Pomen dušikovih spojin mošta pri stresnih alkoholnih fermentacijah

Keber, Sara (author), Košmerl, Tatjana (mentor)

Hranilo, ki ga moštu najpogosteje primanjkuje je dušik, natančneje kvasovkam dostopni dušik (YAN), katerega vsebnost je pokazatelj potenciala kakovosti pridelanega vina. V primeru pomanjkanja YAN se kvasovke soočajo z zahtevnimi razmerami alkoholne fermentacije, ki nemalokrat vodijo do počasne ali zaustavljene fermentacije. To se pogosto zgodi pri fermentaciji moštov pozne trgatve, moštov, pridelanih iz grozdja, okuženega z botritisom ali zelo bistrih moštov, ki imajo lahko tudi večjo vsebnost sladkorjev in majhno vsebnost YAN. Z različnimi pristopi v vinogradu in med alkoholno fermentacijo (AF) lahko vinarji pomembno vplivajo na kakovost pridelanega vina. Zanimal nas je vpliv dodatka različnih sodobnih hranil za kvasovke, ki vsebujejo povečano vsebnost dušikovih spojin v mošte treh različnih sort, ki predstavljajo zahtevne razmere za izvedbo AF, na potek AF, na kemijsko sestavo in senzorično kakovost pridelanih vin. Pri tem smo v vsak mošt dodali tri različna hranila za kvasovke (Go-Ferm Sterol Flash, Go-Ferm Protect Evolution, Fermaid O), ter uporabili različen čas in temperaturo rehidracije starterske kulture kvasovk ICV D47. Prišli smo do zaključka, da se kinetika in hitrost alkoholne fermentacije vzorcev z različnimi hranili razlikujeta, prav tako pa se razlikujeta pri uporabljenih moštih treh različnih sort, pri čemer sta si pri sortah malvazija in laški rizling zelo podobni. Fermentacija mošta sorte žametna črnina (ŽČ) se je namreč zaradi večje začetne vsebnosti YAN in manjše sladkorne stopne hitreje zaključila. Poleg tega smo pri ŽČ drugi dodatek hranil izvedli v 2/3 AF in ne v 1/3 AF kot pri ostalih dveh sortah, pri katerih sta se ob tem dodatku kinetika in hitrost AF izboljšali. Ugotovili smo, da razen pri ŽČ, hranila niso vplivala na dober zaključek AF v pridelanem vinu (vsebnost reducirajočih sladkorjev je bila relativno visoka), so pa pri vseh sortah vplivala na boljšo kinetiko in hitrost AF in imela pozitiven vpliv na kemijsko sestavo pridelanih vin.

• Language: Slovenian
• Keywords: vino, mošt, alkoholna fermentacija, Saccharomyces cerevisiae, dušikove spojine, hranila za kvasovke, YAN
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: BF - Biotechnical Faculty
• Publisher: [S. Keber]
• Year: 2023
• PID: 20.500.12556/RUL-152211
• UDC: 663.252.4:543.2/.9
• COBISS.SI-ID: 171902211
• Publication date in RUL: 11.11.2023

Secondary language

• Language: English
• Title: Importance of grape must nitrogen compounds in stress alcoholic fermentations

Abstract

The nutrient most often lacking in must is nitrogen, specifically yeast-assimilable nitrogen (YAN), the content of which is an indicator of the fermentability of the must and the quality of the wine produced. When there is a deficiency of YAN, the yeasts are faced with difficult conditions for alcoholic fermentation, often resulting in stuck or sluggish fermentation. This often happens during fermentation of late harvest must, musts which are prouced from grapes, infected with Botrytis, or very clear musts that often have high sugar content and low YAN. With various measures in the vineyard and during alcoholic fermentation (AF), winemakers can significantly influence the quality of the wine produced. We were interested in the influence of the addition of various modern nutrients for yeasts with an increased content of nitrogen compounds to musts of three different varieties, which represent demanding conditions for the implementation AF, on the course of AF, on the chemical and sensory composition of the wines produced. We added three different yeast nutrients to each must (Go-Ferm Sterol Flash, Go-Ferm Protect Evolution, Fermaid O), and used a different time and temperature of rehydration of the ICV D47 yeast starter culture. We concluded that the kineticts and the speed of alcoholic fermentation of the samples with different nutrients are different, and they are also different for the musts of the three different varieties used, with Malvasia and Welschriesling being very similar. Fermentation of Žametna črnina (ŽČ) must was completed more quickly due to its higher initial content YAN and lower sugar content. Moreover, in ŽČ the second addition of nutrients occured at 2/3 of AF and not at 1/3 of AF as in the other two varieties, where the cinetics and speed of AF improved by this addition. We found that, except for ŽČ, nutrients did not affect the good completion of AF in the produced wine (the content of reducing sugars was relatively high), but they did affect the better kinetics and speed of AF in all varieties. For the most part, the nutrients had a positive effect on the chemical composition of the wine produced.

• Keywords: wine, must, alcoholic fermentation, Saccharomyces cerevisiae, nitrogen compounds, yeast nutrients, YAN