Volatile prof ile and multivariant analysis of Sanhuang chicken breast in combination with Chinese 5-spice blend and garam masala

Rni Andlee, Dnni Zhng, Shui Jing,*, Yin Zhng, Yun Liu,*

a Department of Food Science & Technology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China

b Key Laboratory of Meat Processing of Sichuan, Chengdu University, Chengdu 610106, China

Keywords:Chicken breast Chinese 5-spice blend Garam masala Volatile compounds Qualitative techniques Multivariant analysis

A B S T R A C T Sanhuang chicken is a popular native breed in China and well-known for delicious flavour. Spices could enhance the chicken meat flavour and work well in preservation. Chinese 5-spice blend (CS) and garam masala (GM) are routinely using spices in China and Pakistan, respectively. The f lavour prof iles of Sanhuang chicken breast (CB) and its blends with CS and GM were obtained by electronic nose (E-nose), solid-phase microextraction gas chromatography-mass spectrometry (SPME GC-MS) and GC-ion mobility spectrometry(GC-IMS). Principal component analysis (PCA) eff iciently discriminated the aroma prof iles of three chicken formulations. The GC-chromatographs revealed the signif icant aroma alterations of chicken breast meat after marination with spices. Aldehydes were the major contributors of chicken aroma, while most of the aromatic hydrocarbons were generated by spices. Almost all chicken key-compounds produced by oxidation reaction were either reduced or eliminated by marination, showing the antioxidation capacity of spices leading to meat preservation. GC-IMS is not only a rapid and comprehensive detection method, but also proved to be more sensitive than GC-MS. The substantial role of both traditional spices in enhancing f lavour quality of chicken meat, and their exposure as functional ingredients in Chinese and Pakistan cuisines could lead to the crosscultural meat trade opportunities.

1. Introduction

Chicken meat is one of the most consumed meats as protein source having high nutritional value and widely appreciated by consumers [1]. Short production cycle, higher economic return and conversion rate of feed makes the poultry products cheaper in comparison to red meat. Chicken meat provides one-third of the food proteins globally [2]. China produces 10 billion chickens in number annually, ranking first in the world [3]. Sanhuang chicken (three yellow chicken) is a popular native breed in South China and widely eaten meat due to its fatty skin, delicious flavour, soft and tender f lesh [4]. The global market of chicken meat is increasing with every passing day and the consumers’ preferences to purchase meat are generally persuaded by appearance, texture, and f lavour of meat [5].The chicken f lavour is further augmented by marination with various edible items that not only enhance the flavour but also work in preservation and salt reduction [6,7]. Spices are the best source of aforementioned functions and having pleasant flavour. It has been practiced in various food products particularly in meat, to enrich the good f lavour since ancient times [8]. It has also been considered as a positive liking driver in plant-based meat alternative products in which meat itself is not used [9].

Asia has a long history of using spices, where Chinese 5-spice blend (CS) and garam masala (GM) are the most popular and routinely using spices in China and Pakistan, respectively. CS is a local market product, mainly designed with cinnamon, Szechwan pepper, cloves, fennel, and star anise [10]. GM is usually prepared by mixing different ingredients that varies in number and quantity according to the region, however the five main ingredients, including cinnamon, black pepper, cloves, cumin seeds, and black cardamom are considered the basic not only in Pakistan but in India. Pakistan(Indian Subcontinent) has been recognised as the “Spice Bowl of the World” since prehistoric times. Generally, Spices have been used as medicinal plants and in the preparation of curries for a long time [8].Both traditional spices (CS and GM) not only contribute delightful flavour but also proved to retain a huge number of functional ingredients such as antioxidants and could be a good resource of meat preservation [10,11]. Spices are widely added to meat in order to enhance its flavour, but the flavour profile is not enough studied, and very little number of volatile organic compounds (VOCs) have been identified in the spices as well as chicken-spices blends (CSBs) [12].

Aroma is composed of different VOCs, which are generated by the various complex biochemical changes in the inherent components of meat, including Maillard reactions, lipid oxidation, and Strecker and amino acids degradation [13]. Multiple classes of VOCs have been found in meat, while its composition is significantly differed with the cooking method, chicken type, organ part and added ingredients [14-16].However, some of the widely reported volatile aroma-active compounds are hexanal, heptanal, octanal, nonanal, decanal, (E)-2-nonenal, (E,E)-2,4-decadienal, and 1-octen-3-one [15]. Apart from generation of VOCs from other sources, aroma originated from spices could add up in the meat production process [17]. To analyse the volatile profile, precise and quantitative analytical techniques are necessary. Electronic nose (E-nose) can imitate the biological olfactory system and perform micro- as well as macro-analysis of aroma compounds of the objects to present the complete aroma outline [18]. Moreover, researchers have usually combined it with gas chromatography-mass spectrometry (GC-MS) along with headspacesolid-phase microextraction (HS-SPME) to obtain the quantitative and qualitative information of volatile compounds. SPME is simple,inexpensive and easily automated extraction technique that could substantially extract the volatile compounds of chicken and spices’samples [12]. SPME-GC-MS has the advantages of strong qualitative and quantitative ability, high separation efficacy and sensitivity.However, some compounds at trace level could not be separate by such techniques; therefore, a faster and more sensitive analytical technique “ion mobility spectrometry (IMS)” can be use, which characterizes VOCs by mobility of gas phase ions in a perpetual electric field even at trace levels [19].

