Apple Aroma Research Articles

Characterisation of QMB sensors by means of the BET adsorption isotherm

A calibration protocol was established for a quartz microbalance-based electronic nose (QMBE-nose) that was used for apple aroma measurements. A gas-mixing panel was built to generate a broad concentration range of single apple volatile compounds and of mixtures of two compounds. The response of each QMB sensor was modelled with BET adsorption isotherms. Results show that the affinity of the different sensors to relative humidity can be described well with the BET parameters. The sensors could also be characterised with this model for affinity towards single apple volatiles and mixtures of two apple volatile compounds. By means of multivariate analysis on all sensor responses, the different compounds could be discriminated well and also quantified accurately. The results showed the potential of the QMBE-nose to quantify and discriminate different apple volatile compounds. Also, the established calibration protocol offers an easy and fast tool to characterise new sensors or investigate new application possibilities.

Representativeness of Apple Aroma Extract Obtained by Vacuum Hydrodistillation: Comparison of Two Concentration Techniques

ABSTRACT: Vacuum hydrodistillation, which is a very gentle work‐up procedure, has never been used for the extraction of apple aroma. During the concentration of aroma that follows vacuum hydrodistillation, some very volatile components can be lost. The aim of this study was to compare 2 different concentration techniques, liquid‐liquid extraction and solid phase extraction, to obtain an apple aroma extract as close as possible to fresh apple. After the elimination of solvent from the extract by gas chromatography, the study of the odor characteristics of solvent‐free extracts was made possible. Vacuum hydrodistillation was convenient for fresh apples.

Changes in the order of elution of some organic compounds in high-resolution gas chromatography on polar columns depending on the injection method and water content in the sample

During the GC analysis of apple aroma essence using a capillary column with polar stationary phases, i.e., bonded/crosslinked polyethylene glycol (HP-Innowax) and acid-modified polyethylene glycol (FFAP) the phenomenon of changing the elution order of some compounds was observed (“cross-over phenomenon”). The elution order within two pairs of closely eluting compounds: 2-methylbutyl acetate/pentan-3-ol (internal standard) and trans-2-hexen-1-al/2-methylbutan-1-ol differed between samples introduced onto the column with direct injection and with static headspace method. Experiments carried out on standard solutions of investigated compounds in water–acetone mixtures of gradually reduced water ratio (99:1 to 0:100) proved that changes of elution times leading first to co-elution and subsequently to reversion of elution order of compounds within both pairs depended on the amount of water in the injected sample. The same effect was observed while the amount of water was diminished by reducing the sample volume introduced into the column.

Sensory evaluation of character impact components in an apple model mixture.

Food aromas generally are complex mixtures of volatiles. In the present study, we investigated the joint effects of hexyl acetate, trans-2-hexenal and 1-hexanol on the multi-attribute perception of an apple aroma. The first two substances were identified earlier as positive contributors to the apple aroma (high character impact), whereas the third component was identified as an irrelevant or negative contributor (low character impact). Aroma quality was quantified using a set of eight graphic rating scales. All three components had significant effects on the aroma profiles. These effects consist mainly of an effect of each component on the attribute that described its individual character and an effect of all three components on ratings on the main character attribute 'apple'. As expected, the high impact components increased 'apple' ratings, whereas the low character impact component decreased 'apple' ratings. Furthermore, intensity ratings on the attribute that corresponded with the odour of the low impact component were suppressed by the presence of high impact components. These results indicate that the contributions of odorants to the mixture's aroma are not linear combinations of separate odour intensities, because sensory interactions were observed. In addition, humans detect components in complex mixtures more accurately than studies on identification performance have suggested. We conclude that for an adequate assessment of the effects of multiple mixture components on changes in aroma perception, it is sufficient to employ multiple response scales measuring intensities of attributes that are distinctive with respect to the expected qualitative changes. Results of this approach should be subjected to multivariate methods of statistical analysis.

Volatility of patulin in apple juice.

Patulin is a mycotoxin produced by certain fungi, such as those found commonly on apples. The patulin content of apple juice is a regulatory concern because patulin is a suspected carcinogen and mutagen. A simple model of the apple juice concentration process was carried out to examine the possible contamination of patulin in apple aroma, a distillate produced commercially in the concentration of apple juice. The results show no evidence for patulin volatility, and document a reduction in patulin content by at least a factor of 250 in the apple distillate obtained from apple juice. Furthermore, a survey of several commercial apple aroma samples found no evidence of patulin content.

