Leif Poll

Odour thresholds of some important aroma compounds in raspberries

ZusammenfassungDie Geruchsschwellen von 24 Aromastoffen der Senga Sengana Erdbeeren wurden mit Duo-Trio-Tests bestimmt. Die Werte wurden mit den Konzentrationen der Aromastoffe in der Frucht verglichen, und die Aromastoffe wurden in Gruppen nach den Aromawerten (Konzentration/Schwelle) eingeteilt. Die wichtigsten Komponenten waren Ethylbutanoat, Ethylhexanoat und 2,5-dimethyl-4-hydroxy-3(2H)-furanon, aber auch Komponenten in Konzentrationen unter den Schwellenwerten hatten Einfluß auf den Geruch.SummaryThe odour tresholds of 24 aroma compounds in Senga Sengana strawberries were determined using duo-trio tests. The threshold values were compared with concentrations in the fruit, and the compounds divided into groups according to their aroma values (concentration/threshold). The most important compounds were ethyl butanoate, ethyl hexanoate and 2,5-dimethyl-4-hydroxy-3(2H)-furanone, but even compounds in concentrations below the threshold values had some influence on the odour.

Evaluation of the aroma composition of some strawberry (Fragaria ananassa Duch) cultivars by use of odour threshold values

ZusammenfassungDie Zusammensetzung der Aromastoffe der Erdbeersorten Elsanta, Elvira, Dania, Bogota, Pandora und Senga Sengana wurden analysiert und die Konzentrationen mit den Geruchschwellen verglichen, um die wichtigste Komponente zu bestimmen. 2,5-Dimethyl-4-hydroxy-3(2H)-furanon, Linalool und Ethylhexanoat wurden als allgemein wichtige Aromakomponenten der Erdbeeren gefunden, während Ethylbutanoat, Methylbutanoat,γ-Decalacton und 2-Heptanon sortenspezifische Aromakomponenten sind.SummaryThe aroma composition of the strawberry cultivars Elsanta, Elvira, Dania, Bogota, Pandora and Senga Sengana was analysed and the concentrations were compared with the odour threshold values to determine the most important compounds. 2,5-Dimethyl-4-hydroxy-3(2H)-furanone, linalool and ethyl hexanoate were found to be important general strawberry aroma compounds whereas ethyl butanoate, methyl butanoate,γ-decalactone and 2-heptanone were found to be important cultivar-specific aroma compounds.

Discrimination between freshly made and stored reconstituted orange juice using GC Odour Profiling and aroma values

Abstract The aroma of freshly made and stored reconstituted orange juice was analyzed by GC– MS and GC–FID. The importance of the individual compounds was evaluated by calculation of aroma values. For comparison, the same samples were evaluated by a GC-sniffing technique called GC Odour Profiling, using a panel of five assessors. Both methods showed that there were significant differences between freshly made and stored juice, but the two methods did not always show the same compounds/odours to be important. On the other hand, many similarities were seen, as ethyl butanoate, β -pinene, limonene, octanal and linalool were shown to be important by both methods. In conclusion, both methods proved to be useful for identifying important aroma compounds in orange juice and for discrimination between fresh and stored juice.

Influence of Drying and Irradiation on the Composition of Volatile Compounds of Thyme (Thymus vulgaris L.)

An investigation of the influence of air-drying, freeze-drying, γ- and β-irradiation and storage for up to 10 months on the composition of volatile compounds in thyme herb (Thymus vulgaris L.) is presented. Altogether, 70 constituents were identified (53 positively and 17 tentatively), including those considered most important for thyme flavour. Quantitative results did not reveal significant differences in the composition of irradiated and non-irradiated samples, and the reduction of the amount of some volatile compounds after drying was comparable for air-dried and freeze-dried herb. The largest changes in flavour composition were observed during storage, especially the reduction in the concentration of monoterpene hydrocarbons.

Influence of volatile compounds produced by yeasts predominant during processing of Coffea arabica in East Africa on growth and ochratoxin A (OTA) production by Aspergillus ochraceus

The effects of volatile compounds produced during coffee processing by Pichia anomala, P. kluyveri and Hanseniaspora uvarum on growth of Aspergillus ochraceus and production of ochratoxin A (OTA) were studied. On malt extract agar (MEA) and on coffee agar (CA), exposure of A. ochraceus to the gaseous phase of malt yeast glucose peptone (MYGP) plates inoculated with P. anomala, P. kluyveri and H. uvarum inhibited fungal growth, with the two Pichia spp. showing the strongest effect. The main esters and alcohols produced by the three yeasts were ethyl acetate, isobutyl acetate, 2‐phenyl ethyl acetate, ethyl propionate and isoamyl alcohol. The individual esters and alcohols were found to affect fungal growth. The most effective compound in inhibiting fungal growth was 2‐phenyl ethyl acetate; which at 48 µg/l headspace completely inhibited growth of A. ochraceus. Exposure of A. ochraceus to the gaseous phase of MYGP plates inoculated with P. anomala, P. kluyveri and H. uvarum prevented production of OTA. On CA medium, only the headspace of P. anomala and P. kluyveri prevented OTA production. Furthermore, when A. ochraceus was exposed to the headspace of the individual volatile compounds, 2‐phenyl ethyl acetate was the most effective in preventing OTA production. Prevention of OTA seems to be due to reduction of fungal biomass. Copyright

