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Effective sulfur dioxide (SO2) management is crucial in winemaking to minimize oxidative changes in wine flavor during storage. This study explored the impact of various SO2 management techniques on Solaris white wine’s flavor components and sensory properties. Five treatments were administered: ‘SO2 in juice’ (50 mg/L SO2 added to juice pre-fermentation), ‘Control’ (60 mg/L SO2 added post-fermentation), ‘Low SO2’ (50 mg/L SO2 post-fermentation), ‘High SO2’ (100 mg/L SO2 post-fermentation), and ‘No SO2’ (no SO2 added). The ‘Control’ followed a standard procedure, in which the achieved level of free sulfite is measured and extra SO2 added to reach the recommended level of free sulfite for the pH of the wine. Here, 50 + 10 mg/L was added. Volatile compounds were analyzed using dynamic headspace sampling coupled with gas chromatography–mass spectrometry after 0, 3, 6, and 12 months of storage. Sensory evaluation by a trained panel after 12 months revealed stronger perceptions of ‘overall impression’, ‘chemical’, ‘bitter’, ‘overripe fruit’, and ‘honey’ notes in the ‘No SO2’ and ‘SO2 in juice’ wines. The data underscore the significant influence of SO2 management on the flavor stability of Solaris white wines, emphasizing the need for strategic SO2 interventions during winemaking to enhance sensory quality over time.

The market of non-alcoholic and low-alcohol beer has grown continuously thanks to the advocacy for healthy and responsible drinking. Non-alcoholic and low-alcohol products usually possess less higher alcohols and acetates and more aldehyde off-flavors due to the manufacturing processes. The employment of non-conventional yeasts partially mitigates this problem. In this study, we used proteases to optimize the wort amino acid profile for better aroma production during yeast fermentation. The design of experiments was applied to increase the leucine molar fraction, aiming to boost 3-methylbutan-1-ol and 3-methylbutyl acetate (banana-like aromas). This led to an increase from 7% to 11% leucine in wort after protease treatment. The aroma output in the subsequent fermentation, however, was yeast-dependent. An 87% increase of 3-methylbutan-1-ol and a 64% increase of 3-methylbutyl acetate were observed when Saccharomycodes ludwigii was used. When Pichia kluyveri was employed, higher alcohols and esters from valine and isoleucine were increased: 58% more of 2-methylpropyl acetate, 67% more of 2-methylbutan-1-ol, and 24% more of 2-methylbutyl acetate were observed. Conversely, 3-methylbutan-1-ol decreased by 58% and 3-methylbutyl acetate largely remained the same. Apart from these, the amounts of aldehyde intermediates were increased to a varying extent. The impact of such increases in aromas and off-flavors on the perception of low-alcohol beer remains to be evaluated by sensory analysis in future studies.

The yeast Yarrowia lipolytica is well known for its versatile production of metabolites from various substrates, but, although isolated from, e.g., wild-fermented Belgian Sour beers, it is rarely considered a starter culture in fermented beverages. In this study, we aimed to elucidate the ability of Y. lipolytica to ferment brewers’ wort containing iso-α-acid for 7 days at low and high aeration and at 20 °C and 30 °C, with a special focus on amino acid consumption and production of volatile aroma compounds. Y. lipolytica was able to grow in the wort under all four conditions, although the growth was inhibited. Furthermore, it only consumed glucose and fructose, and no ethanol was formed. Moreover, under high aeration conditions, Y. lipolytica consumed 75–80% of the amino acids in the wort. Interestingly, no esters were produced during the fermentations, and only five higher alcohols (1-propanol, 2-methyl-1-propanol, 3-methyl-1-butanol, 3-methyl-3-buten-1-ol, and 2-phenylethanol), two aldehydes (3-methylbutanal and (E)-2-nonenal), two ketones (cyclopentanone and 9-oxabicyclo [6.1.0]nonan-4-one), one fatty acid (3-methyl-butanoic acid), and one benzene derivate (1,2,4-trimethyl-benzene) were produced. These results may contribute to the potential use of Y. lipolytica in a traditional brewery for the production of novel beers; e.g., alcohol-free beer.

