Aroma Generation Research Articles

Comprehensive foodomics analysis reveals key lipids affect aroma generation in beef

Lipids are vital precursors to beef aroma compounds, but the exact lipid molecules influencing aroma generation remain unconfirmed. This study employs gas chromatography–olfactometry–mass spectrometry and absolute quantitative lipidomics to identify beef's aroma and lipid profiles and to examine lipid alterations post-thermal processing. The aim is to understand the role of lipids in aroma generation during beef's raw-to-cooked transition. Eighteen key aroma compounds were identified as significant contributors to the aroma of beef. 265 lipid molecules were quantified accurately, and we found that triglycerides containing C18:1 or C18:2 chains, such as TG(16:0_18:1_18:1), TG(16:0_18:1_18:2), TG(16:0_16:1_18:1), as well as phosphatidylcholine and phosphatidylethanolamine containing PC(16:1e_20:4), PC(16:0e_20:4), PC(18:2e_18:2), and PE(16:1e_20:4), played important roles in the generation of key aroma compounds in beef. C18:1, C18:2, C18:3, and C20:4 were key substrates for the formation of aroma compounds. In addition, lysophosphatidylcholine and lysophosphatidylethanolamine containing unsaturated fatty acid chains may serve as important aroma retainers.

Comprehensive analysis of the effects of the traditional stir-fry process on the dynamic changes of volatile metabolites in Hainan camellia oil

The traditional stir-fry process before pressing is crucial to manufacture Hainan camellia oil. To assess the effects of the stir-fry process on Hainan camellia oil, six samples across different stir-fry stages were analyzed. The stir-fry process modified odors, volatile metabolite profiles, and human health-promoting functions of Hainan camellia oil. Totally, 350 volatile metabolites were detected, and heterocyclic compounds were revealed as the main contributors of strong aroma. Potential indicators for monitoring the stir-fry degree were established. Eight key aroma volatile metabolites were identified, including three new ones (1-octen-3-one, 2,3-butanedione, and vanillin). Lipids degradation and the Millard reaction are probably the main pathways for aroma generation. Over-stir-fry treatment diminished the contents of some important volatile metabolites but increased the risk of arising burnt odor. Our work offered insights into the effects of the stir-fry process and over-stir-fry treatment on Hainan camellia oil, which is meaningful for improving the hot-pressing technique.

Exploring the correlation of microbial community diversity and succession with protein degradation and impact on the production of volatile compounds during cold storage of grouper (Epinephelus coioides)

Microorganisms, proteins, and lipids play crucial and intricate roles in the aroma generation of aquatic products. To explore the impact of the interaction between microorganisms and proteins on the volatile compounds (VOCs) in grouper, this study employed whey protein isolate (WPI) to inhibit lipid oxidation and reduce mutual interference. Changes in bacterial profiles, metabolites, and VOCs were detected. Eighteen key VOCs associated with the overall flavor of grouper were identified, and the potential relationships among microorganisms, proteins, and VOCs were explored using a correlation network. Five microorganisms (Vibrio, Vagococcus, Pseudomonas, Psychrobacter, and Shewanella) closely related to characteristic flavor compounds were identified. Additionally, 30 differential metabolites related to proteins and six metabolic pathways were screened. Therefore, this study unveils the potential interaction between microorganisms and proteins in flavor formation and provides new insights into the relationships among microorganisms, proteins, and VOCs.

Unraveling the influence of lipids on aroma generation in non-smoked bacon during boiling through untargeted lipidomics analysis

This study explored the key lipid precursors that influence the aroma in the lean portion of bacon by investigating the alterations in volatiles and lipid profiles during boiling of bacon. A total of 19 key aroma compounds were identified, with the highest concentration reached after 20 min of boiling. Lipidomic analysis revealed 1211 distinct lipid molecules, predominantly composed of glycerides and glycerophospholipids. Notably, the triglyceride (TG) (16:0/18:0/18:1) and TG (18:0/18:1/18:1) were assumed to contribute to the retention of aroma compounds. Multivariate statistical analysis identified 569 differentially abundant lipids which serve as biomarkers for distinguishing between various boiling times. Correlation analysis identified 67 lipid molecules that exhibited a high correlation (r < −0.8) with aroma compounds, including 23 TG and 9 phosphatidylethanolamine (PE). Removal of the fat portion from bacon and subsequent prolonged boiling resulted in a notable reduction in the glycerolipid content of the bacon, accompanied by a corresponding decline in the concentration of aroma compounds. Consequently, the application of a suitable processing method can result in an optimal aroma of bacon prior to consumption, and TG and PE play vital roles in the formation of aroma.

