Nel corso degli ultimi anni l’introduzione nel settore enologico di pratiche di produzione innovative ha permesso di sfruttare al meglio il potenziale di vinificazione delle uve e, di conseguenza, produrre vini qualitativamente migliori che possono essere considerati prodotti di pregio. Tra queste, spicca sicuramente l’impego di enzimi enologici, che vengono generalmente aggiunti prima, durante oppure al termine della fermentazione alcolica a seconda dell’azione desiderata. L’obbiettivo di tale processo è quello di massimizzare la resa in mosto e l’estrazione dalle uve di componenti varietali capaci di valorizzare le caratteristiche tecnologiche e sensoriali del vino, ma anche per agevolare e velocizzare le diverse operazioni di chiarifica e stabilizzazione. Lo studio in esame ha lo scopo di valutare se l’utilizzo di un preparato enzimatico con attività arabinasi, aggiunto all’avvio della fermentazione alcolica e macerazione, è idoneo a promuovere una maggiore estrazione polifenolica e polisaccaridica nel corso della macerazione. Uve delle cultivar Nebbiolo e Cabernet sauvignon sono state raccolte a maturità tecnologica, divise in porzioni omogenee e poi pigiate separatamente predisponendo per ogni varietà due serie di campioni, uno contenete l’enzima in esame e l’atro operante da controllo. I mosti ottenuti sono stati fermentati con due lieviti diversi per valutare possibili differenze date dall’attività del lievito. Per valutare l’efficacia del trattamento enzimatico sono state condotte una serie di analisi di laboratorio sia al momento della svinatura che dopo due settimane dall’imbottigliamento, procedendo con delle letture spettrofotometriche per la quantificazione di polifenoli totali, antociani, colore e polisaccaridi totali. In aggiunta, sono state eseguite anche delle analisi HPLC per esaminare in dettaglio i profili acidi-zuccheri e antocianici dei vini. Dai risultati ottenuti si evince una influenza positiva nell’estrazione di flavonoidi non-antocianici nei vini ottenuti dal mosto di Nebbiolo fermentato con il secondo lievito testato e trattato con arabinasi. Analisi più approfondite hanno evidenziato come l’enzima abbia però interferito solo a livello tannini ad elevato peso molecolare, senza modificare la concentrazione di tannini oligomeri, caratterizzati da maggiore astringenza e amaro. Inoltre, sempre in questo campione, l’enzima ha favorito una maggiore estrazione di polisaccaridi. Anche nella varietà Cabernet sauvignon l’enzima ha portato a cambiamenti significativi. Si sono registrati aumenti considerevoli nella concentrazione fenolica a fine fermentazione alcolica, ma solo nei vini fermentati con il primo lievito testato. Tuttavia, al contrario di quanto visto nel Nebbiolo, nessuna variazione rilevante è stata individuata a livello di polisaccaridi totali. Guardando inoltre ai parametri tecnologici dei vini a fine sperimentazione, il trattamento sembra aver modificato l’evoluzione di alcuni acidi organici in una parte dei vini trattati. In particolare si è notata una riduzione significativa di succinato al termine della vinificazione per entrambe le varietà fermentate tramite il primo lievito testato e un aumento di acido tartarico solo nei vini di Nebbiolo fermentati con il secondo lievito testato.