Our previous cross-cultural consumers-based study showed that aroma have a significant and positive role in liking of chicken meat marinated with CS and GM by Chinese and Pakistani consumers [20].Moreover, various kinds of chicken meat studies for volatile compounds are available, but aroma profile developed by addition of spices is not enough studied. Due to the profound impact of spices on chicken meat flavour and palatability, and importance of CS and GM in Asian countries, this study provides information of aroma profile of chicken-spices at first-stage formulation levels. This study characterized the major VOCs of Sanhuang chicken breast and its blends with CS and GM by means of E-nose, GC-MS, and GC-IMS. Along with our previous consumers-based study [20],this research can assist food traders in cross-cultural chicken meat business by tracing basic volatile compounds in chicken meat.Furthermore, impact of two traditional spices on chicken aroma could enhance the flavour quality of chicken meat and help in meat preservation.

2. Materials and methods

2.1 Material preparation

Chicken breast fillets of freshly slaughtered Sanhuang broilers(Haobang, Linxia Yikelamu Food Co., Ltd., Linxia County, Gansu,China) were obtained from an online shop. The fillets were delivered to the laboratory within one hour of slaughtering in the ice packed cooler. The breast fillets were washed with ultrapure water (Chengdu Haoneng Technology Co., Ltd., Chengdu, China), extra fat was removed, and cutted into 1-2 mm diameter cubes by odour-free stainless-steel knife. These chicken meat cubes were stored in odourfree sealed aluminium foil bags at 80 °C until further analysis and overnight thawed at 4 °C before use.

2.2 Sample processing

The most commonly used quantities of ingredients of both spices’blends were selected to prepare the blends for this study. Ingredients of garam masala were purchased from an online seller shop, imported from northwest region of Pakistan to China. In present study, GM was mainly designed with cinnamon (0.125%), black pepper (0.5%), cloves(0.125%), cumin seeds (1.0%), and black cardamom (0.6%) [11].To make sure the uniformity of preparations of both spices, and to avoid effect of preservatives of commercial CS, the ingredients of CS were purchased from local market (Shanghai China), and madeup of cinnamon (0.5%), Szechwan pepper (0.5%), cloves (0.1%),fennel (0.5%), and star anise (0.5%) [10]. The chicken breast fillets were minced homogenously by a grinding machine (IKA®A11 Basic analytical grinding mill, Staufen, Germany). Minced chicken meat was marinated for 2 h with spices (0.5%,m/m) and 1% noniodized refined salt (Zhongyan Yangtze River Salinization Co., Ltd.,Yingcheng, China), while the plain chicken sample was dish up only by salt. After marination of 2 hours, it was boiled in 1:1 (m/V)ultrapure water for 20 min at 80 °C in a water bath (Jinghong,Shanghai, China) [21]. In this study, the plain chicken breast, chicken with Chinese-5-spice blend, and chicken with garam masala samples are abbreviated as CB, C + CS, and C + GM, respectively.

2.3 Analysis of volatile compounds using the E-nose system

Headspace aroma of chicken samples was traced by E-nose(Shanghai Bosin Industrial Development Co., Ltd., Shanghai, China)provisioned with assortment of metal oxide semiconductor (MOS)sensors. The MOS sensors have high cross-selectivity and sensitivity properties and could efficiently propagate response signals to the various volatile compounds. Due to the high sensitivity, each sensor generated different response signals while detecting various groups of volatiles. In present study, the sensors assortment comprised of 14 MOS sensors, including s1 (amines and ammonia), s2 (sulfides and hydrogen sulfide), s3 (hydrogen), s4 (ethanol and other organic solvents), s5 (aldehydes, alcohols, ketones and aromatic compounds),s6 (biogas, natural gas and methane), s7 (flammable gases), s8 (volatile organic compounds), s9 (natural gas and liquid gas), s10 (flammable gases and liquid gas), s11 (ethanol, alkanes, smoke and natural gas),s12 (ethanol and organic solvents), s13 (cooking odour and smoke),and s14 (natural gas and methane) [22,23].

