Similarity of aroma attributes in hot-air-dried shrimp (Penaeus vannamei) and its different parts using sensory analysis and GC–MS

Comparative Analysis of the Nutritional Composition and Flavor Profile of Different Muscle Parts of Hybrid Abalone (Haliotis discus hannai ♀ × H. fulgens ♂)

This study analyzed the basic nutritional components and amino acid, fatty acid, and mineral composition of hybrid abalone Haliotis discus hannai ♀ × H. fulgens ♂ adductor (AM), transition (TM), and skirt (SM) muscles. The taste characteristics of the muscles were measured via electronic tongue, and the volatile compounds were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) analysis. Compared to SM, AM and TM exhibited relatively similar basic nutritional compositions. Although SM exhibited the highest moisture content (84.67%), its protein content (only 11.83%) and total carbohydrate content (only 0.19%) were significantly lower than those of AM (20.42% and 4.14%) and TM (19.10% and 4.48%). The ash and fat contents were similar across the three muscle parts. The amino acid composition was consistent across three parts, and AM showed the highest total amino acid content, ratio of essential amino acids, and essential amino acid index. All three muscle parts were rich in polyunsaturated fatty acids, but the content was higher in AM and TM than in SM. The mineral elements were rich in variety, with high K, P, Mg, and Zn contents. Bitterness intensities were lower and umami and richness intensities were higher in AM and TM than in SM. The contents of volatile compounds related to fishy odor were higher in TM and SM than in AM. The results provided a scientific basis for the intensive processing and comprehensive utilization of Haliotis discus hannai ♀ × H. fulgens ♂.

Shrimp lipids improve flavor by regulating characteristic aroma compounds in hot air-dried shrimp

Hot air-dried shrimp (HDS) has a strong fishy smell greatly reducing its flavor quality. This study aimed to investigate the regulation of total lipids, phospholipids and triglycerides isolated from shrimp for improving the characteristic volatile flavor of HDS. It was found that three lipids could promote the formation of aroma compounds with pleasant characteristic aromas (e.g., pyrazines). Phospholipids and triglycerides inhibited the formation of trimethylamine, a key component of fishy smell, with phospholipids exhibiting the best inhibitory effect (47.70 ± 2.63 %), greatly improving the flavor quality of HDS. Aldehydes, unsaturated ketones, and furans, primarily derived from the thermal degradation of C18:1, C18:2, and C22:6, were key intermediate compounds promoting the Maillard reaction. Lipids inhibited trimethylamine by prompting the formation of pyrazines. Maillard reaction was the key pathway for lipids to improve the flavor quality of HDS. This study can provide theoretical support for the development of high-quality thermally processed shrimp products.

Heat and Mass Transfer in Shrimp Hot-Air Drying: Experimental Evaluation and Numerical Simulation

Shrimp is one of the most popular and widely consumed seafood products worldwide. It is highly perishable due to its high moisture content. Thus, dehydration is commonly used to extend its shelf life, mostly via air drying, leading to a temperature increase, moisture removal, and matrix shrinkage. In this study, a mathematical model was developed to describe the changes in moisture and temperature distribution in shrimp during hot-air drying. The model considered the heat and mass transfer in an irregular-shaped computational domain and was solved using the finite element method. Convective heat and mass transfer coefficients (57.0-62.9 W/m2∙K and 0.007-0.008 m/s, respectively) and the moisture effective diffusion coefficient (6.5 × 10-10-8.5 × 10-10 m2/s) were determined experimentally and numerically. The shrimp temperature and moisture numerical solution were validated using a cabinet dryer with a forced air circulation at 60 and 70 °C. The model predictions demonstrated close agreement with the experimental data (R2≥ 0.95 for all conditions) and revealed three distinct drying stages: initial warming up, constant drying rate, and falling drying rate at the end. Initially, the shrimp temperature increased from 25 °C to around 46 °C and 53 °C for the process at 60 °C and 70 °C. Thus, it presented a constant drying rate, around 0.04 kg/kg min at 60 °C and 0.05 kg/kg min at 70 °C. During this stage, the process is controlled by the heat transferred from the surroundings. Subsequently, the internal resistance to mass transfer becomes the dominant factor, leading to a decrease in the drying rate and an increase in temperatures. A numerical analysis indicated that considering the irregular shape of the shrimp provides more realistic moisture and temperature profiles compared to the simplified finite cylinder geometry. Furthermore, a sensitivity analysis was performed using the validated model to assess the impact of the mass and heat transfer parameters and relative humidity inside the cavity on the drying process. The proposed model accurately described the drying, allowing the further evaluation of the quality and safety aspects and optimizing the process.

