Are Chicken Breasts or Thighs Healthier?

Intrinsic tryptophan fluorescence intensity

The intrinsic tryptophan fluorescence intensity of myosin extract (protein concentration of 0.5 mg/mL) was observed using the method reported by Lee et al. (2021c). Scanning of the myosin extract was conducted between 300 and 400 nm at an excitation wavelength of 280 nm (Varioskan LUX), with a scanning speed of 1,000 nm/min, and excitation and emission slit widths of 5 nm.

The secondary structure of the myosin extract was measured using circular dichroism spectroscopy (Chirascan VX, Applied Photophysics, Leatherhead, UK). The myosin extract was diluted to a protein concentration of 0.5 mg/mL. A single spectrum was obtained with two replicates in a scan rate of 100 nm/min, a response time of 0.25 s, and a bandwidth of 1.0 mm. The data were expressed in millidegrees, and the scanning range was set between 200 and 260 nm. To estimate the content of secondary structural components, including α-helices, β-sheets, β-turns, and random coils in the spectrum, CDNN software (version 4.0, Gerald Böhm, Bioinformatics, Germany, CD Spectra Deconvolution Ver. 2.1) was used.

For in vitro digestion, the ground chicken muscles were vacuum-packed and cooked at 80°C to reach a core temperature of 75°C, followed by cooling to 25°C. Cooked samples were chopped to simulate mastication.

The elderly in vitro digestion model herein was designed based on previous studies by Hernández-Olivas et al. (2020) and Minekus et al. (2014). All the digestive enzymes that were used herein were purchased from Sigma-Aldrich (St. Louis, MO, USA). The simulated salivary fluid (pH 7.0), gastric fluid (pH 6.0), and duodenal fluid (pH 7.0) contained 75 U/mL α-amylase from Aspergillus oryzae (EC 3.2.1.1), 1,500 U/mL pepsin from Porcine mucosa (EC 3.4.23.1), 50 U/mL trypsin (EC 3.4.21.4) and 12.5 U/mL chymotrypsin (EC 3.4.21.1) from bovine pancreas, 1,000 U/mL pancreatic lipase from porcine pancreas (EC 3.1.1.3), and 5 mM porcine bile extract (EC 232-369-0). Digestive fluid was mixed with the digesta from the previous compartment at 50:50 (vol/vol) during digestion. Each digestion was conducted for 120 min at 37°C and a rotational speed of 100 rpm, except for oral digestion, which was conducted for 2 min. All digesta samples were stored at −70°C until analysis, immediately after digestion. Control samples were prepared for digestion under the same conditions through addition of distilled water instead of meat samples to exclude protein content from the digestive enzymes.

Herein, the size fractionation of the digesta was conducted to determine protein digestibility after in vitro digestion. After sequential filtration using a centrifugal filter with molecular weight cut-offs of 10 and 3 kDa (Amicon Ultra-15, Millipore, Billerica, MA, USA) according to the manufacturer’s protocol, the protein content of the filtrate and whole digesta was measured using the Kjeldahl method to represent the amount of protein digested under 3 kDa. Protein digestibility was calculated using the following Eq. (1):

Digestibility (%) = 100 × (Protein content in the filtrate – Protein content of the control filtrate))/Protein content in the whole digesta.

(1)

This study used three iterations in three batches with analysis using a mixed model, and the batches (carcasses) were described as random effects. The least-squares mean and SE of the least-squares mean was used to express the results. The significance of the main effects was evaluated using Tukey’s multiple comparison test (p<0.05). The results were statistically analyzed using SAS software (version 9.3, SAS Institute, Cary, NC, USA).

Table 1 shows the results of the muscle characterization in this study. The pH of chicken breast and thigh used in this study was 5.81 and 6.49, respectively, with significantly higher pH in the thigh (p<0.05). The breast and thigh showed different proximate compositions, with higher crude protein and crude ash contents in the breast (p<0.05), and conversely, higher crude fat content in the thigh (p<0.05). Moreover, the thigh had higher protein carbonyl content than the breast (p<0.05).

Property	Breast	Thigh	SEM1)
pH	5.81B	6.49A	0.005
Proximate composition
Moisture (%)	76.13	76.57	0.265
Crude protein (%)	21.40A	19.15B	0.115
Crude fat (%)	1.07B	3.10A	0.230
Crude ash (%)	1.40A	1.19B	0.068
α-Amino groups (mM/g)	0.23B	0.27A	0.002
Protein carbonyl (nmol/mg)	4.01B	5.06A	0.215

Muscle fiber type differentiates the contractile characteristics and metabolic patterns (glycolytic and oxidative) that influence muscle-to-meat conversion and overall meat quality. As the slow- and fast-twitch muscle fibers have oxidative and glycolytic metabolism before slaughter, respectively, muscles predominantly composed of fast-twitch fibers possess more glycogen than those composed of slow-twitch fibers (Karlsson et al., 1999). The lower glycogen content in type I fibers can inhibit pH decline in muscles that are rich in type I fibers after slaughter (Vaskoska et al., 2021), which explains the higher pH of the thigh. Moreover, compared to fast-twitch fibers, slow-twitch fibers have a greater ability to use cellular lipids as fuel for ATP production due to their high mitochondria content and respiratory enzymes, resulting in high triglyceride content in muscle fibers (Karlsson et al., 1999). Therefore, the higher stored triglyceride content in the thigh resulted in higher crude fat and lower crude protein content than in the breast. This oxidative metabolic property of slow-twitch fibers also requires a greater ability to deliver oxygen to the muscle; as such, the chicken thigh has a higher heme protein content (including hemoglobin and myoglobin) than the breast (Gong et al., 2010). As heme proteins and transition metal ions are important factors that affect the oxidative susceptibility of meat proteins (Jongberg et al., 2014), the metal ion-induced acceleration of protein oxidation results in higher protein carbonyl content in the thigh.

