Effects of Different Processing Methods on the Quality and Flavor Characteristics of Shiqi Pigeon (Columba livia domestica) Meat

TL;DR

This study compares how boiling, roasting, and frying affect the texture, color, and flavor of Shiqi pigeon meat.

Contribution

The study provides new insights into how different cooking methods alter pigeon meat's quality and flavor characteristics.

Findings

Fried pigeon meat was the hardest and chewiest, while boiled meat was the softest.

Frying caused the most significant color change and protein structure alteration in pigeon meat.

Electronic nose analysis effectively distinguished flavor differences between cooking methods.

Abstract

This study investigated the effects of boiling, roasting, and frying on the quality and flavor characteristics of Shiqi pigeon (Columba livia domestica) meat. Changes in color, texture, microstructure, and volatile profiles were systematically evaluated using colorimetry, texture profile analysis, scanning electron microscopy, electronic nose analysis, and Fourier transform infrared spectroscopy (FTIR). Thermal processing significantly influenced physicochemical properties and flavor profiles. Fried samples exhibited the highest hardness (27.79 N), chewiness (33.13 mJ), and maximum shear force (30.23 N), while boiled samples showed the lowest hardness (22.12 N) and puncture hardness (12.20 N), indicating improved tenderness. Electronic nose PCA explained 85.4% of total variance (PC1: 59.5%; PC2: 25.9%), clearly discriminating the three treatments. Color measurements showed that frying induced the greatest total color difference (ΔE > 1, p < 0.05), followed by roasting and boiling. FTIR analysis revealed pronounced shifts in amide I bands in fried samples, indicating stronger protein secondary structure alterations. Overall, different thermal processing methods produced distinct quality and flavor characteristics in pigeon meat, providing scientific guidance for process optimization and product development.

Figures

Full text

1. Introduction

Poultry meat is a major component of the human diet due to its high nutritional value, including high-quality proteins, essential amino acids, minerals, and vitamins [1,2,3]. Pigeon meat has attracted increasing attention as a high-value poultry protein source because of its favorable nutritional profile and distinctive flavor characteristics [4,5,6]. Compared with other poultry meats, pigeon meat contains higher proportions of umami-related amino acids and abundant fatty acids, providing a strong chemical basis for its unique sensory properties [7]. Shiqi pigeon (Columba livia domestica), a representative local breed in southern China, has long been consumed in traditional tonic diets. Thermal processing conditions, particularly temperature and duration, substantially affect meat composition and flavor precursors, thereby determining final sensory quality [8,9,10]. Prolonged heating at elevated temperatures has been shown to reduce free amino acid levels, highlighting the sensitivity of meat flavor to cooking parameters [11,12]. Meanwhile, local poultry breeds exhibit considerable potential for developing high-quality meat products with distinctive flavor traits [13,14]. Meat flavor formation involves complex reactions among amino acids, nucleotides, and lipids during heating, with the Maillard reaction and lipid oxidation serving as the dominant pathways for volatile compound generation [15,16,17]. Volatile organic compounds (VOCs) produced through these reactions are the primary contributors to flavor perception [18,19]. Although extensive studies have focused on chicken and other mainstream poultry meats [20,21,22], systematic investigations into the nutritional and flavor changes in traditional pigeon meat during thermal processing remain limited. Therefore, this study investigated changes in the physicochemical properties and volatile flavor compounds of Shiqi pigeon during cooking, providing insights into flavor formation mechanisms and supporting the development of high-quality pigeon meat products.

