Food Aroma Research Articles

Thin-layer chromatography in spices analysis

ABSTRACTSpices are the dried parts of aromatic plants, excepting the leaves, usually used for flavoring, seasoning and imparting aroma in foods. They contain many classes of valuable compounds, which can also exert different biological activities, such as antioxidant and antimicrobial activity. Since spices contain important bioconstituents, they are often adulterated in economical purposes, not only by the botanical and geographical origin, but also by adding or subtracting of different substances which affect in a negative manner their quality. The aim of this paper is to overview the TLC methods used in the analysis of spices, in order to evaluate their composition and biological activities, and also to detect the adulteration.

Sensory Characteristics of Various Concentrations of Phenolic Compounds Potentially Associated with Smoked Aroma in Foods.

This research describes the sensory odor characteristics of 19 phenolic compounds (11 phenol derivatives, six guaiacol derivatives, and two syringol derivatives) that have been associated with smoked aroma in previous literature. Seven concentrations varying from 1 to 100,000 ppm of each chemical were examined. A highly trained descriptive panel used a recently published lexicon for smoky aroma and flavor and found that smoked aroma compounds have many different attributes that make up smokiness. Musty/dusty, musty/earthy, pungent, acid, smoky, woody, burnt, ashy, cedar, creosote or petroleum-like collectively imparted smoked aroma. Most of the phenolic compounds were described as having smoky characteristics at low concentrations, generally at 1 and 10 ppm, except 3,4-dimethylphenol at 5000 ppm. 2,6-Dimethylphenol was not associated with smoky characteristics. This research is the first to evaluate a set of phenolic compounds for their sensory characteristics using a professionally developed set of sensory attributes.

A Review on Food Fermentation and the Biotechnology of Lactic Acid Bacteria

Fermented foods are among the first processed food products consumed since the development of human civilizations. Food fermentation processes can be categorized by the primary metabolites and microorganisms involved. Lactic acid bacteria (LAB) are a large group of closely related bacteria that have similar properties such as lactic acid production, which is an end product of the fermentation. Biotechnology is the use of living systems and organisms to develop or make useful products, or any technological applications that uses biological systems, living organisms or derivatives, to make or modify products or processes for specific use. Depending on the tools and applications, it often overlaps with the fields of bioengineering and biomedical engineering. Some of the applications were identified in this paper to include biotechnology in food fermentation to enhance properties such as the taste, aroma, shelf-life, texture and nutritional value of food. When used regularly, LAB fermented foods boost the immune system and strengthen the body in the fight against pathogenic bacterial infections, bacteriocins produced by LAB may become a potential drug candidate for replacing antibiotics in order to treat multiple drugs resistance pathogens in the future. The modern extension of food/feed fermentation technology consists of processes designed to obtain particular compounds using microbial metabolism as the chemical machinery. Thus, LAB fermentation is not only of a major economic importance, and the starting food materials, but it also promotes human health and increase food/feed production in the world.

Direct Injection Analysis of Fruit VOCs by PTR-ToF-MS: The Apple Case Study.

The instrumental characterization of volatile organic compounds (VOCs) is essential to have a precise, reliable, and reproducible estimation of food aroma and, therefore, of the overall product quality. In this report, we introduce four analytical approaches based on PTR-MS (proton transfer reaction-mass spectrometry) technology suitable to fully investigate the complexity of apple aroma. In our opinion, these proposed methodologies can be applied, with slight modification, to every kind of fruit for destructive and nondestructive rapid VOC fingerprinting.

The Influence of Food Aromas on Restaurant Consumer Emotions, Perceptions, and Purchases

ABSTRACTThe effect of basil, bacon, and hickory-smoked beef aromas on customers’ emotions, perceptions of food quality, and the restaurant environment, as well as entrée selection was investigated. Following an experiment, a survey with 196 responses showed that food aromas had a positive influence on some emotions (pleasure, but not arousal), as well as customers’ impressions of the general food quality and restaurant environment; however, the hypotheses that food aromas influenced congruent entrée choices (e.g., the basil aroma increased purchase of basil containing entrees) were not supported. The findings have direct applications for the restaurant industry and offer suggestions for research.

