Similarly, a slight increase in pH was observed between the 10- and 30-min treatments within the same power level group. This suggests that an initial ultrasonic exposure may be sufficient to induce observed changes in protein structure or acid release, and that extending the treatment duration may not result in further acidification. The pH shift may also have been influenced by the temperature increase brought on by part of the sonication energy being converted to heat [34], [35]. However, the effect of ultrasound on meat pH can be influenced by various factors such as acoustic intensity, frequency, and application time [36]. Nonetheless, a correlation between the pH of meat and lightness has been proposed, suggesting that a lower pH could be linked to a higher lightness because of the antagonistic interaction with meat pH [37].

3.2. Effect of US treatments on free amino acids (FAAs)

FAAs can affect the flavor and taste of meat through the Strecker degradation and Maillard reaction [38]. Aspartame (Asp) and glutamate (Glu) were considered umami tastes in cooked chicken [39], and crab meat [40]. While arginine (Arg), isoleucine (Ile), leucine (Leu), valine (Val), phenylalanine (Phe), methionine (Met), and histidine (His) have a bitter taste. Glycine (Gly), alanine (Ala), and serine (Ser) are sweet tasting, while lysine (Lys) and proline (Pro) have both sweet and bitter tastes, respectively. Furthermore, individual amino acids can impart sour and salty tastes [38]. These FAAs are responsible for the savory flavor of foods and play a pivotal part in enhancing the palatability and nutritional value of chicken meat [41]. The variations in the FAA content of chicken meat samples following different ultrasonic treatments are shown in Fig. 1. Both essential and non-essential FAAs were significantly elevated by ultrasound (p < 0.05). The sample that was exposed to 300 W/30 min had the largest amounts of Asp and Glu, suggesting that longer exposure times to ultrasonic waves and higher power intensities facilitate protein breakdown and FAAs extraction (Fig. 1A). Our findings align with those of Gu et al. [42], who observed that ultrasonic treatment (200–600 W) increased the FAAs concentration in white yak meat. During ultrasonication, cavitation bubbles collapse with considerable force, leads to the formation of OH− by water molecules, disrupting protein structure and releasing FAAs [43]. Moreover, the heat produced by ultrasonic waves has the ability to denature proteins and liberate FAAs. Additionally, the enhanced solubility of proteins caused by ultrasonic waves increases their susceptibility to proteolytic enzymes, which hydrolyze proteins into FAAs [44].

Fig. 1.

Free amino acid (FAAs) contents of chicken breast influenced by different ultrasonic treatments (A) Umami taste FAAs, (B) Sweet taste FAAs, (C) Bitter taste FAAs, and (D) Bitter/sweet/sulfurous taste FAAs. Different letters indicate significant differences (p < 0.05).

Ultrasonication increased the concentration of volatile flavor molecules specifically aldehydes, alcohols, and ketones, in spiced beef [44]. According to the authors, ultrasound pretreatment facilitates the breakdown of proteins and lipids into small molecules, including aldehydes, ketones, esters, and FAAs, through secondary oxidation of lipids, ultimately leading to the formation of flavor compounds. However, when spiced beef was ultrasonicated at 400–1000 W, the levels of Glu and Asp decreased [44]. That reduction may be related to the ultrasonic destruction of the myofibrillar structure, which enhanced the migration of amino acids from boiled meat to soup [44]. Furthermore, negatively charged FAAs in the meat can bind to H+ in the water, resulting in their loss [44]. Fig. 1A shows that while Asp and Glu dramatically decreased when processing time was increased from 10 min to 30 min at higher ultrasound intensities (500 W and 800 W), overall FAAs content increased significantly with increasing ultrasound power. The reason for this is likely the denaturation of proteins caused by ultrasonic treatment, which exposes amino acids that were previously hidden within the protein structure. Apart from Asp and Glu, other essential amino acids such as Lys, Leu, and Arg exhibited a considerable upsurge following ultrasound treatment Fig. 1C, D. It is favorable from a nutritional perspective that the level of these amino acids increased following ultrasonication, as they are essential and cannot be produced by the body [41].

