The Effect of Low-Temperature Heat Treatment on the Physicochemical Properties of Bovine Semitendinosus Muscle

Abstract

This study aimed to investigate the impact of various low-temperature heat treatments, namely sous vide (SV), dynamic temperature roasting (ΔT), and slow roasting (R), on the quality of bovine semitendinosus (ST) muscle. The effects on textural and color properties, myoglobin denaturation cooking loss, and consumer acceptance were examined. The samples treated with the SV cooking methods at 55 °C (SV55) and 65 °C (SV65) showed the lowest WBSF values (p ≤ 0.05). Sous vide at lower temperatures (SV55 and SV65) preserved the highest levels of redness a* (p ≤ 0.05) and exhibited the smallest color differences ΔE (p ≤ 0.05) between the perimeter and center cross-sections. Dynamic temperature roasting with a constant temperature difference between the product core and the oven interior of 40 °C (ΔT40) and 20 °C (ΔT20) and roasting at 75 °C (R75) led to lower color differences in the cross-sections compared to the SV methods (p ≤ 0.05). Among all methods, slow cooking, particularly sous vide, resulted in the highest product quality, with higher consumer acceptance scores for juiciness, tenderness, and color. However, it was comparable to ΔT20 samples in terms of WBSF, tenderness, color acceptance, and overall quality. These results suggest that ΔT20 roasting can serve as an alternative to the SV method, achieving a similar quality of ST muscle product in a significantly shorter time.

1. Introduction

Meat and meat products are generally cooked before eating because cooking meat is essential for a palatable and safe product [1,2].

Recently, increasing consumer awareness about food and nutrition has led to modifications in cooking methods. As a result, alternative heat treatment (HT) techniques have gained significant attention in both culinary and scientific communities due to their potential to enhance meat product quality. These are methods based mainly on the principle of low temperature and long time (LTLT). One of the most commonly used LTLT HT methods is sous vide (SV) cooking [3]. Sous vide is a French word that means “under vacuum”. SV cooking involves slow heating of raw materials or sets/compositions of raw materials that are cooked at precisely controlled low temperatures under 100 °C (usually 50–85 °C) over extended periods (up to 48 h), typically within vacuum-sealed pouches, in the case of meat, aiming to improve tenderness, juiciness, and overall sensory attributes [4,5]. The parameters of the SV process depend on factors such as intramuscular connective tissue, myofibrillar protein composition, meat thickness, and type of cut [4,6]. This technique enhances process efficiency by minimizing cooking loss while simultaneously maintaining a higher nutritional value and sensory characteristics of the meat [7].

A common approach to cooking a beef roast is dry roasting at a consistent temperature, especially for cuts with low connective tissue content [8]. Classic meat cooking methods often involve exposing meat to high temperatures for short durations, leading to significant moisture loss, protein denaturation, and collagen shrinkage, which result in tougher meat textures. In contrast, LTLT cooking aims to minimize these adverse effects by maintaining lower temperatures that prevent rapid moisture loss and excessive protein denaturation [6,9]. SV contributes to maintaining the cellular structure by limiting protein interactions and gelation, which enhances the meat’s water-holding capacity [10]. This is due to the dissolution of collagen and the formation of gelatin under saturated steam conditions [11,12]. Additionally, sous vide heat treatment lowers the generation of heterocyclic aromatic amines (HAAs) in meat products compared to pan frying [13], grilling, and roasting [14]. It also helps inhibit lipid oxidation due to the absence of oxygen in vacuum packaging and the use of low temperatures in the SV process. In contrast to traditional high-temperature methods such as roasting, grilling, microwaving, and frying, where meat is exposed to oxygen and higher temperatures, lipid oxidation is accelerated [15].

Cooking temperature and duration significantly influence the physical properties of meat and its eating quality and safety. The primary factors determining meat toughness are myofibrillar proteins and connective tissue proteins, such as collagen and elastin [16,17,18]. Meat tenderness and color are the main criteria for quality assessment [19]. The formation of meat product tenderness during heating is linked to transformations in muscle tissue. This includes the denaturation of intramuscular connective tissue and myofibrillar protein components [20,21]. Additionally, color changes occur depending on the form of myoglobin and its degree of denaturation [22]. During cooking, three forms of myoglobin interconvert and are degraded through oxygenation, oxidation, and reduction reactions, ultimately influencing the appearance of meat color [16].