In recent years, the establishment of innovative production practices in the wine sector has allowed to exploit the oenological potential of grapes and, therefore, produce wines with better quality properties that can be considered valuable products. Among these, certainly stands the use of oenological enzymes of exogenous production, which are commonly added throughout the winemaking process with different aims, such as to maximize the grape juice yield, increase phenolic extraction, facilitate filterability, and speed up clarification and stabilization processes. The purpose of this study is to assess whether the adoption of an enzyme preparation presenting arabinase activity, added at the beginning of alcoholic fermentation and maceration, would be suitable to promote a greater polyphenolic and polysaccharide extraction during red grape skin maceration. Nebbiolo and Cabernet sauvignon were used in this study. Grapes were harvested at technological maturity, divided into homogeneous portions, and then crushed, preparing for each variety two sets of samples, one containing the enzyme under investigation and the other operating as control. Grape musts were fermented with two different selected yeast in order to evaluate possible changes due to yeast activity. To evaluate the effectiveness of the enzymatic treatment, wines were analysed at the devatting phase and two weeks after bottling. Spectrophotometric readings were carried out for the quantification of total flavonoids, polysaccharides, and colour. In addition, HPLC analysis were also carried out to examine in detail the acid-sugar composition and the anthocyanin profile of wines. The results show a positive influence in the extraction of non-anthocyanin flavonoids at the end of the experimentation in wines treated with arabinases deriving from Nebbiolo must fermented with with the second yeast tested. Further analyses have shown that the enzyme was able to increase high molecular weight tannin content without changing the concentration of oligomeric tannins. In addition, always in this sample, the enzyme treatment has favoured a higher concentration of polysaccharides in the final wine. Even in the variety Cabernet sauvignon, the enzyme has led to significant changes. Considerable increases in phenolic concentration have been recorded at the end of alcoholic fermentation, but only in wines fermented with the first yeast tested. However, contrary to what has been observed for Nebbiolo wines, no significant variation has been found in the total polysaccharide concentration. Moreover, the treatment seems to have modified the evolution of organic acids in some treated wines. In particular, there was a significant reduction of succinate at the end of the vinification process for both varieties fermented through the first yeast tested and an increase of tartaric acid only in Nebbiolo wines treated with the second yeast tested. In conclusion, it is possible to confirm that the enzymatic treatment was able to promote polyphenolic and polysaccharide compounds extraction during the maceration of Nebbiolo grapes fermented with one of the two yeasts tested. While, as regards Cabernet sauvignon, positive findings were found only on total phenols concentration.
INFLUENCE OF OENOLOGICAL ENZYME TREATMENTS ON PHENOLIC AND POLYSACCARIDE EXTRACTION DURING CULTIVAR NEBBIOLO AND CABERNET SAUVIGNON RED WINEMAKING
STEFINI, MATTEO
2021/2022
Abstract
In recent years, the establishment of innovative production practices in the wine sector has allowed to exploit the oenological potential of grapes and, therefore, produce wines with better quality properties that can be considered valuable products. Among these, certainly stands the use of oenological enzymes of exogenous production, which are commonly added throughout the winemaking process with different aims, such as to maximize the grape juice yield, increase phenolic extraction, facilitate filterability, and speed up clarification and stabilization processes. The purpose of this study is to assess whether the adoption of an enzyme preparation presenting arabinase activity, added at the beginning of alcoholic fermentation and maceration, would be suitable to promote a greater polyphenolic and polysaccharide extraction during red grape skin maceration. Nebbiolo and Cabernet sauvignon were used in this study. Grapes were harvested at technological maturity, divided into homogeneous portions, and then crushed, preparing for each variety two sets of samples, one containing the enzyme under investigation and the other operating as control. Grape musts were fermented with two different selected yeast in order to evaluate possible changes due to yeast activity. To evaluate the effectiveness of the enzymatic treatment, wines were analysed at the devatting phase and two weeks after bottling. Spectrophotometric readings were carried out for the quantification of total flavonoids, polysaccharides, and colour. In addition, HPLC analysis were also carried out to examine in detail the acid-sugar composition and the anthocyanin profile of wines. The results show a positive influence in the extraction of non-anthocyanin flavonoids at the end of the experimentation in wines treated with arabinases deriving from Nebbiolo must fermented with with the second yeast tested. Further analyses have shown that the enzyme was able to increase high molecular weight tannin content without changing the concentration of oligomeric tannins. In addition, always in this sample, the enzyme treatment has favoured a higher concentration of polysaccharides in the final wine. Even in the variety Cabernet sauvignon, the enzyme has led to significant changes. Considerable increases in phenolic concentration have been recorded at the end of alcoholic fermentation, but only in wines fermented with the first yeast tested. However, contrary to what has been observed for Nebbiolo wines, no significant variation has been found in the total polysaccharide concentration. Moreover, the treatment seems to have modified the evolution of organic acids in some treated wines. In particular, there was a significant reduction of succinate at the end of the vinification process for both varieties fermented through the first yeast tested and an increase of tartaric acid only in Nebbiolo wines treated with the second yeast tested. In conclusion, it is possible to confirm that the enzymatic treatment was able to promote polyphenolic and polysaccharide compounds extraction during the maceration of Nebbiolo grapes fermented with one of the two yeasts tested. While, as regards Cabernet sauvignon, positive findings were found only on total phenols concentration.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14240/85265