Mechanisms of ammonia-like off-flavors formation in dried shrimp: Contribution of spoilage microbiota and their metabolism

Dried shrimp is susceptible to ammonia-like off-flavors (ALOF) during storage, yet the formation mechanisms are still not fully clear. This study analysed the contribution of different parts of dried shrimp to ALOF and characterised the formation mechanisms mainly from microbiological spoilage and amino acid metabolism points. Results showed that head viscera were the main contributors to ALOF, and visceral bacteria were the primary source of microorganisms in stored dried shrimp. The sensory scores of groups without head viscera kept at 0-1 during the storage, indicating no smellable ammonia odour. Analysis of off-flavor indicators showed that visceral bacteria promoted protein degradation and amino acid metabolism. Both amino acid deamination and decarboxylation activities of spoilage microbiota contributed to ALOF formation; however, deamination activities of visceral microbiota were more prominent, particularly for bitter amino acids metabolism. These results provide guidelines for controlling ALOF generation in dried shrimp products during storage.

The formation pathway of flavor compounds in steamed Antarctic krill (Euphausia superba) based on untargeted metabolomics

This study investigated the impact of steaming on the flavor and metabolic profile of Antarctic krill, aiming to elucidate the pathways responsible for flavor development and metabolic shifts during processing. HS-SPME-GC-MS identified key volatile compounds, including alcohols, aldehydes, ketones and so on. The results demonstrated a significant increase in nonanal content from 2.23 ± 0.06 μg/kg to 8.14 ± 1.26 μg/kg after steaming. The formation pathways of two key flavor compounds, nonanal and 1-octen-3-ol, were attributed to fatty acid degradation. Hierarchical clustering and volcano plot showed metabolic shifts between raw and steamed krill, with differential metabolites like hydroquinone and gamma-aminobutyric acid emerging as key contributors to flavor changes. Furthermore, metabolic network further linked these shifts to reactions involving amino acids, nucleotide and other compounds during steaming, impacting the overall taste.

Optimizing color enhancement in dried Penaeus vannamei through high-humidity hot air impingement cooking: Enzyme inactivation, reduced drying time, and Maillard reaction inhibition

This study was aimed to evaluate the potential of high-humidity hot air impingement cooking (HHAIC) on Penaeus vannamei, focusing on its drying characteristics, microstructure, water distribution, enzyme activity, astaxanthin content, antioxidant capacity, color, and Maillard reaction. Results demonstrated that a 3 min HHAIC significantly improved the shrimp's color and optimized astaxanthin content with a notable increase in scavenging capacity based on an in-vitro as antioxidation activity evaluation. Compared to the untreated samples, HHAIC could significantly inactivate polyphenol oxidase by 95.76%. Also, it suppressed the Maillard reaction by decreasing 5-hydroxymethylfurfural content and shortened the drying time by 40%. In addition, the low-field nuclear magnetic resonance and microstructure analysis showed alterations in the shrimp muscle fiber structure and water distribution. This study indicated that HHAIC could elevate quality, enhance appearance, and reduce the processing time of dried shrimp, presenting valuable implications for industry progress.

Intelligent Evaluation and Dynamic Prediction of Oyster Freshness with Electronic Nose Based on the Distribution of Volatile Compounds Using GC-MS Analysis

The quality of oysters is reflected by volatile organic components. To rapidly assess the freshness level of oysters and elucidate the changes in flavor substances during storage, the volatile compounds of oysters stored at 4, 12, 20, and 28 °C over varying durations were analyzed using GC-MS and an electronic nose. Data from both GC-MS and electronic nose analyses revealed that alcohols, acids, and aldehydes are the primary contributors to the rancidity of oysters. Notably, the relative and absolute contents of Cis-2-(2-Pentenyl) furan and other heterocyclic compounds exhibited an upward trend. This observation suggests the potential for developing a simpler test for oyster freshness based on these compounds. Linear Discriminant Analysis (LDA) demonstrated superior performance compared to Principal Component Analysis (PCA) in differentiating oyster samples at various storage times. At 4 °C, the classification accuracy of the optimal support vector machine (SVM) and random forest (RF) models exceeded 90%. At 12 °C, 20 °C, and 28 °C, the classification accuracy of the best SVM and RF models surpassed 95%. Pearson correlation analysis of the concentrations of various volatile compounds and characteristic markers with the sensor response values indicated that the selected sensors were more aligned with the volatiles emitted by oysters. Consequently, the volatile compounds in oysters during storage can be predicted based on the response information from the sensors in the detection system. This study also demonstrates that the detection system serves as a viable alternative to GC-MS for evaluating oysters of varying freshness grades.