Five grams of the cooked chicken samples were weighed into 20 mL E-nose vials and lidded tightly. The samples were stand for 30 min at room temperature ((21 ± 2) °C) to obtain headspace, prior to the processing by the E-nose device. The VOCs from headspace of the samples were absorbed through the sensor array for 60 s at a rate of 0.6 L/min. After completion of one sample, the system was purged for 120 s at the same flow rate with the clean air to rebalance it before the insertion of next sample. Seven replicates were prepared for each chicken formulation [24].

2.4 SPME GC-MS

Five grams of aliquot of chicken sample was added into 20 mL of GC-vail and bottle-head was closed with aluminium wrapping. The chicken was cooked inside the GC-vail to control the loss of volatiles;however, the tight capping was avoided preventing the accumulation of pressure. After cooking for 20 min at 80 °C in a water bath, the sample was cooled at room temperature for 10 min before subjection to SPME. The volatile compounds were extracted by SPME and separated using GC-MS. In 5 g of sample, 10 μL of 2-octanol(411 mg/L in ethanol) was added as an internal standard (IS) to facilitate quantitative analysis. To reduce the operation error, IS was added on the inter-wall of the headspace bottle. Thus, during extraction of volatile compounds, the volatiles and internal standard could uniformly extracted on SPME fibre [14,24]. The PTFE/BYTL septum were used to evade the loss of volatile compounds.The extraction was held at 60 °C, and temperature was maintained by placing vails in a water bath. After 10 min of equilibration,extraction was performed for 50 min by using 75 μm carboxen/polydimethylsiloxane SPME-fibre, conditioned at 230 °C for 30 min.After 1 hour of adsorption, the fibre was desorbed in a GC injector(7890A, Agilent Technologies, Inc., CA, USA) at 250 °C for 5 min.Chromatographic separations were performed by HP-INNOWAX capillary column (60 m × 0.25 mm × 0.25 μm: J&W Scientific Inc.,Folsom, CA, USA). The oven temperature was set at 50 °C for 3 min,inclined to 230 °C with 4 °C/min, and held for 10 min. Helium was used as a carrier gas, with a flow rate of 1 mL/min in a split ratio of 2:1. The split ratio (2:1) has been selected based on previous volatiles characterization study of chicken breast base [12], and pre-liminary experiments. The detector (MS apparatus) worked at a rate of 4.45 scans/s in a range ofm/z= 35 450, operated with 35 U emission current and 70 eV ionization voltage.

The identification of volatile compounds was done by mass spectra (MS) and/or comparison of retention indices (RI) with the data in standard NIST database. RI values were calculated byn-alkanes series (C4-C40: Sigma, Aldrich Trading Co., Ltd., Shanghai, China),under the same chromatographic conditions. Semi-quantitation of plain chicken breast and chicken-spices blends was done by calculating the specific segment of GC peak area of each volatile to the peak area of IS (2-octanol) x IS Quality [21].

2.5 GC-IMS analysis

The samples prepared by same method for GC-MS were characterized using GC-IMS (Flavorspec, G.A.S. Instrument,Dortmund, Germany) equipped with a SE-54 capillary column(15 m × 0.53 mm × 1 μm: Restek, Inc. Oklahoma, USA). Five grams of the sample was cooked by the same method as GC-MS in the GC-vail. After cooking, 500 μL headspace was injected into the heating injector by using heated syringe at 85 °C temperature. The drift tube temperature was set at 45 °C and the column temperature was 60 °C. A sample gas, the high-purity nitrogen was used at a flow rate of 150 mL/min. The flow rate of carrier gas was 2 mL/min, then it was inclined to 15 mL/min within 8 min, to 80 mL/min within 10 min, to 130 mL/min within 5 min, and finally to 145 mL/min within 5 min. Each sample was processed in 4 replicates.

To calculate the RI,n-ketones (C4-C9) (Sinopharm Chemical Reagent Beijing Co., Ltd., Beijing, China) were used as external references by the laboratory-analysis view (LAV) software in the GC-IMS device. The volatile compounds have been characterized in comparison of drift time (DT) and RI with the IMS database retrieval software (GAS, Dortmund, Germany), and NIST library. The VOCs intensities were obtained by the height of the selected signal peak by Gallery Plot analysis (version 1.0.7, GAS, Dortmund, Germany) [25].Two-dimensional top view was obtained by the Reporter plug-in,and volatile compounds were directly compared with the Gallery plot plug-in of the GC-IMS by means of fingerprint graphics.

