Characterization of aroma compounds and effects of amino acids on the release of esters in Laimao baijiu.

BACKGROUND: Laimao baijiu is a typical soy-sauce aroma-type baijiu in China. Amino acids are non-volatile compounds in baijiu and are beneficial to human health. Aroma is one of the important indicators that are used to evaluate the quality of baijiu. The interaction between aroma-active compounds and non-volatile compounds can also affect the release of aroma compounds. In this study, we identified the active-aroma compounds and amino acids in Laimao baijiu by stir bar sorptive extraction (SBSE), gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS), and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). The interaction between amino acids and key esters was investigated by sensory analysis and partition coefficients. RESULTS: A total of 63 aroma compounds and 21 amino acids were identified. Twenty-one esters were identified from them as major aroma-active ester compounds with odor activity values ≥ 1. Finally, sensory analysis revealed that l-alanine had a significant effect on the strength of the aromas of esters, suggesting that low concentrations of amino acids were more likely to promote the release of esters and high concentrations were more likely to inhibit this. The partition coefficient can be a good explanation for this phenomenon. CONCLUSION: l-Alanine can significantly affect the aroma intensity of key ester aroma compounds in Laimao baijiu, and the effects of different concentrations of amino acids are different. This work shows that amino acids, as non-volatile compounds, have a regulatory effect on the release of aroma compounds in alcoholic beverages, which may provide new technical support for the aroma modulation of alcoholic beverages. © 2022 Society of Chemical Industry.

Adhesion advances: from nanomaterials to biomimetic adhesion and applications.

The field of adhesion has revealed a significant impact on numerous applications such as wound healing, drug delivery, electrically conductive adhesive, dental adhesive, and wood industry. Nanotechnology has continued to be the primary means to achieve adhesion. Among them, biological systems based on the unique structure of the nano-levels have developed excellent adhesion capabilities after billions of years of evolution and natural selection. Therefore, the research on bionic adhesion inspired by biological systems has gradually emerged. This review firstly focuses on the mechanism of adhesion, and secondly reports the effects of different nanomaterials on adhesion properties. Then based on the structure of mussels, geckos, tree frogs, octopuses, and other organisms, the research progress of biomimetic nanotechnology to achieve adhesion is summarized. Finally, the applications, challenges, and future directions of nanotechnology in new adhesive materials are provided.

Comparative Study on Volatile Compounds and Taste Components of Different Durian Cultivars Based on GC-MS, UHPLC, HPAEC-PAD, E-Tongue and E-Nose.

In order to comprehensively evaluate the aroma-active substances and taste components of durian, solid-phase microextraction combined with gas chromatography mass spectrometry (SPME/GC-MS), high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and ultra-high-performance liquid chromatography (UHPLC) were used to test the key components of three popular durian cultivars. A total of 27 volatile compounds, 5 sugars, 27 organic acids and 19 free amino acids were detected in Black Thorn (BT) durian. A total of 38 volatile compounds, 4 sugars, 27 organic acids and 19 free amino acids were detected in Monthong (MT) durian. A total of 36 volatile compounds, 4 sugars, 27 organic acids and 20 free amino acids were detected in Musang King (MK) durian. Finally, the flavor differences of the three durians were evaluated using electronic nose (e-nose) and electronic tongue (e-tongue), and different cultivars were classified through principal component analysis (PCA).

Characterization of the Key Aroma Compounds of Three Kinds of Chinese Representative Black Tea and Elucidation of the Perceptual Interactions of Methyl Salicylate and Floral Odorants.

Jinjunmei (JJM), Keemun (KM), and Dianhong (DH) are the representative black teas in China, and they have always been favored by consumers. In this study, we aim to obtain the aroma characteristic information of volatile components in black tea samples through headspace solid-phase microextraction (HS-SPME), solvent-assisted flavor evaporation (SAFE), and gas chromatography-mass spectrometry combined with gas chromatography-olfactometry technology. The results showed that 70 compounds including α-methylbenzyl alcohol (isomer of ß-phenylethanol) were identified as odorants. Among them, 39 compounds such as linalool and geraniol showed a high degree of aroma contribution. Furthermore, the Feller's additive model was used to explore the perceptual interactions among the methyl salicylate and the floral compounds (10 groups): five groups of binary compounds showed masking effect after mixing, one group showed additive effect, and four groups showed synergistic effect. The ratio (R) was compared with the aroma index (n) of Steven's law, which found a high-fitness exponential relationship. The results of this study help to provide additional and new theoretical guidance for improving the aroma quality of black tea.