Effects of community ecological network construction on physicochemical, microbial, and quality characteristics of inoculated northeast sauerkraut: A new insight in food fermentation processes

The enhancement of the quality of northeast sauerkraut can be achieved by inoculation with lactic acid bacteria. However, a comprehensive ecological understanding of the intricate dynamic processes involved is currently lacking, which could yield valuable insights for regulating sauerkraut fermentation. This study compares spontaneously sauerkrauts with the sauerkrauts inoculated with autochthonous Lactiplantibacillus plantarum SC-MDJ and commercial L. plantarum, respectively. We examine their physicochemical properties, quality characteristics, bacterial community dynamics, and ecological network interactions. Inoculation with L. plantarum leads to reduced bacterial community richness and niche breadth, but an increase in robustness, interactions, and assembly processes. Notably, there appears to be a potential correlation between bacterial community structure and quality characteristics. Particularly, sauerkraut inoculated with L. plantarum SC-MDJ may produce a sourness more quickly, possibly attributed to the enhanced ecological role of L. plantarum SC-MDJ. This study establishes a foundation for the targeted regulation of sauerkraut fermentation.

Insight into the correlation of key taste substances and key volatile substances from shrimp heads at different temperatures

This study aimed to investigate taste substances of shrimp heads stored at 20 °C, 4 °C, -3 °C, and - 18 °C, and the correlation between taste substances and 25 key volatile substances. Notably, samples stored at 20 °C showed significant changes in bitter amino acids and hypoxanthine, and quickly deteriorated. Samples stored at 4 °C for 14 d or - 3 °C for 30 d facilitated the development of umami amino acids, sweet amino acids, and IMP. Furthermore, samples stored at -18 °C for 30 d demonstrated no significant changes in taste profile. Changes in taste substances through quantitative analysis were consistent with changes in taste profile through e-tongue analysis. Based on the results of O2PLS (VIP > 1), Cys, Arg, Glu, Ser, Val, Ala, Ile, ADP, and IMP were correlated with 25 key volatile substances. This study provides fundamental data for the storage, transportation, and value-added utilization of shrimp heads.

Advanced detection tools in food fraud: A systematic review for holistic and rational detection method based on research and patents

Modern food chain supply management necessitates the dire need for mitigating food fraud and adulterations. This holistic review addresses different advanced detection technologies coupled with chemometrics to identify various types of adulterated foods. The data on research, patent and systematic review analyses (2018-2023) revealed both destructive and non-destructive methods to demarcate a rational approach for food fraud detection in various countries. These intricate hygiene standards and AI-based technology are also summarized for further prospective research. Chemometrics or AI-based techniques for extensive food fraud detection are demanded. A systematic assessment reveals that various methods to detect food fraud involving multiple substances need to be simple, expeditious, precise, cost-effective, eco-friendly and non-intrusive. The scrutiny resulted in 39 relevant experimental data sets answering key questions. However, additional research is necessitated for an affirmative conclusion in food fraud detection system with modern AI and machine learning approaches.

Effect of osmotic dehydration combined with vacuum freeze-drying treatment on characteristic aroma components of peach slices

Hot air drying (HD), vacuum freeze drying (FD), and pilot-scale freeze drying (PSFD) are extensively used to prepare peach slices. However, the aroma of hot air drying and vacuum freeze-drying is yet to be addressed. In this study, HS-SPME-GC-MS was used to characterize and quantify the volatile compounds in peach slices. First, 33, 36, and 46 volatile compounds were identified and quantified in the HD, FD, and PSFD groups, respectively. PSFD is preferable to HD and FD in terms of the volatile compound types, content, and aroma profiles. PSFD was selected for subsequent permeation and dehydration experiments. The key aroma compounds with an OAV ≥ 1 were found in the PSFD30 group. GC-O analysis was conducted on the PSFD30 group, leading to the preliminary identification of 2-methylbutanal, pentanal, hexanal, 2-hexenal, phenylacetaldehyde, ethyl acetate, 2-methylbutyl acetate, ethyl lactate, linalool, methyl heptenone, and γ-octalactone as distinctive aromas in dried peach slices.

