Volatile flavor release from foods during eating

Classical analyses for volatile flavors (headspace or distillation/extract methods) give information on either the volatiles present in the air above a food before eating or the total volatile composition of the food. When foods are eaten, however, many changes take place (such as hydration/dilution with saliva, increase in surface area, etc.) that affect the release of volatiles from the food and therefore the profile of volatiles that are sensed in the nose. If we wish to study the relationship between flavor volatiles and the sensory properties of a food, it seems logical to measure the volatile profile that exists during eating. Although volatile flavor release during eating has been measured using a variety of sensory and psychophysiological analyses, only recently have instrumental methods been developed to measure the release of volatile compounds in humans as they eat. Whereas the sensory data give an overall measure of flavor perception, instrumental analyses can potentially follow the release of each and every flavor volatile and thus give a full picture of the aroma profiles generated during eating. From these instrumental measurements, a number of key factors have been identified. First, it has been shown that the volatile profile measured during eating is indeed different from the headspace profile of whole foods. Second, it is clear that the volatile profile in‐mouth changes with time as the state of the food changes with chewing. Third, the volatile release from low‐water foods is affected by the rate and extent of hydration in‐mouth. The ability to measure aroma before, during, and after eating may lead to an understanding of the links between aroma release, interaction of volatiles with aroma sensors in the nose, and the overall perception of food flavor.     

Volatile profiles of aromatic and non-aromatic rice cultivars using SPME/GC–MS

Rice (Oryza sativa L.) is enjoyed by many people as a staple food because of its flavour and texture. Some cultivars, like scented rice, are preferred over others due to their distinctive aroma and flavour. The volatile profile of rice has been explored by other investigators, some of whom have also determined a corresponding aroma using GC/olfactometry. However, little research has been done to determine if different aromatic rice cultivars produce different flavour volatiles that would make them more desirable than others when cooked. In this study, seven aromatic and two non-aromatic cultivars were examined for their volatile profiles both before and after storage using solid phase microextraction (SPME) fibres in conjunction with gas chromatography/mass spectrometer (GC–MS). Ninety-three volatile compounds were identified, 64 of which had not been previously reported in rice. Differences were found in the volatile compounds of aromatic and non-aromatic rice besides 2-acetyl-1-pyrroline (2-AP). Most of the volatile compounds were present in freshly harvested rice and rice following storage, with very few new compounds being identified only after storage. Dellrose, an aromatic cultivar, and Cocodrie, a non-aromatic cultivar, had the most complex volatile profiles (over 64 volatiles). Sixteen compounds were found only in the aromatic cultivars, and some volatiles were found to be unique to specific aromatic cultivars. However, no distinctive pattern was observed that would identify a cultivar as being derived from Basmati, Khao Dawk Mali 105 (i.e. jasmine), or other sources of aroma. This study showed that there is a great diversity of volatiles in both aromatic and non-aromatic rice cultivars and, with further research, this may lead to a better understanding of the combination of compounds that gives a cultivar a unique flavour.     

Aroma characterisation and UV elicitation of purple basil from different plant tissue cultures

Exposure to stressful environmental conditions can induce severe metabolic variations in basil (Ocimum basilicum) aroma. The aromatic profiles of Dark Opal and Red Rubim varieties (in vivo plants, in vitro shoots, callus, and suspension cultures) were investigated for the first time. The established calli represented the most interesting miniaturised aromatic plant systems, as they were able to emit many typical basil volatiles with very low amounts of phenylpropanoids (1–2%). The hydrocarbon monoterpenes and oxygenated volatiles emitted from calli of both varieties were greatly and conversely affected by UV-C and UV-B, in comparison with the non-irradiated samples. As calli of both varieties still maintained very low levels of phenylpropanoids even after UV elicitation, they might be regarded not only as efficient in vitro plant models to study volatile compounds under UV stress conditions, but also as safe aromatic biomass in comparison with in vivo basil plants.     

Partition Distribution of Aroma Volatiles from Orange Juice into Selected Polymeric Sealant Films

The sorption of organic volatiles from orange juice by polymeric food contact materials was investigated. Three sealant films were evaluated, a commercial low density polyethylene and two developmental films, an ethylene vinyl alcohol copolymer of high ethylene content and a co-polyester. Samples of the films were immersed in the juice for 24 days at 22°C and the level of sorbed volatiles monitored as a function of time. Three probe compounds (d-limonene, neral and geranial) were selected as being representative of orange juice flavor components. A gas chromatographic technique was developed to quantify the level of probe compounds in juice and films. Results compared favorably to the more traditional bromide-bromate titration method. Sorption of organic volatiles by one of the developmental films (co-polyester) was significantly lower than the others.     