Organic Hollow Mesoporous Silica as a Promising Sandalwood Essential Oil Carrier.

As film-forming agents, fillers and adsorbents, microplastics are often added to daily personal care products. Because of their chemical stability, they remain in the environment for thousands of years, endangering the safety of the environment and human health. Therefore, it is urgent to find an environmentally friendly substitute for microplastics. Using n-octyltrimethoxysilane (OTMS) and tetraethoxysilane (TEOS) as silicon sources, a novel, environmentally friendly, organic hollow mesoporous silica system is designed with a high loading capacity and excellent adsorption characteristics in this work. In our methodology, sandalwood essential oil (SEO) was successfully loaded into the nanoparticle cavities, and was involved in the formation of Pickering emulsion as well, with a content of up to 40% (w/w). The developed system was a stable carrier for the dispersion of SEO in water. This system can not only overcome the shortcomings of poor water solubility and volatility of sandalwood essential oil, but also act as a microplastic substitute with broad prospects in the cosmetics and personal care industry, laying a foundation for the preparation and applications of high loading capacity microcapsules in aqueous media.

Characterization of Volatile Compounds of Rosa roxburghii Tratt by Gas Chromatography-Olfactometry, Quantitative Measurements, Odor Activity Value, and Aroma Intensity.

Rosa roxburghii tratt (RRT), widely distributed in the southwest of China, is favored by consumers for its good taste and healthy functions. In this study, thirty-seven compounds of Rosa roxburghii Tratt (RRT) were identified and quantified by gas chromatography-olfactometry (G-O) and gas chromatography-mass spectrometry (GC-MS) analysis. Furthermore, ethyl 2-methylpropanoate, ethyl butanoate, ethyl 2-methylbutyrate, and ethyl hexanoate were present with much higher odor activity values (OAVs) than other compounds. The key notes were confirmed by omission tests. Possible interaction among key notes was investigated through odor intensity determination and sensory analysis. It showed fruity and woody notes had synergistic effects. Full factorial design was used to evaluate the notes contribution to the whole odor. One important finding is the major effect of order interactions, fruity note (X1) and woody note (X4) especially, emphasizing the existence of complex interactions occurring between odor notes. The interaction X1X4 was further investigated. The woody note has a positive effect when the fruity note is also in the mixture but tends to show a negative effect otherwise.

Characterization of Odor-Active Volatiles and Odor Contribution Based on Binary Interaction Effects in Mango and Vodka Cocktail.

Thirty-six volatile compounds, composed of 18 esters, 10 terpenes, and 8 others, were detected by headspace-solid phase microextraction (HS-SPME) equipped with gas chromatography-mass spectrometry (GC-MS) in mango and vodka cocktail. Moreover, these compounds were detected by olfactometry using aroma intensities. Comparing these compounds revealed that the aroma intensities (AIs) of limonene, 3-carene, myrcene, ß-caryophyllene, and citronellyl propanoate were higher than others (AIs ≥ 4). In this context, limonene was selected as the reference compound on the basis of the strongest component model. The aim of this study was to determine the perceptual interaction between limonene and 3-carene, myrcene, ß-caryophyllene, citronellyl propanoate, respectively, in a binary mixture. In addition, feller's addition model revealed that limonene presented an addition effect when combined with 3-carene, myrcene, ß-caryophyllene, and citronellyl propanoate. It could be stated that these compounds played an important role in the aroma of mango and vodka cocktail. The results demonstrated that molecular structure and the ratio between compounds affected the synergistic effect, and compounds with similar structure and aroma were more prone to undergo addition and synergy.

Olfactory Impact of Terpene Alcohol on Terpenes Aroma Expression in Chrysanthemum Essential Oils.