Dynamic changes and the effects of key procedures on the characteristic aroma compounds of Lu’an Guapian green tea during the manufacturing process

As a kind of green tea with unique multiple baking processes, the flavor code of Lu’an Guapian (LAGP) has recently been revealed. To improve and stabilize the quality of LAGP, further insight into the dynamic changes in odorants during the whole processing is required. In this study, 50 odorants were identified in processing tea leaves, 14 of which were selected for absolute quantification to profile the effect of processes. The results showed that spreading is crucial for key aroma generation and accumulation, while these odorants undergo significant changes at the deep baking stage. By adjusting the conditions of the spreading and deep baking, it was found that low-temperature (4 °C) spreading for 6 h and low-temperature with long-time baking (final leaf temperature: 102 °C, 45 min) could improve the overall aroma quality. These results provide a new direction for enhancing the quality of LAGP green tea.

Metabolic behavior of Aspergillus oryzae in salt-reduced soy sauce and its regulation for the brewing process

Soy sauce fermentation process initiates with the involvement of Aspergillus oryzae, which serves as the primary beneficiary in salt-reduced fermentation (SRF) process. This investigation aimed to scrutinize the metabolic activities of A. oryzae in salt-reduced soy sauce and examine its subsequent impacts on the microecology and flavor profile. SRF amplified the central carbon and protein metabolism of A. oryzae, leading to improved substrate utilization efficiency, which in turn facilitated the colonization of Lactobacillus and the maintenance of a co-occurrence equilibrium within the microbiota. Consequently, Ascomycetes established a fundamental module for aroma generation, exhibiting robust interconnections. SRF facilitated A. oryzae in supplying amino acid precursors vital to produce phenylacetaldehyde derivatives. Furthermore, SRF prompted an up-regulation of the β-oxidation pathway in A. oryzae, effectively suppressing the generation of undesirable fatty rancidity odor (fatty aldehyde) derived from fatty acids. These metabolic characteristics of A. oryzae play a pivotal role in enhancing the quality of salt-reduced soy sauce.

Impact of non-Saccharomyces yeasts derived from traditional fermented foods on beer aroma: Analysis based on HS-SPME-GC/MS combined with chemometrics

In recent years, numerous studies have demonstrated the significant potential of non-Saccharomyces yeasts in aroma generation during fermentation. In this study, 134 strains of yeast were isolated from traditional fermented foods. Subsequently, through primary and tertiary screening, 28 strains of aroma-producing non-Saccharomyces yeast were selected for beer brewing. Headspace-solid phase microextraction (HS-SPME) combined with gas chromatography–mass spectrometry (GC–MS) and chemometrics were employed to analyze the volatile flavor substances in beer samples fermented using these strains. Chemometric analysis revealed that distinct species of non-Saccharomyces yeast had a unique influence on beer aroma, with strains from the same genus producing more similar flavor profiles. Accordingly, 2,6-nonadienal, 1-pentanol, phenyl ethanol, isoamyl acetate, ethyl caprate, butyl butyrate, ethyl propionate, furfuryl alcohol, phenethyl acetate, ethyl butyrate, ethyl laurate, acetic acid, and 3-methyl-4 heptanone were identified as the key aroma compounds for distinguishing among different non-Saccharomyces yeast species. This work provides useful insights into the aroma-producing characteristics of different non-Saccharomyces yeasts to reference the targeted improvement of beer aroma.