Methods used for extraction of plant volatiles have potential to preserve truffle aroma: A review

Truffles are considered one of the world's most highly prized foods mainly due to their desirable organoleptic properties and rarity. However, truffles are seasonal (harvested mostly in winter from June to August in the Southern Hemisphere and from December to February in the Northern Hemisphere) and extremely perishable. Truffles deteriorate rapidly showing undesirable changes within 10 days from harvest in aroma and visual appearance after harvest. The very short postharvest shelf life (about 7–10 days) limits the potential for export and domestic consumption all year round. Several preservation methods have been studied to prolong their shelf life without the loss of aroma. However, all traditional preservation techniques have their own shortcomings and remain challenging. The extraction of natural truffle aroma volatiles for food applications could be a potential alternative to replace the existing synthetic flavoring used for processed truffle products. Four commonly used extraction methods for recovering volatile compounds from plants, namely, supercritical carbon dioxide extraction, Soxhlet extraction, distillation, and cold pressing, are critically analyzed. Up to date, existing research about the extraction of aroma volatiles from truffles is limited in the literature but based on the volatility of the key truffle volatile compounds, supercritical carbon dioxide extraction may offer the best possibility so that a natural truffle-based product that can be used in food applications throughout the year can be made available.     

Effect of fusel oil addition on volatile compounds in papaya wine fermented with Williopsis saturnus var. mrakii NCYC 2251

The impact of fusel oil addition on volatile compounds formation in papaya wine fermented with yeast Williopsis saturnus var. mrakii NCYC2251 was studied with a view to enhancing papaya wine aroma production. Time-course papaya juice fermentations were carried out using W. saturnus var. mrakii NCYC2251 with fusel oil added (0, 0.1 and 0.5% v/v). Fermentation characteristics in terms of yeast growth, Brix and pH changes were similar for all fermentations except for those added with 0.5% (v/v) fusel oil. The addition of 0.5% (v/v) fusel oil inhibited yeast growth. A wide range of volatile compounds were produced during fermentation including acids, alcohols, esters and aldehydes with esters being the most abundant volatile compounds produced. The addition of 0.1% (v/v) fusel oil reduced the production of undesirable volatiles such as ethyl acetate and acetic acid, while increasing the desirable volatiles production such as ethanol and acetate esters. This study suggests that papaya juice fermentation with W. saturnus var mrakii NCYC 2251 together with a low concentration of added fusel oil can be another means of modulating papaya wine aroma compound formation.     

Volatiles and primary metabolites profiling in two Hibiscus sabdariffa (roselle) cultivars via headspace SPME-GC-MS and chemometrics

Hibiscus sabdariffa (roselle) is a plant of considerable commercial importance worldwide as functional food due to its organic acids, mucilage, anthocyanins, macro and micro-nutrients content. Although Hibiscus flowers are emerging as very competitive targets for phytochemical studies, very little is known about their volatile composition and or aroma, such knowledge can be suspected to be relevant for understanding its olfactory and taste properties. To provide insight into Hibiscus flower aroma composition and for its future use in food and or pharmaceutical industry, volatile constituents from 2 cultivars grown in Egypt, viz. Aswan and Sudan-1 were profiled using solid-phase microextraction (SPME) coupled to GCMS. A total of 104 volatiles were identified with sugar and fatty acid derived volatiles amounting for the major volatile classes. To reveal for cultivar effect on volatile composition in an untargeted manner, multivariate data analysis was applied. Orthogonal projection to latent structures-discriminant analysis (OPLS-DA) revealed for 1-octen-3-ol versus furfural/acetic acid enrichment in Aswan and Sudan-1 cvs., respectively. Primary metabolites contributing to roselle taste and nutritional value viz. sugars and organic acids were profiled using GC-MS after silylation. The impact of probiotic bacteria on roselle infusion aroma profile was further assessed and revealed for the increase in furfural production with Lactobacillus plantarum inoculation and without affecting its anthocyanin content. This study provides the most complete map for volatiles, sugars and organic acids distribution in two Hibiscus flower cultivars and its fermented product.     