Characterization of Changes in `Gala' Apple Aroma during Storage Using Osme Analysis, a Gas Chromatography-Olfactometry Technique

Changes in the odor-active volatile compounds produced by `Gala' apples [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. `Gala'] were measured after 4, 10, and 20 weeks storage at 1 °C in regular atmosphere (RA) or controlled atmosphere (CA), and 16 weeks in CA followed by 4 weeks in RA. Aroma was evaluated using the gas chromatography-olfactometry method Osme. Production of volatile esters decreased along with corresponding fruity aromas during CA storage. Hexyl acetate, butyl acetate, and 2-methylbutyl acetate were emitted in the largest amounts and perceived with the strongest intensities from RA-stored fruit. While hexyl acetate and butyl acetate concentrations and aroma intensities decreased during CA storage, 2-methylbutyl acetate remained at the RA concentration until apples had been stored 16 weeks in CA. Perception intensities of methylbutyrate esters with apple or berrylike odors decreased less than straight chain esters in CA-stored fruit. 4-Allylanisole, ß-damascenone, and 1-octen-3-ol, as well as an unknown compound with a watermelon descriptor, were perceived more in RA-stored fruit than in CA-stored apples. Factor analysis indicated the importance of these compounds in `Gala' apples stored 4 weeks in RA. Even though these compounds do not have an apple odor, they contribute to fresh `Gala' aroma.

Effects of hexanal, trans-2-hexenal, and storage temperature on shelf life of fresh sliced apples.

In this paper, the effects of hexanal and trans-2-hexenal, which are both natural molecules characterizing apple aroma, on the microbial population and on color retention of fresh sliced apples were evaluated. In particular, a central composite design (CCD) was developed to assess the individual and interactive effects of the chosen volatile molecules and storage temperatures on (i) the growth of the naturally occurring microflora, (ii) the evolution over time of an inoculated spoilage yeast (Pichia subpelliculosa), and (iii) the enzymatic browning reaction in minimally processed apples. The inclusion of hexanal and trans-2-hexenal in the storage atmosphere of apple slices determined a significant extension of shelf life also when P. subpelliculosa was inoculated at levels of 10(3) colony-forming units/g and abusive storage temperatures were used. In fact, the presence of these molecules in the packaging atmospheres considerably prolonged the lag phases of the inoculated yeast and reduced the growth potential of naturally occurring bacteria. Moreover, the addition to the modified atmosphere of low levels of the hexanal increased the color stability of the products up to 16 days.

Apple superficial scald preventi1on by vapour treatments

Superficial scald is a postharvest physiological disorder of apples characterized by browning of apple skin during prolonged storage. It has been hypothesized that conjugated triene hydroperoxides (CTH) attack cell membranes causing membrane perturbation and the manifestation of the disorder. The purpose of this study was to compare the common synthetic antioxidant diphenylamine (DPA) treatment with postharvest vapour treatments for superficial scald prevention. Apples cv. ‚Granny Smith™ were treated with ethanol, methanol and »apple aroma« vapours. The influence of these treatments on scald susceptibility and sensorial quality of apples was examined. The ethanol treatments were effective in superficial scald prevention but they caused a high incidence of internal browning after two months of storage. The 10 day treatments at 20 °C developed very pronounced internal browning after storage. The aroma treatment was the least effective in apple scald prevention but no internal disorders appeared after storag...

Characterization of `Gala' Apple Aroma and Flavor: Differences between Controlled Atmosphere and Air Storage

Aroma and flavor characters of `Gala' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. `Gala'] were identified by 10 trained panelists. A vocabulary of 13 aroma descriptors and 16 flavor descriptors were used to characterize changes in controlled atmosphere (CA) and air, or regular atmosphere (RA) storage over 20 weeks. When compared with RA storage, the intensity of fruity (pear, banana, and strawberry) and floral descriptors decreased after 10 weeks in CA for whole and cut fruit aroma and flavor. During the entire storage period under CA, aroma of cut apples retained high vegetative and citrus characters but had a less intense anise aroma. Sourness and astringency were significantly higher for CA-stored apples, and sweetness was significantly lower. A musty note was perceived in whole apples stored in CA for 20 weeks. Aroma of whole fruit stored for 16 weeks in CA followed by 4 weeks in RA was higher in fruitiness, banana, floral, and anise characters when compared with apples stored 20 weeks in CA. There was no difference between fruit stored in CA followed by RA versus CA stored apples for flavor and aroma of cut fruit. Changes in descriptor ratings during storage are discussed in relation to gas chromatography and olfactometry data obtained with the Osme method.

