Marisa Carmela Caruso

Function of yeast species and strains in wine flavour.

The diversity and the composition of the yeast micropopulation significantly contribute to the sensory characteristics of wine. The growth of each wine yeast species is characterized by a specific metabolic activity, which determines concentrations of flavour compounds in the final wine. However, it must be underlined that, within each species, significant strain variability has been recorded. The wide use of starter cultures, mainly applied to reduce the risk of spoilage and unpredictable changes of wine flavour, can ensure a balanced wine flavour, but it may also cause a loss of characteristic aroma and flavour determinants. Thus, the beneficial contribution from the yeast increases when starter cultures for winemaking are selected on the basis of scientifically verified characteristics and are able to complement and optimise grape quality and individual characteristics. Here we report the characterization of a large number of strains of different wine yeast species, isolated from spontaneous wine fermentations and included in the culture collection of the Basilicata University.

Effects of pH, temperature and NaCl concentration on the growth kinetics, proteolytic activity and biogenic amine production of Enterococcus faecalis.

In this work, the combined effects of temperature, pH and NaCl concentration on the growth dynamics of Enterococcus faecalis EF37, its proteolytic activity and its production of biogenic amines have been studied. The effects of the selected variables have been analysed using a Central Composite Design. The production of biogenic amines, under the adopted conditions, was found to be mainly dependent on the extent of growth of E. faecalis. Its proteolytic activity was not a limiting factor for the final amine production, because in the system studied (skim milk) an excess of precursors was guaranteed. Quantitatively, the most important biogenic amine produced was 2-phenylethylamine but substantial amounts of tyramine were detected in all the samples. This work confirms that the main biological feature influencing the biogenic amine formation is the extent of growth of microorganisms, like E. faecalis, characterised by decarboxylase activity. In the traditional and artisanal cheeses produced using raw milk, enterococci usually reach levels of 10(7) cells/g. With this perspective, it is important that the presence of biogenic amines due to the activities of these microorganisms is maintained within safe levels, without affecting the positive effects of enterococci on the final organoleptic characteristics of the cheese.

The species-specific ratios of 2,3-butanediol and acetoin isomers as a tool to evaluate wine yeast performance

The isomers of 2,3-butanediol [R,R; S,S; R,S (meso-form)] and of acetoin (R,S) were determined in laboratory wine fermentations carried out by 50 yeast strains, 10 for each of the following species, Saccharomyces cerevisiae, Kloeckera apiculata, Candida stellata, Metschnikowia pulcherrima and Brettanomyces bruxellensis, in order to evaluate if such parameters might be used to differentiate wines obtained with different yeast species. According to analysis of variance (ANOVA), the strains of the same species behaved similarly, whereas the five yeast species behaved differently so that species-specific profiles were recognized. Moreover, the discriminant analysis grouped the wines into five groups, each including the 10 wines obtained by the 10 yeast strains of the same species. Trials were also included where musts partially fermented by non-Saccharomyces species were inoculated with a selected strain of S. cerevisiae to complete fermentation, and the content in 2,3-butanediol and acetoin isomers was again determined and statistical analysis was performed. Although the final values of these parameters resembled those obtained in pure fermentation with S. cerevisiae, statistical analysis discriminated wines according to the yeast species performing the first fermentation phase.

Metabolic diversity of Saccharomyces cerevisiae strains from spontaneously fermented grape musts

One hundred and fifteen Saccharomyces cerevisiae strains from Aglianico del Vulture, a red wine produced in Southern Italy, were characterized for the production of some secondary compounds involved in the aroma and taste of alcoholic beverages. The strains exhibited a uniform behaviour in the production levels of n-propanol, active amyl alcohol and ethyl acetate, whereas isobutanol, isoamyl alcohol and acetaldehyde were formed with a wide variability. Only five strains produced wines close to the reference Aglianico del Vulture wine for the traits considered. Of these, two strains were selected, underwent to tetrad analysis and the single spore cultures were tested in grape must fermentation. The progeny of one strain showed a significant metabolic variability, confirming the necessity to test starter cultures for the segregation of traits of technological interest. Our findings suggest the selection of specific strains for specific fermentations as a function of the vine variety characteristics in order to take the major advantage from the combination grape must/S. cerevisiae strain.

Focused Review: Agmatine in Fermented Foods

Polyamines (PAs) are ubiquitous substances considered to be bioregulators of numerous cell functions; they take part in cell growth, division, and differentiation. These biogenic amines are also involved in tissue repair and in intracellular signaling; in fact, because of their polycationic character, they interact to a large extent with membrane phospholipids and may play an important role in the regulation of membrane-linked enzymes. The intracellular polyamine content derives from the simultaneous regulation of the synthesis, catabolism, uptake, and elimination of the polyamines; furthermore, PAs are present in all cell types at different concentrations, but the highest levels are found in rapid-turnover tissues. In addition to spermidine, spermine, and putrescine, also agmatine (AGM), deriving from arginine and identified in mammals in the 1990s, is a polyamine and several studies have reported its potentially positive role in the production of secretagogues, and in neuronal, vascular, metabolic, and therapeutic functions. Because of the low arginine decarboxylase (ADC) activity in mammalians, the amounts of AGM found in their tissues can be only minimally ascribed to an endogenous de novo synthesis by ADC, while a substantial quantity of AGM may be of dietary origin. Several food products contain only small amounts of polyamines, while higher concentrations can be found in fermented foods. PAs could also be considered as indicators of freshness in fish and meat products; as these moieties are produced during food storage, it would seem to confirm the main role of microorganisms in their synthesis. In particular, high levels of AGM are present in alcoholic beverages, such as wine, beer, sake, which would seem to confirm the role of yeasts in AGM production. Although many biological functions have been attributed to polyamines, high levels of these compounds in foodstuffs can have toxicological effects; however, no safe level for the intake of polyamines in a diet has yet been established. In this paper the presence of AGM in different foodstuffs is discussed, also taking into account the various factors affecting its presence and concentration.