The key point of our work was evaluating the impact of terpene alcohols on the aroma expression of terpenes recombination in Chrysanthemum essential oils. Using pure commercial products, various aromatic recombinations were prepared, consisting of terpenes recombination and six terpene alcohols, all the concentrations found in Chrysanthemum essential oils. There were five groups of terpene alcohols mixtures performed very interesting with the addition or omission tests. The "olfactory threshold" of the terpenes recombination had a notable decrease when adding isoborneol, d-Fenchyl alcohol respectively through the Feller's additive model analysis. Furthermore, the descriptive test indicated that the addition of terpene alcohols mixture had the different effect on fruity, floral, woody, green, and herbal aroma intensity. Specifically, when isoborneol was added to the terpenes recombination in squalane solution, it was revealed that isoborneol had a synergy impact on herbal and green notes of the terpenes recombination and masked the fruity note.

Production of a transparent lavender flavour nanocapsule aqueous solution and pyrolysis characteristics of flavour nanocapsule.

Flavour plays an important role and has been widely used in many products. Usually, the components of flavour are volatile and the sensory perception can be changed as a result of volatilization, heating, oxidation and chemical interactions. Encapsulation can prevent the loss of volatile aromatic ingredients, provide protection and enhance the stability of the core materials. This work concentrated on production of a transparent lavender flavour nanocapsule aqueous solution. The results showed that a transparent lavender flavour microcapsule aqueous solution can be produced using hydroxypropyl-ß-cyclodextrin (HP-ß-CD) as wall material. The combination and interaction of flavour and wall materials were investigated by pyrolysis. Pyrolysis characteristics and kinetic parameters of the flavour nanocapsule were determined. During thermal degradation of blank HP-ß-CD and flavour-HP-ß-CD inclusion complex, three main stages can be distinguished. Due to the vaporization of lavender flavour encapsulated in HP-ß-CD, the thermogravimetric (TG) curve of blank HP-ß-CD shows a leveling-off from room temperature to 269 °C, while the TG curve of flavour-HP-ß-CD inclusion complex is downward sloping in this temperature range. The kinetic parameters are helpful in understanding the mechanism of molecular recognition between hosts and guests.

A review of the preparation and application of flavour and essential oils microcapsules based on complex coacervation technology.

This paper briefly introduces the preparation and application of flavour and essential oils microcapsules based on complex coacervation technology. The conventional encapsulating agents of oppositely charged proteins and polysaccharides that are used for microencapsulation of flavours and essential oils are reviewed along with the recent advances in complex coacervation methods. Proteins extracted from animal-derived products (gelatin, whey proteins, silk fibroin) and from vegetables (soy proteins, pea proteins), and polysaccharides such as gum Arabic, pectin, chitosan, agar, alginate, carrageenan and sodium carboxymethyl cellulose are described in depth. In recent decades, flavour and essential oils microcapsules have found numerous potential practical applications in food, textiles, agriculturals and pharmaceuticals. In this paper, the different coating materials and their application are discussed in detail. Consequently, the information obtained allows criteria to be established for selecting a method for the preparation of microcapsules according to their advantages, limitations and behaviours as carriers of flavours and essential oils.

Effects of gallic acid on the release of aroma compounds in Moutai Baijiu.

Due to the trace concentrations of gallic acid (GA), the interaction mechanism between GA and flavor compounds is limited, and the effects on the aroma compounds of Moutai Baijiu are even more unclear. In this study, the aroma compounds and phenolic compounds in Moutai Baijiu were investigated by stir bar sorptive extraction (SBSE), gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). A total of 63 volatiles and 10 phenolic compounds were identified, and 16 esters and 4 alcohols were identified as the important aroma substances (odor activity values ≥1). The effect of GA on the release of aroma compounds was investigated by sensory analysis and partition coefficient. The results showed that GA mainly inhibited the volatilization of alcohols, low concentrations of GA promoted the release of esters, and high concentrations slowed down or even inhibited the release effect affected by the hydrophobicity of aroma compounds. UV spectroscopy and thermodynamic analysis further revealed that the interaction of GA with 1-propanol was attributed mainly to hydrogen bonding and van der Waals forces, and the interaction with other compounds was mainly influenced by hydrophobic effects. These results show that gallic acid can effectively control the release of the aromas of Moutai Baijiu, highlight the important role of GA on the volatiles of baijiu, and provide theoretical support for further healthy improvement of the sensory quality of baijiu.