Generation of key aroma compounds in fat and lean portions of non-smoked bacon induced via lipid pyrolysis reaction

This study explored the evolution of key aroma compounds and their lipid precursors in the lean (LN) and fat (FT) portions of non-smoked bacon during hot air drying. The results showed that the LN portion contained most of the aroma compounds in the bacon (>88%). The volatile content of the FT portion increased as the drying time increased, whereas that of the LN portion reached a maximum within 24 h and then decreased. Based on the highest volatile contents (4889.48 ± 202.06 µg/kg) and sensory scores, 24 h was considered the optimal drying time. For key aroma compounds, hexanal and 2,3-octanedione were derived from free fatty acids and polar lipids. Notably, 1-octen-3-ol was generated only from polar lipids in the FT and LN portions. The 2-undecenal and (E, E)-2,4-decadienal were produced by the oxidation of neutral lipids in the FT portion. Dihydro-5-pentyl-2(3H)-furanone was derived from polar lipids in the LN portion. Altogether, these findings provide theoretical insights into improving the aroma of bacon by optimizing raw material selection and processing methods.

Analysis of the key aroma components of Pu'er tea by synergistic fermentation with three beneficial microorganisms

Aroma is a key indicator of the quality and value of Pu'er tea. A total of 36 aroma components were detected,which Saccharomyces, Rhizopus, and Aspergillus niger, were in the ratios of 2:1:2, 2:2:2, and 2:3:2 inoculated to ferment Pu'er tea, comparing with natural fermentation. In addition, 12 key aroma compounds were identified by analysing ROAVs. Methoxyphenyl compounds and β-ionone were the primary contributors to the formation of aged and woody aroma when fermenting Pu'er tea naturally or using Rhizopus, while linalool and its oxides, benzyl alcohol, hexanal, and limonene were the primary contributors to the formation of floral and fruity aroma when fermenting Pu'er tea using synergistic fermentation with Saccharomyces, Rhizopus, and Aspergillus niger. This study identified the key aroma components of the Pu'er tea fermented using five methods, which revealed and demonstrated the potential application of synergistic effects of different microorganisms in the changes of aroma of Pu'er tea.

GC-MS, GC-IMS, and E-Nose Analysis of Volatile Aroma Compounds in Wet-Marinated Fermented Golden Pomfret Prepared Using Different Cooking Methods

The cooking method is extremely important for the production of low-salt, wet-marinated, fermented golden pomfret because it strongly influences its flavor components and organoleptic quality. There are also significant differences in flavor preferences in different populations. The present study analyzed differences in the aroma characteristics of wet-marinated fermented golden pomfret after boiling, steaming, microwaving, air-frying, and baking using a combination of an electronic nose, GC-IMS, and SPME-GC-MS. Electronic nose PCA showed that the flavors of the boiled (A), steamed (B), and microwaved (C) treatment groups were similar, and the flavors of the baking (D) and air-frying (E) groups were similar. A total of 72 flavor compounds were detected in the GC-IMS analysis, and the comparative analysis of the cooked wet-marinated and fermented golden pomfret yielded a greater abundance of flavor compounds. SPME-GC-MS analysis detected 108 flavor compounds, and the results were similar for baking and air-frying. Twelve key flavor substances, including hexanal, isovaleraldehyde, and (E)-2-dodecenal, were identified by orthogonal partial least-squares discriminant analysis (OPLS-DA) and VIP analysis. These results showed that the cooking method could be a key factor in the flavor distribution of wet-marinated fermented golden pomfret, and consumers can choose the appropriate cooking method accordingly. The results can provide theoretical guidance for the more effective processing of fish products and the development of subsequent food products.