Vapour partition of aroma compounds in strawberry flavoured custard cream and effect of fat content

Gas–matrix partition coefficients (k) of volatile compounds of a strawberry flavour added to a complex model system (custard dessert, COST action 921 recipe) were determined. The influence of fat content on the volatility of the strawberry aroma compounds was investigated using full fat milk- (FFM) and skimmed milk- (SM) custards. For the purpose of this study, the phase ratio variation (PRV) method was used because of its easy application for a mixture of volatiles without requiring any calibration. From the 15 aroma compounds present in the flavouring mixture, seven were volatile enough to be detected and concentrated enough to allow the calculation of k values. Gas–matrix partition coefficients were compared to gas–water partition coefficients. For some aroma compounds (ethyl hexanoate, ethyl butanoate, and hexanal) a significantly lower k value was observed in FFM-custard than in water, indicating a retention effect caused by the matrix. As expected, the fat content and the hydrophobicity of the volatile compounds were of great importance to explain the differences between partition coefficients in SM custards and in FFM custards: for SM-custard, a higher release in the vapour phase was observed than for FFM-custard; the more hydrophobic the aroma compound, the higher the effect. Moreover, ethyl butanoate and hexanal were less retained in SM-custard than in water. This may be attributed to a salting-out effect due to sucrose.     

Volatile constituents of unripe and ripe kundang fruits (Bouea macrophylla Griffith)

Kundang, a seasonal, tropical fruit is consumed either as raw (unripe) or ripe in south-east Asia. Investigations performed by using gas chromatography-mass spectrometry revealed volatile constituent compounds in ripe fruits to be much higher than unripe fruits. Nearly 82 compounds (comprising 99.96% of the total volatiles) and 121 compounds (encompassing 97.33% of the total volatiles) were identified in unripe and ripe fruits, respectively. Results generated is envisaged to enhance the existing database on tropical fruits volatile profiles, as well as benefit local food industries (to exploit the unique fragrance character impact compounds for aroma essence production) for commercial usage.     

Scalping of ethyloctanoate and linalool from a model wine into plastic films

The scalping of aroma compounds may affect the sensory properties of wines packed in plastic, such as those commercialized in aseptic multilayer packages, by reducing the intensity and changing the character of the original aroma. Up to date, no study has focused on the scalping of wine aroma compounds. The present study aimed at determining the sorption kinetics of two wine volatiles, chosen on the basis of their low threshold and high odor activity value, in linear low density polyethylene (LLDPE) and cast polypropylene (CPP), from a model solution simulating wine composition. The experimental data were satisfactorily fitted by the Fick's Second Law, as to prove an ideal Fickian transport diffusional character of the phenomenon. Sorption was determined by means of MHS-SPME, a technique recently developed to quantify volatile compounds from solid matrices. Ethyloctanoate was sorbed more into CPP than LLDPE, and at much higher extent than linalool, as a consequence of the different polarity of the molecules. The amount of ethyloctanoate lost at the steady state determines a significant variation of its odor activity value and the imbalance of the original aroma composition.     

Volatile flavor compounds in yogurt: a review

Considerable knowledge has been accumulated on the volatile compounds contributing to the aroma and flavor of yogurt. This review outlines the production of the major flavor compounds in yogurt fermentation and the analysis techniques, both instrumental and sensory, for quantifying the volatile compounds in yogurt. The volatile compounds that have been identified in plain yogurt are summarized, with the few key aroma compounds described in detail. Most flavor compounds in yogurt are produced from lipolysis of milkfat and microbiological transformations of lactose and citrate. More than 100 volatiles, including carbonyl compounds, alcohols, acids, esters, hydrocarbons, aromatic compounds, sulfur-containing compounds, and heterocyclic compounds, are found in yogurt at low to trace concentrations. Besides lactic acid, acetaldehyde, diacetyl, acetoin, acetone, and 2-butanone contribute most to the typical aroma and flavor of yogurt. Extended storage of yogurt causes off-flavor development, which is mainly attributed to the production of undesired aldehydes and fatty acids during lipid oxidation. Further work on studying the volatile flavor compounds-matrix interactions, flavor release mechanisms, and the synergistic effect of flavor compounds, and on correlating the sensory properties of yogurt with the compositions of volatile flavor compounds are needed to fully elucidate yogurt aroma and flavor.     

Effects of hypobaric and temperature-dependent storage on headspace aroma-active volatiles in common squid miso

The purpose of this study was to elucidate the effects of storage at hypobaric (10 kPa) atmosphere at room temperature (25 °C) and at a low temperature of 10 °C at atmospheric pressure on the headspace volatiles of miso prepared from common squid meat during 270 days of storage. Based on the odor active values of the volatiles detected, 2-methylpropanal, 3-methylbutanal, 3-methyl-1-butanol, n-ethyl decanoate, 2,3-butanedione, dimethyl disulfide, methional, and 2-methyl butanoic acid were identified as key aroma compounds in squid miso. Low-temperature storage appeared to retard volatile compound formation and extent the shelf life. Hypobaric storage induced a significant reduction in lipid oxidation products, particularly aldehydes and ketones. The contents of sulfur-containing compounds and acids were significantly low; however, esters had relatively higher levels in hypobaric conditions. Production of furans and their derivatives were also found to be controlled by hypobaric storage. Therefore, hypobaric storage can be considered as an effective means of preserving squid miso and related fish paste products to prolong shelf-life in order to maintain aroma attributes.     