Certain ultrasound characteristics, such power, frequency, and length of treatment, determine which FAAs are released and to what extent. For example, samples treated with 300 W/30 min and 800 W/10 min had the highest concentration of Asp, whereas samples treated with 300 W/30 min and 500 W/10 min had the highest concentration of Glu. On the other hand, 300 W/10 min samples had the lowest Pro concentration (Fig. 1D). Therefore, there is no single optimal condition for enhancing the content of all FAAs in chicken breast meat. Nonetheless, the results showed that 500 W/10 min ultrasound treatment increased (73.87 %) the total amount of FAAs in chicken breast, followed by 300 W/30 min (67.18 %). The treatments with 800 W/30 min and 500 W/30 min produced the lowest percentage increase in total FAAs in chicken breast (i.e., 35.66 % and 36.66 %, respectively). This implies that the hydrolysis of chicken proteins and the release of FAAs are significantly influenced by the intensity and duration of ultrasonic treatments.

3.3. Effect of US treatments on color

The results on the CIE L*a*b* color parameters are consistent with previous studies [45], [46], which found that sonicated meat was more light (higher L*), less redness (lower a*), and more yellow (higher b*) than control samples. The L* value was highest for the 800 W/10 min treatment and lowest for the control group Fig. 2. Although treatment power level had a more substantial impact on color changes than treatment duration, the lightness of the samples was influenced by both the power and time of ultrasound treatment. Because ultrasound treatment modifies structure and composition of muscle fibers and myoglobin pigments, it may affect the light scattering and absorption properties of meat [47]. The increased lightness for the 800 W/10 min treatment could be a result of myoglobin oxidation and degradation, which could reduce redness and increase the reflectance of meat [48]. According to the authors, the increase in free water at the surface of the meat, which causes the meat to reflect more light, frequently corresponds with an increase in lightness (L*) of meat. It is possible that the meat's surface structures were changed by sonication and cavitation, which encouraged the release of water and increase the L* values [46]. Another theory states that the increased L* values in sonicated-samples point to a possible ultrasound-induced lightening effect, most likely due to the disruption of muscle fibers and the release of light-scattering myofibrillar proteins.

Fig. 2.

Effect of different US treatments on the color parameters of chicken meat samples. Different letters indicate significant differences (p < 0.05).

The impact of sonication on the redness of chicken breast samples, as measured by the a* parameter, was not found to be statistically significant. The a* and b* values varied between 1.05 and 1.36 and 10.10 to 13.41, respectively. The redness and yellowness of meat are mainly influenced by the concentration and chemical state of myoglobin, which is the primary pigment responsible for meat color. The absence of consistent trends in a* and b* values across treatments suggests that ultrasound may have more complex effects on redness and yellowness, potentially involving pigment oxidation or interactions with other meat components, as reported in some studies [27], [48].

3.4. Effect of US treatments on cooking loss

Ultrasonication showed no significant difference in cooking loss when compared to untreated samples, which aligns with previous research on hen breast muscle [10], [49], chicken breast meat batter [50], and beef semitendinosus muscle [11]. However, samples sonicated at 300 W had a considerably lower (p < 0.05) cooking loss than untreated meat, suggesting that ultrasound treatment caused the meat to retain more water during cooking (Table1). The results are consistent with those of Zhang et al. [51], which stated that cooking loss increased with increasing ultrasound intensity and time. As a result, the lowest cooking loss was observed in meat thawed at 300 W, while the highest cooking loss was observed in meat thawed at 500 W. Similarly, ultrasound treatment decreased cooking loss % and increased the cooking yield of beef muscles at higher temperatures [29]. It has been shown that applying ultrasound treatments to meat can improve structural characteristics of myosin by producing more sulfhydryl groups, changing α-helices into loose β-sheet forms, perhaps lowering dense clumping, and enhancing the muscle proteins' capacity to retain water [42]. Nonetheless, in our study, the myofibrillar structure was likely severely damaged at 500 W and 800 W, which led to a considerable loss of water in the myofibroblasts during ultrasonication. The cavitation impact of ultrasound on the muscle tissue involves the production and collapse of bubbles in a liquid can damage muscle cells and lead to increase water loss during cooking [52].