Rapid discrimination of strain-dependent fermentation characteristics among Lactobacillus strains by NMR-based metabolomics of fermented vegetable juice.

In this study, we investigated the applicability of NMR-based metabolomics to discriminate strain-dependent fermentation characteristics of lactic acid bacteria (LAB), which are important microorganisms for fermented food production. To evaluate the discrimination capability, six type strains of Lactobacillus species and six additional L. brevis strains were used focusing on i) the difference between homo- and hetero-lactic fermentative species and ii) strain-dependent characteristics within L. brevis. Based on the differences in the metabolite profiles of fermented vegetable juices, non-targeted principal component analysis (PCA) clearly separated the samples into those inoculated with homo- and hetero-lactic fermentative species. The separation was primarily explained by the different levels of dominant metabolites (lactic acid, acetic acid, ethanol, and mannitol). Orthogonal partial least squares discrimination analysis, based on a regions-of-interest (ROIs) approach, revealed the contribution of low-abundance metabolites: acetoin, phenyllactic acid, p-hydroxyphenyllactic acid, glycerophosphocholine, and succinic acid for homolactic fermentation; and ornithine, tyramine, and γ-aminobutyric acid (GABA) for heterolactic fermentation. Furthermore, ROIs-based PCA of seven L. brevis strains separated their strain-dependent fermentation characteristics primarily based on their ability to utilize sucrose and citric acid, and convert glutamic acid and tyrosine into GABA and tyramine, respectively. In conclusion, NMR metabolomics successfully discriminated the fermentation characteristics of the tested strains and provided further information on metabolites responsible for these characteristics, which may impact the taste, aroma, and functional properties of fermented foods.

Increase of medium-chain fatty acid ethyl ester content in mixed H. uvarum/S. cerevisiae fermentation leads to wine fruity aroma enhancement

Medium-chain fatty acid (MCFA) ethyl esters, as yeast secondary metabolites, significantly contribute to the fruity aroma of foods and beverages. To improve the MCFA ethyl ester content of wine, mixed fermentations with Hanseniaspora uvarum Yun268 and Saccharomyces cerevisiae were performed. Final volatiles were analyzed by gas solid phase microextraction-chromatography-mass spectrometry, and aroma characteristics were quantitated by sensory analysis. Results showed that mixed fermentation increased MCFA ethyl ester content by 37% in Cabernet Gernischt wine compared to that obtained by pure fermentation. Partial least-squares regression analysis further revealed that the improved MCFA ethyl esters specifically enhanced the temperate fruity aroma of wine. The enhancement of MCFA ethyl esters was attributed to the increased contents of MCFAs that could be induced by the presence of H. uvarum Yun268 in mixed fermentation. Meanwhile, the timing of yeast inoculations significantly affected the involving biomass of each strain and the dynamics of ethanol accumulation.

Effects of two enzyme extracts of Aspergillus niger on green tea aromas.

Green tea was investigated in terms of its aroma changes induced by two enzyme extracts of Aspergillus niger, i.e., crude enzyme extracted from fermentation using tea stalk medium (CETSM) and crude enzyme yielded in potato dextrose medium. The result showed that the former had significant effects on sensory indexes and volatile constituents, with significant increases in toasty and mushroom notes, while the latter had little influence on the aforementioned indexes. In addition, the volatile constituents were significantly affected; in particular, the contents of cis-3-hexenol, 1-octen-3-ol, eucalyptol, hexanol, and benzaldehyde increased. Furthermore, gas chromatography-olfactometry (GC-O) analysis showed that an increase in 1-octen-3-ol strengthened the mushroom note. These results indicate that CETSM contains some novel enzymes that can modify the aroma profile of green tea. This study also provides valuable information and suggestions to use fermented enzymes to modify food aromas.