Methyl-Branched Flavor Compounds in Fresh and Processed Apples

Methyl-branched volatiles in apples and processed apples are investigated. The ratio of 3-methyl-branched and 2-methyl-branched flavor compounds was determined and the enantiomeric distribution of the latter investigated. The enantiomeric ratios of 2-methyl-branched volatiles are analyzed, using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as an efficient enantioselective stationary phase in capillary GC. 2-Methylbutanoic acid and the corresponding esters (methyl−n-hexyl ester), 2-methylbutanol, and 2-methylbutyl acetate were detected as genuine flavor compounds favoring (S)-configuration and high enantiomeric purity (>99%). 3-Methylbutanoic acid, 3-methylbutanol, and 3-methylbutyl acetate are proved to be not genuine compounds of the apple aroma but fermentation products. Keywords: Apple flavor; methyl-branched volatiles; enantioselective capillary gas chromatography; enantioselective multidimensional gas chromatography (enantio-MDGC)

Permeation of apple aroma compounds in reverse osmosis

Abstract This work studies the permeation of apple juice aroma compounds through a reverse osmosis spiral wound aromatic polyamide membrane of 99.2% NaCl rejection. A model solution of apple juice aroma was used as feed. Experiments were carried out at different transmembrane pressures (1.5–3.5 MPa) and feed flows (200–600 l/h; Reynolds numbers between 100 and 300). Temperature was set at 25°C. Rejection was observed to increase with transmembrane pressure and feed flow. The preferential sorption-capillary flow model was used to estimate the experimental rejection using only data on the permeation of a solute taken as reference (NaCl) and on the permeation of pure water. Good agreement between experimental and estimated rejection was found for the most hydrophilic aroma compounds, while a slightly higher rejection than the experimental one was predicted for the least hydrophilic compounds.

SENSORY ANALYSIS OF AROMA ATTRIBUTES OF YOUNG AIRÉN WHITE WINES DURING STORAGE IN THE BOTTLE

ABSTRACTAirén white wines stored in the bottle under usual commercial conditions for 6, 18, 30, and 42 months were studied to determine the effect of in‐bottle storage time on the organoleptic characteristics of the wine and to evaluate shelf‐ life in the absence of careful storage conditions. Sensory descriptive analysis was applied by a panel of 12 trained assessors, and multivariate analysis was applied to follow the changes taking place in the different attributes and determine shelf‐ life in the bottle. Stored in the bottle, young Airén white wines were judged to have a moderately strong fresh‐citric, floral, and apple aroma for up to 18 months, while wines stored longer in the bottle had a sweet‐raisin and a spicy‐green pepper aroma. Significant differences existed between wines stored in the bottle 18, 30 and 42 months based on disappearance of the fresh‐citric aroma and the gradual appearance of a spicy‐green pepper flavor. Commercial storage conditions should be revised for young Airén white wines to retain their favorable sensory characteristics for longer periods.

Heat Treatment Temporarily Inhibits Aroma Volatile Compound Emission from Golden Delicious Apples

Volatile compounds were collected by porous polymer trapping from Golden Delicious apples (Malus domestica Borkh.) that had been heat-treated for 4 days at 38 °C, a treatment developed to reduce physiological and pathological disorders during storage, and then stored at 1 °C. Heat treatment of apple fruits markedly inhibited emission of total volatile esters (compounds commonly associated with apple aroma) and total volatiles (comprised principally of the volatile esters and α-farnesene) of apple within 1 day of treatment. However, after an extended refrigerated storage at 1 °C, the heat-treated fruit recovered and produced more total volatiles, increasing from 4% compared to non-heat-treated fruit directly after heat treatment to 145% of non-heat-treated fruit after 6 weeks of storage. Total volatile production of non-heat-treated fruit declined over 5-fold during the 6 weeks of cold storage, while that of heat-treated fruit increased over 6-fold. Total volatile esters from heat-treated fruit declined af...

The effect of hydrolysis conditions on the aroma released from Semillon grape glycosides

A glycoside fraction was isolated from a Semillon juice and hydrolysed in vitro by acid-catalysis at elevated temperature, or by glycosidase enzyme action, or by a sequence of glycosidase and acid treatments. The hydrolysates were evaluated in a white wine medium by sensory descriptive analysis. To evaluate aroma released by in situ hydrolysis of glycosides, wine prepared from the Semillon juice was also assessed, before and after elevated temperature storage, together with Semillon wines from earlier vintages. Descriptive analysis of these samples showed that enzyme-catalysed hydrolysates had no detectable effect on aroma, while acid-hydrolysis produced significant aroma and conferred sensory properties similar to those of bottle-aged wines, i.e. diminished floral and apple aroma attributes, and enhanced honey, nutty, oak, toasty and tobacco attributes. A similar effect on aroma attributes was found for the heated young Semillon wine, which was not scored significantly differently from a three-year-old Semillon wine, except for the lime attribute. The glycosyl-glucose concentration of the Semillon wines was correlated with the sensory scores of the wines, indicating that the extent of in situ hydrolysis of glycosides in wines relates to the development of flavour as a result of storage or accelerated hydrolysis. This study has demonstrated a close association among the aroma properties of Semillon grape glycosides hydrolysed in vitro at elevated temperature, in situ under natural conditions, and in situ at elevated temperature, and supports acid-catalysed hydrolysis of grape glycosides as the mechanism of varietal aroma development in wine.