2. Materials and Methods

2.1. Materials and Equipment

Petroleum ether (boiling range 60–90 °C, analytical grade) was purchased from Guanghua Sci-Tech Co., Ltd. (Shantou, China). Ethanol (absolute ethanol, analytical grade, purity ≥ 99.7%) was obtained from Guangshi Reagent Technology Co., Ltd. (Zhaoqing, China). Phosphate-buffered saline (PBS, 1×, pH 7.4) was supplied by Guangzhou Teno Biotechnology Co., Ltd. (Guangzhou, China). Corn germ oil was purchased from Yihai Kerry Oils & Grains Industries (Shanghai, China). A biological microscope (model BA210-T) was obtained from Motic Group Co., Ltd. (Xiamen, China). A multifunction ceramic cooktop (model H21-HST2105) was purchased from Midea Life Appliances Manufacturing Co., Ltd. (Foshan, China). An electric oven (air fryer, model KD50DQ852) was obtained from Zhejiang Supor Co., Ltd. (Taizhou, China). Texture analysis was performed using a texture analyzer (model EVS-iPro, specification 25-2810-02) purchased from Beijing Ying Sheng Hengtai Technology Co., Ltd. (Beijing, China). A colorimeter (model LS172) was obtained from Linshang Technology Co., Ltd. (Shenzhen, China). Microstructural observations were conducted using a field-emission scanning electron microscope (model Sigma 500, ZEISS, Jena, Germany). Fourier transform infrared spectra were recorded using an Fourier transform infrared spectroscopy (FTIR, model Nicolet iS500, Thermo Fisher Scientific, Waltham, MA, USA).

2.2. Sample Preparation

Pigeon meat samples were subjected to different thermal processing methods, including boiling, roasting, and frying [12]. A simplified schematic illustration of the sample preparation procedure is shown in Figure 1. Fresh pigeons were purchased from Guangdong Baoning Agriculture and Animal Husbandry Technology Co., Ltd. (Meizhou, China). Twenty-five-day-old Shiqi pigeons that met slaughter hygiene standards were selected for the experiments. After defeathering, the pigeons were skinned, visible fat deposits were removed, and the carcasses were thoroughly washed with distilled water. The prepared pigeon meat was then cut into appropriate portions for subsequent thermal processing. For boiling, pigeon meat samples were placed in a stainless-steel pot containing 1000 mL of water and cooked for 12 min using a Midea multifunction ceramic cooktop operated at a power of 1200 W. For roasting, pigeon meat samples were processed using a Supor air fryer with a rated power of 1200 W. The air fryer was preheated at 180 °C for 5 min, followed by roasting at 180 °C for 25 min. For frying, 1000 mL of edible oil was added to a stainless-steel pot and heated using a Midea multifunction ceramic cooktop at 1200 W. When the oil temperature reached 100 °C, the pigeon meat was added and fried for 12 min. After thermal processing, the samples were allowed to cool to room temperature and were then subjected to subsequent analyses. In all experiments, the pectoralis major (breast muscle) was selected for analysis due to its homogeneous fiber composition and commercial relevance. All samples were obtained from the same anatomical location to minimize variability associated with muscle type. The orientation of muscle fibers was carefully controlled during texture and structural analyses to ensure consistency.

2.3. Electronic Nose Analysis

An intelligent odor analysis system (AIRSENSE, model PEN 3, Schwerin, Germany) was used to evaluate the samples. For sample preparation, meat portions were finely minced, and 2.0 g of the homogenized sample was rapidly and accurately weighed into headspace vials, which were then sealed with polytetrafluoroethylene (PTFE)/silicone septa. All samples were equilibrated at room temperature for 30 min prior to analysis. Headspace measurements were subsequently performed for 60 s. Each sample was analyzed in triplicate, and the mean value was reported.

2.4. Scanning Electron Microscopy (SEM) Observation

Meat samples were collected from the central region of the processed products. For fried and roasted meats, sections containing the outer crust together with the underlying muscle tissue were selected, direct observation of frying-induced pore formation and localized carbonized areas. Surface oil visible to the naked eye was first removed using absorbent paper. The samples were then gently rinsed for 10–30 s with an ethanol/petroleum ether mixture (1:1, v/v), followed by rapid drying using a stream of warm air.

After pretreatment, all samples were cut into small blocks (approximately 5 mm × 5 mm × 1 mm) and fixed in 2.5% (v/v) glutaraldehyde solution (pH 7.2) at 4 °C for 10 h. The fixed samples were rinsed with phosphate-buffered saline (PBS) three times (10 min each), and residual surface liquid was removed using filter paper. Thin slices (1 mm) were placed flat on aluminum foil, pre-frozen at −80 °C for 2 h, and subsequently subjected to vacuum freeze-drying until a constant weight was reached.