In gastronomy, SV is commonly used as a pre-cooking technique for meat. It shortens the main heat treatment time, enhances flavor concentration, and improves the final cooking yield [23].

Several low-temperature cooking techniques exist besides sous vide, each offering specific benefits for meat processing. One such method is slow roasting. During the roasting in a forced-air convection oven, the transfer of heat and moisture occurs within a dynamically evolving, complex porous structure. For slow roasting, meat is cooked at temperatures between 50 °C and 90 °C over an extended period [6,24]. This technique effectively loosens connective tissues while retaining moisture. The product is mainly kept isothermally for a long time, from hours to even days at a temperature of 60 °C or lower [25], at 80 °C [6,9], or at successively increasing temperatures [26]. The thermal processing in which the external temperature is increased continuously, in line with the increase in temperature in the meat core, is called delta-T cooking [26].

The semitendinosus muscle (ST) located in the hind part of beef carcass (eye of round) is known for its relatively high collagen content, which can contribute to increased toughness when subjected to traditional high-temperature cooking methods [27,28]. However, muscles with a high amount of connective tissue (e.g., semimembranosus, SM) are generally believed to require moist heat cooking methods, such as braising [29]. Consequently, exploring the effects of different methods of LTLT cooking on the physicochemical properties of bovine ST muscle is of particular interest. Notably, ΔT roasting remains underexplored in scientific publications, with limited research addressing its impact on meat quality compared to other heat treatment methods. Therefore, this study aimed to assess the effects of various low-temperature heat treatments, with special attention to ΔT roasting at different temperature increase dynamics, on the quality of meat products from bovine semitendinosus muscle. LTLT’s influence on textural properties, color, cooking loss, and the degree of myoglobin denaturation in the final product was determined in this study as well.

2. Materials and Methods

2.1. Raw Material and Preparation

Six beef semitendinosus (ST) muscles, obtained from a homogenous production batch at a slaughterhouse, were purchased from a local butcher’s market. The product was chilled to 4 °C and obtained 48 h post-slaughter. The animals (Simmental bulls) were slaughtered on the same day in a Polish butchery in accordance with internal regulations and under Polish General Veterinary Inspectorate inspection. Muscles, commercially vacuum-packaged, were transported to the laboratory in a box with ice at 2–4 °C within 1 h and wet aged for 5 days at 2 ± 1 °C. After aging, the muscles were trimmed of surface fat. Muscles were divided into portions in a cuboid shape with the dimensions of 5 cm × 5 cm × 15 cm (sample weight: 350–380 g). The head and the tail of each muscle were discarded to minimize the variability within the muscle. Each portion was randomly assigned to a specific heating method. Each HT method involved six portions. Cooking order was determined through randomization to ensure an unbiased estimate of error variance.

2.2. Heat Treatments

ST muscle samples were subjected to the following heat treatment (HT) methods: sous vide (SV), isothermal roasting (R), and dynamic increasing temperature roasting (ΔT). The samples intended for SV cooking were vacuum-packed using a Vac-20 SL2A packaging machine (Edesa Hostelera S.A., Barcelona, Spain) with an in-package vacuum level of 2.5 kPa. The SV samples were cooked using sous vide cooking equipment (CSVT 76EM, RM GASTRO, Praha, Czech Republic) at 55 °C (SV55), 65 °C (SV65), and 75 °C (SV75) for 6 h, 4 h, and 3 h, respectively, based on preliminary experiments. For the designated sous vide cooking times, the final core temperatures reached 52.1 °C for SV55, 63.4 °C for SV65, and 71.3 °C for SV75. After unpacking, all samples exhibited a clear, transparent exudate from the product.

Roasting (R) treatment was carried out in a convection—steam oven (Model CPE-110, Küppersbusch Hausgeräte GmbH, Gelsenkirchen, Germany) at 75 °C (R75) until the core temperature reached 70 °C. ΔT processes, where a constant temperature difference was maintained between the product’s core and the oven interior, with ΔT = 40 (ΔT40) and ΔT = 20 (ΔT20), were conducted in the same type of oven and also reached a final core temperature of 70 °C. The control HT involved boiling in water (CON) until the core temperature reached 70 °C. The temperature was monitored using an EMT-50-K recorder equipped with a needle thermocouple NiCr-NiAl type TP-151 (Czaki Thermo-Product, Raszyn-Rybie, Poland). After cooking, the sealed meat samples were cooled in ice water for 15 min and then stored overnight in a cold room (3 ± 1 °C) [30]. Samples intended for the consumer acceptance test were not cooled.

