Odor Fingerprinting of Chitosan and Source Identification of Commercial Chitosan: HS-GC-IMS, Multivariate Statistical Analysis, and Tracing Path Study.

Chitosan samples were prepared from the shells of marine animals (crab and shrimp) and the cell walls of fungi (agaricus bisporus and aspergillus niger). Fourier-transform infrared spectroscopy (FT-IR) was used to detect their molecular structures, while headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) was employed to analyze their odor composition. A total of 220 volatile organic compounds (VOCs), including esters, ketones, aldehydes, etc., were identified as the odor fingerprinting components of chitosan for the first time. A principal component analysis (PCA) revealed that chitosan could be effectively identified and classified based on its characteristic VOCs. The sum of the first three principal components explained 87% of the total variance in original information. An orthogonal partial least squares discrimination analysis (OPLS-DA) model was established for tracing and source identification purposes, demonstrating excellent performance with fitting indices R2X = 0.866, R2Y = 0.996, Q2 = 0.989 for independent variable fitting and model prediction accuracy, respectively. By utilizing OPLS-DA modeling along with a heatmap-based tracing path study, it was found that 29 VOCs significantly contributed to marine chitosan at a significance level of VIP > 1.00 (p < 0.05), whereas another set of 20 VOCs specifically associated with fungi chitosan exhibited notable contributions to its odor profile. These findings present a novel method for identifying commercial chitosan sources, which can be applied to ensure biological safety in practical applications.

Volatile-compound fingerprinting and discrimination of positional isomers in stamp-pad ink tracing using HS-GC-IMS combined with multivariate statistical analysis.

The rising crime rate associated with document forgery has a significant impact on public safety and social stability. In document fraud cases, determining the origin of a particular stamp-pad ink is the most important objective. In this study, a comprehensive analysis of the volatile compounds in quick-drying stamp-pad inks from six commonly used brands were performed for the first time, utilizing a combination of headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and multivariate statistical analysis methods. Visual and comparative analysis of the differential volatile components among different stamp-pad ink samples was conducted using fingerprints and volcano plots. A total of 127 volatile compounds were accurately identified, with ketones, esters, alcohols, and aldehydes being the most abundant compounds in the stamp-pad inks. Hierarchical clustering analysis (HCA), including dendrograms and clustering heatmaps, was utilized to explore the correlations between these compounds and the samples. Additionally, the precise identification of positional isomers and functional group isomers of aliphatic compounds was achieved. To achieve accurate discrimination of various stamp-pad ink samples, a multivariate statistical analysis method was utilized to establish a classification model for them. Based on the results obtained from HS-GC-IMS, effective discrimination among different brands of stamp-pad ink samples was achieved through principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). The model exhibited excellent performance, with the fit index of dependent variables (R2Y) and the predictive index of the model (Q2) values of 0.99 and 0.984, respectively. These results provided significant theoretical evidence for the application of HS-GC-IMS as an efficient technique in the analysis of volatile compounds, identification of positional isomers and functional group isomers, as well as tracing the origin of stamp-pad ink and analyzing the formation time of documents.

Rapid authentication of Chaenomeles species by visual volatile components fingerprints based on headspace gas chromatography-ion mobility spectrometry combined with chemometric analysis.

INTRODUCTION: Chaenomeles, including Chaenomeles speciosa (ZP), Chaenomeles sinensis (GP), Chaenomeles tibetica (XZ), and Chaenomeles japonica (RB), has been widely used as food in China for thousands of years. However, only ZP, was recorded to be the authentic medicinal Chaenomeles. Therefore, the rapid and accurate method for the authenticity identification of Chaenomeles species is urgently needed. OBJECTIVE: To develop a method for rapid differentiation of Chaenomeles species. METHODS: The visual volatile components fingerprints based on headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) combined with chemometric analysis, including principal component analysis (PCA), linear discriminant analysis (LDA) and partial least-squares discriminant analysis (PLS-DA), were utilised for the authentication of Chaenomeles species. RESULTS: The visual volatile components fingerprints by the GC-IMS intuitively showed the distribution features of the volatile components for different Chaenomeles samples. The LDA and PLS-DA models successfully discriminated Chaenomeles species with original discrimination accuracy of 100%. Fifteen volatile compounds (VOCs) (peaks 9, 12, 13, 19, 23, 24, 35, 48, 57, 65, 67, 76, 79, 80, 83) were selected as the potential species-specific markers of Chaenomeles via variable importance of projection (VIP > 1.2) and one-way analysis of variance (P < 0.05). CONCLUSIONS: This study showed that the visual volatile components fingerprints by HS-GC-IMS combined with chemometric analysis is a meaningful method in the Chaenomeles species authentication.