The surface microstructure of the dried samples was examined using scanning electron microscopy (model Sigma 500, ZEISS, Jena, Germany). Prior to observation, the samples were sputter-coated with a thin layer of gold electrical conductivity. Gold coating was carried out either at 50 mA for 30 s or at 3 mA for 6 min. SEM imaging was performed at accelerating voltages of 15 kV and 20 kV. The resulting micrographs were used for qualitative comparison and, where appropriate, further statistical analysis.

2.5. Texture Profile Analysis (TPA) and Mechanical Properties of Meat

Texture characteristics of the meat samples were determined using a texture analyzer equipped with a 50 mm cylindrical compression probe, a TMS light-duty single-blade combined shear probe, and a PA5S cylindrical probe for puncture testing. Texture profile analysis, shear force, and puncture force were evaluated separately [23]. Pigeon breast meat subjected to three different thermal processing methods was cut into cubic samples (10 mm× 10 mm× 10 mm) for TPA double-compression and shear force measurements. For puncture testing, the pigeon breast meat was cut into blocks of 15 mm × 15 mm × 10 mm. During all measurements, the fiber orientation of the meat samples was kept consistent to minimize directional effects on texture results. For TPA testing, the test speed was set at 60 mm/s, the trigger force was 0.75 N, and the compression strain was 50%. Each sample was subjected to three consecutive measurements, and the mean value was reported. Shear force testing was conducted at a test speed of 60 mm/s with a trigger force of 0.75 N. Puncture tests were performed at a test speed of 60 mm/s, with a trigger force of 0.75 N and a puncture distance of 20 mm. All shear and puncture measurements were carried out in triplicate, and average values were used for subsequent analysis.

2.5.1. Meat Color Changes Under Different Processing Times

For each of the three thermal processing methods, pigeon breast meat samples were collected at processing times ranging from 0 to 12 min. At 2 min intervals, one sample from the left and right breast was taken and photographed to record color changes during thermal processing.

2.5.2. Meat Color Changes During Different Thermal Processing

The selected time intervals (0–12 min, at 2 min increments) were based on preliminary tests and typical cooking practices for pigeon meat. Processing beyond 12 min resulted in excessive browning, moisture loss, and hardening, which were not representative of normal edible conditions. Therefore, 12 min was set as the maximum processing time. Before measurement, the colorimeter was calibrated using a standard white plate. Color values were recorded at five positions on each sample, and the mean value was calculated. Results were expressed as L*, a*, and b* values.

The same measurement procedure was applied to roasted and boiled samples. Color analysis was conducted following the method described by Wenqian Lei et al. [24].

The total color difference (ΔE) was calculated according to the following equation:

$$[eqn]$$

where ΔL*, Δa*, and Δb* represent the differences in lightness, redness, and yellowness between each sample and the corresponding mean values at 0 min, respectively.

2.6. Fourier Transform Infrared Analysis

FTIR analysis was performed using a Fourier transform infrared spectrometer [25]. Steamed, fried, and roasted meat samples were collected, and small portions were excised from the central region of each sample. Visible connective tissue and surface carbonized areas were carefully removed. The meat samples were then cut into thin slices with a thickness of approximately 2 mm and evenly spread on freeze-drying trays. The samples were pre-frozen at −40 °C for at least 4 h and subsequently freeze-dried under low-temperature vacuum conditions for 24–48 h until the sample mass remained essentially constant. After freeze-drying, the meat samples were rapidly ground into a uniform fine powder and passed through an 80-mesh sieve to ensure consistent particle size prior to FTIR measurement.

2.7. Statistical Analysis

All experiments were conducted in triplicate unless otherwise stated, and results are presented as mean ± standard deviation. Statistical analyses were performed using SPSS software (version 27.0, IBM Corp., Armonk, NY, USA). One-way analysis of variance (ANOVA) was applied to evaluate the effects of different thermal processing methods. When significant differences were detected, Duncan’s multiple range test was used for post hoc comparisons. Differences were considered statistically significant at p < 0.05.