2.6 Statistical analysis

Statistics software (IBM Inc., Chicago, USA) with a post-hoc Tukey’s test atα≤ 0.05. Principal component analysis (PCA) was used to envision the aroma profile of E-nose and GC-MS data. PCA was performed using SPSS (IBM Inc. Chicago, IL, USA), and 3D plot was obtained by Origin software (version 8, OriginLab, USA). Partial least squares regression (PLS-R) was applied to visualize the data profile of three chicken samples in correlation with volatile compounds and E-nose sensors. PLS-R was accomplished by XLSTAT 2019(Addinsoft, NY, USA). The GC-MS descriptive analysis was performed by the analysis of variance (ANOVA) using SPSS. The GC-IMS data was analysed by means of the general linear model procedure.

3. Results

3.1 E-Nose analysis

E-nose was applied as a fast analytical tool to assess the effect of spices on the aroma of chicken breast. The spatial distribution and distances of chicken aroma was analysed by PCA (Fig. 1a). As shown in the PCA 3D plot, the three principal components (PCs), PC1,PC2 and PC3 explained 26.52%, 49.21% and 18.83% of variances,respectively. The placement of three chicken formulations on distinct positions has shown that not only the spices influenced the chicken aroma, but different spices also made a prominent change between CSBs. Therefore, samples were further subjected to the volatile compounds analysis to evaluate the reason of aroma differences among chicken formulations.

Fig. 1 PCA results based on (a) E-nose data and, (b) GC-MS data(concentrative volatile compounds) representing the overall aroma profiles and spatial distributions of three chicken samples.

3.2 VOCs obtained by GC-MS

The volatile compounds detected in the three chicken samples by GC-MS are listed in Table 1. A total of 121 VOCs, including alcohols, aldehydes, furans, ketones, acids, aromatic hydrocarbons,esters, ethers, and phenols were identified in three chicken samples.Aromatic hydrocarbons (25.62%), alcohols (25.62%), and aldehydes(17.36%) were the predominated groups of volatiles in all chicken formulations. To trace the origination’ point of VOCs identified in CSBs by GC-MS and GC-IMS, volatile compounds of spices (CS and GM) were characterized by GC-MS and presented in Table S1.

To illustrate the aroma profile difference between one obtained by overall headspace (E-nose), and concentrative volatile compounds,PCA was generated by GC-MS data (Fig. 1b). Three principal components accounted for 83.83% (PC1 = 38.49%; PC2 = 26.52%;and PC3 = 18.83%) of the variability, squeezing the major aroma information of all chicken samples in a single PCA plot.

The Venn diagram (Fig. 2) was plotted to trace the number of related volatiles among spices and chicken samples. A total of 4 VOCs were detected in all five samples, namely styrene,benzaldehyde, acetic acid andp-cymene. There were 10, 6, 3, 7 and 9 volatile compounds only detected in CB, C + CS, C + GM, CS and GM, respectively. Volatile compounds identified only in CB were heptanal, (E,E)-2,4-decadienal, tetradecanal, (E)-2-decenal, 1-butanol,1-nonanol, 2-pentylfuran, 2,3-octanedione, 1-octen-3-one andp-xylene. Volatiles present only in C + CS were ethenone, sabinene hydrate, cosmene, ethyl decanoate, linalool oxide and 2-methoxybenzaldehyde, while only 3 compounds were present in C + GM,namely 2-isopropenyl-5-methylhex-4-enal, carvone and citral. Seven compounds were identified only in CS and nine in GM. Both spices have shared nine compounds, includingβ-ocimene, cinnamic acid,thymol andα-pinene. Thirteen compounds in C + CS were arise from CS, including estragole, methyl ester, camphor, 1,4-dimethoxybenzene and cinnamyl alcohol. On the other side, GM contributed eleven volatiles to the C + GM, including 3-phenylpropanol,α-pentylbenzene methanol, methyl salicylate, isoeugenol and carotol.

Table 1 The concentration (μg/kg) of VOCs in CB and CSBs identified by GC-MS.

Table 1 (Continued)

Table 1 (Continued)

Fig. 2 Venn diagram showing the number of related volatile compounds in three chicken samples and two spices blends.

3.3 Correlation between E-nose and GC-MS analysis

PLS-R correlation loading plot was drawn based on the significant volatile compounds among three chicken formulations, to correlate the chicken objects with volatile compounds and the E-nose sensors.The results of correlation loading plot of the PLS-R are shown in Fig. 3. Thex-matrix represents the volatile compounds andy-matrix represents E-nose sensors sensing scores. The outer and inner ellipses correspond toR2= 1.0 and 0.5, respectively. The E-nose sensors sensing scores and volatile compounds located in the outer and inner ellipses have shown the effective explanation by PLS-R model.