Comparison of volatiles in raw and boiled potatoes using a mild extraction technique combined with GC odour profiling and GC–MS

Abstract Aromas of raw and boiled potatoes were compared using a mild extraction technique, ensuring preservation of the very labile composition of potato aroma during analysis. The extracts were evaluated by GC–MS and GC-sniffing using a panel of four judges. A total of 29 compounds were identified by GC–MS in raw potatoes and 25 in boiled. Twenty compounds were found in both raw and boiled potatoes, but most often in very different concentrations. During GC-sniffing, 33 odours were detected in boiled, and 27 in raw potatoes. Eight odours corresponded to compounds identified by GC–MS. Another four odours could be tentatively identified. It is concluded that the change in aroma during boiling of potatoes depends on compounds from lipid oxidation as well as compounds from other types of reactions, for instance the Strecker-degradation.

Volatile compounds of Soumbala, a fermented African locust bean (Parkia biglobosa) food condiment

Aims:  To determine the profile of volatile compounds responsible for the aroma of Soumbala produced spontaneously and with pure and mixed cultures of Bacillus subtilis and Bacillus pumilus.

Aroma analysis of apple juice: Influence of salt addition on headspace volatile composition as measured by gas chromatography and corresponding sensory evaluations

Abstract Sensory response to the aroma of a food depends on the composition and concentrations of the volatiles of the headspace. When analyzing the headspace composition by gas chromatography, salts are often added to the sample as a means of increasing the concentration of the aroma compounds in the vapor phase (e.g. enrichment of the vapor phase). This will only give a correct impression of the original aroma when all volatile components are affected equally. In this study on apple juice aroma, it is demonstrated that the degree of headspace enrichment resulting from salt addition is different for esters, aldehydes and alcohols, In our collection system, the average degree of enrichment at 40°C (described in terms of Relative Peak Areas—RPA) was greater than 4 for alcohols, between 1·75 and 3·50 for aldehydes and less than 1·75 for esters. How these differences can be useful when trying to identify gas chromatography peaks is also discussed. Sensory evaluations showed that aroma response is changed when salt is added to the juice, resulting in an increased aroma intensity and off-aroma. Fruit aroma was not affected. A comparison of the sensory responses with headspace gas chromatographic measurements indicates that increase in off-aroma can be related to the increase in alcohol percentage in the headspace. From these results it can be noted that, when attempting to correlate sensory scores with aroma component concentrations as measured by headspace gas chromatography, it is most important that the test conditions utilized for each analysis correspond as closely as possible with each other.

Changes in the composition of aromatic compounds and other quality parameters of strawberries during freezing and thawing

Six strawberry cultivars were analysed, as fresh and as frozen and thawed fruit, for their content of anthocyanins, ascorbic acid, titratable acid, soluble solids and aromatic compounds. During freezing and thawing the content of titratable acid and soluble solids remained constant, whereas the content of anthocyanins and ascorbic acid decreased. The composition of aromatic compounds was also changed during freezing and thawing and greatest decreases were found fortrans-2-hexenal and hexanol. The content of volatile acids, linalool and methyl hexanoate was doubled after freezing and thawing, and, for all cultivars except from Pandora and Dania, ethyl butanoate and ethyl hexanoate increased strongly. This cultivar-dependent ethyl ester formation occurred during thawing rather than during freezing.

Effect of irradiation and storage on the composition of volatile compounds in basil (Ocimum basilicum L.)

The influence of γ and β-irradiation and storage time on the composition of the volatile compounds in basil (Ocimum basilicum L.) has been examined. Dried basil was exposed to γ- and β-rays at the doses of 3, 10 and 30 kGy, and volatile components were isolated by simultaneous distillation-extraction in a Likens-Nickerson apparatus. Sixty-five compounds were identified in the extracts and quantitatively evaluated; the major component was methylchavicol (88%). Quantitatively important volatile compounds in basil were found to be reduced during storage. Only slight (not significant) differences in the content of some constituents, including methyl-chavicol, methyleugenol and 1,8-cineole were found between irradiated and non-irradiated basil herb.