Enhancing the experience of food and drink via neuroscience-inspired olfactory design

Olfactory cues, both orthonasal (when we inhale) and retronasal (when we swallow/breathe out from the back of the nose), play a crucial role in the experience, and enjoyment, of food and drink. However, the design of product packaging glassware, and even plateware has typically not been optimized to deliver the ideal orthonasal hit. This review highlights a number of recent attempts by packaging manufacturers to improve the orthonasal experience for the consumer. The various ways in which modernist chefs, molecular mixologists, culinary artists, and designers have been playing with the delivery of both foreground and background aromas and scents in order to complement the dishes and drinks they serve is also examined. Finally, I highlight some of the ways that technology may be used to deliver food aromas in the future, and stress the need for more research in order to determine whether enhanced olfactory design (e.g. in scent-enabled cutlery and packaging) may one day be used to help nudge consumers toward healthier eating behaviours. The important distinction between natural and synthetic (or better said, between perceived natural vs. perceived synthetic) aromas is also discussed, as this will likely play an important role in determining the future uptake of such innovative olfactory delivery solutions.

Influence of fumigants on sunflower seeds: Characteristics of fumigant desorption and changes in volatile profiles

Fumigation of transport containers is common practice to protect stored products from pests. Yet little is known about the desorption times and effects of the highly toxic gases used in this process. To shed light on the behavior of fumigants in real food, we treated sunflower seeds (Helianthus annuus L.) with 100ppm phosphine (PH3), methyl bromide (MeBr) or 1,2-dichloroethane (DCE) for 72h. The compound concentrations in the air were then analyzed by thermal desorption/2D gas chromatography coupled to mass spectrometry and flame photometric detection (TD-2D-GC–MS/FPD). A desorption time of several months was observed for DCE, whereas PH3 and MeBr were outgassed in a matter of days. To investigate possible interactions between gases and constituents of the seeds, non-fumigated, fumigated and outgassed samples were analyzed by headspace solid-phase microextraction GC–MS. We observed significantly different volatile profiles in fumigated and subsequently outgassed seeds compared to non-fumigated seeds. Whereas PH3-treated seeds released far more terpenoids, the volatile pattern of seeds exposed to DCE revealed significantly fewer terpenoids but more aldehydes. These changes are likely to affect food aroma characteristics.

Combination of odour‐stimulation tools and surface response methodology for odour recombination studies

AbstractThe objective of this study was to evaluate the relative impact of 12 odour‐active compounds on the odours of three different non‐processed semi‐hard kinds of cheese using a combination of different odour stimulation tools. Based on a previous study, eight odorants were identified as contributors to the basic odour of the cheeses, and four additional odorants were identified as contributors to the specificity of each cheese. The eight basic odorants were dispatched into four vessels of an olfactometer, which delivered mixtures following a Box‐Behnken design. Each odour mixture was compared with each real cheese odour based on a direct similarity rating. An optimal basic composition of the four olfactometer vessels for each of the three cheeses was obtained. One vessel that contained a mixture of four odorants significantly impacted the odour similarity scores; thus, the four odorants (3‐methyl butane‐1‐ol, butanoic acid, 3‐methylbutanoic acid and dimethyl trisulphide) were individually tested along with four additional odorants (2,3‐dimethyl pyrazine, benzaldehyde, methyl 2‐methyl‐3‐furyl disulphide and gamma heptalactone) in a second experiment using the olfactoscan technique. A paired comparison between real cheese odours and the odour mixtures delivered by the olfactometer combined with odorants eluted from a gas‐chromatograph indicated that dimethyl trisulphide primarily contributed to one of the cheese odours and butanoic acid contributed to another cheese odour. Gamma heptalactone had a positive impact, whereas benzaldehyde and 1‐octen‐3‐one had a negative impact, on the similarity between the recombined odour and the odour of the third cheese. This original approach is a promising tool for the reformulation of food aromas.