Mushroom alcohol(1-octen-3-ol)and other 7 aroma compounds selected from Chinese dry-cured hams can enhance saltiness perception.

Reducing NaCl content in food while maintaining acceptability poses a significant challenge. Odor-induced saltiness enhancement (OISE) emerges as a promising solution. This study utilized gas chromatography-olfactory (GC-O) in conjunction with gas chromatography-mass spectrometry (GC-MS) to identify 37 key volatile compounds in three representative Chinese dry-cured hams. These compounds had an odor activity value (OAV) of ≥1 or a modification frequency (MF) of ≥30%. Subsequently, quantitative descriptive analysis (QDA) identified eight odorants associated with saltiness. These included 1-octen-3-ol, nonanal, heptanal, 2-methylbutanal, 3-methyl-butanal, benzaldehyde, octanal, and 2,6-dimethylpyrazine. Remarkably, these odorants significantly intensified saltiness (P < 0.05) when added to a low-concentration NaCl solution (0.3%), compared to zero or high concentrations (0.75% and 0.8%). As a result, traditional Chinese salty meat products offer a promising source of odorants for enhancing saltiness, compensating for reduced NaCl content through OISE.

Inclusion complexes of ß-cyclodextrin with isomeric ester aroma compounds: Preparation, characterization, mechanism study, and controlled release.

Cyclodextrins (CDs) have been discovered to provide an efficient solution to the limited application of ester aroma molecules used in food, tobacco, and medication due to their strong smell and unstable storage. This work combined molecular modeling and experimental to analyze the conformation and controlled release of isomeric ester aroma compounds/ß-CD inclusion complexes (ICs). The investigation revealed that ester aroma compounds could be effectively encapsulated within the ß-CD cavity, forming ICs with low binding affinity. Furthermore, the key driving forces in ICs were identified as hydrogen bonds and van der Waals interactions through theoretical simulation. Results from the Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and Isothermal titration calorimetry (ITC) experiments confirmed the intermolecular interaction predicted by the molecular model. Notably, the release rate of aroma compounds from L-menthyl acetate/ß-CD (LMA/ß-CD) IC exceeded that of terpinyl acetate/ß-CD (TA/ß-CD) IC. This difference is attributed to the length of the chain of aroma molecules and the variation in the position of functional groups, influencing the stable formation of ICs with ß-CD. These findings hold potential implications for refining the application of ICs across diverse industries.

Unraveling the contribution of aroma-active and chiral compounds to different grade of Yashi Xiang teas using stir bar sorptive extraction.

Yashi Xiang (YSX) is a flavor of Fenghuang Dancong tea and famous for its name and floral aroma, which is a type of semi-fermented oolong tea. However, previous research into the aroma characteristics of YSX tea mostly focused on the aroma compounds, and little research on chiral compounds in YSX has been performed. Therefore, the current study was conducted to explore the aroma characteristics of YSX tea from the perspective of enantiomers of chiral compounds. A total of 12 enantiomers were determined in this study, among them, (R)-(-)-α-ionone, (S)-(+)-linalool, (1S,2S)-(+)-methyl jasmonate, (S)-z-nerolidol, (R)-(+)-limonene, and (S)-(-)-limonene have important effects on the aroma components of YSX tea. The ER ratios of the enantiomers were different in samples of different grades. Therefore, this parameter can be used to identify the grade and authenticity of YSX tea. PRACTICAL APPLICATION: The study illuminates the aroma characteristics of YSX tea from the perspective of enantiomers of chiral compounds, which have important effects on the aroma components of YSX tea. It established an ER ratio system to effectively distinguish the grade and authenticity of YSX tea by comparing the ER of YSX tea. Focusing on analyzing the chiral compounds in the aroma of YSX tea is helpful in providing a theoretical basis for the authenticity of the precious tea and improving of the quality of YSX tea products.

Investigation of Lactone Chiral Enantiomers and Their Contribution to the Aroma of Longjing Tea by Odor Activity Value and S-Curve.