2.3. pH Value Evaluation

The pH of the muscles was determined using the method described by Wyrwisz et al. [31], with measurements taken from the central part of the ST muscle. pH results were obtained using a Testo 205 series pH meter equipped with an insertion glass electrode, which was placed directly into the samples (2 cm deep into the meat samples). The electrode was calibrated using pH 4.0 and 7.0 buffer solutions before measurement. Each measurement was performed with five repetitions in different locations, taking the mean value as the assay result. The temperature of samples during measurements was 2 ± 1 °C.

2.4. Spectrometric Quantification of Basic Meat Composition

Beef composition (water, fat, protein, and total connective tissue content) was determined using a near-infrared spectrometer NIRFlex N-500 (Büchi) (Flawil, Switzerland). Measurements were taken using a NIRFlex Solids module of spectral range 12,500–4000 cm⁻¹ in reflectance mode [19]. Meat portions of 100 g were homogenized and placed in a Petri dish, forming a 0.5 cm thick layer covering the surface. Measurements were performed with three repetitions, taking the mean value as the assay result.

2.5. Color Measurement

The color properties of the beef product were assessed using a chromometer (Model CR-400, Konica Minolta Inc., Tokyo, Japan) in the L*a*b* system. The measurements were performed with an 8 mm diameter measuring head, a D65 illuminant (6500 K color temperature), and a standard 2° observer. This device was calibrated with a white standard (L* = 98.45, a* = −0.10, b* = −0.13). Color coordinates, including L* (lightness), a* (ranging from green −a* to red +a*), and b* (ranging from blue −b* to yellow +b*), were recorded on the cross-section of the sample, which was cut perpendicularly to the muscle fiber orientation. Five measurements were taken at different locations within the perimeter cross-section (within 1 cm from the edge) (PC-S), and five measurements were taken at different locations within the central cross-section (CC-S) [6]. Data from the raw ST sample were collected after a 30-min blooming period under refrigerated conditions. The degree of color uniformity across the cross-section was determined using the color difference coefficient (ΔE) between the PC-S and the CC-S calculated using Equation (1) as follows:

$$∆E=\sqrt{{\left(L_x^{\mathrm{*}}-L_0^{\mathrm{*}}\right)}^2+{\left(a_x^{\mathrm{*}}-a_0^{\mathrm{*}}\right)}^2{+\left(b_x^{\mathrm{*}}-b_0^{\mathrm{*}}\right)}^2}$$

(1)

where L*₀, a*₀, and b*₀ are the color coordinates of the ST product in the PC-S, and L*_x, a*_x, and b*_x are the color coordinates of the ST product in the CC-S.

2.6. Myoglobin Denaturation

Myoglobin was measured according to the method of Sen et al. [32], with slight modification, as described by Xu et al. [33]. Myoglobin was extracted from the center of each steak after the color measurement of raw and cooked samples. Briefly, 1 g of the sample was homogenized in 9 mL of cold (1 °C) 40 mM phosphate buffer (pH 6.8) for 30 s using a homogenizer (IKA TM-18 Basic, Staufen, Germany). The homogenized mixtures were then centrifuged at 9000× g for 15 min at 4 °C using a Universal 320R centrifuge (Hettich, Tuttlingen, Germany) and filtered through Whatman No. 1 filter paper. Immediately before measurement, 50 µL of freshly prepared 10% sodium dithionite was added to 1 mL of the filtrate. The spectrophotometric measurement (UV-1800, Shimadzu Co., Kyoto, Japan) was performed immediately at 433 nm. The percentage denatured myoglobin (DM) was calculated as following using Equation (2):

$$DM \left(\%\right)=\left({\displaystyle \frac{{Abs}_{433 nm}in raw beef-{Abs}_{433 nm} in cooked beef}{{Abs}_{433 nm}in raw beef}}\right)\times \mathrm{}100$$

(2)

2.7. Cooking Loss

The cooking loss (CL) percentage was calculated by measuring the sample mass before (M_i) and after (M_f) HT, once the sample had cooled to ambient temperature (n = 3). HT was carried out as described in Section 2.2. CL was calculated using Equation (3):

$$CL=1-{\displaystyle \frac{M_f}{M_i}}·100\%$$

(3)