A Savory Odorant in Sweet Potato Shochu: 2-Methyl-3-(Methyldithio)-Furan

The purpose of this work is to determine the key odorants (KO) in shochu, a Japanese spirit made from sweet potato, barley, rice, soba, or sugarcane extract fermented with 20% rice koji. Each carbohydrate source produces a mild flavored spirit, but sweet potato produces shochu with a strong savory character. The KOs released by sweet potato, barley, rice, and sugarcane shochus were determined using headspace solid-phase micro-extraction (HS-SPME), gas chromatography-olfactometry (GC-O) dilution analysis to determine aroma characteristics, gas chromatography-mass spectrometry (GC-MS), and authentic standards to determine identity. The five top KOs found in sweet potato shochu were ethyl octanoate, ethyl cinnamate, 2-methyl-3-furanthiol, β-damascenone, 2-methyl-3-(methyldithio)-furan. The five top KOs in barley, rice, and sugarcane shochus were ethyl octanoate, ethyl hexanoate, isoamyl acetate, ethyl 2-methylbutanoate, and ethyl isobutyrate. The unique savory aroma of sweet potato was found to have higher levels of ethyl cinnamate, 2-methyl-3-furanthiol, and 2-methyl-3-(methyldithio)-furan while the five top KOs in barley-, rice-, and sugarcane-derived shochus were esters common in most alcoholic fermentations. There is growing evidence that a small number of odorants determine our perception of food aroma. The first challenge is to determine what these key odorants are and second to determine the rules used by the olfactory system to create odor images. This research identifies candidates for the unique aroma of sweet potato shochu.

Voltammetric determination of trace amounts of diacetyl at a mercury meniscus modified silver solid amalgam electrode following gas-diffusion microextraction

A new approach was developed for the determination of trace amounts of diacetyl in food products using gas-diffusion microextraction (GDME) and subsequent detection by differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE). Diacetyl is a vicinal diketone responsible for the buttery aroma in many fermented foods and beverages. Its determination is important not only for evaluation of the final product quality (note of mention: health related concerns were associated with continuous diacetyl exposure) but also to monitor fermentation. GDME, a technique combining gas-diffusion and microextraction, particularly aimed to volatile and semi-volatile analytes, seemed the best way to selective extract diacetyl. A solution of 0.05% o-phenylenediamine (OPDA) prepared in a Britton-Robinson buffer (pH 5.0) was chosen as the extracting solution. This solution simultaneously extracts, pre-concentrates and derivatizes diacetyl to 2,3-dimethylquinoxaline (DMQ), enhancing the extraction selectivity and making the analyte electroactive. After finding the optimum conditions for the extraction process (10min at 60°C with 1.0mL of OPDA at pH 5.0), the DPV measurements at the m-AgSAE were conducted with a scan rate of 7mVs−1, a modulation amplitude of 50mV and a modulation time of 100ms. Under these conditions, the resulting DMQ could be easily measured at a potential of −0.6V vs. Ag|AgCl (3molL−1 KCl). The amalgam electrode keeps the advantages of classic mercury electrodes, like high sensitivity, while being environmentally friendly. The GDME/m-AgSAE produced suitable method features for the determination of low amounts of diacetyl (as DMQ) in alcoholic beverages, and in fact, to the best of our knowledge, the limit of quantification of 0.18µgL−1 is one of the lowest reported in literature.

Production of the renewable extremophile lipase: Valuable biocatalyst with potential usage in food industry

In the food industry, biocatalysts provide ecofriendly procedures to accomplish biochemical reactions with high specificity in moderate conditions. In this regard, enzymes are welcomed as process aids in food processing. Microbial lipases, especially of extremophiles, are one of the most useful enzymes for biotechnology and food industry. Accordingly, thermo-halophile GDSL lipase-encoding gene from Rhodothermus marinus, RD, was cloned and expressed in Escherichia coli. The enzyme revealed the highest hydrolytic activity (1055.3Umg−1) towards p-nitrophenyl butyrate (C4) at 70°C/pH 8.5 and retained 78.6% of its initial activity after 60min incubation at this temperature. The enzyme was recovered by covalent immobilization on chitosan coated Fe3O4-nanoparticles (CS-MNPs) and the potential to synthesize aroma ester methyl acetate in n-hexane was investigated. The reaction yields were 22% and 67% for free and immobilized enzyme, respectively. This study provides a time-saving, economic, biocompatible and a renewable catalyst to synthesize natural flavor compounds. This biocatalyst has excellent potential in food industry and can be applied for lipid processing or to improve the aroma of foods. In addition to exhibiting good stability in high temperatures and organic solvents, RD lipase from Rhodothermus marinus can also be considered as an excellent candidate in organic synthesis in harsh industry conditions.

