1,721,078 research outputs found
NEW APPROACHES TO MUST CLARIFYING AND WINE FINING FOR GETTING COLLOIDAL STABILITY
No full textPer via degli svantaggi inerenti l’uso di bentonite nella produzione di vini bianchi, la ricerca di alternative ha assunto di recente una grande importanza. Il lavoro presentato in questa tesi ha l’obiettivo di valutare l’applicabilità di tre approcci innovativi alla stabilizzazione colloidale dei vini: l’uso di chitosano, l’applicazione dei PEF e il riutilizzo di colonne di scambio cationico.
L’aggiunta di chitosano è risultata nella rimozione delle chitinasi dal vino, permettendo di raggiungere un soddisfacente livello di stabilità. Gli effetti sul colore e sugli aromi, quando non significativi, non sono risultati essere peggiori rispetto ai risultati ottenuti da trattamenti con bentonite.
L’applicazione dei PEF aveva lo scopo di innescare la denaturazione e l’aggregazione delle proteine tramite un sistema di trattamento-raffreddamento e filtrazione finale. I risultati suggeriscono che un buon grado di stabilità viene raggiunto solo con trattamenti particolarmente energetici ma questo a danno del colore del prodotto.
Infine, lo scopo dello studio sulle resine di scambio cationico era quello di valutare la rigenerazione di questo supporto per un molteplice utilizzo operativo. La rimozione delle proteine adsorbite sul supporto è risultata essere possibile in specifiche condizioni di pH e forza ionica, con un consumo di acqua relativamente basso.The search for fining alternatives to bentonite has assumed great importance in white winemaking due to the drawbacks of bentonite application. The research here presented aimed at observing the viability of three innovative approaches to wine stabilization, namely chitosan addition, PEF treatments and cation exchange applicability.
Chitosan successfully removed chitinases from wine, allowing at the same time a sufficient degree of colloidal stability. Collateral effects on color and aroma compounds were non-significant or acceptable when compared with the effects observed for bentonite applications reported in literature.
The use of PEF was aimed at accelerating protein unfolding and aggregation and was coupled to an in-line cooling and filtration system for efficient removal of colloidal aggregates. The results collected suggested that the treatment was capable of inducing a satisfactory colloidal stability only in high- energetic double-treated wine samples, with some deleterious consequences on the color.
Finally, the aim of the research for cation-exchange resins application was to find environmentally friendly cleaning procedures to regenerate the resin capacity and allow reuse of the same resin for further cycles of fining. The removal of proteins bound to the resin was possible under specific pH and ionic strength conditions with relatively low consumption of water
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Chitosan as bentonite replacement for white wine fining
No full textAlternative methods have been proposed to counteract the drawbacks [1, 2] of bentonite, traditionally used to lower the risk of wine haze. Enzymatic degradation of wine proteins [3], ultrafiltration [4] and novel fining agents such as negatively charged polysaccharides like carragenans [5] have been proposed. The addition of chitin [6] as a specific agent for the removal of chitinase proteins would be a good choice for wine fining, but chitin is not allowed by EU regulation. Fungoid Fungine chitosan [7] from Aspergillus niger is the only type of chitosan accepted in winemaking to control Brettanomyces spp population [8], and to remove ochratoxin A and metals [9]. The effects of chitosan on wine have been insofar focused on evaluating antioxidant activity [8] and removal of procyanidins and cinnamic acids [10].
Due to its structural similarity with chitin and the activity of chitinases under wine conditions [11], chitosan could be capable to interact with grape chitinases and to remove them. This work aims to fill the lack of data concerning the effect of chitosan on the removal of proteins from wines.
One Moscato wine was treated with two chitosan powders, which were characterized for the deacetylation degree, the molecular weight and the solubility. After filtration, the wine was analysed for its haze potential, proteins, total polyphenol index, Folin-Chocalteu. HPLC analyses were carried out to outline any interaction with organic acids and phenolics. Finally, GS-MS analysis quantified the free and glycosylated aroma compounds. The results showed a significant reduction of protein content and haze potential, thus indicating a positive action of chitosan as fining agent. Negligible reductions interested the total polyphenols, while significant depletions of flavons, flavan-3-ols and cinnamic acids occurred. Tartaric and malic were affected also, as like as free aroma compounds, whilst no difference interested the glycosylated forms
PEF treatment of must and wine for on-line clarifying and fining
No full textPEF application in winemaking mainly concerns the extraction of phenolic compounds from grape skins for red wines production. PEF-mediated fermentation control has also been tested with interesting results, and a considerable part of information has been collected on enzymes. There is a lack of data concerning the efficiency of PEF on the stability of chitinases and thaumatin-like proteins and, thus, on the application of PEF for wine fining purposes. This work aimed to test whether the application of PEF could trigger the cascade of phenomena that lead to the formation of haze in wines and if the altered condition allows an in-line filtration system to remove the aggregates and to stabilize the product. Parallel investigations of the stability of the color studied any possible deleterious consequence on the quality. The samples used for the study were 2016 Vitis vinifera L. cv Moscato bianco must and Vitis vinifera L. cv Sauvignon blanc wine. PEF treatments with monopolar square wave pulses were performed in a lab-scale continuous system. The must and wine samples were pumped at 25 L/min into a PEF treatment chamber with 1 cm distance between the stainless-steel electrodes. Acquisition of voltage and current was via a digital oscilloscope. Two different experimental plans were devised, one for the Muscat must and one for the Sauvignon blanc wine. On Muscat must the PEF treatment consisted of two different trials with a total input energy of W=100 kJ/ and W=150 kJ/kg, respectively. With regard to Sauvignon blanc wine, an additional trial with a cooling step subsequent to the heating induced by the PEF treatment was applied. At the inlet and outlet of the PEF system thermocouples recorded temperature every second. Sixteen hours after the treatment, the samples were filtered on 0.45 μm membranes and stored at 20°C for turbidity and color determinations up to 12 months. The results outlined that a combination of PEF treatments and membrane filtration reduced the Sauvignon blanc wine heat instability. Conversely, the Muscat must a significant increase of ΔNTU suggesting the inefficiency of the PEF treatments, possibly induced by the interaction with polysaccharides. As to the effects on color, Muscat must did not show any significant variation, while Sauvignon blanc wine showed a significant degree of pinking that disappeared 12 months after the PEF treatments
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No full textDeepening the fining mechanism: role of bentonite parameters on removal of biogenic amines and volatile phenols in an oxidized Roero Arneis wine
No full textThis work planned the fining of a oxidized Roero Arneis with 1 g L-1 of three different bentonite labels. The wine was spiked with amounts of 4-ethylphenol (4-EP) and 4-vinylphenol (4-VP) over the sensory threshold and levels of BA close to concentrations that can cause negative physiological effect. The elemental analyses of bentonite samples were conducted with an energy dispersive X-ray detector coupled to a scanning electron microscope. The surface charge density, the specific surface area (SSA), the pH and the swell index were measured using the methods described by O.I.V. and International Enological Codex. 4-EP and 4-VP, BA and o-quinone concentrations were determined in wine before and after fining through UPLC-MS methods
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