Role of the cultivar in choosing Clementine fruits with a high level of health-promoting compounds.

Thirteen cultivars and two hybrids of Clementine fruits (Citrus clementina Hort. Ex. Tan) cultivated in Italy were characterized according to pH, titratable acidity, total soluble solids, total polyphenols, carotenoids, vitamin C, hesperidin, rutin, narirutin and naringin and radical scavenging activity. The presence of rutin in Clementine fruit juice is reported for the first time here. The results indicated that all chemical parameters statistically differentiated each cultivar (P < 0.001). In particular, principal component analysis showed a clear discrimination of five cultivars from all the other varieties based on vitamin C and total polyphenols for the Caffin cultivar, which showed also the highest antioxidant activity; narirutin for the Etna hybrid cultivar; hesperidin, rutin and total soluble solids for the SRA 89 cultivar; and naringin, hesperidin and rutin for the Esbal cultivar. Moreover, the Mandalate hybrid cultivar showed the lowest antioxidant activity as well as vitamin C and total polyphenols content, while titratable acidity and naringin level were the highest. The antioxidant activity assessed in all the fruits was closely correlated with vitamin C and total polyphenols content, rather than with the flavonoid compounds.

Prediction of the antioxidant activity of extra virgin olive oils produced in the Mediterranean area

A chemical characterisation was conducted on 75 commercial extra virgin olive oils (EVOO) produced in the years 2011-2012 in Southern Italy from five different olive monovarieties (Coratina, Leccino, Maiatica, Ogliarola del Vulture and Ogliarola del Bradano). The possibility of estimating the antioxidant activity of EVOO by using a chemical index as predictor of this property was considered. In order to build up and validate an antioxidant activity predictive model, the relationship between the antioxidant activity and the chosen chemical parameters was systematically investigated. The results indicated that oil antioxidant activity, measured as IC50, could be satisfactorily predicted, for olive oils from the considered region, by using a simple index, such as the K225 value of oil samples, which represents a spectrophotometric index of the compounds responsible for oil bitterness measured at 225 nm.

Extra virgin olive oil bitterness evaluation by sensory and chemical analyses.

An experimental investigation was performed on blend extra virgin olive oils (EVOOs) from different cultivars and EVOO from different olive monovarieties (Coratina, Leccino, Maiatica, Ogliarola) with the aim to evaluate the possibility of estimating the perceived bitterness intensity by using chemical indices, such as the total phenol content and the compounds responsible for oil bitterness measured spectrophotometrically at 225 nm (K225 value), as bitterness predictors in different EVOO. Therefore, a bitterness predictive model, based on the relationship between the perceived bitterness intensity of the selected stimuli and the chosen chemicals parameters has been built and validated. The results indicated that the oil bitterness intensity could be satisfactorily predicted by using the K225 values of oil samples.

Nutritional quality of seeds and leaf metabolites of Chia (Salvia hispanica L.) from Southern Italy

Chia (Salvia hispanica L.) is an expanding functional food crop from Central America, but little is known about effects of new growing environments and agronomical treatments on seed quality. The quality of seeds produced in Europe has never been reported and there’s a lack of information on secondary metabolites of leaves, an emerging product of Chia. In this work, the nutritional quality and oxidative stability of Chia seeds produced in Southern Italy (Basilicata region) have been evaluated, taking into account also different nitrogen fertilization strategies. The quality of seeds produced in Basilicata has been also compared with that of commercially available seeds from traditional and new production areas. Oil extracted from Italian Chia seeds was not quantitatively significantly different, but more rich in chlorophyll, carotenoids and α-linolenic acid than in commercial seeds. Oxidative stability, polyphenols and antioxidant activity were also influenced by seed source. Fertilization system affected free acidity, chlorophyll and carotenoids, whereas it reduced p-Anisidine value, phenols and oxidative stability. Moreover, the metabolic profile of Chia leaves has been reported for the first time; in particular, several flavonoids and hydroxycinnamic acids, and the two uncommon flavonoids acetyl vitexin and acetyl orientin were found.

Automated multiple development method for determination of glycerol produced by wine yeasts

A rapid and efficient analytical method for the determination of glycerol in wines is described. This method utilizes high-performance thin layer chromatography (HPTLC) plates coupled with an automated multiple development system with an elution gradient based on acetonitrile–acetone–hexane on silica gel layers. The absence of clean-up procedures, sometimes only centrifugation, makes this method suitable also for the large-scale control of alcoholic beverages. In particular the capacity of different wine yeast species (Saccharomyces cerevisiae, Zygosaccharomyces bailii, Kloeckera apiculata and Saccharomycodes ludwigii) to produce glycerol was determined. Generally, the strains of S. cerevisiae produced elevated amounts of glycerol together with Z. bailii, whereas K. apiculata strains formed the lowest amounts of glycerol, exhibiting also a great strain variability.