ChemInform Abstract: Enantioselective Synthesis of the Apple Aroma Constituent 1,3,3‐ Trimethyl‐2,7‐dioxabicyclo(2.2.1)heptane (III) via Asymmetric Dihydroxylation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enantioselective Synthesis of the Apple Aroma Constituent 1,3,3-Trimethyl-2,7-dioxabicyclo[2.2.1]heptane via Asymmetric Dihydroxylation

The enantiomers of 1,3,3-trimethyl-2,7-dioxabicyclo[2.2.1]heptane (1) were prepared in two steps from 6-methylhept-5-en-2-one using Sharpless asymmetric dihydroxylation.

Volatiles of cold and burning fragrance candles with lavender and apple aromas

AbstractComparative investigations on cold and burning fragrance candles were carried out to identify possible changes of the volatiles caused by the heat of the flame. Headspace analysis of the volatiles of candles with lavender and apple aroma using GC, GC‐FTIR‐MS and a GC‐sniffing technique showed nearly the same combination of volatiles before and after burning of the candles. Only a slight decrease of the concentration of alcohols was found. Fragrance candles can therefore be used in the correct aromatherapeutical sense, because the unchanged biologically active fragrance compounds can be inhaled.The dominating components in the headspace of the lavender fragrance candles (cold/burning) were mainly the terpenes 1,8‐cineole (25.9/25.9%), linalol (10.8/6.2%), linalyl acetate (10.0/9.6%), camphor (8.8/9.6%), lavandulyl acetate (7.0/9.2%) and limonene (6.5/3.3%). The fragrance candles with apple aroma furnished a totally different spectrum of volatiles as no terpenes, but esters of mainly aliphatic alcohols with short‐chain aliphatic acids dominated: 2‐(1,1‐dimethylethyl)‐cyclohexyl acetate (17.7/15.4%), butyl acetate (16.7/20.6%), 2‐methylnonan‐3‐one (5.5/4.9%), propyl acetate (5.4/4.5%), phenyl benzoate (5.2/5.3%), isoamyl acetate (4.9/4.3%), (Z)‐hex‐2‐enal (4.1/5.2%), amyl butyrate (3.8/2.9%), hexyl butyrate (3.6/4.3%), ethyl valerate (3.3/4.2%) and amyl acetate (3.1/2.9%) were found as main constituents (concentration higher than 3%).

Comparative study of the aromatic profiles of two different plum species: Prunus salicina Lindl and Prunus simonii L

AbstractVolatile compounds of two plum species (Prunus salicina Lindl and Prunus simonii L) were analyzed by capillary gas chromatography‐mass spectrometry using simultaneous vacuum distillation extraction. Aroma patterns were identified and quantified. A total of 60 compounds were identified, of which 23 were unique to P simonii. The profile of P simonii, as well as a study of the odor unit values of some identified compounds, indicated a much stronger aroma than P salicina. Hexyl acetate, which produces a characteristic apple aroma, was present in P simonii at levels 50‐fold higher than in the studied cultivars of P salicina.

Comparative Absorption of Low Molecular Aroma Compounds into Commonly Used Food Packaging Polymer Films

ABSTRACTFive polymer films commonly used in food packages were stored in an aqueous solution of 10 apple aroma compounds. Substances absorbed by the polymers were determined by a supercritical fluid extraction/gas chromatography method. Polypropylene absorbed most aromas, more than 2× amounts absorbed by low density polyethylene. Polyamide and polyester absorbed very small amounts of the aromas. Esters and aldehydes were absorbed much more than alcohols. Molecular size also affected absorption, larger molecules being absorbed to a greater extent than smaller ones. For most materials the absorption equilibrium was reached within a week.

Activity coefficients of aroma compounds in model solutions simulating apple juice

This study aims to present data on the activity coefficients of apple aroma compouds at infinite dilution in solutions that simulate apple juice at different temperatures and to correlate these experimental data with temperature by using some of the one-parameter models based on the Wilson, NRTL, or UNIQUAC equations