The Role of Biotechnology in Food Production and Processing

Biotechnology is the use of living systems and organisms to develop or make useful products, or any technological applications that uses biological systems, living organisms or derivatives thereof, to make or modify products or processes for specific use. Depending on the tools and applications, it often overlaps with the fields of bioengineering and biomedical engineering. Some of the applications were identified in this paper to include biotechnology in food fermentation to enhance properties such as the taste, aroma, shelf-life, texture and nutritional value of food. Biotechnology in the production of enzymes to bring about desirable changes in food, biotechnology in the production of food ingredients; flavours, fragrances, food additives and a range of other high valued-added products, genetically modified starter cultures, genetically modified foods, the use of all these modern technologies in diagnostics for food testing, the role of biotechnology in food production by increasing food production, improved harvesting, storage and nutritional value, better raw materials, better flavour and the production of food containing vaccines, the safety of food produced with biotechnology as well as the risks and benefits of biotechnology in food production.

Characterization of C-S lyase from Lactobacillus delbrueckii subsp. bulgaricus ATCC BAA-365 and its potential role in food flavour applications.

Volatile thiols have substantial impact on the aroma of many beverages and foods. Thus, the control of their formation, which has been linked to C-S lyase enzymatic activities, is of great significance in industrial applications involving food flavours. Herein, we have carried out a spectroscopic and functional characterization of a putative pyridoxal 5'-phosphate (PLP)-dependent C-S lyase from the lactic acid bacterium Lactobacillus delbrueckii subsp. bulgaricus ATCC BAA-365 (LDB C-S lyase). Recombinant LDB C-S lyase exists as a tetramer in solution and shows spectral properties of enzymes containing PLP as cofactor. The enzyme has a broad substrate specificity toward sulphur-containing amino acids with aminoethyl-L-cysteine and L-cystine being the most effective substrates over L-cysteine and L-cystathionine. Notably, the protein also reveals cysteine-S-conjugate β-lyase activity in vitro, and is able to cleave a cysteinylated substrate precursor into the corresponding flavour-contributing thiol, with a catalytic efficiency higher than L-cystathionine. Contrary to similar enzymes of other lactic acid bacteria however, LDB C-S lyase is not capable of α,γ-elimination activity towards L-methionine to produce methanethiol, which is a significant compound in flavour development. Based on our results, future developments can be expected regarding the flavour-forming potential of Lactobacillus C-S lyase and its use in enhancing food flavours.

The Broadly Tuned Odorant Receptor OR1A1 is Highly Selective for 3-Methyl-2,4-nonanedione, a Key Food Odorant in Aged Wines, Tea, and Other Foods.

Key food odorants are the most relevant determinants by which we detect, recognize, and hedonically evaluate the aroma of foods and beverages. Odorants are detected by our chemical sense of olfaction, comprising a set of approximately 400 different odorant receptor types. However, the specific receptor activity patterns representing the aroma percepts of foods or beverages, as well as the key food odorant agonist profiles of single-odorant receptors, are largely unknown. We aimed to establish comprehensive key food odorant agonist profiles of 2 unrelated, broadly tuned receptors, OR1A1 and OR2W1, that had been associated thus far with mostly non-key food odorants and shared some of these agonists. By screening both receptors against 190 key food odorants in a cell-based luminescence assay, we identified 14 and 18 new key food odorant agonists for OR1A1 and OR2W1, respectively, with 3-methyl-2,4-nonanedione emerging as the most potent agonist for OR1A1 by 3 orders of magnitude, with a submicromolar half maximal effective concentration. 3-Methyl-2,4-nonanedione has been associated with a prune note in oxidized wine and is an aroma determinant in tea and apricots. Further screening against the entire set of 391 human odorant receptors revealed that 30 or 300 μmol/L 3-methyl-2,4-nonanedione activated only 1 receptor, OR1A1, suggesting a unique role of OR1A1 for the most sensitive detection of this key food odorant in wine, tea, and other food matrices.

