Astringent Food Compounds and Their Interactions with Taste Properties

Astringency is traditionally thought to be induced by plant tannins in foods. Because of this current research concerning the mechanism of astringency is focused on tannin‐protein interactions and thus on precipitation, which may be perceived by mechanoreceptors. However, astringency is elicited by a wide range of different phenolic compounds, as well as, some non‐phenolic compounds in various foods. Many ellagitannins or smaller compounds that contribute to astringent properties do not interact with salivary proteins and may be directly perceived through some receptors. Generally, the higher degree of polymerization of proanthocyanidins can be associated with more intense astringency. However, the astringent properties of smaller phenolic compounds may not be directly predicted from the structure of a compound, although glycosylation has a significant role. The astringency of organic acids may be directly linked to the perception of sourness, and this increases along with decreasing pH. Astringency can be divided into different sub‐qualities, including even other qualities than traditional mouth‐drying, puckering or roughing sensations. Astringency is often accompanied by bitter or sour or both taste properties. The different sub‐qualities can be influenced by different astringent compounds. In general, the glycolysation of the phenolic compound results in more velvety and smooth mouthdrying astringency. Flavonol glycosides and other flavonoid compounds and ellagitannins contribute to this velvety mouthdrying astringency. Additionally, they often lack the bitter properties. Proanthocyanidins and phenolic acids elicit more puckering and roughing astringency with some additional bitter properties. Quercetin 3‐O‐rutinoside, along with other quercetin glycosides, is among the key astringent compounds in black tea and red currants. In foods, there are always various other additional attributes that are perceived at the same with astringency. Astringent compounds themselves may have other sensory characteristics, such as bitter or sour properties, or they may enhance or suppress other sensory properties. Components contributing to these other properties, such as sugars, may also have similar effects on astringent sensations. Food components eliciting sweetness or fattiness or some polymeric polysaccharides can be used to mask astringent subqualities. Astringency can generally be referred to as a negative contributor to the liking of various foods. On the other hand, perceptions of astringent properties can vary among individuals. Many genetic factors that influence perceptions of taste properties, such as variations in perceiving a bitter taste or variations in saliva, may also effect the perception of astringency. Individuals who are more sensitive to different sensations may notice the differences between astringent properties more clearly. This may not have effects on the overall perception of astringency. However, in many cases, the liking of astringent foods may need to be learned by repetitive exposure. Astringency is often among the key sensory properties forming the unique overall flavour of certain foods, and therefore it also influences whether or not a food is liked. In many cases, astringency may be an important sub‐property suppressed by other more abundant sensory properties, but it may still have a significant contribution to the overall flavour and thus consumer preferences. The results of the practical work of this thesis show that the astringent phenolic compounds are mostly located in the skin fractions of black currants, crowberries and bilberries (publications I–III). The skin fractions themselves are rather tasteless. However, the astringent phenolic compounds can be efficiently removed from these skin fractions by consecutive ethanol extractions. Berries contain a wide range of different flavonol glycosides, hydroxycinnamic acid derivatives and anthocyanins and some of them strongly contribute to the different astringent and bitterness properties. Sweetness and sourness are located in the juice fractions along with the majority of sugars and fruit acids. The sweet and sour properties of the juice may be used to mask the astringent and bitterness properties of the extracts. Enzymatic treatments increase the astringent properties and fermented flavour of the black currant juice and decrease sweetness and freshness due to the effects on chemical compositions (IV). Sourness and sweetness are positive contributors to the liking of crowberry and bilberry fractions, whereas bitterness is more negative (V). Some astringent properties in berries are clearly negative factors, whereas some may be more positive. The liking of berries is strongly influenced by various consumer background factors, such as motives and health concerns. The liking of berries and berry fractions may also be affected by genetic factors, such as variations in the gene hTAS2R38, which codes bitter taste receptors (V).Siirretty Doriast

Impact of malolactic fermentation with Lactobacillus plantarum on volatile compounds of sea buckthorn juice

Malolactic fermentation using sea buckthorn (Hippophaë rhamnoides) juice as raw material was performed with six different strains of Lactobacillus plantarum. Increasing juice pH from 2.7 to 3.5 or adapting cells to low pH (i.e. acclimation) prior to inoculation allowed malolactic fermentation with all tested strains. Moreover, reducing pH of the growth medium from 6 to 4.5 with l-malate had little or no impact on biomass production. Volatile profile of sea buckthorn juice was analyzed with HS-SPME-GC-MS before and after fermentation. A total of 92 volatiles were tentatively identified and semi-quantified in sea buckthorn juice, majority of which were esters with fruity odor descriptors. Esters and terpenes with mainly fruity descriptors were decreased in both inoculated and control juices. Microbial activity increased the levels of acetic acid (vinegar-like), free fatty acids (cheese-like), ketones (buttery-like), and alcohols with fruity descriptors. Conversely, aldehydes associated with “green” aroma were decreased as a result of fermentation. Juices fermented with DSM 1055 had the highest acid and alcohol content while fermentation with DSM 13273 resulted in the highest content of ketones. Compared to inoculation with other strains, fermentation with strains DSM 16365 and DSM 100813 resulted in rapid malolactic fermentation, less volatile acids, and lower loss of esters and terpenes important for natural sea buckthorn flavor.</p