Characterization of the effect of non-Saccharomyces cerevisiaes on the non-volatile constituents and volatile profiles of low-alcoholic pomegranate beverages

To create the low-alcoholic beverages with excellent nutritional properties and flavor qualities, pomegranate juice was fermented with 16 strains of non-Saccharomyces yeasts from 9 species without added sugar. The effects of different yeasts on the non-volatile constituents (vitamins, organic acids, polyphenols), volatile compounds and sensory characteristics of the fermented beverages were comprehensively evaluated. The study revealed that non-Saccharomyces fermentations resulted in a higher abundance of polyphenols compared to the pomegranate juice and S. cerevisiae WLS21 (Sc21). The monomer phenols in Meyerozyma guilliermondii 12 (Mg12) were approximately twice the total of CK and 1.3 times of Sc21. Moreover, they led to a higher concentration of volatile compounds than the pomegranate juice. A total of 94 volatile compounds were identified in the pomegranate fermented beverages. In contrast to S. cerevisiae, Wickerhamomyces anomalus 1-1 and 10 (Wa1-1, Wa10), Pichia kudriavzevii 8 (Pk8) and Mg12 resulted in more acetate esters, and Zygosaccharomyces rouxii IFO 1130 and 53 (Zr1130, Zr53) yield higher levels of ethyl esters. A total of 40 volatiles with a relative odour activity value (rOAV) of ≥ 0.1 were identified, of which 14 were selected for principal component analysis (PCA). The sensory analysis confirmed that Zr1130, Zr53, Wa1-1, Wa10 and Pk8 strains exhibited superior aroma generation compared to Sc21. Furthermore, the partial least-squares regression (PLSR) analysis revealed that cherry, red fruits, black currant, citrus fruits, raspberry, black berry, pineapple, floral, sour and alcoholic odours had a significantly positive impact on the overall acceptability of the fermented beverages.

Generation of aroma in three-line hybrid rice through CRISPR/Cas9 editing of BETAINE ALDEHYDE DEHYDROGENASE2 (OsBADH2).

Aroma or fragrance in rice is a genetically controlled trait; Its high appreciation by consumers increases the rice market price. Previous studies have revealed that the rice aroma is controlled by a specific gene called BETAINE ALDEHYDE DEHYDROGENASE (OsBADH2), and mutation of this gene leads to the accumulation of an aromatic substance 2-acetyl-1-pyrroline (2-AP). The use of genetic engineering to produce aroma in commercial and cultivated hybrids is a contemporary need for molecular breeding. The current study reports the generation of aroma in the three-line hybrid restorer line Shu-Hui-313 (SH313). We created knock-out (KO) lines of OsBADH2 through the CRISPR/Cas9. The analysis of KO lines revealed a significantly increased content of 2AP in the grains compared with the control. However, other phenotypic traits (plant height, seed setting rate, and 1000-grain weight) were significantly decreased. These KO lines were crossed with a non-aromatic three-line hybrid rice male sterile line (Rong-7-A) to produce Rong-7-You-626 (R7Y626), R7Y627 and R7Y628. The measurement of 2-AP revealed significantly increased contents in these cross combinations. We compared the content of 2-AP in tissues at the booting stage. Data revealed that young spike stalk base contained the highest content of 2-AP and can be used for identification (by simple chewing) of aromatic lines under field conditions. In conclusion, our dataset offers a genetic source and illustrates the generation of aroma in non-aromatic hybrids, and outlines a straightforward identification under field conditions.

Unraveling the role of germination days on the aroma variations of roasted barley malts via gas chromatography-mass spectrometry based untargeted and targeted flavoromics.

Roasting imparts malts with an increased amount of hedonic aromas. However, the relationship between the production of roasted malts and the generation of characteristic malt aromas remains unclear. In this study, roasted barley malts (RM) were prepared from three consecutive germination days (3, 4, 5D), and the aroma profiles among RM and base malt were holistically compared via HS-SPME-GC-MS/O-based flavoromics. Furthermore, the wort color, free amino acids, reducing sugars, and fatty acids compositions were determined before-and-after roasting. Results showed that roasting could flatten variations of precursors regardless of germination days. Additionally, based on quantitation of 53 aromas, a PLS-DA model was applied to differentiate all malts by 17 aromas with VIP≥1. As for aroma harmony, RM with 4D-germination outstood due to a pleasant nutty note with the highest sweet-to-nutty index of 0.8. This work answers how germination days would impact the aroma of RM for the first time.