The effects of ultrasound treatment on cooking loss can vary depending on the meat type and treatment conditions. For instance, a significant decrease in cooking loss in ultrasound-treated goose breast meat samples (800 W for 5–30 min) highlighted the potential impact of high power ultrasound treatment on reducing cooking loss [53]. In contrast, the samples in our research that utilized longer sonication periods (30 min) exhibited a higher degree of cooking loss. This may be related to the expansion of the spaces between muscle fibers and connective tissue (as depicted in Fig. 5), in addition to the disruption of the myofibrillar protein structure [29]. The increased cooking loss observed at 800 W may have negative implications for the quality of cooked chicken breasts, as moisture-deficient chicken breasts can be dry and tough. However, cooking loss readings in this study were relatively small. Therefore, it is possible that increased cooking loss may not be noticeable in cooked chicken breasts.

Fig. 5.

Microstructural changes in raw (control) and ultrasonicated samples chicken breast samples treated for 10 and 30 min (magnification 500×). The yellow arrows correspond to the areas of “interfibrillar spaces” while the red arrows demonstrate “collagenous fibers”. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

3.5. Effect of US treatments on textural properties

The impact of ultrasound on the texture attributes of hardness, adhesiveness, springiness, cohesiveness, gumminess, and chewiness is clearly demonstrated in Fig. 3(A–G). It is evident that the use of ultrasound has a significant influence (p < 0.05) on these attributes, with the exception of resilience. Hardness, which refers to the amount of force required to produce a specific deformation, has been widely studied in relation to ultrasound treatment of meat [54]. Previous research has shown that ultrasound treatment have the ability to disrupt muscle fibers and degrade connective tissue, which in turn leads to a more tender meat product with reduced hardness while improved springiness or elasticity [55], [56], [57], [58], [59], [60], [61], [62]. However, it is important to note that excessive intensity or prolonged treatment duration can result in protein denaturation, leading to an increase in hardness to some extent [56]. The sonication effects on sample hardness varied across different treatment durations and intensities, indicating a substantial interaction between treatment power and treatment time. For instance, the hardness of 300 W samples decreased (from 337.8 g to 234.8 g), while the hardness of 500 W samples increased (from 171.4 g to 360.8) as the treatment time increased from 10 to 30 min, respectively.

Fig. 3.

Effects of ultrasonication on texture profile analysis: (A) hardness, (B) adhesiveness, (C) springiness, (D) cohesiveness, (E) gumminess, (F) chewiness, and (G) resilience properties of chicken breast sample. The different lowercase letters means significant difference at p < 0.05 among ultrasonic processing. Error bars represent ± standard deviations.

In comparison to the control samples, the samples subjected to 800 W/30 min ultrasound treatment had the highest values for hardness, adhesiveness, springiness, and gumminess. The formation of protein gels on the surface of the meat by heat or other stresses may be responsible for the increase in adhesiveness, springiness, and gumminess [63]. The tenderness and springiness of meat are affected by the extent of fiber swelling, which is influenced by the denaturation of myosin and α-actinin [63]. The relationship between the intensity of ultrasound and meat texture is complex, showing an initial decline in some textural parameters, followed by a potential increase with excessive intensity or prolonged treatment duration. Finding the optimal treatment conditions to achieve the desired texture depends on the specific application. For example, to create a juicy and tender chicken breast, it may be more effective to treat with less ultrasonic power or for a shorter period of time. Conversely, to produce a chicken breast that is firm and has a good bite, ultrasound treatment at a higher power or for a longer duration may be more effective.