Fig. 3 PLSR correlation loading plot for significant VOCs (x-matrix) and chicken samples and E-nose sensors (y-matrix). s1-s14 shows the sensor 1 to 14, respectively. Ellipses represent R2 = 0.5 and 1.0, respectively.

Although GC-MS is an instrumental gold standard in volatile compounds analysis and identified the major number of VOCs, the samples were subjected to the GC-IMS to detect the low threshold compounds due to its high separation efficiency.

3.4 VOCs obtained by GC-IMS

The RI, retention time (RT) and DT of volatile compounds detected in the chicken samples by GC-IMS are listed in Table S2.Among 81 VOCs, the highest percentage of volatiles (54.32%) were unknown compounds, which could not be identified due to the limited information of GC-IMS database. Among identified groups, the most abundant were alcohols (17.28%) following by ketones (16.05%) and aldehydes (14.81%), including monomers and dimers.

The intensity traces of volatile compounds detected by GC-IMS have been presented in Fig. 4. The top view of the 3D topographic map of the three chicken samples with different formulations is shown in Fig. 4a. Thex-axis represents ion relative drift time of the gas chromatograph andy-axis represents the RT. Most of the signals emerged in the DT of 1.0-1.5 RIP relative and RT range of 150-500 s.The VOCs are represented as coloured data points, and the concentrations are coded by the intensities of colours, such as red represents the higher intensities, following by light blue and white. In the scale of DT from 1.0 to 1.5 ms, the C + CS represented the greatest number of signals, and CB represented the least. Compounds present in CB with significant increase were mostly separated at initial RT of 150 400 s,including 2,6-dimethylpyrazine, ethyl propanoate, 2-propanone,3-methylbutyl acetate, 2-hexenol, and monomers and dimers of pentanal, 2-hexanone, 1-hexanol and 2-heptanone. The compounds generated in CSBs were mostly detected at retention time of 500 to 1 200 s with a significant change between the blends. Most compounds of CSBs were not identified by GC-IMS, though their intensities were very dense, such as 1, 2, 35, 40 and 41 in C + CS, and 3 and 6 in C + GM. The complete volatiles’ prolife of three chicken formulations with measured intensities of all compounds counting monomers and dimers has been presented in Fig. 4b. Each column signifies a sample with replicates and each row signifies a volatile compound, and the signal peak colour represents the substance concentration. A substantial difference among intensities of each compound within different samples has been observed herein.

4. Discussion

4.1 Multivariant analysis

PCA is an extrapolation method used to contract the data dimensions and elevate the feature indexes by obtaining the principal components [26]. In our study, the clear discrimination among chicken samples analysed by PCA has showed the significant impact of spices on chicken aroma.E-nose not only discriminated the aroma profiles of the three chicken samples, but also gave a clue of the comparative dissimilarities among various formulations. This is correlated with a previous study which showed the impact of spices on aroma of chicken meat by visual distinction (PCA) [7]. The nearby placement of CB with C + CS, and far away from C + GM revealed that C + CS retained more aroma characteristics of plain chicken breast, while GM imparted more aroma to chicken meat. The same aroma pattern of chicken samples distribution has been observed by PCA obtained by quantitative data of volatile compounds in this study. However, the clearer distinction among chicken formulations by PCA obtained by GC-MS suggested that separation of volatile compounds might distinguish the aroma better, and thoroughly discrete among various samples. The differences among aroma profiles of chicken formulations could be attributed to the differences in the types and concentrations of volatile compounds.

Fig. 4 (a) Comparison of volatile profiles of chicken samples (a replicate of each sample) with two-dimension spectra 1, (b) Profile of volatile compounds of four replicates of three chicken samples despite of intensities, including monomers and dimers. The samples are presented in rows, and compounds are presented in columns.The colour intensities in both figures are correlated with the concentration intensities of compounds. Digits 1-4 with sample names represents their replicates.

The PLS-R has been proved as an effective correlation analysis for correlating multiple objects from distinct sources in a single point.Literature has shown that MOS sensors effectively discriminated the volatile compounds of meats of chicken [27], dry-cured ham [23], beef and sheep [28]. Therefore, E-nose equipped with an array of MOS sensors had effectively detected the signals generated by headspace of chicken. Moreover, our study has revealed that the sensors were more influenced by the volatiles generated from the spices as compared to plain chicken meat, therefore MOS sensors could be a good tool for profiling the spices aroma. The compounds near to the outer layers illustrate the high correlation among three selected variables. Among six groups of volatiles, the high correlation has been observed for alcohols, hydrocarbons, and aldehydes, following by phenols and acids. Only one ketone “2-octanone” has been subjected to PLS-R,and sensors have shown less sensitivity towards it; however, the high concentration in CB has been clearly distinguished. 2-Octanone has the characteristic aroma of blue cheese and considered to have an off-flavour note in chicken meat which is produced due to the lipid peroxidation [29], consequently its large quantity in Iberian dry-ham is an indication of its bad quality even it has their characteristic aroma at low level [30]. Therefore, the significant decrease in oxidation of meat due to the antioxidant activity of spices could result in reduction of off-flavour note.