3. Results and Discussion

3.1. Volatile Profile Analysis Using an Electronic Nose System

Figure 2a–c present the electronic nose response profiles of pigeon meat subjected to frying, roasting, and boiling. For all treatments, the dynamic response curves (left panels) exhibited a rapid increase in sensor signals followed by gradual stabilization, reflecting a typical adsorption–equilibrium response pattern. Among the ten sensors, R(7) and R(2) showed relatively stronger responses, although their intensities and response kinetics varied depending on the thermal processing method.

The radar plots (right panels) revealed differences in sensor response distributions among treatments. Fried and roasted samples displayed more pronounced and dispersed response patterns, whereas boiled samples showed generally lower signal intensities and a more compact distribution. Statistical analysis (one-way ANOVA, p < 0.05) indicated processing-dependent variations in several sensor channels. Roasted samples exhibited relatively higher responses in R(7), boiled samples showed stronger signals in R(2), and fried samples demonstrated rapid signal development in R(8) [26]. In contrast, R(9) exhibited comparatively small variation among treatments (p > 0.05) under the present experimental conditions.

Principal component analysis (PCA) was applied as an exploratory multivariate tool to visualize differences among samples. The first two principal components accounted for 85.4% of the total variance (PC1: 59.5%; PC2: 25.9%), indicating that most variability in the dataset was captured within two dimensions. The PCA score plot showed separation among boiled, roasted, and fried samples, suggesting distinct multivariate response patterns associated with each thermal processing method. The distribution along PC1 and PC2 was generally consistent with the sensor response characteristics observed in the radar plots. Similar applications of PCA combined with electronic nose analysis have been reported for distinguishing processing-related flavor differences in meat products [27,28] (Figure 3).

3.2. Microstructural Morphology Analysis of the Microstructure of Pigeon Meat

As shown in Figure 4, the SEM images illustrate distinct microstructural differences in pigeon meat subjected to boiling (a), roasting (b), and frying (c) [29]. In the boiled samples, muscle fibers exhibited noticeable fracture and moderate shrinkage, with clearly enlarged gaps between adjacent fiber bundles, resulting in a relatively loose and disordered surface structure. This morphology is likely associated with collagen solubilization and protein denaturation under moist heating conditions, which weakens connective tissue integrity and promotes fiber separation. In contrast, roasted samples showed more severe fiber fracture and pronounced shrinkage, accompanied by the formation of a compact and rigid surface layer. The reduced inter-fiber spacing observed in roasted meat can be attributed to intense protein denaturation and dehydration induced by dry heat, leading to strong contraction of muscle fibers. Compared with boiling and roasting, fried samples did not exhibit extensive fiber fracture but displayed a markedly loosened structure, with signs of partial fusion of muscle fibers. The high temperature during frying accelerates internal moisture migration and evaporation, while rapid surface dehydration may hinder effective moisture release from the interior, resulting in disruption of the fiber framework. Continuous moisture loss further promotes pore formation and collapse within the solid matrix, giving rise to a loosened microstructure. Consistent with previous observations reported by Xue Liang et al. [30], muscle fiber disruption was observed in pigeon meat processed by all three thermal methods, which can be generally attributed to protein denaturation and shrinkage induced by high-temperature treatment.

It should be noted that SEM sample preparation procedures, including solvent rinsing and freeze-drying, may induce minor structural modifications such as shrinkage or pore formation. Therefore, the present observations are primarily intended for comparative qualitative analysis rather than absolute morphometric quantification.

3.3. Texture Analysis of Pigeon Meat

As shown in Table 1, thermal processing significantly affected the texture properties of pigeon meat. Fried samples exhibited the highest hardness (27.79 N), chewiness (33.13 mJ), gumminess (11.94 N), and puncture hardness (18.68 N), indicating a firm structure but reduced tenderness. In contrast, boiled samples showed the lowest hardness (22.12 N) and chewiness (23.51 mJ), reflecting a softer and more tender texture, while roasted samples displayed intermediate values for most parameters.

