Mikael Agerlin Petersen

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.

Comprehensive analysis of chromatographic data by using PARAFAC2 and principal components analysis.

The most straightforward method to analyze an obtained GC-MS dataset is to integrate those peaks that can be identified by their MS profile and to perform a Principal Component Analysis (PCA). This procedure has some important drawbacks, like baseline drifts being scarcely considered or the fact that integration boundaries are not always well defined (long tails, co-eluted peaks, etc.). To improve the methodology, and therefore, the chromatographic data analysis, this work proposes the modeling of the raw dataset by using PARAFAC2 algorithm in selected areas of the GC profile and using the obtained well-resolved chromatographic profiles to develop a further PCA model. With this working method, not only the problems arising from instrumental artifacts are overcome, but also the detection of new analytes is achieved as well as better understanding of the studied dataset is obtained. As a positive consequence of using the proposed working method human time and work are saved. To exemplify this methodology the aroma profile of 36 apples being ripened were studied. The benefits of the proposed methodology (PARAFAC2+PCA) are shown in a practitioner perspective, being able to extrapolate the conclusions obtained here to other hyphenated chromatographic datasets.

Differential transfer of dietary flavour compounds into human breast milk

Transfer of dietary flavour compounds into human milk is believed to constitute the infants early flavour experiences. This study reports on the time-dependent transfer of flavour compounds from the mothers diet to her breast milk using a within-subject design. Eighteen lactating mothers completed three test days on which they provided a baseline milk sample prior to ingestion of capsules containing 100 mg d-carvone, l-menthol, 3-methylbutyl acetate and trans-anethole. Milk samples were collected 2, 4, 6 and 8 h post-ingestion and analysed by a dynamic headspace method and gas chromatography-mass spectroscopy. The recovery quantities were adjusted for variations in milk fat content. Concentration-time profiles for d-carvone and trans-anethole revealed a maximum around 2 h post-ingestion, whereas the profile for l-menthol showed a plateau pattern. The ester 3-methylbutyl acetate could not be detected in the milk, but a single determination showed traces (<0.4 ppb) in a 1 h milk collection. Flavour compounds appeared to be transmitted differentially from the mothers diet to her milk. The results imply that human milk provides a reservoir for time-dependent chemosensory experiences to the infant; however, volatiles from the diet are transferred selectively and in relatively low amounts.

Influence of sous vide processing, steaming and boiling on vitamin retention and sensory quality in broccoli florets.

ZusammenfassungBei dieser Untersuchung wurde untersucht, in welchem Ausmaß das Sous-Vide-Kochen, Dämpfen und das übliche Kochen von Broccoli-Sträußchen einen Einfluß auf die Retention der Ascorbinsäure bzw. Vitamin-B6 und Folsäure hat. Frisch hergestellte Proben wurden ebenfalls sensorisch beurteilt. Bei allen Arten der Wärmebehandlung ergab sich, daß die Ascorbinsäure die höchste Retention hatte und daher als ungeeigneter Indikator einer Vitaminretention im allgemeinen ist. Bei Vergleich der drei Arten der Wärmebehandlung hat sich erwiesen, daß das Kochen die niedrigste Retention aller geprüften Vitamine (45–64% in 5 min) ergab, das Sous-Vide-Kochen dagegen die höchste Retention (97–100% in 5 min). Beim Dämpfen war die Retention etwas niedriger (83–100% in 5 min). Die sensorischen Bewertungen zeigten, daß sous-vide-gekochte sowie gedämpfte Broccoli-Sträußchen allgemein von besserer Qualität waren als die gekochten.AbstractIn this study the effect of sous vide processing, steaming and traditional boiling of broccoli florets on retention of ascorbic acid, vitamin B6 and folacin was investigated. Freshly prepared samples were also sensorily evaluated. In all heat treatments ascorbic acid was found to have the highest retention, and was therefore judged not to be suitable as an indicator for vitamin retention in general. When the three types of heat treatment were compared, boiling showed lowest retention of all the vitamins examined (45–64% in 5 min), whereas sous-vide processing gave the highest retentions (97–100% in 5 min). Retentions during steaming were a little lower (83–100% in 5 min). Sensory evaluation showed that sous-vide cooked and steamed broccoli florets generally had higher acceptability than boiled.

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.

Ghanaian cocoa bean fermentation characterized by spectroscopic and chromatographic methods and chemometrics.

Export of cocoa beans is of great economic importance in Ghana and several other tropical countries. Raw cocoa has an astringent, unpleasant taste, and flavor, and has to be fermented, dried, and roasted to obtain the characteristic cocoa flavor and taste. In an attempt to obtain a deeper understanding of the changes in the cocoa beans during fermentation and investigate the possibility of future development of objective methods for assessing the degree of fermentation, a novel combination of methods including cut test, colorimetry, fluorescence spectroscopy, NIR spectroscopy, and GC-MS evaluated by chemometric methods was used to examine cocoa beans sampled at different durations of fermentation and samples representing fully fermented and dried beans from all cocoa growing regions of Ghana. Using colorimetry it was found that samples moved towards higher a* and b* values as fermentation progressed. Furthermore, the degree of fermentation could, in general, be well described by the spectroscopic methods used. In addition, it was possible to link analysis of volatile compounds with predictions of fermentation time. Fermented and dried cocoa beans from the Volta and the Western regions clustered separately in the score plots based on colorimetric, fluorescence, NIR, and GC-MS indicating regional differences in the composition of Ghanaian cocoa beans. The study demonstrates the potential of colorimetry and spectroscopic methods as valuable tools for determining the fermentation degree of cocoa beans. Using GC-MS it was possible to demonstrate the formation of several important aroma compounds such 2-phenylethyl acetate, propionic acid, and acetoin and the breakdown of others like diacetyl during fermentation. Practical Application: The present study demonstrates the potential of using colorimetry and spectroscopic methods as objective methods for determining cocoa bean quality along the processing chain. Development of objective methods for determining cocoa bean quality will be of great importance for quality insurance within the fields of cocoa processing and raw material control in chocolate producing companies.