Overall, the highly influenced groups of volatiles were alcohols and acids in C + CS, and hydrocarbons and phenols in C + GM. Even if the nature of compounds varied between both blends, the aroma notes of these compounds were almost similar descripted by spicy,woody, herbal and terpene odour. Although all sensors efficiently detected and discriminated the chicken samples but s6, s8 and s10 were more efficient to sense volatile compounds of CB, s2 and s4 of the C + CS, and s1, s3 and s9 of the C + GM. Particularly, the signals generated by s1 were more sensitive to the limonene, carvacrol andp-cymene; s3 to the cumin acid, humulene andγ-terpineol; and s7, s8 and s12 to the 2-octen-1-ol. The compounds with chickeny, umami,vegetable and mushroom like aroma were significantly higher in plain chicken. The most effective volatile compound of CB to be sensed by sensors was nonanal. Nonanal is a key aldehyde of chicken meat which has citrus and green flavour [15]. It is the oxidation product of oleic acid, and its concentration is relatively higher in breast than the other parts of chicken [14]. This finding was well observed in our study as the chicken breast has a considerable higher concentration of nonanal but it was significantly reduced by addition of spices which could be due to their antioxidation activity.

4.2 Volatile compounds analysis

The characteristic aroma of chicken is highly influenced by spices. Spices retard the oxidative rancidity and inhibit the expansion of off-flavour in meat products [10,12]. Our study has shown that not only spices influenced the types and concentrations of volatile compounds of chicken breast meat, but difference between spices also exhibited a significant change to the aroma.

The characteristic flavour of chicken is highly influenced by aldehydes, due to their lower odour thresholds [15]. Aldehydes are mainly generated by lipid oxidation, however some can also be produced by Maillard-induced amino acids degradation, and interaction between lipid and Maillard reaction [31]. A previous study has reported that hexanal, nonanal, octanal, pentanal, (E,E)-2,4-decadienal, (E)-2-decenal and 1-octen-3-ol are the most potent aldehydes contributing to the characteristic flavour of the chicken meat [15]. These compounds could improve richness and complexity of chicken aroma, with vegetable-like, mushroom-like, almondlike, fatty, citrusy, green, piney, and most importantly chicken-like notes. Hexanal has a green and grassy odour which is usually present in highest amount in meat [15], originated by oxidation ofn-6 fatty acids (arachidonic and linoleic acids) and known as a major oxidation product in dry-cured meat products [32]. (E,E)-2,4-decadienal has the characteristic odour of cooked “fatty” and “chicken-like” note and has been recognized as the primary odorant of chicken, which could be formed by the autoxidation of arachidonic and linoleic acids [32]. The highest content of key aldehydes in plain chicken and its significant reduction or elimination by addition of spices could be due to the reduction in oxidation by the antioxidation of spices.However, the benzaldehyde was significantly increased in CSBs with highest amount in C + CS, which could be originate from the spices [30]. Benzaldehyde and acetaldehyde are produced in result of Strecker degradation of amino acids by the Maillard reaction [12].Apart from key aldehydes, some others were generated from spices in this study, and some were developed after the marination of chicken with spices, such as 2-methoxy-benzaldehyde, hexadecanal andβ-methyl-cinnamaldehyde in C + CS, and citral, hexadecanal and 2-isopropenyl-5-methylhex-4-enal in C + GM. However, the reason or mechanism of generation of new aldehydes is unknown which need to be focus on the future studies.

Although, alcohols were present in high percentage in chicken but due to their high odour thresholds, they are usually assumed to be less significant to the chicken meat flavour [14]. However, derived from poly-unsaturated fatty acid oxidation, branched- and long-chain alcohols have pretty low odour threshold values which impact chicken odour [33].Moreover, in high intensities, other alcohols also could contribute to the fatty, woody and herb-like notes to the meat products [34].Alcohols could produce by lipid oxidation, Strecker degradation and Maillard-type reactions [35]. 1-Octen-3-ol is an alcohol with“fatty” attribute, contributing the characteristic flavour of chicken in boiled chicken meat [12], which is present in highest concentration in plain chicken breast reflecting its importance for chicken flavour.Moreover, literature showed that the addition of spices could increase the concentration of alcohols in chicken meat [7,12], which was also observed in our study. The possible reason is their origination from the spices, such as substantial content of alcohols was generated in both CS and GM spices’ blends.