2.8. Warner–Bratzler Shear Force Determination

The Warner–Bratzler shear force (WBSF) was measured using a universal testing machine (Model 5965, Instron, Norwood, MA, USA) equipped with a Warner–Bratzler shear attachment featuring a V-notch blade. The procedure followed the method described by Wyrwisz et al. [19]. After heat treatment, a 2.5 cm thick steak was obtained from the central part of the meat samples, sealed in PA/PE bags, cooled in cold water, and stored overnight at 3 ± 1 °C. Then, six cores (1.27 cm in diameter and 2.5 ± 0.2 cm in length) were cut parallel to the muscle fiber orientation. The direction of shear force was perpendicular to the muscle fibers’ orientation. A 500 N load cell was used, and the crosshead speed was set at 200 mm/min.

2.9. Consumer Acceptance

Consumer acceptance of the meat was assessed following the method of Patinho et al. [34] with some modifications to evaluate the influence of the heat treatment method. Attributes such as taste, cross-section color, juiciness, tenderness, and overall quality were evaluated using a 10 cm unstructured hedonic scale. The scale featured defined endpoints, ranging from 0 (significantly dislike) to 10 (extremely like), following the European Norm PN-EN ISO 11136:2017-08 [35] and PN-EN ISO 5492:2009 [36]. The consumer acceptance test of meat samples was assessed by a group of 45 consumers (60% females and 40% males). The consumers were aged between 23 and 45 years old. All subjects declared themselves as consumers of meat and meat products. Each sample was coded with a three-digit code. After heat processing, the meat was sliced across the muscle fibers into 0.5 cm thick slices, with a quarter of the slice (35–40 g) immediately served on a disposable dish for evaluation. Each consumer assessed seven samples per session. The samples were served under consistent conditions, maintaining uniform temperature and illumination. Consumers were given diluted unsweetened tea between samples for palate cleansing.

2.10. Statistical Analysis

The effect of ST muscle heat treatment on examined parameters was analyzed using Statistica 13.3 (StatSoft Inc., Tulsa, OK, USA). Verification of the difference significance of investigated parameters was studied using LSD Fisher’s test with a significance level of α = 0.05.

3. Results and Discussion

3.1. Characterization of Raw Material—Beef ST

Table 1. Mean ± SD of pH, basic composition (water, fat, protein, and total connective tissue content), and color (L*, a*, b*) of ST.

Parameter	Mean ± SD
pH	5.69 ± 0.25
Water, %	75.51 ± 1.08
Fat, %	1.36 ± 0.38
Protein, %	22.89 ± 0.86
Total connective tissue, %	1.34 ± 0.39
L*	49.85 ± 3.18
a*	23.93 ± 2.63
b*	12.58 ± 2.12

shows the descriptive data of pH and the basic composition of ST muscle at 48 h post-mortem. The observed results indicate that the raw meat was of normal quality (without defects) [28,37,38,39].

3.2. Cooking Loss and WBSF

Table 2. The impact of the heat treatment (HT) method on cooking time (CT), CL, and WBSF of the product obtained from ST muscle (mean ± SD).

HT Method	CT (Min)	CL (%)	WBSF (N)
CON	47.24 ± 3.54	37.12 ± 2.56 e	44.29 ± 3.45 d
SV55	360 *	22.55 ± 2.84 b	26.47 ± 3.18 a
SV65	240 *	26.28 ± 3.08 c	28.26 ± 3.85 ab
SV75	180 *	31.19 ± 2.87 d	32.84 ± 3.26 c
ΔT20	135.25 ± 8.28	18.78 ± 3.12 a	29.65 ± 2.98 b
ΔT40	82.21 ± 5.28	19.54 ± 3.28 a	33.68 ± 3.77 c
R75	116.22 ± 11.26	21.32 ± 2.49 ab	29.84 ± 2.46 b

*—based on preliminary experiments; letters (a, b…) show the significant differences in a column (p ≤ 0.05).

summarizes the CT, CL, and WBSF changes of ST muscle cooked using various methods. CT corresponded to the duration required to reach a core temperature of 70 °C. The exception was the SV treatments, for which the duration was determined based on preliminary experiments. The shortest process was boiling in water (47.24 min), while the longest, excluding SV, was ΔT20 (135.25 min). Increasing ΔT from 20 to 40 reduced the heat treatment time by 53 min.