Establishing the relations of characteristic aroma precursors and volatile compounds for authenticating Tibetan pork.

Tibetan pork has been favored for its unique aromas, which originate from chemical reactions between characteristic precursors in cooking. The precursors (e.g., fatty acids, free amino acids, reducing sugars, and thiamine) of Tibetan pork ((semi-) free range) from different regions in China, comprising Tibet, Sichuan, Qinghai, and Yunnan, and commercial pork (indoor reared) were compared in this study. Tibetan pork was characterized by higher ω-3 polyunsaturated fatty acids (i.e., C18:3n3), higher essential (i.e., valine, leucine, and isoleucine), aromatic (i.e., phenylalanine), and sulfur-containing (i.e., methionine and cysteine) free amino acids, higher thiamine, and lower reducing sugars. Boiled Tibetan pork exhibited higher heptanal, 4-heptenal, and 4-pentylbenzaldehyde compared with commercial pork. The results from multivariate statistical analysis revealed that precursors combined with volatiles exhibited discriminating capability for characterizing Tibetan pork. The precursors in Tibetan pork exerted a certain effect on characteristic aroma generation, probably arising from promoting chemical reactions in cooking.

Characterisation of Cooked Cheese Flavour: Non-Volatile Components.

This work examined the role of selected non-volatile compounds in cooked cheese flavour, both as tastants and as precursors of aroma generation in the Maillard reaction. The effect of cooking on the concentration of selected non-volatile compounds (organic acids, sugars, amino acids, γ-glutamyl dipeptides, and diketopiperazines) in six cheeses (mature Cheddar, mozzarella, Parmesan, and mild Cheddar (low, medium, and high fat)) was determined. Sugars, amino acids, and γ-glutamyl dipeptides were extracted and analysed by LC, whereas diketopiperazines were extracted by solid-phase extraction and analysed by GC-MS. Sugars, amino acids, and γ-glutamyl dipeptides decreased in concentration during cooking, whereas diketopiperazines and some organic acids increased in concentration. Diketopiperazines were above the taste threshold in some cooked cheeses and below the threshold in uncooked cheeses. The role of fat content in cooked cheese flavour is discussed. Furthermore, γ-glutamyl dipeptide concentration increased during 24 months of ageing in low, medium, and high-fat Cheddars, with similar levels of γ-glutamyl dipeptide detected in aged low and high-fat Cheddars. This work will give valuable insight for the dairy industry to inform the development of cheeses, especially low-fat variants, for use in cooked foods.

Aroma generation in sponge cakes: The influence of sucrose particle size and sucrose source.

The influence of sucrose source and particle size was investigated in relation to the volatile and aromatic properties of sponge cakes. Six sponge cake formulations were studied using two sucrose sources (sugarbeet and sugarcane), at two particle sizes (large and small) with controls. Volatiles profiles and odour active compounds were identified by gas chromatography mass spectrometry and olfactometry. Sixty two volatile compounds were identified, incorporating twenty five odour active compounds/co-eluting compounds, with 5 odours perceived without any corresponding volatile. Particle size had the greatest impact on volatile abundance, with particle size especially influencing pyrazine abundance. Five odour active volatiles (methional, furfural, 2,3-dimethylpyrazine, heptanal and (E)-2-octenal) contributed most to the aroma of these sponge cakes. Small particle size particularly from sugarbeet yielded higher levels of some Maillard and caramelisation reaction compounds, such as furfural (spicy/ bready), where larger particle size supressed volatile abundance in comparison to the control.

Eight Typical Aroma Compounds of 'Panguxiang' Pear during Development and Storage Identified via Metabolomic Profiling.