3.6. Effect of US treatments on compositional characteristics

Fourier Transform Infrared (FTIR) spectroscopy has been widely used for meat to identify the primary functional groups associated with compositional changes [64]. The FTIR spectra (% transmittance vs. wavenumber) of raw and ultrasound-treated chicken samples are illustrated in Fig. 4, covering a range of 4000 to 400 cm⁻¹. The mean FTIR spectra of the classes display noticeable variations in the 3000–2800 cm⁻¹, 1800–1700 cm⁻¹, and 1700–1000 cm⁻¹ ranges, which are mostly related to variations in the composition of lipid and proteins [65]. Treatments with higher intensities and longer durations (500–800 W for 10 and 30 min) displayed more variations in peak intensities and positions than treatments with lower intensities and shorter durations (300 W/30 min and 300 W/10 min).

Fig. 4.

FTIR analysis of control and ultrasonicated chicken breast samples.

The FTIR spectrum of the treated chicken meat showed higher peaks at 3500 cm⁻¹, which increased the hydroxyl (OH) band strength, indicating residual moisture in the samples. This suggests that ultrasound treatment caused some disruption of the cell membranes in chicken meat, allowing more water to enter the cells. The broad absorption band in the range of 3500 to 3000 cm⁻¹ is attributed to the symmetric stretching vibrations of O–H and N–H bonds in alcohols and amides or proteins, respectively [65]. Strong peaks at 3300 cm⁻¹ are commonly referred to as the amide A and amide B bands and are associated with the N-H vibration and the first overtone of the amide II vibration [66]. A slight decrease in peak intensity and a shift towards lower wavenumbers around 3300 cm⁻¹ and 1640–1634 cm⁻¹ was observed in sonicated samples, suggesting protein denaturation or degradation. Similarly, ultrasound decreased the amount of α-helix and increased β-sheet content when compared to natural beef protein [67].

The ultrasonicated samples displayed an increase in peak intensity in the range of 2800–3200 cm⁻¹, which is related to fat content and corresponds to C-H symmetric and asymmetric stretching. The treated samples showed a significant increase in peak intensity at 1450 cm⁻¹, indicating the presence of lipid oxidation and the formation of hydroperoxides and aldehydes. On the other hand, the ultrasonicated samples displayed a slight decrease in peak intensity at 1240 cm⁻¹, which suggests phospholipid degradation and the release of fatty acids. Additionally, treatments with longer durations (800 W/30 min, 500 W/30 min, 300 W/30 min) showed more carbohydrate breakdown and carboxylate formation than treatments with shorter durations (800 W/10 min, 500 W/10 min, 300 W/10 min) as evidenced by the increase in peak intensity at 1050 cm⁻¹ and 1413 cm⁻¹. These changes could potentially affect the flavor, color, and shelf life of meat samples.

3.7. Effect of US treatments on microstructure

As seen in Fig. 5, the use of ultrasonic treatment caused a variety of changes in the microstructure of chicken breast meat. Multiple thin bundles of collagenous fibers with alternating adhesion and divergence were present in the untreated samples, leading to the creation of numerous slits within the collagen fiber. The arrangement of these fibers was systematic and regular (Fig. 5, control). After sonication was applied to the muscle, the collagenous fibers appeared disordered and staggered, and the fiber arrangements became loosened (as shown in Fig. 5B–D). As the duration of ultrasound exposure increased, noticeable changes in the collagen fibers were observed, including granulation and denaturation, which became more pronounced (Fig. 5F–H). These changes were likely caused by the denaturation and shrinkage of the collagen fibers during the sonication [63]. Following the treatment, the muscle cells ruptured, leading to the contraction of the sarcomere and an increase in the extracellular space, intracellular cavities, and canals. Furthermore, protein aggregates appeared in the extracellular space as granulates (Fig. 5G and H). The 800 W/30 min treated sample displayed a far more pronounced degree of structural alterations compared to the untreated sample. In most areas, the characteristic striations within the muscle fibers were almost absent or barely visible, indicating a significant disorganization of proteins within the muscle cells. This level of muscle fiber disruption, fat cell rupture, and cavitation damage would likely result in significant changes to the texture, tenderness, and juiciness of the meat.