Flavor profile and role of macromolecules in the flavor generation of shrimp meat and valorization of shrimp by-products as a source of flavor compounds: a review

Shrimps are a widely cultivated species among crustaceans worldwide due to their nutritional profile and delicacy. Because of their unique flavor, shrimp-based food products are gaining consumer demand, so there is a need to understand the flavor chemistry of shrimp meat. Further, the processing and macromolecules of shrimp meat play a significant role in flavor generation and suggest a focus on their research. However, shrimp processing generates a large amount of solid and liquid waste, creating disposal problems and environmental hazards. To overcome this, utilizing these waste products, a rich source of valuable flavor compounds is necessary. This review comprehensively discusses the nutritional aspects, flavor profile, and role of macromolecules in the flavor generation of shrimp meat. Besides, recent trends in analyzing the aroma profile of shrimp and the benefits of shrimp by-products as a source of flavor compounds have been addressed. The delicious flavor of shrimp meat is due to its volatile and nonvolatile flavor compounds. Proteins play a major role in the textural and flavor adsorption properties of shrimp meat-based products. Green extraction technologies, especially ultrasonication, are recommended for valorizing shrimp by-products as a source of flavor compounds, which have enormous applications in the food and flavor industries.

The odor deterioration of tilapia (Oreochromis mossambicus) fillets during cold storage revealed by LC-MS based metabolomics and HS-SPME-GC-MS analysis

Odor deterioration of tilapia during cold storage is unavoidable and affects flavor and quality severely. Odor is characterized by the abundance of volatile compounds and metabolites. In this study, headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and metabolomic analysis were applied to explore the volatile compounds, differential metabolites, and metabolic pathways related to the odor deterioration of tilapia during cold storage. A total of 29 volatile compounds were detected to be associated with the odor deterioration of tilapia. And 485 differential metabolites were screened, of which 386 differential expressions were up-regulated and 99 differential expressions were down-regulated. Three major metabolic pathways including linoleic acid metabolism, alanine, aspartate, glutamate metabolism, and nucleotide metabolism were obtained. A potential metabolic network map was also proposed. This study contributes to revealing the metabolic mechanisms of odor deterioration in tilapia during cold storage and providing a theoretical reference for the regulation of flavor and quality.

Effect of Drying Process on the Formation of the Characteristic Flavor of Oyster (Crassostrea hongkongensis)

Oysters are nutritious and tasty but difficult to store. Drying can extend the storage period of oysters and give them a unique flavor. In this study, the effects of four drying procedures, namely, vacuum freeze drying (VFD), vacuum drying (VD), natural sun-drying (NSD), and hot air drying (HAD), on the flavor characteristics of oysters (Crassostrea hongkongensis) were investigated using blanched oysters as a control (CK). Results showed that HAD produced more free amino acids than the other methods, but VFD retained the most flavor nucleotides. Compared with cold drying (VFD), hot drying (VD, NSD, and HAD) increased the abundance of organic acids, betaine, and aroma substances. Glutamic acid, alanine, AMP, hexanal, octanal, heptanal, (E, E)-2,4-heptadienal, (E)-2-decenal, nonanal, etc., are defined as the characteristic flavor compounds of dried oysters, with umami, sweet, green, fatty, and fruity aromas being the main organoleptic attributes of dried oysters. Glutamic acid, glycine, betaine, IMP, pentanal, ethyl heptanoate, (E, Z)-2,4-nonadienal, 1-octen-3-one, 2-hexenal, 2-octenal, hexanal, decanal were defined as markers to distinguish different drying methods. Overall, HAD showed improved flavor qualities and characteristics and was better suited for the highly commercialized production of dried oysters.

Evaluation of Aroma Characteristics of Dried Shrimp (Litopenaeus vannamei) Prepared by Five Different Procedures

Litopenaeus vannamei is one of the most popular shrimp species in the world and has been reported in studies on its dryness and flavor. However, the aroma characteristics of shrimps dried with different drying methods are compared in a unified way, and there are few reports on the difference in aroma of different shrimps dried. In order to clarify the difference in aroma characteristics of shrimp dried produced by different drying methods. In this study, blanched shrimp (BS) was used as a control to analyze the aroma characteristics of shrimp dried by five different procedures (SD-BFDP) samples, namely vacuum freeze-dried shrimp (VFDS), vacuum dried-shrimp (VDS), heat pump-dried shrimp (HPDS), hot air dried-shrimp (HADS) and microwave vacuum-dried shrimp (MVDS). An electronic nose (E-nose) was used to obtain the aroma fingerprint of SD-BFDP samples. Headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used for qualitative and quantitative analysis of volatile compounds in SD-BFDP samples. Partial least squares regression (PLSR) was used to analyze potential correlations between sensory attributes and aroma-active compounds (AACs). Partial least squares-discrimination analysis (PLS-DA) was used to screen for signature aroma compounds. The results of the E-nose showed that there were differences in the aroma fingerprints of the SD-BFDP samples, and the E-nose could distinguish the five kinds of SD-BFDP. The qualitative and quantitative results of GC-MS showed that the types and contents of the main volatile components of SD-BFDP samples were different. 15 AACs were screened from SD-BFDP based on odor activity value (OAV). The PLSR results showed good correlations between certain sensory attributes and the majority of AACs. PLS-DA results displayed that aroma attributes of SD-BFDP samples could be distinguished by six signature aroma compounds, including trimethylamine, 2,5-dimethylpyrazine, 2-ethyl-5-methylpyrazine, nonanal, 3-ethyl-2,5-dimethylpyrazine, and octanal. These research results reveal that shrimps dried in different procedures have unique aroma characteristics, which could provide a theoretical basis for the rapid identification of aroma attributes of dried shrimps in the future. From a flavor perspective, MVD is the best drying method.