The lowest CL values were observed in samples treated with ΔT20 (18.78%) and ΔT40 (19.54%), whereas the CON heat treatment resulted in the highest CL (37.12%; p ≤ 0.05) (Table 2). The lower cooking losses observed in the ΔT methods may be explained by the gradual and more controlled heating process, which minimizes instant protein denaturation and structural damage, thereby better preserving the water-holding capacity of the meat [40]. In the SV method, an increase in heat treatment temperature led to a significant rise in CL (p ≤ 0.05). However, increasing ΔT from 20 to 40 did not cause significant changes in CL. The observed effect may be attributed to the increase in internal temperature, which induces protein denaturation, reducing water-binding capacity and leading to protein network shrinkage. Consequently, this shrinkage increases internal pressure within the product, forcing excess water to be expelled from the surface through convective mass transfer. Additionally, the unbalanced pressure contributes to further shrinkage, resulting in greater water loss from the meat structure [1,41].

The boiled sample (CON) had the highest shear force value (44.29 N), which was significantly higher than that of the other samples (p ≤ 0.05). In contrast, the samples treated with the SV55 and SV65 methods showed the lowest WBSF values (26.47 N and 28.26 N, respectively; p ≤ 0.05). These samples also exhibited the highest tenderness among all those tested. Lowering the ΔT (the temperature difference between the product’s center and the oven interior) from 40 to 20 led to a significant (p ≤ 0.05) reduction in WBSF values, from 33.68 N to 29.65 N, respectively. The difference in tenderness between ΔT20 and ΔT40 results from the duration of exposure to higher temperatures. Using a higher ΔT value (ΔT40) in roasting may have contributed to reduced tenderness, as a higher final temperature was reached in the oven. This could be caused by the fact that ΔT20 samples were exposed to a maximum temperature of 90 °C (a final core temperature of 70 °C + ΔT20 = 90 °C in the oven). In contrast, ΔT40 samples were exposed to temperatures above 90 °C, resulting in a reduction in their tenderness.

The slowest roasting samples, ΔT20 and R75, had similar tenderness (p > 0.05), while the ΔT40 sample had a comparable WBSF value to the SV75 sample. According to Sullivan and Calkins [42], consumers find beef tenderness acceptable when the WBSF value is below 39 N. Based on these findings, it can be concluded that ST muscle products processed using LTLT methods demonstrated a considerably high and acceptable level of tenderness.

The denaturation of meat proteins, which involves structural changes, primarily depends on the rate at which heat penetrates the surface of the meat and the internal heat conduction within the product during heat treatment [2,43]. Ishiwatari et al. [44] show that the denaturation of key proteins, including myosin, sarcoplasmic proteins, collagen, and actin, takes place at different temperature ranges. The degree of protein denaturation during HT is determined by the heat flux supplied to the product as well as the time of exposure to the higher temperature of the heating medium [45]. Tornberg [1] also observed that protein denaturation is influenced by both the heating temperature and the type of protein and indicated that myosin denatures at temperatures between 54 and 58 °C, while sarcoplasmic proteins undergo denaturation between 65 and 67 °C. Additionally, actin denatures at a higher temperature range, occurring between 80 and 83 °C. When collagen is heated in the presence of water, it dissolves, leading to the loosening of connective tissue and an improvement in meat tenderness. However, it is important to note that the denaturation of myofibrillar proteins can have the opposite effect, increasing meat hardness [46] by causing thermal shrinkage of both muscle fibers and connective tissue [47,48].

3.3. Color Changes

Table 3. The changes in color coordinates L*, a*, and b* on the PC-S and CC-S surfaces and the ΔE values on the cross-section of the product obtained from ST muscle depending on the HT method.