The antagonistic activities of native Debaryomyces hansenii strains isolated from Danish cheese brines were evaluated against contaminating molds in the dairy industry. Determination of chromosome polymorphism by use of pulsed-field gel electrophoresis (PFGE) revealed a huge genetic heterogeneity among the D. hansenii strains, which was reflected in intra-species variation at the phenotypic level. 11 D. hansenii strains were tested for their ability to inhibit germination and growth of contaminating molds, frequently occurring at Danish dairies, i.e., Cladosporium inversicolor, Cladosporium sinuosum, Fusarium avenaceum, Mucor racemosus, and Penicillium roqueforti. Especially the germination of C. inversicolor and P. roqueforti was significantly inhibited by cell-free supernatants of all D. hansenii strains. The underlying factors behind the inhibitory effects of the D. hansenii cell-free supernatants were investigated. Based on dynamic headspace sampling followed by gas chromatography-mass spectrometry (DHS-GC-MS), 71 volatile compounds (VOCs) produced by the D. hansenii strains were identified, including 6 acids, 22 alcohols, 15 aldehydes, 3 benzene derivatives, 8 esters, 3 heterocyclic compounds, 12 ketones, and 2 phenols. Among the 71 identified VOCs, inhibition of germination of C. inversicolor correlated strongly with three VOCs, i.e., 3-methylbutanoic acid, 2-pentanone as well as acetic acid. For P. roqueforti, two VOCs correlated with inhibition of germination, i.e., acetone and 2-phenylethanol, of which the latter also correlated strongly with inhibition of mycelium growth. Low half-maximal inhibitory concentrations (IC50) were especially observed for 3-methylbutanoic acid, i.e., 6.32–9.53 × 10–5 and 2.00–2.67 × 10–4 mol/L for C. inversicolor and P. roqueforti, respectively. For 2-phenylethanol, a well-known quorum sensing molecule, the IC50 was 1.99–7.49 × 10–3 and 1.73–3.45 × 10–3 mol/L for C. inversicolor and P. roqueforti, respectively. For acetic acid, the IC50 was 1.35–2.47 × 10–3 and 1.19–2.80 × 10–3 mol/L for C. inversicolor and P. roqueforti, respectively. Finally, relative weak inhibition was observed for 2-pentanone and acetone. The current study shows that native strains of D. hansenii isolated from Danish brines have antagonistic effects against specific contaminating molds and points to the development of D. hansenii strains as bioprotective cultures, targeting cheese brines and cheese surfaces.

This study investigated the spoilage potential of yeast strains Kluyveromyces marxianus (Km1, Km2 and Km3), Pichia kudriavzevii Pk1 and Torulaspora delbrueckii Td1 grown in skyr in cold storage. Yeast strains were isolated from skyr and identified by sequencing of the 26S rRNA gene. K. marxianus yeasts were grown in skyr to high numbers, generating large amounts of volatile organic compounds (VOC) associated with off-flavours, among them were alcohols (3-methyl-1-butanol, 2-methyl-1-propanol and 1-hexanol), esters (ethyl acetate and 3-methylbutyl acetate) and aldehydes (hexanal, methylbutanal and methylpropanal). Growth of P. kudriavzevii Pk1 led to moderate increases in several alcohols and esters (mostly, 3-methyl-1-butanol and ethyl acetate), whereas only minor shifts in VOCs were associated with T. delbrueckii Td2. The levels of the key aroma compounds, diacetyl and acetoin, were significantly decreased by all K. marxianus strains and P. kudriavzevii Pk1. In contrast to the other yeast species, K. marxianus was able to utilize lactose, producing ethanol and carbon dioxide. Based on the overall results, K. marxianus was characterised by the highest spoilage potential. The study revealed the differences between the yeast species in fermentative and spoilage activities, and clarified the role of yeast metabolites for off-flavour formation and quality defects in skyr during cold storage.

Fresh roselle are high in moisture and deteriorate easily, which makes drying important for extending shelf-life and increasing availability. This study investigated the influence of different drying methods (oven-drying, freeze-drying, vacuum-drying, and sun-drying) on the quality of roselle calyx expressed as physicochemical properties (moisture content, water activity, soluble solids, color), volatile compounds, and microstructure. Oven-drying and freeze-drying reduced moisture content most while vacuum-drying and sun-drying were not as efficient. All drying methods except sun-drying resulted in water activities low enough to ensure safety and quality. Vacuum-drying had no impact on color of the dry calyx and only small impact on color of water extract of calyx. Drying reduced terpenes, aldehydes, and esters but increased furans. This is expected to reduce fruity, floral, spicy, and green odors and increase caramel-like aroma. Sun-drying produced more ketones, alcohols, and esters. Scanning electron microscopy revealed that freeze-drying preserved the cell structure better, and freeze-dried samples resembled fresh samples most compared to other drying techniques. The study concludes that freeze-drying should be considered as a suitable drying method, especially with respect to preservation of structure.