Typically, after being exposed to ultrasound for 30 min, muscle fibers often become separated from one another in both muscles. The observations revealed that the interfibrillar area of both muscles increased when they were exposed to the same ultrasonication intensity for 30 min. For instance, the interfibrillar space in bovine meat expanded as a result of sonication at 45 kHz with an intensity of 11 W/cm² and 37 kHz with intensities of 16 and 28 W/cm², respectively [25], [27]. But when it comes to chicken meat, Zou et al. [68] found that ultrasonicated chicken (at 200 W, 20 kHz, intensity of 15.6 W/cm²) had more fractured myofibrils and dissolved contents with tiny gaps than the control sample. In our study, the most evident change was the disruption and fracture of muscle fibers caused by the ultrasonic vibrations that put stress on the muscle fibers and rupture them [69]. Furthermore, the distinctive striations found in muscle fibers, which represent the arrangement of contractile proteins, may appear less defined or even absent in certain areas. Ultrasonication also results in the bursting of fat cells in the meat, which are visible as wide gaps between muscle fibers. This fat being released to the surrounding tissue may impact the texture and flavor of meat [69]. Apart from its main purpose, ultrasonic treatment can cause microscopic holes as a result of subsequent collapse of bubbles within the liquid [27]. On the other hand, as muscle fibers and fat cells break down, fluids are released into the meat, which can improve its flavor and make it juicier and tender.

4. Conclusion

This study has provided valuable insights into the various effects of ultrasonication on the physicochemical quality, palatability, and amino acid profile of chicken breast meat. Although there is conflicting evidence regarding the impact of ultrasonic treatment on other quality factors such as pH, color, and texture, the research indicates that ultrasound treatment does have an impact on a number of meat quality parameters. The results showed substantial changes in essential amino acids that play a crucial role in the development of the savory and umami flavors in ultrasonicated meat samples. Moreover, the data from the color analysis suggests that using ultrasound treatment can lead to chicken meat with a lighter shade, which may be appealing to consumers as it is often associated with freshness and superior quality. Ultrasound treatment at 300 W resulted in a significant decrease (p < 0.05) in cooking loss compared to untreated meat, indicating that the treatment helped retain water in the meat during cooking. The impact of ultrasound treatment on meat hardness varied depending on the treatment duration and intensity, suggesting a strong interaction between these factors. Additionally, FTIR analysis showed that chicken meat treated with ultrasound had higher transmittance than control chicken meat, suggesting that the treatment altered the molecular structure of the meat. Specifically, the FTIR spectrum showed a reduction in the intensity of the amide I and amide II bands, which are associated with denaturation of proteins. In the untreated sample, the muscle fibers were elongated, parallel, and well-defined, showing clear striations indicative of an organized arrangement of actin and myosin filaments, as revealed by SEM. On the other hand, the ultrasonicated sample displayed a rougher and less smooth surface than the untreated sample, which was attributed to the combined effects of muscle fiber disruption, fat cell rupture, and cavitation. These changes suggest that ultrasonication can improve the tenderness, juiciness, and visual appeal of chicken breast meat, offering potential benefits for both consumers and the food industry.

Funding

Not applicable.

CRediT authorship contribution statement

Ume Roobab: Writing – original draft, Software, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Bo-Ru Chen: Writing – review & editing, Methodology, Data curation. Ghulam Muhammad Madni: Writing – review & editing, Software, Data curation. Shi-Man Guo: Writing – review & editing, Methodology, Data curation. Xin-An Zeng: Writing – review & editing, Supervision, Resources, Project administration, Conceptualization. Gholamreza Abdi: Writing – review & editing, Software, Funding acquisition, Conceptualization. Rana Muhammad Aadil: Writing – review & editing, Supervision, Conceptualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.