T.B. Toldam-Andersen

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.

Instrumental and sensory characterisation of Solaris white wines in Denmark

This study aimed to investigate the volatile and non-volatile compositions as well as sensory properties of the most common monovarietal white wine (var. Solaris) in Denmark. Using dynamic headspace sampling (DHS) coupled to gas chromatography-mass spectrometry (GC-MS), 79 volatile compounds were identified. Among the major non-volatile components glycerol, sulphite, sugars and organic acids were analysed. A primary sensory difference was observed among wine samples, half of which were characterised by floral and fruity flavours (peach/apricot, Muscat, melon, banana and strawberry) while the remainder were described by less pleasant flavours, such as chemical, wood and rooibos/smoke. Partial least squares regression (PLS) showed that acetates and ethyl esters of straight-chain fatty acids were associated with floral and fruity odours while ethyl esters of branched-chain fatty acids were less associated with them. The study also suggested that differences in vintage were less characteristic than differences caused due to sulphite management by producers.

Influence of growing conditions at different latitudes of Europe on strawberry growth performance, yield and quality

The site effect of five locations from north (Stjordal, Norway, 63 ◦ 36 � N) to south (Ancona, Italy, 43 ◦ 31 � N) was evaluated in strawberry regarding yield performance, fruit quality, length of fruit developing time from anthesis to harvest start and length of the harvest season. Cv. Elsanta was grown at all sites while cv. Korona was cultivated in north and central Europe and cv. Clery in central and south Europe. Yield was more affected by seasonal and growing conditions than by latitude. Anthesis was delayed as influenced by cultivar up to 58 days from south to north and was nearly maintained until harvest start. Duration of fruit development was negatively related to daily mean temperature and increased with higher latitude. 29-34 days were required from anthesis to harvest start for cv. Elsanta, 29-36 for cv. Korona and 27-38 for cv. Clery. Corresponding GDD values (growing degree days; 3 ◦ C base temperature) were independent from latitude and accounted to 334-355 for cv. Elsanta, 301-385 for cv. Korona and 320-434 for cv. Clery. Daily mean temperature decreased about 2 ◦ C from south to north during anthesis to harvest start which induced a calculated 5.2 days longer fruit development period in the north. From harvest start to harvest end, GDD values varied for all cultivars between 297-402 GDD showing no influence of the latitude. However, simple summing of GDD values do not correctly describe the time of fruit development (from anthesis to the ripe fruit) for the whole fruiting period of a plant. GDDs for individually tagged flowers increased notably from the first third to the last third of the developing period due to increasing temperature as the season proceeded. The fruit quality standards dry matter, soluble solids and titratable acidity were influenced by latitude giving northern sites in general the highest values. Fruits grown at the southern sites were redder compared to those of the north.

Yeast species associated with different wine grape varieties in Denmark

Abstract Yeasts naturally occurring on different grape varieties, grown in Denmark, were isolated from two interspecific grape varieties and one hybrid in the years 2008 and 2009 from three different vineyards. The analysed grapes harbored a total yeast plate count of 103–104 CFU/ml. A total of 200 isolates were grouped according to their rep-PCR profiles and representative isolates identified by sequencing of the 26S rRNA D1/D2 region and selected phenotypic tests. The yeast microflora on the grapes was dominated by non-Saccharomyces yeasts. Twelve different yeast species belonging to six genera were detected, including Rhodotorula fujisanensis, Rhodotorula glutinis, Rhodotorula nothofagi, Cryptococcus carnescens, Cryptococcus festucosus, Cryptococcus spp., Cryptococcus victoriae, Cryptococcus wieringae, Hanseniaspora uvarum, Metschnikowia fructicola, Kazachstania servazzii and Sporobolomyces roseus and the yeast-like ascomycetous fungi, Aureobasidium pullulans. To our knowledge, this study is the first of its kind reporting on the yeast composition of grapes grown in Denmark, and thus providing important information for the production of high-quality Danish wines.

Influence of Pre-Fermentation Treatments on Wine Volatile and Sensory Profile of the New Disease Tolerant Cultivar Solaris

Solaris is a new disease tolerant cultivar increasingly cultivated in cool climate regions. In order to explore the winemaking processes’ potential to make different styles of Solaris wines, the effects of different pre-fermentation treatments (direct press after crushing, whole cluster press, cold maceration, and skin fermentation) on the volatile profile, chemical, and sensory properties of Solaris wines were investigated. Cold maceration treatment for 24 h and fermentation on skin led to wines with lower acidity and higher glycerol and total polyphenol indexes. Sensory analysis showed that cold maceration enhanced “apricot” and “apple” flavor while skin fermentation gave rise to increased “rose” and “elderflower” flavor. The PLS regression model revealed that fruity flavor of cold macerated wines was related to a combination of esters while β-damascenone and linalool were correlated to the “rose” and “elderflower” flavor. This study provides information about pre-fermentation techniques that allowed the possibility of obtaining wines with different styles.