HT Method		PC-S			CC-S			ΔE
		L*	a*	b*	L*	a*	b*
CON	$\overline{X}$	56.54 a, Y	5.34 a, X	8.26 a, X	53.33 a, X	8.24 a, Y	9.16 a, X	4.48 f
	SD	±0.66	±0.84	±0.58	±1.43	±0.41	±0.32	±0.64
SV55	$\overline{X}$	57.12 ab, X	20.01 f, X	11.58 d, X	56.56 b, X	20.42 e, X	12.15 c, X	0.86 a
	SD	±1.84	±0.46	±0.82	±2.19	±0.83	±0.65	±0.28
SV65	$\overline{X}$	58.84 ab, X	15.83 d, X	10.11 c, X	57.94 b, X	16.27 c, X	10.98 b, X	1.35 b
	SD	±1.01	±0.59	±1.02	±1.67	±1.21	±0.38	±0.49
SV75	$\overline{X}$	62.68 c, X	8.12 b, X	9.22 b, X	61.15 d, X	9.03 b, Y	9.88 a, X	1.97 c
	SD	±1.18	±0.73	±0.26	±1.04	±0.41	±0.38	±0.35
ΔT20	$\overline{X}$	59.75 b, X	19.12 e, X	10.28 c, X	59.29 c, X	19.57 e, X	11.12 b, X	1.49 b
	SD	±0.49	±0.95	±0.46	±0.85	±0.59	±0.38	±0.38
ΔT40	$\overline{X}$	62.22 c, X	13.14 c, X	11.24 d, X	61.98 d, X	15.52 c, Y	12.54 c, Y	2.68 e
	SD	±1.08	±0.49	±0.75	±1.47	±1.06	±0.43	±0.47
R75	$\overline{X}$	60.83 b, X	16.21 d, X	12.02 e, X	60.75 cd, X	18.32 d, Y	12.81 c, X	2.29 d
	SD	±1.15	±0.94	±0.44	±1.22	±0.29	±0.47	±0.52

PC-S—perimeter of cross-section; CC-S—center of cross-section. * (a, b…) show the significant differences in a column (p ≤ 0.05); (X, Y…) show the significant differences in a row (p ≤ 0.05).

presents the effect of different heat treatment (HT) methods on the color parameters (L*, a*, b*) of the perimeter and center of the cross-section of ST muscle, as well as the total color difference (ΔE). The study of the color components on both the sample’s perimeter and center allowed us to assess the degree of color uniformity across the product’s cross-section during heat treatments at different heating rates.

The significantly highest L* lightness values, both at the perimeter and center of the ST muscle section, were observed in the SV75 and ΔT40 samples (62.68/61.15 and 62.22/61.98, respectively, p ≤ 0.05). In contrast, the lowest L* lightness was recorded in the product treated with the CON method (56.54/53.33, p ≤ 0.05). This effect can be attributed to variations in cooking loss across different methods. Shen et al. [49] have shown that steaks with higher moisture content reflect more light, leading to increased L* values. Furthermore, the CON-treated product exhibited the lowest redness values both at the perimeter (a* = 5.35) and the center (a* = 8.24) of the cross-section. In contrast, the samples processed using SV55 and ΔT20 showed the highest redness, with values of 20.01 and 19.12 at the perimeter and 20.42 and 19.57 at the center, respectively (p ≤ 0.05). The increased redness in SV and ΔT samples resulted from lower center temperatures, which minimized myoglobin denaturation, preserving the red color in the cooked ST muscle. In contrast, the high cooking temperature in the boiled sample led to browning, reducing a* values [33]. Similarly, Dominguez-Hernandez et al. [25] reported that elevated cooking temperatures intensified myoglobin denaturation, leading to a decrease in a* values.

In addition, a significant difference (p ≤ 0.05) in yellowness (b*) was observed among the various HT methods. The highest b* value at the perimeter of the cross-section was found in samples prepared using R75 (12.02, p ≤ 0.05), while in the center of the cross-section, the highest b* values were recorded in samples treated with R75, ΔT40, and SV55 (12.81, 12.54, and 12.15, respectively, p ≤ 0.05).

Analyzing ΔE values, the most uniform color across the cross-section (indicated by the lowest ΔE) was observed in samples treated with the SV55 method, followed by SV65 and ΔT20 (0.86, 1.35, and 1.49, respectively, p ≤ 0.05). The highest ΔE was recorded in samples prepared using the CON method (4.48, p ≤ 0.05). The noticeable color difference in the cross-section of the CON sample was primarily due to a significant variation in redness (a*) and lightness (L*) between the perimeter and the center. According to the CIE (International Commission on Illumination) classification, the high ΔE value of the CON sample (4.48) indicates a clearly perceptible color difference, while the ΔE value of the SV55 sample (0.86) falls within the range of an imperceptible difference, even for a trained observer. The absence of a color difference in the cross-section of the CON sample was mainly attributed to differences in redness (a*) and lightness (L*) between PC-S and CC-S.