Additionally, the α-amino group content in the 10% TCA-soluble fraction that contained small amino acids and peptides with 3–4 residues was higher in the thigh (p<0.05), indicating greater postmortem protein degradation. In general, fast-twitch fibers are considered to have faster postmortem proteolysis due to having a higher calpain-to-calpastatin ratio than slow-twitch fibers, as calpastatin activity is positively correlated with slow MHC isoforms (Christensen et al., 2004). However, calpain is highly sensitive to pH and exhibits optimum activity at neutral pH (Bhat et al., 2018). The rapid pH decline and lower ultimate pH of the breast may have induced lower calpain activity and an increase in protein denaturation, resulting in a greater breakdown of proteins in the thigh. However, Christensen et al. (2004) reported that the postmortem degradation of proteins depends more on the variations between muscles rather than the fiber type itself, and that the difference in the α-amino group content cannot be entirely explained by muscle fiber composition.

Overall, the two muscles exhibit different biochemical traits, which may be attributed to differences in their metabolic processes.

Intrinsic tryptophan fluorescence intensity of myosin in chicken breast andthigh muscles

The hydrophobicity of proteins is known to largely contribute to their structural stability. The intrinsic fluorescence intensity of tryptophan, an aromatic amino acid, was monitored to determine the aromatic hydrophobicity of myosin in chicken breast and thigh tissues (Fig. 2). In the wavelength range of 300 to 400 nm, the breast muscle had a higher intrinsic tryptophan fluorescence intensity than the thigh muscle (Fig. 2A). When comparing the fluorescence intensity at 328 nm, which showed the highest intensity in both muscles (Fig. 2B), the breast had a significantly higher fluorescence intensity (p<0.05). This result indicates that the thigh has a higher aromatic surface hydrophobicity than the breast, which is consistent with previous studies. Boyer et al. (1996) reported that both aromatic and aliphatic hydrophobicity was higher in slow-twitch myosin than in fast-twitch myosin; the study showed that the aromatic surface hydrophobicity of slow-twitch myosin was 1.5-fold higher than that of fast-twitch myosin. Glorieux et al. (2017) also reported higher aromatic surface hydrophobicity in the thigh due to different myosin isoforms in the two muscles. Therefore, it appears that slow-twitch myosin has more hydrophobic residues on its surface than fast-twitch myosin. As the hydrophobic residues exposed on the surface form aggregates with hydrophobic interactions by thermal treatment (Mitra et al., 2017), the higher surface hydrophobicity of the chicken thigh can negatively influence the digestive susceptibility of proteins. This is further discussed in the succeeding sections.

A,B Different upper case letters indicate significant differences between means (p<0.05).

3 Reasons to use chicken thighs vs. breasts

FAQ

Are chicken thighs healthier than breasts?

Which piece of chicken is healthiest?

If you’re switching out red meat for chicken, you’ll want to stick with chicken breast, as it’s the healthiest cut of the bird.

What is better for losing weight, chicken breast or chicken thighs?

If you’re trying to lose weight, then chicken breast is the best cut for you. It is the leanest part of the chicken, which means it has the fewest calories but the most protein. For example, chicken breast is ideal for bodybuilders on a cut, since it has the fewest calories.

Are chicken thighs a good source of protein?

Both chicken breasts and chicken thighs are good sources of lean protein. The difference between the two meats is largely due to the type of muscle tissue and their myoglobin content. The white meat in chicken breasts contains more protein and less fat, while the dark meat in chicken thighs contains more vitamins and minerals.

What is the difference between chicken breast and chicken thighs?

Chicken breasts are the meat from the pectoral muscle on the underside of the chicken, while chicken thighs are the meat cut from the upper section of the leg, between the breast and the drumstick.

Is chicken thigh fat good or bad?

Most of the thigh meat fat is monounsaturated fat or “good fat,” according to the American Heart Association. Still, there’s more saturated fat (the so-called “bad fat”) in chicken thigh meat compared to white breast meat. But most of the saturated fat is in the skin of both thighs and breasts — so simply remove the skin before you cook them.

Are chicken thighs more lean than chicken breasts?

Although they’re less lean than chicken breasts, thighs can often be cooked in less oil and rely on their own fat to stay moist during the cooking process,” says Shannon Garcia, MDS, RD of Kiss in the Kitchen blog. That extra fat also makes chicken thighs a little easier to cook with because you’re less likely to overcook and dry them out. 4.

Are chicken thighs your favorite?

You’re not alone if you’ve been overlooking chicken thighs: That same survey showed two in five Americans say chicken breast is their favorite.