Aroma is an appreciated fruit property, and volatile flavor plays a key role in determining the perception and acceptability of fruit products by consumers. However, metabolite composition that contributes to the aroma in fruit quality is unclear. In this study, we detected 645 volatile organic compounds of 'Panguxiang' pear in total, including esters, alcohols, alkanes, acids, ketones, terpenes and aldehydes. In addition, the levels of sugars, organic acids and amino acids in 'Panguxiang' pear were investigated using high-performance liquid chromatography. In the aroma generation, glucose was the dominant sugar, followed by sucrose and fructose. At the development transferred storage stage, organic acids may not participate in aroma biosynthesis. The amino acids that may play potential roles in aroma substance synthesis are tyrosine and glycine. Through metabolomics analysis at different stages of 'Panguxiang' pear, we selected 65 key metabolites that were significantly related to glucose, sucrose, fructose, tyrosine and glycine, according to the trends of metabolite concentrations. Finally, we chose eight candidate metabolites (e.g., three esters, two aldehydes, one alcohol, one acid and one ketone) as the representative aroma substances of the 'Panguxiang' pear compared to the metabolome of the 'Korla' at stage Z5. Data and results from this study can help better understand the variations in aroma quality among pear varieties and assist in developing breeding programs for pear varieties.

Combining gas chromatography-ion mobility spectrometry and olfactory analysis to reveal the effect of filled-N2 anaerobic treatment duration on variation in the volatile profiles of gabaron green tea

Gamma-aminobutyric acid green tea (GAGT) is a tea with health benefits by a special anaerobic process to increase the GABA content. However, the effect of this special processing on tea flavor during processing has been rarely reported. In this study, GC-IMS was combined with principal component analysis (PCA) to clarify the effects of different times of anaerobic treatment on the volatile profiles in finished GAGT. GC-O-MS and quantitative descriptive analysis (QDA) were used to investigate the flavor characteristics of GAGT infusion. The results showed that the aroma abundance of GAGT peaked at about 8 h after anaerobic treatment, and then the GAGT flavor delayed. At this point, the differential compounds including nonanal, octanal, heptanal and linalool could be perceived by panalists. Other compounds that didn't change very much in content during processing but had high FD factors, such as β-damascenone, (E)-β-ionone, 1-octen-3-ol and 1-octen-3-one, were also screened as odor-active compounds. Together, they constitute the characteristic flavors of “sweet”, “ketchup” and “slightly fermented” of GAGT infusion. This study will help to better understand the mechanism of GAGT aroma generation and improve the processing.

Microwave heating and conduction heating pork belly: Influence of heat transfer modes on volatile compounds and aroma attributes

This work was conducted to compare the differences in odor attributes and the formation causes of pork belly cooked by different heating modes and the feasibility of achieving convenient and delicious cooking of stir-fried pork cuisines by modifying the heat transfer mode of the microwave. The effects of traditional pan-heating (TH), microwave heating (MH), and microwave combined with conduction heating (MH + CH) on sensory aroma attributes, aroma profile, free fatty acids, and volatile compounds of pork belly were investigated. The results showed that the pork belly heated by TH had the lowest total amount of stable volatile compounds (1695.41 μg/kg) and contents of free fatty acids (751.44 mg/100g), but the balanced distribution and the rich contents of volatile compounds derived from thermal processing resulted in the better aroma quality of pork belly. In contrast, although the pork belly cooked by MH had higher free fatty acids contents (1215.32 mg/100g) and the highest volatile compounds (5410.56 μg/kg), due to the cell destruction effect and the molecular movement acceleration of microwave, the contents of volatile compounds derived from spices were too high, leading to the disharmony of aroma characteristics. However, the pork belly cooked with MH + CH not only promoted the production of free fatty acids (1434.23 mg/100g), but also increased the generation and retention of pork characteristic aroma by changing the heating modes. Compared with MH, it enhanced the uniformity of aroma distribution and improved the overall aroma similarity to TH.

Flavor components detection and discrimination of isomers in Huaguo tea using headspace-gas chromatography-ion mobility spectrometry and multivariate statistical analysis