REVIEW: Aroma of Wheat Bread Crumb

ABSTRACT Bread aroma is an important parameter for bread quality, and this review aims to provide an overview of aroma compounds identified in bread crumb and how these compounds are formed. More than 150 volatile compounds were identified in bread crumb, and they mainly originated from the fermentative activity of yeast, from oxidation of flour lipids, and to a lower extent from Maillard reactions. Of those volatile compounds, 45 compounds can be characterized as aroma compounds, because they most likely can be sensed when the bread is eaten because of their high odor activity values and flavor dilution factors. The influence of ingredients and mixing conditions on bread aroma has scarcely been investigated. The fermentation conditions (yeast level and strain as well as fermentation temperature and time) were found to significantly influence the aroma of bread crumb. Yeast level and strain mainly influence formation of compounds directly related to the fermentative activity of yeast, whereas fermentation...

Sensory based quality control utilising an electronic nose and GC-MS analyses to predict end-product quality from raw materials

The objective of the present study was to investigate if an electronic nose, comprising six metal oxide sensors (MOS) could predict the sensory quality of porcine meat loaf, based on measuring the volatiles in either the raw materials or the meat loaf produced from those raw materials. A multivariate data analysis strategy involving analysis of variance partial least squares regression (APLSR) and principal component analysis (PCA) was used to determine causal and predictive relationships between the raw material and meat loaf samples, sensory analysis, electronic nose, and GC-MS measurements. The results showed that the six MOS sensors in the Danish odour sensor system (DOSS) could detect the raw materials that led to unacceptable products, as determined by sensory profiling and in-house sensory quality control (QC), and separate those raw materials from each other, based on the volatile composition, as determined by GC-MS. However, the electronic nose was unable to detect all the sensory unacceptable meat loaf samples themselves due to changes in the volatile composition after cooking. Analysis of the GC-MS compounds identified from raw materials and meat loaf samples indicate that two MOS sensors mainly responded to alcohols and to a lesser degree to aldehydes and alkanes, whereas two other sensors most likely responded to low molecular weight sulphur compounds. Thus, the results indicate that measuring volatiles with the MOS sensors in the DOSS system, on raw materials for processed meat products, may be a feasible strategy in sensory based quality control, and may also have potential in predicting the sensory quality of the end product.

Potential use of electron spin resonance spectroscopy for evaluating the oxidative status of potato flakes

During storage for up to 52 weeks, under mildly accelerated conditions (22 °C, atmospheric air), potato flakes (1% lipid, dried to aw=0.4) were found to undergo oxidative changes as indicated by a slight decrease in headspace oxygen. The headspace concentration of hydrocarbons (ethane and pentane) steadily increased during storage, and the increase was reduced with added antioxidants. For a product without added antioxidants, three short-chain aldehydes increased slightly, but other secondary oxidation products did not change significantly (including thiobarbituric acid reactive substances). Long chain aldehydes (identified by GC–MS) were abundant in fresh products, but decreased during storage. The level of free radicals, as a marker of early events in oxidation and measured directly by electron spin resonance spectroscopy (ESR), increased significantly during the first 2 weeks of storage, followed by a marked decrease for the period of 2–22 weeks of storage to reach a steady state level. Throughout the period of storage, ESR spectrometry was able to rank products protected by natural antioxidant extracts according to increasing level of free radicals: Unprotected>Coffee>Green tea, Grape skin>Rosemary. Hydrocarbons evolved according to a similar pattern and it can be concluded that ESR spectrometry provides a method for detecting early stages of oxidation in this type of low fat dried products.

Influence of malt roasting on the oxidative stability of sweet wort.

Influence of malt roasting on the oxidative stability of sweet wort was evaluated based on radical intensity, volatile profile, content of transition metals (Fe and Cu) and thiols. Malt roasting had a large influence on the oxidative stability of sweet wort. Light sweet worts were more stable with low radical intensity, low Fe content, and ability to retain volatile compounds when heated. At mild roasting, the Fe content in the wort increased but remained close to constant with further roasting. Dark sweet worts were less stable with high radical intensities, high Fe content, and a decreased ability to retain volatiles. Results suggested that the Maillard reaction compounds formed during the roasting of malt are prooxidants in sweet wort. A thiol-removing capacity was observed in sweet wort, and it was gradually inhibited by malt roasting. It is possibly caused by thiol oxidizing enzymes present in the fresh malt.