Cohesiveness varied only slightly among treatments (0.43–0.45), suggesting limited effects of processing method on internal structural integrity. Springiness increased from boiling (2.46 mm) to roasting (2.53 mm) and frying (2.78 mm), while resilience was highest in roasted samples (0.18), indicating enhanced elastic recovery under moderate dehydration. Fried samples exhibited the highest maximum shear force (30.23 N), whereas roasted samples showed the lowest value (17.25 N). Boiled samples displayed the lowest puncture hardness (12.20 N), consistent with a loosened muscle fiber structure. Adhesiveness was markedly higher in roasted meat (0.24 N·mm) than in boiled and fried samples (0.07 N·mm). The frying produced pigeon meat with high chewiness but low tenderness, boiling resulted in a soft and tender texture, and roasting yielded intermediate texture properties. These differences are consistent with the microstructural changes observed by SEM, highlighting the strong influence of thermal processing conditions on meat texture. The observed differences in texture parameters are consistent with findings reported for other poultry species. Previous studies on chicken breast meat have shown that frying significantly increases hardness and chewiness due to intensified protein denaturation and moisture loss, whereas boiling generally produces a softer texture as a result of collagen solubilization and reduced structural rigidity. Similar trends have also been observed in beef and pork subjected to dry-heat treatments. These comparisons suggest that the texture modifications observed in Shiqi pigeon meat follow general thermal denaturation mechanisms common to muscle foods, although breed-specific differences in muscle fiber composition may modulate the magnitude of these effects.

3.4. Color Characteristics

3.4.1. Color Changes in Pigeon Meat During Different Thermal Processing Processes

Figure 5 illustrates the visual color changes in pigeon meat subjected to frying, roasting, and boiling at processing times ranging from 0 to 12 min. Distinct color evolution patterns were observed among the three thermal treatments, indicating clear differences in browning behavior and reaction intensity.

During frying, the color of pigeon meat changed rapidly with increasing processing time. Pronounced browning was observed at the early stage of heating, and the surface color gradually deepened from light brown to dark brown with prolonged frying time, indicating an accelerated browning process. In contrast, roasted samples exhibited relatively moderate color changes throughout the processing period. The meat surface largely retained a reddish appearance, although slight browning became noticeable at extended roasting times, suggesting a slower and less intense color transformation compared with frying. For boiled samples, color changes also occurred rapidly during the initial stage, with the meat gradually turning from pink to light brown. However, after approximately 8 min of boiling, further color changes became less pronounced, indicating that the browning reaction tended to reach a plateau under moist heating conditions. The color changes observed under all three thermal processing methods can be primarily attributed to non-enzymatic browning reactions, particularly the Maillard reaction [31]. However, the rate and extent of browning differed markedly among treatments, which is likely related to differences in heat transfer efficiency and reaction environment. Although roasting was conducted at a higher nominal temperature (180 °C) compared with frying (oil temperature 100 °C), browning intensity depends not only on the set temperature but also on heat transfer efficiency, surface dehydration rate, and the local reaction environment. Direct contact between the meat surface and hot oil may enhance heat transfer and promote rapid surface dehydration, thereby facilitating localized Maillard reactions. However, surface temperature was not directly measured in this study. Therefore, the observed browning differences should be interpreted as resulting from combined thermal and environmental effects rather than temperature alone.

3.4.2. Changes in Color Parameters (L*, a*, b*) and Total Color Difference (ΔE) of Pigeon Meat During Boiling, Roasting, and Frying as Measured by a Colorimeter

Figure 6 presents the changes in lightness (L*), redness (a*), yellowness (b*), and total color difference (ΔE) of pigeon meat subjected to boiling, roasting, and frying. Panels (A–D) correspond to L*, a*, b*, and ΔE values, respectively. For each processing method, statistical comparisons were conducted between samples processed for 2, 4, 6, 8, 10, and 12 min and those at 0 min (p < 0.05, p < 0.01, ns indicates not significant). Using the mean L*, a*, and b* values at 0 min as reference points, the calculated ΔE values for all treatments exceeded 1, indicating visually perceptible color changes during boiling, roasting, and frying. The significance analysis further confirmed that the color differences were statistically meaningful. During boiling, L* and b* values initially increased and then decreased, while a* values continuously declined, which may be associated with progressive myoglobin denaturation under moist heating conditions [32]. In the roasting process, L* and b* values gradually increased and a* values decreased; however, the overall magnitude of change was relatively small, indicating only mild browning. This limited variation may be attributed to the relatively slow heat transfer of hot air, resulting in insufficient thermal intensity to induce vigorous Maillard reactions within 12 min. In contrast, frying induced pronounced color changes. The L* value increased at the early stage and subsequently decreased with extended frying time. The a* value decreased sharply between 2 and 4 min and then slightly increased, while the b* value continuously increased before showing a slight decline at later stages. These pronounced variations reflect evident browning during frying, which can be attributed to intense Maillard reactions promoted by high temperature heating [33]. Overall, the differences in L*, a*, b*, and ΔE evolution among boiling, roasting, and frying highlight the critical role of heating medium and thermal intensity in regulating color development during pigeon meat processing. Comparable browning behavior has been reported in chicken and other poultry meats, where dry heating promotes stronger Maillard reactions and lipid oxidation, leading to darker surface coloration. The relatively moderate color change observed during roasting in the present study aligns with reports indicating that hot air heating results in slower heat penetration compared with direct oil contact during frying. These cross-species similarities further support the role of heat transfer efficiency and moisture conditions in regulating meat color development.