Odor activity value (OAV) and S-curve were used to study the content, proportion, and contribution of lactone chiral enantiomers in Longjing tea. A total of 10 enantiomers were identified in this study, among which (S)-(-)-δ-decalactone (45.4-84.4 µg/L), (S)-(-)-γ-decalactone (31.5-109 µg/L), (S)-(-)-γ-nonanolactone (23.4-72.8 µg/L), and (S)-(-)-γ-undecalactone (21.1-56.2 µg/L) presented the highest concentrations. Furthermore, (R)-(+)-γ-nonanolactone (OAV: 2-7), (S)-(-)-γ-nonanolactone (OAV: 1-5), (S)-(-)-δ-decalactone (OAV: 2-4), (R)-(+)-δ-decalactone (OAV: 1-3), and (R)-(+)-γ-undecalactone (OAV: 1-5) were determined as enantiomeric compounds that play an important role in the perceived aroma of Longjing tea. Compared with the aromatic reconstitution (AR), the threshold increased to different degrees after adding γ-nonanolactone, γ-decalactone, δ-decalactone, γ-undecalactone, and their chiral enantiomers. This finding indicated that these compounds exert significant effects on the overall aroma of the AR. The contribution of racemates and chiral enantiomers to the AR threshold and aroma is completely different. In view of the difference between racemic and enantiomers' aroma characteristics in Longjing tea, the analysis and identification of chiral enantiomers are necessary to enrich and improve the accurate analysis of the flavor profile of Longjing tea.

Recent advances of magnetic chitosan hydrogel: Preparation, properties and applications.

Magnetic chitosan hydrogels are organic-inorganic composite material with the characteristics of both magnetic materials and natural polysaccharides. Due to its biocompatibility, low toxicity and biodegradability, chitosan, a natural polymer has been widely used for preparing magnetic hydrogels. The addition of magnetic nanoparticles to chitosan hydrogels not only improves their mechanical strength, but also endows them with magnetic thermal effects, targeting capabilities, magnetically-sensitive release characteristics, easy separation and recovery, thus enabling them to be used in various applications including drug delivery, magnetic resonance imaging, magnetothermal therapy, and adsorption of heavy metals and dyes. In this review, the physical and chemical crosslinking methods of chitosan hydrogels and the methods for binding magnetic nanoparticles in hydrogel networks are first introduced. Subsequently, the properties of magnetic chitosan hydrogels were summarized including mechanical properties, self-healing, pH responsiveness and properties in magnetic fields. Finally, the potential for further technological and applicative advancements of magnetic chitosan hydrogels is discussed.

Research progress of starch as microencapsulated wall material.

Starch is non-toxic, low cost, and possesses good biocompatibility and biodegradability. As a natural polymer material, starch is an ideal choice for microcapsule wall materials. Starch-based microcapsules have a wide range of applications and application prospects in fields such as food, pharmaceuticals, cosmetics, and others. This paper firstly reviews the commonly used wall materials and preparation methods of starch-based microcapsules. Then the effect of starch wall materials on microcapsule properties is introduced in detail. It is expected to provide researchers with design inspiration and ideas for the development of starch-based microcapsules. Next the applications of starch-based microcapsules in various fields are presented. Finally, the future trends of starch-based microcapsules are discussed. Molecular simulation, green chemistry, and solutions to the main problems faced by resistant starch microcapsules may be the future research trends of starch-based microcapsules.

Preparation and characterisation of linalool oil-in-water starch-based Pickering emulsions and the effects of the addition of cellulose nanocrystals on their stability.

Creaming could be generated during storage of the starch-based Pickering emulsions. And cellulose nanocrystals in the solution are usually dispersed by relatively strong mechanical force, otherwise they may appear in the form of aggregates. In this work, we investigated the effects of cellulose nanocrystals on the stability of the starch-based Pickering emulsions. Results showed that the stability of Pickering emulsions was significantly improved by adding cellulose nanocrystals. Cellulose nanocrystals increased the viscosity, electrostatic repulsion and steric hindrance of the emulsions, which delayed the movement of droplets and obstructed the contact between droplets. This study provides new insights into the preparation and stabilisation of starch-based Pickering emulsions.