Active aroma compounds assessment of processed and non-processed micro- and macroalgae by solid-phase microextraction and gas chromatography/mass spectrometry targeting seafood analogs

The odor of four algae was investigated and compared to evaluate the potential of these algae to mimic shrimp aroma. Solid-phase microextraction followed by gas chromatography analysis coupled with sensory analysis was used for performance assessment. The volatile organic compounds were determined in non-processed, raw samples (r), and processed cooked (c) and cooking water (w) samples for two microalgae [Nannochoropsis oceanica (NO) and Tetraselmis chuii (TC)], two macroalgae [Ulva rígida (UR) and Saccharina latíssima (SL)], and shrimp Vannamei cong (SH). The results showed significant differences in the composition of volatile compounds between macroalgae and microalgae. The key odorants in macroalgae were octanal, 2-octenal, nonanal, and β-ionone, and in microalgae were 1,5-octadien-3-ol, hexanal, 2,4-decadienal, 2-octenal, octanal, nonanal, 3,5-octadien-2-one, and terpenes. The PCA analysis of GC-MS data showed odor similarities between the studied samples, which were divided into five main groups: (1) TC(c) and TC(w); (2) TC(r) and NO(c); (3) NO(r), NO(w), and SL(w); (4) SL(c), UR(r), UR(c), and UR(w); and (5) SL(r). The data from the sensory analysis show bigger similarities between the macroalgae and the shrimp odor. Overall, the data provided indicate that the cooking water and cooked samples are very similar in key components of odorants. These features allow the possibility to use algae and their processed resulting products as a shrimp flavor replacement in non-animal-based food formulations, thus decreasing the pressure on seafood crops and aquaculture-associated issues leading to more sustainable livestock. Furthermore, circularity and waste reduction may be further enabled by the use of otherwise wasted cooking water as an odorant agent.

The Role of Amino Acids in the Formation of Aroma-Active Compounds during Shrimp Hot Air Drying by GC-MS and GC-IMS

In the present paper, the role of amino acids of Penaeus vannamei was investigated in the formation of volatile substances during drying. The variations in volatile substances among samples with different moisture contents (raw, 45%, 30%, 15%, and 5%) were obtained by gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS). The amino acid contents of the above samples were measured by the amino acid automatic analyzer. Correlation between pyrazines and the various amino acid contents was analyzed by the Pearson correlation coefficient. Their correlation was verified by conducting addition assays. The types and contents of volatile components increased significantly in samples with moisture contents between 30% and 5%. The most obvious increases in the type, content and odor activity value of pyrazines were observed in this range. Basic amino acids (Arg, Lys, and His) had a strong correlation with the formation of pyrazines. Addition assays verified that the addition of Arg and Lys increased the content of pyrazines in shrimp after drying.

Real-Time Monitoring of the Quality Changes in Shrimp (Penaeus vannamei) with Hyperspectral Imaging Technology during Hot Air Drying

Hot air drying is the most common processing method to extend shrimp's shelf life. Real-time monitoring of moisture content, color, and texture during the drying process is important to ensure product quality. In this study, hyperspectral imaging technology was employed to acquire images of 104 shrimp samples at different drying levels. The water distribution and migration were monitored by low field magnetic resonance and the correlation between water distribution and other quality indicators were determined by Pearson correlation analysis. Then, spectra were extracted and competitive adaptive reweighting sampling was used to optimize characteristic variables. The grey-scale co-occurrence matrix and color moments were used to extract the textural and color information from the images. Subsequently, partial least squares regression and least squares support vector machine (LSSVM) models were established based on full-band spectra, characteristic spectra, image information, and fused information. For moisture, the LSSVM model based on full-band spectra performed the best, with residual predictive deviation (RPD) of 2.814. For L*, a*, b*, hardness, and elasticity, the optimal models were established by LSSVM based on fused information, with RPD of 3.292, 2.753, 3.211, 2.807, and 2.842. The study provided an in situ and real-time alternative to monitor quality changes of dried shrimps.