3.5. FTIR Analysis of Pigeon Meat

The FTIR spectra of pigeon meat subjected to boiling (a), roasting (b), and frying (c) are presented in Figure 7. Clear variations in peak intensity and slight shifts in peak position were observed among treatments, indicating processing-related modifications in molecular interactions.

The broad absorption band around 3286 cm^−1^, assigned to O–H and N–H stretching vibrations [34], was most intense in boiled samples and decreased in roasted and fried samples. This pattern suggests possible differences in hydrogen bonding environments under moist and dry heating conditions. The band near 2925 cm^−1^, associated with lipid –CH stretching vibrations [35], showed higher intensity in fried samples, which may be related to oil absorption during processing. Changes in the amide I (approximately 1600–1700 cm^−1^) and amide II (~1535 cm^−1^) regions were also observed. Slight shifts and peak broadening in roasted and fried samples compared with boiled samples suggest alterations in protein secondary structure-related spectral features. However, as quantitative deconvolution of the amide I region was not performed, these observations are interpreted as indicative of possible conformational modifications rather than definitive changes in specific secondary structure components. The band at 1075 cm^−1^ (C–O–C stretching), associated with carbohydrate-related structures, showed reduced intensity in roasted samples, which may reflect thermal reactions involving carbohydrate components under dry heating [36]. The absorption near 1235 cm^−1^, attributed to ester-related vibrations, was more pronounced in fried samples, potentially reflecting lipid-associated transformations during oil heating. Additional variations in the fingerprint region (800–500 cm^−1^) further indicate that different thermal processing methods induced distinct structural modifications in pigeon muscle.

4. Conclusions

This study systematically evaluated the effects of boiling, roasting, and frying on the quality and flavor characteristics of Guangdong specialty Shiqi pigeon meat using a multi-analytical approach, including electronic nose analysis, scanning electron microscopy (SEM), texture profiling, colorimetry, and Fourier transform infrared spectroscopy (FTIR). Thermal processing significantly altered the physicochemical properties, microstructure, and odor-related response patterns of pigeon meat. Principal component analysis of electronic nose data (85.4% cumulative variance explained) revealed clear separation among samples subjected to different cooking methods, indicating distinct aroma profiles associated with each treatment. Roasted samples showed more complex and intense sensor response patterns, boiled samples exhibited relatively mild and uniform odor characteristics, and fried samples demonstrated stronger responses associated with oily and browned aroma attributes. Microstructural and texture analyses indicated that boiling resulted in a looser fiber network and softer texture, and roasting produced moderate structural contraction with improved elasticity, whereas frying led to increased hardness and chewiness accompanied by reduced tenderness. These differences were closely associated with variations in protein denaturation, moisture migration, and connective tissue transformation.

Color and FTIR analyses further demonstrated that frying induced the most pronounced browning and structural alterations, followed by roasting, while boiling caused comparatively milder changes. High-temperature dry heating, particularly frying, promoted greater disruption of hydrogen bonding and secondary protein structure rearrangement. Overall, different thermal processing methods generated distinct structural and sensory-related characteristics in Shiqi pigeon meat. These findings provide a scientific basis for optimizing cooking strategies and enhancing product quality in specialty pigeon meat processing.