Preparation and characterization of the dimethyl sulfide-ß-cyclodextrin inclusion complex.

Dimethyl sulfide has been widely used in flavors and can also be used as a solvent and catalyst. However, dimethyl sulfide is volatile, and its lasting power is weak. Furthermore, dimethyl sulfide is insoluble in water and is unstable in some cases. This study concentrated on the encapsulation of dimethyl sulfide in ß-cyclodextrin to form an inclusion complex and to improve the durability, water solubility, and stability of dimethyl sulfide. The product was successfully produced and characterized by scanning electron microscopy, diffraction of X-rays, and thermal analysis. The dimethyl sulfide loading capacity is 6.40±0.08%. Based on the thermal release characteristics of dimethyl sulfide, the kinetic and thermodynamic parameters were obtained. The apparent activation energy, pre-exponential factor, and reaction order of the dimethyl sulfide release reaction were obtained and the values were 95.0 ± 0.1 kJ/mol, 1.03 × 1015 s-1 , and 1, respectively. The activation entropy change, activation enthalpy change, and activation Gibbs free energy change were 41.6 J/K, 95.0 kJ/mol, and 81.3 kJ/mol, respectively, during the process of dimethyl sulfide release at 56.7℃. To make it clear that the dimethyl sulfide molecule interacts with ß-cyclodextrin molecule, molecular simulation was used to investigate the formation process of the dimethyl sulfide-ß-cyclodextrin inclusion complex. The binding energy and the optimized structure were obtained. When the Z coordinate of the S atom in the dimethyl sulfide molecule is 1.1 × 10-10  m, the binding energy attained the minimum value, -51.3 kJ/mol. These basic data are helpful for understanding the dimethyl sulfide-ß-cyclodextrin inclusion complex formation mechanism and the interaction between dimethyl sulfide and ß-cyclodextrin. PRACTICAL APPLICATION: By forming an inclusion complex with ß-cyclodextrin, the stability, durability, and water solubility of dimethyl sulfide can be improved. Dimethyl sulfide-ß-cyclodextrin inclusion complex can be widely used in the food, beverage, flavor, and fragrance industries. The kinetic and thermodynamic parameters, binding energy, and the results of molecular simulation are helpful to understand the dimethyl sulfide-ß-cyclodextrin inclusion complex formation mechanism and the interaction between dimethyl sulfide and ß-cyclodextrin.

Aromatic Profiles and Enantiomeric Distributions of Chiral Volatile Compounds in Pu-Erh Tea.

Pu-Erh tea, as a typical post-fermented tea, can be divided into raw Pu-Erh tea (RAPT) and ripened Pu-Erh tea (RIPT) according to the processing technology. It is famous for its unique aroma after aging. Although previous research on the aroma characteristics of Pu-Erh tea mostly focused on the aroma compounds, little research on chiral compounds in RAPT and RIPT has been performed. Therefore, the current work aims to explore the aroma characteristics of Pu-Erh tea from the perspective of enantiomers of chiral compounds. A total of 15 enantiomers were determined in this study, among which (R)-(-)-2,2,6-trimethylcyclohexanone, (R)-(-)-linalool, (S)-(+)-linalool, (R)-(+)-δ-octanolactone, (R)-(+)-γ-nonanolactone, (2R,5R)-(+)-theaspirone A, and (R)-(-)-dihydroactinidiolide were identified as enantiomeric compounds that play an important role in the aroma of RAPT and RIPT. Furthermore, (2S,5R)-trans-linalool oxide and (R)-(+)-α-terpineol were important contributors to the aroma profile of RAPT, while (S)-(+)-2-methylbutanal, (S)-(-)-limonene, S-(-)-α-terpineol, and (1R,2R)-(-)-methyl jasmonate contributed to the characteristic aroma of RIPT. The addition of these enantiomeric compounds brings the aroma closer to that of the original tea sample. In addition, the analysis of chiral enantiomers of linalool, limonene, theaspirone A, and γ-nonanolactone can provide guidance for the quality and flavor control of Pu-Erh tea aroma.