Characterisation of bound volatile compounds of a low flavour kiwifruit species: Actinidia eriantha

Aroma compounds in fruit are known to occur in free and glycosidically bound forms. The bound volatile fraction of a low flavour kiwifruit species, Actinidia eriantha, was studied. The fruit have a bland and grassy flavour. Glycosidic precursors were isolated from juice by adsorption onto an Amberlite XAD-2 column. After enzymatic hydrolysis with Rapidase AR2000, the released aglycones were analysed by GC–MS. Alcohols, terpenoids and phenolics were the most numerously represented compound classes. Alcohols, benzenoids and phenolics showed the highest concentrations. Major compounds were 2-phenylethanol, furfuryl alcohol, (Z)-3-hexen-1-ol, coniferyl alcohol, isoamyl alcohol and linolenic acid. Several of the bound compounds found, including linoleic, linolenic and benzoic acids and coniferyl alcohol, are precursors of odorous volatiles. Many compounds detected as bound volatiles have not been previously reported as free volatiles in A. eriantha. The bound volatile composition of A. eriantha also showed differences with those of other kiwifruit species.     

The aroma volatile repertoire in strawberry fruit: a review

Aroma significantly contributes to flavor, which directly affects the commercial quality of strawberries. The strawberry aroma is complex as many kinds of volatile compounds are found in strawberries. In this review, we describe the current knowledge of the constituents and of the biosynthesis of strawberry volatile compounds, and the effect of postharvest treatments on aroma profiles. The characteristic strawberry volatile compounds consist of furanones, such as 2,5‐dimethyl‐4‐hydroxy‐3(2H)‐furanone and 4‐methoxy‐2,5‐dimethyl‐3(2H)‐furanone; esters, including ethyl butanoate, ethyl hexanoate, methyl butanoate, and methyl hexanoate; sulfur compounds such as methanethiol, and terpenoids including linalool and nerolidol. As for postharvest treatment, the present review discusses the overview of aroma volatiles in response to temperature, atmosphere, and exogenous hormones, as well as other treatments including ozone, edible coating, and ultraviolet radiation. The future prospects for strawberry volatile biosynthesis and metabolism are also presented. © 2018 Society of Chemical Industry     

Identification of key odor volatile compounds in the essential oil of nine peach accessions

BACKGROUND: Volatile compounds, together with sugars and acids, are the main chemical species determining the characteristic aroma and flavor of food. In peach, more than 100 volatiles have been identified. RESULTS: The essential oil of six peach and three nectarine accessions used in Italian breeding programs was obtained by steam distillation, and the volatiles were investigated. A total of 47 known volatiles, two unidentified compounds and nine hydrocarbons were identified, including 12 aldehydes, six alcohols, three acids, three esters, six terpenes, two phenylalanine derivates, two C₁₃ norisoprenoids, one ketone (C₉) and 10 lactones. A wide variation in the number of volatiles and in their concentration was observed among the nine accessions. Twenty‐one compounds presented odor activity values (OAVs) higher than 1 in at least one of the accessions and were therefore putatively considered as key odorants in the peach volatile composition. CONCLUSION: This study reports the identification, quantification and potency, based on the OAVs, of the most important volatile compounds, along with fruit quality characteristics, of nine different peach/nectarine accessions and will help future peach volatile breeding programs for the selection of odor‐rich accessions to be used in the development of new improved cultivars. Copyright © 2010 Society of Chemical Industry     

Volatiles of grape berries evaluated at the germplasm level by headspace-SPME with GC–MS