Comprehensive Quality Evaluation for Medicinal and Edible Ziziphi Spinosae Semen before and after Rancidity Based on Traditional Sensory, Physicochemical Characteristics, and Volatile Compounds

To comprehensively evaluate the quality of medicinal and edible Ziziphi Spinosae Semen (ZSS, the dried ripe seeds of Ziziphus jujuba var. spinosa) before and after rancidity during storage, some indicators including traditional sensory properties, physicochemical characteristics, and volatile compounds were analyzed. As a result, compared with the normal samples, the rancid samples of ZSS produced a darker color, a bitter taste, and an irritating odor, increased moisture content, electrical conductivity, fatty oil content, and acid value, and decreased water- and alcohol-soluble extract contents and pH value. Among them, the acid value had significant difference (p < 0.01) from 3.90 of normal ZSS to 18.68 mg/g of rancid ZSS. A total of 39 volatile compounds were identified in samples, including 20 in normal ZSS and 38 compounds in rancid ZSS. Nineteen common compounds were identified in normal and rancid samples. Among them, the content of 10 compounds such as δ-limonene, (R,R)-2,3-butanediol, and (R,S)-2,3-butanediol was decreased but that of nine compounds such as acetic acid, n-octanoic acid, and n-nonanoic acid was increased in rancid ZSS. Nineteen unique compounds such as β-phellandrene, α-pinene, and 3-carene were detected and only one compound, δ-cadinene, was not detected in rancid ZSS. In addition, eight short-chain organic acids, acetic, propanoic, butanoic, pentanoic, hexanoic, heptanoic, octanoic, and nonanoic acids, were new products in rancid ZSS, and it was speculated that the production of a series of organic acids might be the material basis of irritating odor after normal ZSS became rancid. This is the first report that a series of short-chain organic acids have been found in a rancid substance. In conclusion, there was a significant difference between normal and rancid ZSS. These indicators could be used as an early warning for judging the rancidity phenomenon of medicinal and edible ZSS. In addition, this is the first comprehensive evaluation about the rancidity process of a medicinal and edible substance.

Early Discrimination and Prediction of C. fimbriata-Infected Sweetpotatoes during the Asymptomatic Period Using Electronic Nose

Sweetpotato is prone to disease caused by C. fimbriata without obvious lesions on the surface in the early period of infection. Therefore, it is necessary to explore the possibility of developing an efficient early disease detection method for sweetpotatoes that can be used before symptoms are observed. In this study, sweetpotatoes were inoculated with C. fimbriata and stored for different lengths of time. The total colony count was detected every 8 h; HS-SPME/GC–MS and E-nose were used simultaneously to detect volatile compounds. The results indicated that the growth of C. fimbriata entered the exponential phase at 48 h, resulting in significant differences in concentrations of volatile compounds in infected sweetpotatoes at different times, especially toxic ipomeamarone in ketones. The contents of volatile compounds were related to the responses of the sensors. E-nose was combined with multiple chemometrics methods to discriminate and predict infected sweetpotatoes at 0 h, 48 h, 64 h, and 72 h. Among the methods used, linear discriminant analysis (LDA) had the best discriminant effect, with sensitivity, specificity, precision, and accuracy scores of 100%. E-nose combined with K-nearest neighbours (KNN) achieved the best predictions for ipomeamarone contents and total colony counts. This study illustrates that E-nose is a feasible and promising technology for the early detection of C. fimbriata infection in sweetpotatoes during the asymptomatic period.