Aroma components are one of the crucial factors in dynamic processes analysis, quality control, and origin traceability. Various categories of Huaguo Tea possessed different taste due to the generation of aroma. In this study, a comprehensive analysis of volatiles was conducted for five popular Huaguo Tea samples (Lemon Slices, Bitter Gourd Slices, Citri Reticulatae Pericarpium, Red Lycium Barbarum, and Black Lycium Barbarum) via gas chromatography-ion mobility spectrometry (GC-IMS) combining with multivariate statistical strategies. Comparison analysis was achieved with the properties of visually and intuitively by drawing of topography plots. A total of one hundred and eighty volatiles were distinguished. Aliphatic isomers were identified simultaneously by fingerprint spectra. Alcohols, aldehydes, esters, and ketones were the most abundant volatiles in Huaguo Tea samples. To characterize the Huaguo Tea precisely and establish an analysis model for their classification, multivariate statistical analysis was applied to distinguish different Huaguo Tea. Satisfied discrimination was obtained by principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA) based on the HS-GC-IMS results with the robustness parameter (R2Y) of 99.4%, and prediction ability parameter (Q2) of 98.6%, respectively. The results provide a theoretical basis for aroma discrimination, isomer identification, and categories analysis of Huaguo Tea.

Analysis of volatile compounds and flavor fingerprint in hairtail (Trichiurus lepturus) during air-drying using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS).

In the present study, changes in volatile compounds during processing were analyzed using the headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), to investigate the generation of aroma in hairtails (Trichiurus lepturus) during air-drying. Physicochemical indices, such as moisture content and thiobarbituric acid reactive substances (TBARS), were also detected. Flavor fingerprints were studied and developed to distinguish the samples of fresh hairtails (0 day) from air-dried hairtails (2 and 4 days). A total of 75 volatile organic compounds (VOCs) were identified in hairtails, in which alcohols, aldehydes, ketones, and esters were the principal contributors to the formation of the overall flavor of hairtails during air-drying. Seven flavor compounds (ethanol, 3-methyl-1-butanol, 1-pentanol, hexanal, octanal, benzaldehyde, and 3-methylbutanal), two flavor compounds (acetoin and dimethyl sulfide), and eight flavor compounds (1-hexanol, 1-octen-3-ol, nonanal, heptanal, 2-heptanone, ethyl acetate, trimethylamine, and ammonia) were identified in 0, 2, and 4 air-dried hairtails as biomarkers, respectively. The results showed that HS-GC-IMS could detect VOCs in different air-dried hairtails rapidly and comprehensively.

Impact of charged ionic species (NaCl and KCl) on the generation of color and volatile aroma compounds during caramelization

During the process of caramelization, volatile and non-volatile flavor and color are generated via the degradation of carbohydrates. This research investigated the effect of the types and concentrations of salts including NaCl and KCl on the generation of volatile aromas and color during caramelization. The solid phase microextraction-gas chromatograph-mass spectrometry (SPME-GC-MS) was used to measure the volatile compounds generated in caramelization. The results demonstrated that increasing content of salt (NaCl or KCl) could significantly improve (P<0.05) the generation of some essential volatile compounds during caramelization such as furfural, 5-methylfurfural, 5-hydroxymethyl-furfural (HMF), propionic acid and butyric acid. However, the ascending amount of salt (NaCl or KCl) had no significant impact (P<0.05) on the color generation of caramel. In conclusion, the usage of salt was beneficial to the generation of more aromatic compounds during caramelization.

A comparative study of savory and toasted aromas in dry cured loins versus dry fermented sausages

Dry cured meat products, loins and sausages, have a different cured aroma due to differences in their formulation and manufacture. In these products, savory and toasted notes produced by sulfur and nitrogenated volatile compounds are essential for cured aroma. The interest of the meat industry to modulate the aroma profile and the creation of specific flavourings recognizes the necessity of gaining knowledge about the pathways involved into aroma generation. For this, a comparative study was done in dry cured loins and sausages. The two products were supplemented with either proline, ornithine or thiamine and compared to a control without supplement. The concentration of these volatile compounds was analysed by GC-MS in SIM mode. Eleven volatile compounds were identified, nine in loins and eight in sausages. Loin aroma was impacted by methional and 2-acetyl-1-pyrroline, contributing to cooked potato and toasted notes; meanwhile, sausage aroma was modulated by 2-methyl-3-furanthiol, methyl 2-methyl-3-furyl disulfide, producing fatty and meaty odors, and methional. The contribution of the microbial starters to the development of sausage aroma seems to have a higher effect than the addition of precursors. In loins, thiamine addition produced the highest concentration of 2-methyl-3-(methylthio)furan, while 2-acetyl-1-pyrroline and 2-acetylpyrrole increased in the proline supplemented loins.