Impact of sequential co-culture fermentations on flavour characters of Solaris wines

Nowadays, the use of non-Saccharomyces yeasts in combination with Saccharomyces cerevisiae is being recognised to enhance the analytical composition of the wines. The aim of this work was to evaluate the influence of indigenous non-Saccharomyces yeasts on the flavour character of wines from the cool-climate grape cultivar Solaris in Denmark. The volatile and non-volatile compounds as well as the sensory properties of wines were evaluated. Solaris wines with Hanseniaspora uvarum sequentially inoculated with S. cerevisiae produced a larger amount of glycerol as well as heptyl acetate and 2-phenylethyl acetate. This co-culture fermentation also produced higher amounts of ethyl acetate and acetic acid, reducing the possibility of its use in winemaking. Three Metschnikowia strains, a M. chrysoperlae strain and two M. fructicola strains, gave a comparable production of volatile compounds. These wines were characterised by several floral and fruity attributes. The Metschnikowia strains turned out to be promising in winemaking from Solaris grapes.

Effect of sequential fermentations and grape cultivars on volatile compounds and sensory profiles of Danish wines

BACKGROUND There has been an increasing interest in the use of selected non-Saccharomyces yeasts in co-culture with Saccharomyces cerevisiae. In this work, three non-Saccharomyces yeast strains (Metschnikowia viticola, Metschnikowia fructicola and Hanseniaspora uvarum) indigenously isolated in Denmark were used in sequential fermentations with S. cerevisiae on three cool-climate grape cultivars, Bolero, Rondo and Regent. During the fermentations, the yeast growth was determined as well as key oenological parameters, volatile compounds and sensory properties of finished rosé wines. RESULTS The different non-Saccharomyces strains and cool-climate grape cultivars produced wines with a distinctive aromatic profile. A total of 67 volatile compounds were identified, including 43 esters, 14 alcohols, five acids, two ketones, a C13-norisoprenoid, a lactone and a sulfur compound. The use of M. viticola in sequential fermentation with S. cerevisiae resulted in richer berry and fruity flavours in wines. The sensory plot showed a more clear separation among wine samples by grape cultivars compared with yeast strains. CONCLUSION Knowledge on the influence of indigenous non-Saccharomyces strains and grape cultivars on the flavour generation contributed to producing diverse wines in cool-climate wine regions.

Unravelling genetic diversity and cultivar parentage in the Danish apple gene bank collection

Characterization of apple germplasm is important for conservation management and breeding strategies. A set of 448 Malus domestica accessions, primarily of local Danish origin, were genotyped using 15 microsatellite markers. Ploidy levels were determined by flow cytometry. Special emphasis was given to pedigree reconstruction, cultivar fingerprinting and genetic clustering. A reference set of cultivars, mostly from other European countries, together with a private nursery collection and a small set of Malus sieversii, Malus sylvestris and small-fruited, ornamental Malus cultivars, was also included. The microsatellite markers amplified 17–30 alleles per loci with an average degree of heterozygosity at 0.78. We identified 104 (23%) duplicate genotypes including colour sports. We could infer first-degree relationships for many cultivars with previously unknown parentages. STRUCTURE analysis provided no evidence for a genetic structure but allowed us to present a putative genetic assembly that was consistent with both PCA analysis and parental affiliation. The Danish cultivar collection contains 10% duplicate genotypes including colour sports and 22% triploids. Many unique accessions and considerable genetic diversity make the collection a valuable resource within the European apple germplasm. The findings presented shed new light on the origin of Danish apple cultivars. The fingerprints can be used for cultivar identification and future management of apple genetic resources. In addition, future genome-wide association studies and breeding programmes may benefit from the findings concerning genetic clustering and diversity of cultivars.

An assessment of Osmia rufa (syn. bicornis) as a pollinator of the sour cherry (Prunus cerasus) cv. Stevnsbaer in eastern Denmark

Summary The sour cherry (Prunus cerasus) cv. Stevnsbaer is self-fertile but it is recommended that bees are placed in the orchards during flowering. The solitary bee Osmia rufa can be managed, and has previously been suggested as an alternative pollinator to Apis mellifera, so consequently, this study investigates the activity and food preferences of this species during flowering of sour cherry (P. cerasus cv. Stevnsbaer). Female O. rufa provisioned a mean of 2.96 ± 1.44 cells each with 6.24 ± 1.46 pollen types during the receptive period of flowering. In all 17 different pollen types were collected of which the most dominant were Salix(41.4% ± 9.34%) and Acer (33.24% ± 8.81%), followed by Betula (8.16% ± 5.08%), P. cerasus (8.16% ± 1.79%) and Fagus (3.56% ± 1.96%). P. cerasus was present in all samples. Nine pollen types were from anemophilous plants and represented 87.94% of the pollen collected. The remaining 8 pollen types were from entomophilous plants. Based on the results it is estimated that a mean of 220,000 O. rufa cocoons would be needed per hectare if the species were to be an effective, supplementary pollinator of P. cerasus cv. Stevnsbaer. Practical, economic and environmental considerations suggest that the use of O. rufa as an alternative pollinator to A. mellifera in this instance is not realistic.

Aroma Analysis and Data Handling in the Evaluation of Niche Apple Juices from 160 Local Danish Apple Cultivars

Old Danish apple cultivars might have potential in the production of speciality apple juices with unique flavor qualities. In the present study, aroma analysis was performed on juices from 160 local apple cultivars. Chromatographic data treatment challenges in the analysis of this large number of samples with very different volatile profiles were overcome with PARAFAC2 and PCA. The main compound groups identified were acetate esters, butanoate esters, and alcohols, and there were large differences in the aroma profiles of the juices of the different apple cultivars.