Quality and volatile compound analysis of shrimp heads during different temperature storage

This study aimed to investigate volatile compounds and quality traits of shrimp heads stored at 20 °C, 4 °C, -3 °C, and -18 °C. With increased storage time, sensory scores gradually decreased, while pH and TVB-N content showed a gradually increase trend. L* showed a decreasing and then increasing tendency. The radar chart and principal component analysis showed variation changes. Three compounds including 2-decanone, dimethyl disulphide and dimethyl tetrasulphide, four compounds including 2-pentanone, 3-methyl-1-butanol, 2-methylbutyric acid, and 2,3,5-trimethylpyrazine, and 3-methylbutyraldehyde were the characteristic volatiles for the samples stored at 20 °C, 4 °C, and -3 °C, respectively. Twenty-five volatile compounds were key volatile compounds, among which nine were potential classification compounds with high variable importance in projection values. Trimethylamine and 2-nonanol were selected as potential markers of spoilage. The study provides the theoretical basis for quality and volatile compound investigations for shrimp heads with further high-quality utilization.

Comparison of the Proximate Composition and Nutritional Profile of Byproducts and Edible Parts of Five Species of Shrimp

The nutritional components of different parts (meat, head, shell and tail) of Litopenaeus vannamei (L.v), Macrobrachium rosenbergii (M.r), Penaeus monodon (P.m), Fenneropenaeus chinensis (F.c), and Penaeus japonicus (P.j) were analyzed and their nutritional values were evaluated. For the five species of shrimp, the meat yield was 37.47–55.94%, and the byproduct yield was 44.06–62.53%. The meat yields of L.v and F.c were the highest (55.94 and 55.92%, respectively), and the meat yield of M.r was the lowest (37.47%). The shrimp contain high amounts of crude protein, and the values of the amino acid score (AAS), chemical score (CS), and essential amino index (EAAI) were greater than or close to 1.00, indicating that shrimp protein had higher nutritional value. The shrimp head was rich in polyunsaturated fatty acids and the ratio of n-6 to n-3 PUFAs was from 0.37 to 1.68, indicating that the shrimp head is rich in n-3 PUFAs and is a good source of n-3 PUFAs. The five species of shrimp were rich in macro- and micro-minerals, especially in shrimp byproducts. The shrimp byproducts were also rich in other bioactive ingredients (astaxanthin), which are also very valuable for developing biological resources. Therefore, shrimp have many nutritional benefits, and their byproducts can also be used to develop natural nutraceuticals, which are considered to be one of the healthiest foods.

Comparison of methodological proposal in sensory evaluation for Chinese mitten crab (Eriocheir sinensis) by data mining and sensory panel

Chinese mitten crab (Eriocheir sinensis) needs sensory evaluation for grading. This study compared data mining (DM) and sensory panel evaluation (SPE), using data visualization (DV) and quantitative descriptive analysis (QDA), respectively. Results showed that Yangcheng Lake Crab (YLC) was the most welcomed for "umami" and "sweet" according to DV; and QDA (7-scale) showed similar results of the highest "aroma-sweet" (Average Score 4.5) and "taste-umami" (Average Score 4.6) in YLC. The difference was that, DV was fast based on big data (1.4 million words); while QDA quantified detailed attributes (principle components > 85.3% averagely) based on highly-trained sensory panel of good distinguishing- and repeating- ability that F value showed 76.4% of all attributes > 5% for panelist averagely, and mean square error < 0.500 except one panelist. In conclusion, DM was quick but qualitative; while SPE was laborious but informative.

Analysis of volatile compound changes in fried shallot (Allium cepa L. var. aggregatum) oil at different frying temperatures by GC-MS, OAV, and multivariate analysis

Flavor is a key attribute of fried oil that shows a critical correlation with temperature. Therefore, selecting the appropriate temperature is important in preparing fried shallot oil (FSO). Volatile compounds from five different FSOs were identified and comparatively studied using gas chromatography-mass spectrometry (GC-MS) coupled with multivariate data analysis, including principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). GC-MS results identified a total of 93 volatiles, among which aldehydes, alcohols, pyrazines, and sulfur-containing compounds were the major compounds. Eighteen compounds had odor active values (OAV) >1. Among the compounds, hexanal, (E)-2-heptenal, (E)-2-octenal, dipropyl disulfide, 2-ethyl-3,5-dimethylpyrazine, and 1-octen-3-ol were important to the overall aroma profile of FSOs. In the PCA model, all the detected FSOs were divided into three clusters, which were assigned as cluster A (FSO5), B (FSO4), and C (the rest FSOs). Multivariate data analyses revealed that nonanal, 2-ethyl-5-methylpyrazine, (E,E)-2,4-decadienal, (E)-2-heptenal, and hexanal contributed positively to the classification of different FSOs. GC-MS coupled with multivariate data analysis could be used as a convenient and efficient analytical method to classify raw materials.