Understanding the volatile organic compounds of 1-methylcyclopropylene fumigation and packaging on yellow-fleshed peach via headspace-gas chromatography-ion mobility spectrometry and chemometric analyses.

Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and chemometric methods were utilized to analyze changes in volatile organic compounds (VOCs) of yellow-fleshed peach by 1-methylcyclopropylene (1-MCP) treatment and modified atmosphere packaging (MAP). Meanwhile, the storage quality of yellow-fleshed peach at room temperature (25°C) was also studied. Yellow-fleshed peach was treated by four methods, namely, nanomaterial packaging (NA), 1-MCP fumigation and nanomaterial packaging (1-MCP-NA), polyethylene (PE) packaging, and 1-MCP fumigation with polyethylene packaging (1-MCP-PE). Changes in the decay rate, firmness, browning index, soluble solid content, and titratable acid of the fruit were then measured at room temperature at 1, 4 and 10 days of storage. Thirty-two VOCs, including terpenoids, alcohols, esters, aldehydes, and ketones, were identified. Seventeen VOCs were found to be significant with predictive variable important in the projection (VIP) > 1 and p < 0.05 by analysis of variance and orthogonal projection to latent structure discriminant analysis (OPLS-DA). After 10 days of storage, the browning index of 1-MCP-NA group was 51.7%, which was lower than the control fruit (PE, 76.7%). Compared with other three treatments, 1-MCP-NA showed the better ability to delay and inhibit decreases in ester and aldehyde contents, and the ethanol content was lowest in the samples treated by 1-MCP-NA during storage. Differences among treatment groups were distinguished by principal component analysis (PCA) and hierarchical clustering heat map. The results showed that 1-MCP-NA could well maintain the quality and flavor stability of yellow-fleshed peach, and it had a good application prospect in the postharvest preservation of yellow-fleshed peach. PRACTICAL APPLICATION: In this study, 1-methylcyclopropylene (1-MCP) combined with nanomaterial (NA) packaging (1-MCP-NA) proved to have a better fresh preservation effect. 1-MCP-NA showed better ability to delay and inhibit decreases in ester and aldehyde contents by HS-GC-IMS technique. It provided a new strategy for postharvest storage of yellow-fleshed peaches.

HS-GC-IMS identification of volatile aromatic compounds of freshly-cooked rice packaged with different disposable lunchboxes.

The rapid development of online-to-offline food delivery service has necessitated the replacement of plastic lunchbox using biodegradable ones. In current study, a total number of fourteen panelists were firstly recruited and trained to investigate how different commercial disposable lunchboxes affect the freshly cooked rice sensory properties during heat preservation (60 °C, 60 min). The lunchboxes were made of pure polypropylene (PP), polypropylene-starch (PP-S), pure wheat-straw and sugarcane-straw (WS & SS) and Paper. The discrepancy of volatile aromatic substances was then analyzed using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) to study the possible mechanism beneath the variations of the influences of different lunchboxes on the aromatic properties of rice. Results showed that, compared with the textural attributes, the aroma was significantly and positively correlated with panelist's acceptability, among which, the aroma of starchy, sulfur and smoky are the most important ones. The moisture absorption plays an important role in affecting the aromatic characteristics of the packaged rice. While all lunchboxes have inhibitory effects on the production of volatile flavor substances including 2,6-Dimethylpyrazine, 2-Acetylpyrazine and γ-Octalactone, pure PP and PP-S lunchboxes generated undesirable flavor substances including 2-Ethyl-1-hexanl and Camphene, and thus reduced panelist's preferences. It was also found that the panelist liked the rice packaged by Paper lunchbox the best because of its better performance in maintaining the aroma of starchy and sulfur, the two substances that are associated with the higher concentration of ethereal and fruity volatile flavor substances. This study provides important information for manufacturers to understand how different disposable lunchboxes may impact the textural and aromatic properties of packaged foods.

Fingerprints and changes analysis of volatile compounds in fresh-cut yam during yellowing process by using HS-GC-IMS.