2-Pentylfuran is a key contributor of chicken meat flavour with“fruity, beanlike and green” aroma, which originates by autoxidation of linoleic acid [15]. In our study, the concentration of 2-pentylfuran was completely eliminated by addition of spices. A previous study also has shown the significant reduction in the 2-pentylfuran by the addition of star anise into the stewed chicken [12]. Thus, not only star anise but other spices could reduce the concentration of 2-pentylfuran,and likewise the mixture of spices could act with more intensity against such precursors.

Ketones are mainly derived from lipid oxidation, or by alcoholic oxidation and Maillard reaction [36]. It is generally considered that contribution of ketones to the chicken aroma is not much higher;though, some ketones are reported as characteristic volatiles of chicken meat, including 1-octen-3-one, 2-heptanone, 2-butanone,2-decanone and 2,3-octanedione [14,15]. The complete elimination or significant reduction of ketones by addition of spices is more related to the antioxidation activity of spices. However, cryptone in both blends and carvone in C + GM were developed by marination in CSBs. Carvone is present in black cardamom and contributed to the pleasant herbaceous aroma [37]. Cryptone is a major constituent of cinnamon with a spicy note, contributing 36.6% of its total essential oil and has shown a potential antimicrobial activity [38]. The reason of generation of new compounds could be due to the complex chemical reactions among chicken meat and various ingredients of spices, which need to be emphasized deeply in future studies.

Acids were not detected by GC-IMS which could be due to its limited database information; nevertheless, some were detected by GC-MS. It can be originated from the oxidation of aldehydes and enzymatic lipolysis [39]. Marination leads to significant reduction or elimination of short-chain acids in CSBs, while long-chain acids were significantly increased or generated from spices into the blends.The short-chain acids are considered to play a considerable role in the aroma of meat due to their low thresholds [40]; therefore, their decrease and low concentrations in blends resulted in reduction of the chicken-like aroma of CSBs. Acetic acid is a short-chain aroma active compound of chicken meat with “sour” note [15] that was significantly reduced by addition of CS, showing the reduction in chicken-like aroma characteristics by addition of spices.

Hydrocarbons could be produced by the oxidative decomposition of lipids, which catalyse irons in myoglobin or haemoglobin [32].Terpenes group of hydrocarbons are the key constituents of essential oils with a characteristic type for each essential oil. The characteristic odour and/or taste is emerged from the one or several major components of essential oils [41]. Terpenes are generally correlated with the spices’ addition, while some have been found in meat in result of their occurrence in animal feed [17]. Our study concedes it as most of the hydrocarbons were obtained in CSBs, while only toluene andp-xylene were contributed by chicken which could be originated from their feed and accumulated in their bodies.p-Cymene was the most abundant compound in C + GM, which could be arrived from the cumin seeds, as it is their characteristic aroma-active component [42].

Esters are generated from the esterification of carboxylic acids and alcohols. Long chain esters have a slight fatty odour, while shortchain esters possessed a fruity flavour [32]. 3-Methylbutyl acetate has been reported as a key aroma-active ester of chicken with “banana”note [15], and its intensity in chicken was substantially reduced by marination with spices. Ethyl butanoate was first time detected in meat samples with a significantly higher concentration in the CSBs.It has a typical kiwifruit aroma and considers as a “predictor of flavour acceptability in kiwifruit” [43]. The generation of most of esters in CSBs indicated the interaction between products of acids and alcohols; however, formation of methyl tetradecanoate and cuminyl acetate was ceased by marination of chicken with spices.

Ethers substantially contributes to the aroma of spices but not to the chicken [15], which was more deemed in our study. Ethers were not produced in plain chicken breast, though a substantial amount was originated from spices into the blends. Anethole and estragole could originated from star anise, with “licorice” and “anise-like” odour,and boosts the pleasantness of the overall flavour. A significant increase of 1,8-cineole in C + GM could be most probably due to their generation from cinnamon [44] and black cardamom [37], which is a characteristic aroma-active component of these spices, and it has also been found in black and white pepper [45]. Therefore, both compounds were present in both CSBs but the significant change in concentrations was more related to the ingredients of spices’blends. In a previous report, these volatiles have been considered as the characteristic aroma of spiced beef meat, and not detected in unseasoned meat [46], which was more related to the present work.

Although phenols have been characterized in chicken meat [15],but in our study some were observed only in CSBs. These findings were similar with a previous report when phenols were detected in spiced pork but not in the unseasoned fresh pork [47]. Thus, phenols’presence in meat could be highly related to the genotype of animal,and it might be not present or present in undetectable (could be trace levels) in Sanhuang chicken breast. Eugenol was the most abundant volatile present in a relatively higher concentration in C + GM. It is the characteristic aroma component of clove oil [48], and the higher amount of clove in GM could be the reason of its significant increase in respective sample.