Proceedings of the 16th Weurman Flavour Research Symposium

Oats are increasingly popular due to their healthiness, and the number of new different types of oat products on the market is constantly increasing. Oats have higher content of lipids compared to many other grains and therefore their quality and volatile compound profile is susceptible to changes. In this study, selected oat samples were investigated using HS-SPME-GC-O panel and trained sensory panel in order to identify the compounds contributing to the odour characteristics. GC-O panel was trained to describe odours and to evaluate odour intensities of oat samples as flour-water mixtures. The odour and flavour characteristics of the same oat samples were characterised using a sensory panel using generic descriptive analysis. The GC-O panel detected 30 odour-active compounds. The most often described compounds were aldehydes, such as hexanal described as ‘green’ and ‘grassy’, or 3-methylbutanal described as ‘chemical’ and ‘pungent’. At the same time, little differences were observed in ‘green odour’ by the sensory panel, whereas more differences were observed in bitter taste and odour and flavour intensities. </p

Phenolic Compound Profiles in Alcoholic Black Currant Beverages Produced by Fermentation with Saccharomyces and Non-Saccharomyces Yeasts

Alcoholic beverages with low ethanol contents were produced by fermenting black currant juice with Saccharomyces and non-Saccharomyces yeasts without added sugar. The effects of different yeasts on the phenolic compounds (anthocyanins, hydroxycinnamic acids, flavonols, and flavan-3-ols) and other selected constituents (the ethanol content, residual sugars, organic acids, and color) of the black currants were assessed. Single yeast-fermented beverages had higher ethanol contents (3.84−4.47%, v/v) than those produced by sequential fermentation. In general, the fermentation of black currant juice increased the contents of organic acids and flavonols, whereas anthocyanin contents decreased. All of the fermentations decreased the contents of glycosylated nitrilecontaining hydroxycinnamic acids, resulting in higher contents of the corresponding aglycons. Fermentation with Saccharomyces bayanus resulted in lower anthocyanin and organic acid contents compared to the other yeasts. Sequential fermentations with Saccharomyces cerevisiae and Metschnikowia pulcherrima led to the highest total hydroxycinnamic acids and anthocyanins among all of the fermentations.</p

Subjective olfaction and responses to food-related odors

Whether self-rated olfactory acuity influences responses to food odors is unclear. The aim of the study was to clarify relationships among subjective olfactory experience (collected using an online survey) and psychophysical responses to food-related olfactory stimuli (collected at a sensory laboratory). We studied how self-rated olfactory function (0-10) was associated with experienced disturbance from everyday odors (0-5), Affective Impact of Odor scale (AIO, Wrzesniewski et al. 1999), and responses to 12 olfactory stimuli (cinnamaldehyde, cis-3-hexenol, beta-ionone, eugenol, 1-octen-3-ol, thymol, allyl-isothiocyanate, anethol, S-(+)-carvone, limonene, allyl-disulphide, and vanillin). The stimuli were rated for their orthonasally perceived intensity (5-point scale), pleasantness (9-point scale), and identity (free naming, scoring judged by the researchers) by 126 individuals (93 women and 33 men; aged 25-61 years, mean age 39 years). Self-rated olfactory function correlated with the disturbance from everyday odors (r = 0.30; p = 0.001), AIO score (r = 0.32; p < 0.001), mean perceived intensity of the odors (r = 0.31; p = 0.001), and identification score (r = 0.20; p = 0.034), but not with the mean pleasantness of the odors. People who rated their olfactory acuity above average (>=6) also rated the disturbance from everyday odors as higher (p = 0.001) and regarded odors in general as more important for liking/disliking foods/places/cosmetics/people (i.e., scored higher in AIO; p = 0.002). They also rated the sampled olfactory stimuli, on average, as more intense (p < 0.001) and scored higher in odor identification (naming; p = 0.001). Our results suggest that the self-assessed olfactory acuity is associated not only with experienced affective impact of odors, but also with psychophysically measured responses to food-derived olfactory stimuli. </div