3.4. Myoglobin Denaturation Changes

The cooked meat color is primarily influenced by heat-induced myoglobin denaturation [50], with a higher degree of denaturation leading to a darker brown appearance [51]. The process of cooking denatures myoglobin, which is responsible for the characteristic dull brown color of cooked meat products. However, the denaturation temperature varies among different redox forms of myoglobin. In meat, myoglobin begins to denature between 55 °C and 65 °C, reaching its maximum denaturation at 75–80 °C [52].

The HT method significantly impacted the extent of myoglobin denaturation (p ≤ 0.05, Figure 1). The CON-treated sample exhibited the highest level of myoglobin denaturation, approaching nearly 100%, which corresponded with its lowest a* values (Table 3). Among all samples, the SV55 treatment resulted in the lowest myoglobin denaturation ratio (33%), followed by the ΔT20 sample (38.3%) (Figure 1). The lower level of myoglobin denaturation in the SV and ΔT samples explains their higher a* values, as shown in Table 3.

Sen et al. [32] reported that the degree of myoglobin denaturation is influenced by heating temperature, with higher cooking temperatures resulting in a greater denaturation ratio and, consequently, lower a* values.

In the present study, although the ΔT40 sample was subjected to the highest HT temperature (110 °C, calculated as 70 °C + ΔT40), its myoglobin denaturation ratio was lower than that of the CON sample. This could be attributed to the fact that heating was halted as soon as the ΔT sample’s core temperature reached 70 °C.

3.5. Consumer Acceptance Rating of ST Muscle

The mean scores for the consumer acceptance test of beef, assessing the impact of the cooking treatments studied, are presented in Figure 2. Low-temperature HT methods resulted in higher consumer ratings for all characteristics tested, except for cross-section color and tenderness, compared to the control (boiling) sample. In contrast, the ΔT40-treated sample received the lowest cross-section color and tenderness ratings. The SV55 treatment led to the highest acceptability of juiciness and cross-section color. Considering the results of instrumental color measurements, the SV55 samples, which exhibited the most uniform color in the cross-section (lowest ΔE) and the highest redness (a*), received the highest consumer ratings. On the other hand, the highest overall quality ratings were recorded for the SV75-treated samples, with slightly lower ratings for the ΔT20- and R75-treated samples. These results correspond with the research of Gil et al. [53], where sous vide cooking was associated with higher juiciness ratings across different muscles compared to traditional cooking methods. Additionally, tenderness ratings were higher in sous vide-treated meat regardless of aging time (2 vs. 21 days). Juiciness is a crucial quality attribute that affects consumer satisfaction with cooked beef following tenderization. The meat’s moisture content, which determines its juiciness, is primarily influenced by total water content and cooking loss. Naqvi et al. [54] showed that low-temperature, long-time sous vide cooking significantly impacts both cooking loss and the total water content of beef. We found that juiciness acceptance decreased as the applied heat treatment temperature increased. Purslow et al. (2018) [12] explained this by noting that most of the water in muscles is retained within myofibrillar proteins. As the temperature increases, the meat structure undergoes greater shrinkage due to the denaturation of myofibrillar proteins, leading to water being squeezed out and resulting in higher toughness.

4. Conclusions

Different heat treatment (HT) methods significantly impact the quality and characteristics of beef ST muscle. Slow-cooking methods like sous vide (SV) at lower temperatures and ΔT roasting methods resulted in lower cooking losses and better tenderness, as indicated by the lower WBSF values. The SV55 method produced the most tender beef, with a significantly lower WBSF value compared to other methods, but SV65, ΔT20, and R75 samples in terms of acceptance tenderness were similar to SV55.

SV heat treatment methods have the most uniform color; however, the ΔT20- treated product was visually indistinguishable from the SV65-treated product. Higher cooking temperatures (as in the CON method) caused significant color changes, resulting in a less desirable appearance. Additionally, the level of myoglobin denaturation, which is a key factor in meat color changes, was lowest in SV-treated samples, which preserved the redness more effectively than the CON method, which correlated with the ΔE values. Slow cooking methods, particularly SV, resulted in the most favorable product quality, with higher consumer acceptance scores for juiciness, tenderness, and color.

There are, therefore, heat treatment methods that can serve as alternatives to the SV method. The ΔT20 method is over 2.5 times shorter than the SV55 method, giving comparable effects. This may translate into lower energy consumption and, ultimately, higher profit margins. From a practical perspective, the use of both sous vide and ΔT roasting in gastronomy reduces cooking loss and improves texture, contributing to better portion control and minimized raw material waste—both crucial economic factors.