Extraction of 2-phenylethanol (PEA) from aqueous phases using tetracyanoborate-based ionic liquids

2-Phenylethanol (PEA) is an important alcohol involved in aroma and flavour of food, soft drinks, candy, ice cream, pudding, chewing gum and cookies. This study investigates the ability of three tetracyanoborate-based ionic liquids (ILs) for the extraction of PEA from aqueous phases. In this regard, experimental measurements of liquid-liquid equilibria (LLE) in the binary systems {IL (1)+PEA or water (2)} and ternary systems of {IL (1)+PEA (2)+water (3)} at temperature T=308.15K and ambient pressure were undertaken. The ILs investigated were 1-hexyl-3-methylimidazolium tetracyanoborate [HMIM][TCB], 1-decyl-3-methylimidazolium tetracyanoborate [DMIM][TCB], and 1-butyl-1-methylpyrrolidinium tetracyanoborate [BMPYR][TCB]. The suitability of the ILs for use as entrainers for the extraction of PEA from water has been evaluated in terms of the selectivity and solute distribution ratio. An immiscibility gap was observed in the binary systems of (IL+water). All ILs showed complete miscibility with PEA in the liquid phase at a temperature T=308.15K. The average selectivity of the extraction of PEA from water increases in the following order: [HMIM][TCB] (Sav=408)<[BMPYR][TCB] (Sav=509)<[DMIM][TCB] (Sav=577). The solute distribution ratio increases in the following order: [HMIM][TCB] (βav=178)<[DMIM][TCB] (βav=198)<[BMPYR][TCB] (βav=241). The best IL with the highest selectivity and acceptable distribution ratio is [DMIM][TCB]. The LLE data for the systems were correlated with the NRTL model. The model satisfactorily describes the solubility of the ternary systems with an average root mean square deviation of σx=0.005.

Structural Features for Furan-Derived Fruity and Meaty Aroma Impressions

Furan derivatives are part of nearly all food aromas. They are mainly formed by thermal degradation of carbohydrates and ascorbic acid and from sugar-amino acid interactions during food processing. Caramel-like, sweet, fruity, nutty, meaty, and burnt odor impressions are associated with this class of compounds. In the presented work, structure-activity relationship (SAR) investigations are performed on a series of furan derivatives in order to find structural subunits, which are responsible for the particular characteristic flavors. Therefore, artificial neural networks are applied on a set of 35 furans with the aroma categories "meaty" or "fruity" to calculate a classification rule and class boundaries for these two aroma impressions. By training a multilayer perceptron network architecture with a backpropagation algorithm, a correct classification rate of 100% is obtained. The neural network is able to distinguish between the two studied groups by using the following significant descriptors as inputs: number of sulfur atoms, Looping Centric Information Index, Folding Degree Index and Petitjean Shape Indices. Finally, the results clearly demonstrate that artificial neural networks are successful tools to investigate non-linear qualitative structure-odor relationships of aroma compounds.

Acceptance of a Complementary Food based on Provitamin A-Biofortified Maize and Chicken Stew

This study aimed to determine the acceptance of a composite complementary food prepared with provitamin A-biofortified maize and chicken stew by caregivers (n=59) in rural KwaZulu-Natal. Grains of two provitamin A-biofortified maize varieties and a white variety (control) were used as the major ingredient in the composite complementary foods. The sensory acceptability of the complementary foods was rated using a five-point facial hedonic scale. Focus group discussions were conducted in order to assess the perceptions of the selected participants about the composite complementary foods. Sensory evaluation results showed that the acceptability of the complementary foods containing the biofortified maize was similar to that of the control. The subjects had positive perceptions about the taste, texture, aroma and colour of the composite complementary food prepared with the two varieties of biofortified maize. The results suggest that provitamin A-biofortified maize has the potential to replace white maize in complementary feeding.