Individual Differences in the Perception of Color Solutions

The color of food is important for flavor perception and food selection. The aim of the present study was to evaluate the visual color perception of liquid samples among Finnish adult consumers by their background variables. Participants (n = 205) ranked six different colored solutions just by looking according to four attributes: from most to least pleasant, healthy, sweet and sour. The color sample rated most frequently as the most pleasant was red (37%), the most healthy white (57%), the most sweet red and orange (34% both) and the most sour yellow (54%). Ratings of certain colors differed between gender, age, body mass index (BMI) and education groups. Females regarded the red color as the sweetest more often than males (p = 0.013) while overweight subjects rated the orange as the sweetest more often than normal weight subjects (p = 0.029). Personal characteristics may be associated with some differences in color associations.</p

Chemical Composition of Juices Made from Cultivars and Breeding Selections of European Pear (Pyrus communis L.)

The phenolic profiles and other major metabolites in juices made from fruits of 17 cultivars and selections of European pears were investigated using UHPLC-DAD-ESI-QTOF-MS and GC-FID, respectively. A total of 39 phenolic compounds were detected, including hydroxybenzoic acids, hydroxycinnamic acids, flavan-3-ols, procyanidins, flavonols, and arbutin. Among these compounds, 5-O-caffeoylquinic acid was the most predominant, accounting for 14–39% of total quantified phenolic contents (TPA) determined in this study. The variations were mainly cultivar dependent. The genetic background effect on the chemical compositions is complex, and breeding selections from the same parental cultivars varied dramatically in chemical compositions. Putative perry pears contained more 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, caffeoyl N-trytophan, caffeoylshikimic acid, coumaroylquinic acid isomer, syringic acid hexoside, procyanidin dimer B2, (+)-catechin, and malic acid, whereas putative dessert pears had higher esters, alcohols, and aldehydes. The results will be helpful in providing industry with phytochemical compositional information, assisting pear selections in commercial utilization. </p

Characterization and Quantification of Nonanthocyanin Phenolic Compounds in White and Blue Bilberry (Vaccinium myrtillus) Juices and Wines Using UHPLC-DAD−ESI-QTOF-MS and UHPLC-DAD

The nonanthocyanin phenolic compounds in juice and wine produced from fruits of white bilberry, a nonpigmented mutant of Vaccinium myrtillus, and blue bilberry (pigmented variety) were analyzed using liquid chromatography with a diode array detector (LC-DAD) and LC-DAD−electrospray ionization-quadrapole/time of flight hybrid mass spectrometry (ESI-QTOF-MS). On the basis of elution order, UV−vis spectra, accurate mass data, and fragmentation pattern and standards, 42 compounds including 22 phenolic acids, 15 flavonols, and 5 flavan-3-ols, were identified in juices and wines prepared from the two bilberry varieties. The levels of most individual nonanthocyanin phenolic compounds in white bilberry products were significantly lower than those in pigmented ones. In bilberry juices, phenolic acids were the most predominant, accounting for approximately 80% of total phenolic content, with p-coumaroyl monotropeins and caffeic acid hexoside being the major phenolic acids. After fermentation, the total contents of phenolic acids, flavonols, and nonanthocyanin phenolic compounds significantly increased, while the content of total flavan-3-ols decreased significantly. p-Coumaroyl monotropeins still dominated in the wine products, while caffeic acid content showed dramatic elevation with the significant drop of caffeic acid hexoside.</p

Comparison of Volatile Composition between Alcoholic Bilberry Beverages Fermented with Non- Saccharomyces Yeasts and Dynamic Changes in Volatile Compounds during Fermentation

The profile of volatile compounds was investigated using headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME–GC–MS) during bilberry juice fermentation with nine non-Saccharomyces yeasts, including Pachysolen tannophilus, Metschnikowia pulcherrima, Hanseniaspora uvarum, Torulaspora delbrueckii, Zygosaccharomyces bailii, Schizosaccharomyces pombe, Lachancea thermotolerans, Issatchenkia orientalis, and Saccharomycodes ludwigii. Dynamic changes in volatile compounds were determined simultaneously with the development of ethanol concentration during fermentation. H. uvarum or I. orientalis produced more ethyl acetate than other yeast strains throughout fermentation, while fermentation with M. pulcherrima resulted in high accumulation of higher alcohols. S. pombe was associated with high productions of pentane-2,3-dione, 3-hydroxybutan-2-one, 2-methylbutanal, and 3-methylbutanal. Among the 59 volatile compounds detected, generally, higher alcohols and monoterpenes accumulated constantly and reached the maximum concentration at the middle or later fermentation stage, whereas aldehydes, ketones, and acetals accumulated first followed by a significant drop. The production and accumulation dynamics of metabolites were highly dependent on the yeast species and the developing ethanol content.</p