Volatile aroma compounds are one of the important characteristics determining fruit quality. Evaluation of volatiles at the germplasm level is useful for future breeding efforts, aimed at improvement of fruit quality, via effects on fruit aroma. The composition and concentration of volatiles in berries of forty-two grape cultivars belonging to seven genotypic groups were evaluated by headspace solid-phase microextraction with GC–MS. Sixty volatiles were detected, of which C₆ compounds were the dominant volatiles in V. amurensis grape, neutral cultivars V. vinifera grapes and hybrid grapes between V. vinifera with V. thunbergii or V. amurensis. Alcohols and carbonyls were relatively low in all Vitis germplasm studied. Terpenoids were abundant in V. vinifera with muscat aroma, while esters were dominant in V. labrusca and its hybrids with V. vinifera or V. amurensis. Via principal component analysis, all the grape germplasm studied could be divided into three groups: (1) V. labrusca and its hybrids with V. vinifera or V. amurensis, (2) V. vinifera with muscat aroma and (3) the others, including V. vinifera without muscat aroma plus V. amurensis, and hybrids between V. vinifera and V. thunbergii or V. amurensis. Seasonal quantitative variations of volatiles were observed, but the qualitative volatile composition of the cultivars was consistent.     

The Effect of pH and Temperature on Cabbage Volatiles During Storage

During storage of shredded cabbage, characteristic sulfurous volatile compounds are formed affecting cabbage aroma both negatively and positively. Selected ion flow tube‐mass spectrometry (SIFT‐MS) was used to measure the concentration of cabbage volatiles during storage. The volatile levels of cabbage samples were measured at pH 3.3 to 7.4 at 4 °C for 14 d, and pH 3.3 at 25 °C for 5 d in order to determine the effect of pH and temperature. Aroma intensity, best aroma, freshness, and off odor were evaluated in a sensory test of the samples at 4 °C. The desirable volatile allyl isothiocyanate was lower in high pH samples (pH 7.4 and 6.4), whereas higher concentrations were detected in low pH samples (pH 3.3 and 4.6). Lipoxygenase volatiles, which produce a fresh green and leafy aroma in cabbage, were generated in very low amounts at any pH value. High pH samples generated significantly higher concentrations of off odors such as dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, and methanethiol. Sensory tests showed that higher pH samples had significantly stronger off odor and lower desirable cabbage aroma than lower pH samples. Thus, sensory results matched the volatile results in that samples at higher pH levels formed the highest amount of undesirable volatiles and the least amount of desirable volatiles. Storage at 25 °C produced similar concentrations of allyl isothiocyanate, but significantly higher levels of off odors, than at 4 °C. Shredded cabbage products should be stored in low pH dressings to minimize formation of off odors and maximize formation of characteristic, desirable cabbage odor.     

Comparison of HS-SPME with hydrodistillation and SFE for the analysis of the volatile compounds of Zisu and Baisu,two varietal species of Perilla frutescens of Chinese origin

Content and composition of the volatiles of Baisu and Zisu, two varieties of Perilla frutescens, obtained by SFE, HS-SPME, and hydrodistillation, were compared. A total of 64 compounds were identified by GC/MS. Perillaldehyde (21.9–58.1%) and perilla ketone (54.5–83.5%) were the main volatile components of Zisu and Baisu, respectively. They might be partly responsible for the aroma and taste of perilla. The abundance of perilla ketone indicates that it is not safe to use Baisu as vegetable, and Baisu should not be used as substitute for Zisu. SFE extracted oil with high yield, and extracted some high molecular-weight compounds that did not contribute to the aroma. The HS-SPME was simple and sensitive for the analysis of volatile compounds of fresh perilla. The results showed that the drying process influenced the volatile components of perilla.     

刺梨汁中挥发性成分测定及其呈香贡献分析

为全面剖析刺梨中挥发性成分的组成及其呈香贡献,采取顶空固相微萃取(headspace-solid phase microextraction,HS-SPME)和溶剂辅助风味蒸发(solvent-assisted flavor evaporation,SAFE)结合GC-MS对刺梨汁挥发性成分进行分析,通过香气活度值(odor activity value,OAV)评估挥发性成分对刺梨汁整体香气的贡献度。结果表明,HS-SPME和SAFE方法在刺梨汁中分别检测到67种和86种化合物,共鉴定出119种挥发性化合物,其中包括酯类49种,醇类28种,酸类9种,醛酮类16种,萜烯类6种,芳香族化合物9种和其他类2种。2种方法对挥发性化合物的提取效率不同,HS-SPME对低沸点强挥发性的化合物提取更为有效,SAFE提取到更多高沸点较难挥发的化合物,两者互补分析获得了较全面的分析结果,鉴定出了刺梨汁中更多种类的挥发性化合物。OAV分析表明,38种挥发性化合物对刺梨的香气有主要贡献作用,主要为酯类、醇类和醛酮类化合物,其中有16种挥发性成分首次被鉴定为刺梨汁中的香气活性成分。该研究可为贮藏和刺梨加工过...