The purpose of this study was to investigate the dynamic change in volatile components during the yellowing process. The volatile components were analyzed by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) and the critical enzyme activities were determined by commercial kits. The results revealed that 29 signal peaks for 20 compounds were identified, which were quantified in all samples: 1 furan, 1 ester, 15 aldehydes, 3 ketones, and 9 alcohols. The contents of most of these compounds increased first and then decreased at 36 h, which were basically consistent with the enzyme activities of LOX, HPL, ADH and AAT. Subsequently, principal component analysis (PCA) results clearly showed that the fresh-cut yams for different yellowing processes were well distinguished by the volatile compounds. These results showed that the potential of HS-GC-IMS-based approaches to evaluate the volatile compound profiles of fresh-cut yam at different stages in the yellowing period.

Effects of thermoultrasonic treatment on characteristics of micro-nano particles and flavor in Greenland halibut bone soup.

In order to investigate the effects of thermoultrasonic treatment (TUT) on the formation of colloidal micro-nano particles (MNPs) and the quality of halibut bone soup, nutrients, particle characteristics, and flavor characteristics were analyzed. The morphology of MNPs was studied using an optical microscope. Results showed that TUT could increase the nutrient content (total sugars, 22.15 mg/100 mL; water soluble proteins, 173.24 mg/mL; fatty acids, 1779.7 mg/100 mL; solids, 3.16 g/100 mL), reduce the particle size (605.92 nm) and interfacial tension. Meanwhile, TUT make the halibut bone soup has better emulsifying characteristics and stability. The contents of flavor substances, such as esters, 5'-nucleotides, organic acids in the halibut bone soup were more abundant, while the contents of hexanal and 1-octen-3-ol and fishy off-flavor were reduced in TUT group. The overall odor and taste outline were more harmonious. Therefore, TUT can be used in the production of high quality fish bone soup, and TUT could be considered as a good deep processing technology for halibut bone and improve economic efficiency.

Flavor Changes of Tricholoma matsutake Singer under Different Processing Conditions by Using HS-GC-IMS.

Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) was used to analyze the changes to volatile compounds in fried Tricholoma matsutake Singer under different heating temperatures and times. A total of 40 signals that corresponded to 24 compounds were identified through this approach. Differences in volatile compounds of T. matsutake samples were shown in topographic plots and fingerprints. The heating temperatures were more important than the heating times in affecting the volatile compounds. Moreover, changes to the main volatile compounds in T. matsutake under different processing conditions were based on the thermal decomposition and a series of chemical reactions of C8 compounds. Principal component analysis (PCA) results showed that samples under different processing conditions could be effectively distinguished. Hence, the combination of HS-GC-IMS and PCA can identify and classify the volatile compounds of T. matsutake quickly and sensitively. This study provides a new supplementary analytical method for the rapid identification of T. matsutake. The above results can provide a theoretical basis for the quality control and change mechanism of flavor in the processing of traditional edible fungi products.

Effect of Frying Conditions on Self-Heating Fried Spanish Mackerel Quality Attributes and Flavor Characteristics.

In this study, we investigated the effects of different frying conditions on the quality characteristics of fried Spanish mackerel (Scaberulous niphonius) to address the food quality degradation of self-heating fish products after frying, sterilization, and reheating. Furthermore, the effect of different moisture contents (65%, 60%, 55%, and 50%) of fried Spanish mackerel on texture, color, and microstructure after sterilization and self-heating were examined. The flavor fingerprints of different frying temperatures (140 °C, 160 °C, 180 °C, and 200 °C) coupled with the optimal moisture content were identified; furthermore, volatile organic compounds (VOCs) were studied using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) with principal component analysis (PCA). The results indicated that the shear force value significantly increased, while the hardness and chewiness significantly decreased simultaneously with decreasing moisture content. Samples containing 65% moisture content showed the highest L*, a*, and W values, while their b* value was the lowest, and the most clearly visible fibrous veins with tiny cracks could be observed in them. Samples fried at 160 °C and 65% moisture content exhibited the richest VOCs, with a greasy or fried aroma. Based on the PCA, there were significant differences in the sample VOCs under different frying conditions. In summary, among all treatments, frying at 160 °C with 65% moisture content resulted in the highest food quality of fish filets. The results of this study could provide a theoretical basis for improving the food quality of self-heated fish products.

Characterization of volatile compounds in differently coloured Chenopodium quinoa seeds before and after cooking by headspace-gas chromatography-ion mobility spectrometry.