Pyrazines are responsible for the “roast” flavour of meat, and mostly produced by using higher temperature which could pertain in frying, grilling, pressure-cooking, or roasting, but not in boiling of meat [16]. Therefore, cooking method could be a reason for lower content of pyrazines in CSBs. Pyrazines are usually generated from the twoα-aminocarbonyls, formed by the Strecker reaction or Maillard reaction [49]. Due to the lower concentrations, pyrazines were detected only by GC-IMS. Only two pyrazines were detected in chicken samples with a higher intensity in CB. The methylpyrazine could be produced by the reaction of ribose and cysteine [50],and 2,6-diethylpyrazine by glucose and aspartic acid [51]. Sulfurcontaining compounds are considered the key contributors of meat flavour and their low threshold values make them more aromasignificant, even at relatively low concentrations [52], however these were not detected in our study neither by GC-MS nor in GC-IMS. The reason could be their lower threshold values that might be dispersed sooner and unable to detect [53]. Furthermore, in a previous report,sulfur-containing compounds were detected by GC-TOF-MS in the various parts of chicken but not in the breast, which shows that the concentration of these compounds might be lower or not present in chicken breast [14].

It is assumed from the current study that the observation of volatiles in particular samples is more respective to their ingredients.Overall, the compounds having characteristic odour of chicken flavour were significantly reduced or completely disappeared in the CSBs, as similar to our previous consumers-based study where plain chicken was scored higher for the chickeny and umami attributes than the CSBs [20]. A significant decline in the key compounds of chicken odour could be the reason of reduction in chicken-like flavour in the blends. Moreover, the umami-oriented volatiles were significantly increased in CB, such as 2-pentylfuran, 2-butanone, 2-heptanone,2-decanone and 1-octen-3-ol [54-56]. The reason of reduction in these compounds could be the spicy note contributed by spices to the chicken meat, thus this may mask or reduce the umami and chickenlike flavour. Previous reports have proved the strong antioxidation capacity of CS [10] and GM [11], which was also noticed in our study through the reduction or elimination of oxidative generative compounds in CSBs. However, the actual mechanism and particular production point of these compounds is still unknown that need to be examined in future studies. Most of the compounds were previously reported in chicken breast with different trends of concentrations,which could be due to the differences in the effect of cooking process,genotype, diet, sex and others [16].

This was the first stage study to help the flavour researchers and food traders to understand the aroma profile of chickenspices blends, and the aroma-active compounds are needed to be identified by GC-O analysis. Collectively various spices’ mixtures,its concentrations, addition methods, marination time, and different processing approaches also could have a major impact on aroma profile that ought to be study to develop the better flavour. SPME have successfully extracted all basic volatiles in chicken and spices,that has also been observed in previous studies [12,14,24]. However,various extraction techniques of volatile compounds could have an influence on the number and concentration of VOCs, and future studies need to be focused on it.

5. Conclusions

This study examined the effects of two traditional spices CS and GM originated from Chinese and Pakistani cuisine on the formation of VOCs in the Sanhuang chicken breast. The E-nose results presented the substantial impact of spices on the chicken breast meat aroma profile, and PLS-R efficiently correlated the volatile compounds with respective sensitive MOS sensors and chicken samples. The qualitative and quantitative data of volatile compounds obtained by GC-MS and GC-IMS have shown that the marination of chicken with spices resulted in reduction or elimination of the key compounds of plain chicken, including hexanal, nonanal, (E,E)-2,4-decadienal,(E)-2-decenal, 1-octen-3-ol and 2-pentylfuran. Variation was found in VOCs despite two different techniques; however, the most important aroma-active compounds were detected by both practices. GC-IMS was more competent in terms of sensitivity and time orientation still the limited data of volatile compounds in its database make it less appropriate to cope-up all separated volatiles. The present data not only provide the aroma profile of Sanhuang chicken breast but also its blends with two well-known traditional spices’ mixtures from different countries, leading to better understandings of enhancing chicken meat flavour. Though, this was the initial study to assist the flavour researchers and food traders to take in the aroma outline of chicken-spices blends, and the aroma-active compounds are needed to be identified. Moreover, the characterization of more complex formulations of spices and individual ingredients of each spice’ blend could be of great interest to see the more volatiles generation, and identify the actual point of generation.

Conflicts of interest

The authors declare that they have no conflicts of interest.

Acknowledgements

This work was funded by National Natural Science Foundation of China (Grant No. 32001824, 31972198, 31901816, 31901813,32001827).

Appendix A. Supplementary data

Supplementary data associated with this article can be found, in the online version, at http://doi.org/10.1016/j.fshw.2022.07.023.