Understanding the genetic architecture of fruit quality traits is crucial to target breeding of apple ( L.) cultivars. We linked genotype and phenotype information by combining genotyping-by-sequencing (GBS) generated single nucleotide polymorphism (SNP) markers with fruit flavor volatile data, sugar and acid content, and historical trait data from a gene bank collection. Using gas chromatography–mass spectrometry (GC-MS) analysis of apple juice samples, we identified 49 fruit volatile organic compounds (VOCs). We found a very variable content of VOCs, especially for the esters, among 149 apple cultivars. We identified convincing associations for the acetate esters especially butyl acetate and hexyl acetate on chromosome 2 in a region of several alcohol acyl-transferases including AAT1. For sucrose content and for fructose and sucrose in percentage of total sugars, we revealed significant SNP associations. Here, we suggest a vacuolar invertase close to significant SNPs for this association as candidate gene. Harvest date was in strong SNP association with a NAC transcription factor gene and sequencing identified two haplotypes associated with harvest date. The study shows that SNP marker characterization of a gene bank collection can be successfully combined with new and historical trait data for association studies. Suggested candidate genes may contribute to an improved understanding of the genetic basis for important traits and simultaneously provide tools for targeted breeding using marker-assisted selection (MAS).

The specialty coffee industry is growing and, as a result, there is an accelerated interest in modulating roast profiles to present customers with new and diverse sensory experiences. The present study investigates the chemical and sensory effects of subtle variations in the ‘development time’ phase of the coffee roasting process. Four roast profiles were studied through sensory descriptive analysis (DA), gas chromatography–mass spectrometry (GC–MS), and nuclear magnetic resonance (NMR). Multivariate analysis showed clear separation of DA, GC–MS, and NMR data. A prolonged development time facilitated a statistically significant shift in the chemical and sensory profile of the coffee. The findings suggest that a short development time increases the fruity, sweet and acidic characteristics of the coffee, whereas a longer development time shifts the balance towards a more roasty, nutty, and bitter profile. The results provide evidence that supports the effect of subtle roast profile modulations. This lays a strong foundation for the inclusion of development time as a critical control parameter in the certification system of the Specialty Coffee Association, quality control, and product development strategies.

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.

In recent decades, intensive selective breeding programs have allowed the development of disease-resistant and flavorsome apple cultivars while leading to a gradual decline of a large number of ancient varieties in many countries. However, the re-evaluation of such cultivars could lead to the production new apple-based products with health beneficial properties and/or unique flavor qualities. Herein, we report the comprehensive characterization of juices obtained from 86 old, mostly Danish, apple cultivars, by employing traditional analysis (ion chromatography, °Brix, headspace gas chromatography/mass spectrometry (GC−MS), and panel test evaluation) as well as an innovative nuclear magnetic resonance (NMR)-based screening method developed by Bruker for fruit juices, known as Spin Generated Fingerprint (SGF) Profiling™. Principal component analysis showed large differences in aroma components and sensory characteristics, including odd peculiar odors and flavors such as apricot and peach, and very different levels of phenolic compounds, acids and sugars among the analyzed juices. Moreover, we observed a tendency for late-season juices to be characterized by higher °Brix values, sugar content and they were perceived to be sweeter and more flavor intense than early-season juices. Our findings are useful for the production of specialty vintage-cultivar apple juices or mixed juices to obtain final products that are characterized both by healthy properties and peculiar sensory attributes.

There is a growing market for the use of hydrolysates from animal side-streams for production of high-protein supplements. However, there can be issues with development of off-flavors, either due to the raw material in question or due to the hydrolysis process itself. This study examined the development of volatile compounds during hydrolysis of hemoglobin. Briefly, porcine hemoglobin was hydrolyzed by 0.5% papain for up to 5 h, and the development of volatile compounds was analyzed via gas chromatography-mass spectrometry. The results showed that there was significant development of a number of volatile compounds with time, e.g., certain Maillard reaction and lipid oxidation products, which are likely candidates for the aroma development during hydrolysis. Furthermore, it was shown that development of a number of the volatiles was due to the hydrolysis process, as these compounds were not found in a control without enzyme.

Milled Roselle (Hibiscus sabdariffa L.) seeds of the UMKL cultivar were analyzed for proximate composition, water and oil absorption capacity, and the influence of storage conditions on storage stability. The storage stability was determined under four types of conditions: light/oxygen (air) (LO), light/nitrogen (LN), darkness/oxygen (air) (DO), and darkness/nitrogen (DN) while monitoring for seven consecutive months. During the storage period, the formation of volatiles was determined using dynamic headspace sampling and Gas Chromatography-Mass Spectrometry (GC-MS) analysis. In total, 85 volatiles were identified, mainly aldehydes, alcohols, ketones, furans, and acids indicating lipid oxidation. It is recommended that milled Roselle seeds should be flushed with nitrogen and stored in darkness. Under these conditions, the seeds can be stored for at least three months without changes in volatile profile. This is important to ensure the good quality of milled Roselle seeds for further commercialization.