Aroma is an important feature of quinoa that influences consumer preferences. Differently coloured quinoa seeds exhibit diverse nutritional characteristics; however, their aromatic profile differences are poorly investigated. The volatile components of 11 quinoa samples were characterized by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). A total of 120 peaks were detected, with 61 compounds identified. White quinoa liberated a high concentration of volatiles with grass (n-hexanol) and green ((E)-2-octenal, (E)-2-heptenal, etc.) aromas before and after cooking, respectively. Raw flaxen samples uniquely released a caramel compound (cyclotene) and exhibited several sweet and caramel volatiles (decanal, 5-methyl-furfural, and 2-furfural) after cooking. Additionally, cooked black quinoa exerted more fruity substances (methyl hexanoate and phenylacetaldehyde). Orthogonal partial least square discriminant analysis clearly distinguished the samples before and after cooking and differentiated the seeds into different colours. The results confirm the potential of HS-GC-IMS to evaluate volatiles in quinoa and are meaningful for quinoa consumption.

Mechanism of aroma compounds changes from sea cucumber peptide powders (SCPPs) under different storage conditions.

A rapid and sensitive measurement technique was used to investigate the mechanism of aroma compounds changes in SCPPs under the storage conditions with hygroscopicity and no-microorganism (HNM), nonhygroscopicity and no-microorganism (NHNM) and hygroscopicity and microorganism (HM) by HS-GC-IMS. The types and signal of aroma compounds increased obviously at the 5th day under the storage condition (HNM and HM). The signal of majority of aroma compounds decreased gradually since the 5th day. However, during the storage of SCPPs for 15 days, the total signals of aldehydes, ketones and alcohols gradually increased and reached a maximum. Thereinto, the saturated aldehydes such as hexanal had been produced as an off-flavor. These off-flavor compounds principally including aldehydes and ketones could be generated through Maillard reaction, while alcohols could be generated by microbial fermentation. The study discovered moisture adsorption and microorganism during storage could affect aroma compounds of SCPPs and the effect of moisture absorption was greater than microorganisms.

Characterization of Volatile Component Changes in Jujube Fruits during Cold Storage by Using Headspace-Gas Chromatography-Ion Mobility Spectrometry.

Volatile components in jujube fruits from Zizyphus jujuba Mill. cv. Dongzao (DZ) and Zizyphus jujuba Mill. cv. Jinsixiaozao (JS) were analyzed under different cold storage periods via headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). Results identified 53 peaks that corresponded to 47 compounds and were mostly alcohols, aldehydes, esters, and ketones. Differences in the volatile components of jujube fruits were revealed in topographic plots and fingerprints. For DZ, 3-pentanone was the characteristic component of fresh fruits. After storage for 15 days, dipropyl disulfide became the most special substance. Moreover, when stored for 30 and 45 days, the fruits had some same volatile components, like 2-pentyl furan and diallyl sulfide. However, for DZ stored for 60 days, esters were the prominent constituent of the volatile components, simultaneously, some new alcohols appeared. For JS, 2-ethyl furan was the representative of fresh fruits, and 2-butoxyethanol content was the most abundant after 15 and 30 days of storage. Different from that in DZ, the content of ester in JS increased after storage for 45 days. Substances such as amyl acetate dimer, methyl salicylate, and linalool greatly contributed to the jujube flavor during the late storage period. Principal component analysis (PCA) showed that fresh samples and refrigerated fruits were effectively distinguished. Heat map clustering analysis displayed the similarity of volatile components in different samples and was in accordance with PCA results. Hence, the volatile components of jujube fruits can be readily identified via HS-GC-IMS, and jujube fruits can be classified at different periods based on the difference of volatile components.

Development of a flavor fingerprint by HS-GC-IMS with PCA for volatile compounds of Tricholoma matsutake Singer.

The flavor fingerprint of Tricholoma matsutake Singer was developed and volatile compounds were investigated by HS-GC-IMS fingerprinting combining with PCA. A total of 25 typical target compounds were identified. The differences of flavor compounds in pileus and stipe of Tricholoma matsutake Singer from different areas were observed. After drying, the concentration of C8 compounds, including 3-octanone, 3-octanol, 1-octen-3-one and 1-octanol, decreased, while the concentration of methanol and 1-pentanol increased. Subsequently, PCA was performed based on the signal intensity of the identified violate compounds, and the results clearly showed that the samples in a relatively independent space would be well distinguished. Combining the signal intensity of the identified violate compounds by HS-GC-IMS and PCA, the samples from different portions of Tricholoma matsutake Singer and different areas were distinguished. The results showed that the flavor fingerprint of Tricholoma matsutake Singer were established by HS-GC-IMS and PCA based on the identified volatile compounds.