Wine grapes technological maturity depending on cultivar and spring cover

Magistritöö Aianduse magistrantuuri õppekavalVeiniviinamarjade küpsus saagikoristusel määrab veini stiili ja kvaliteedi. Viinamarjade tehnoloogilist küpsust hinnatakse marjamahla kuivaine, orgaaniliste hapete sisalduse, marjamahla pH ning suhkrute ja hapete suhtarvu põhjal. Varasem katsetöö Eestis on näidanud, et jaheda suve tingimustes on marjadel probleeme kirjanduses soovitatud tehnoloogiliste parameetrite saavutamisega. Sellest tingituna püstitati hüpotees: külma kliima tingimustes on probleemiks viinamarja sortide saagi tehnoloogiline küpsus, mis on vajalik veini tootmiseks. Magistritöö hüpoteesist lähtuvalt seati töö eesmärkideks selgitada välja sordiomaduste ja kevadkatte mõju veini viinamarjade tehnoloogilise küpsuse parameetritele (mahla kuivaine, orgaanilised happed, pH, suhkrute ja hapete suhtarv). Katse viidi läbi 2019. aastal avamaa tingimustes EMÜ Rõhu Katsejaama istandikus Tartumaal. Sordi mõju hindamise katses olid variandid: `Hasanski Sladki`, `Zilga` ja `Rondo`. Katte mõju katses olid variandid: `Hasanski Sladki` kontrollvariant katteta ja kattega variant ning `Zilga` kattega ja kontrollvariandis kasutati varjutuskangast. Kevadkattena kasutati talveloori (50 g/m², valge), mis paigaldati taimede toestuse külge 3. mail kohe pärast võralõikust ja enne pungade puhkemist ning eemaldati pärast õitsemist 26. juunil. Sortide marjamahla kuivaine sisaldus varieerus vahemikus 15...19 ºBrix. `Rondo` mahla kuivainesisaldus oli madalaim, ainult 15 °Brix. Katses olnud labrusca-tüüpi sortidest `Zilga` ei saavutanud punase veini jaoks soovitatud mahla kuivaine sisaldust (17...18 ºBrix), `Hasanski Sladki` aga ületas soovitatud sisaldust. Kevadkatte kasutamisel oli oluline mõju sordile `Zilga`- kevadkattega suurenes mahla kuivaine sisaldus ja oli 18 ºBrix. Sordile `Hasanski Sladki` kevadkattel mõju polnud. Sortide orgaaniliste hapete sisaldus varieerus vahemikus 0,59-0,98 g/100g. Happerikkamaks sordiks osutus ´Hasanski Sladki´. Kevadkatte kasutamine mõjutas oluliselt katsesortide marjade mahla orgaaniliste hapete sisaldust, sordil `Hasanski Sladki` vähenes orgaaniliste hapete sisaldus 0,12 g/100g võrra. Suhkrute ja hapete suhtarv varieerus vahemikus 16...27. Suurim suhkrute ja hapete suhtarv saadi sordi `Zilga` puhul. Kevadkatete kasutamine ei mõjutanud statistiliselt oluliselt `Zilga` suhtarvu. Sordi `Hasanski Sladki` puhul oli tulemuste erinevus oluline, kevadkattel oli positiivne mõju. Katsemarjade mahla pH-le sordiomadused mõju ei avaldanud ja kõigil sortidel oli see 3.6. Kevadkatete kasutamisel suurenes oluliselt mõlema katsesordi pH. `Zilga` puhul suurenes kevadkatete kasutamisel pH 3.72-ni, `Hasanski Sladki` puhul suurenes pH 3.68-ni. Katsetulemused kinnitasid hüpoteesi ja näitasid, et talveloori kasutamine kevadkattena mõjutab marjade tehnoloogilist küpsust. 2019. aasta tulemustest järeldub, et punase veini jaoks sobiva tehnoloogilise küpsuse saavutamine on külma kliima tingimustes avamaal probleemiks. Iga katsevariandi puhul leidus tehnoloogilisi parameetreid, mis olid probleemsed. Saak sobib aga väiksema alkoholisisaldusega roosa ja valge vahuveini valmistamiseks.The maturity of wine grapes at harvest determines the style and quality of the wine. Grapes technological maturity is assessed on the basis of the soluble solids, organic acid content, juice pH and soluble solids/acid ratio. Previous experimental work in Estonia has shown that due to relatively cool summers berries have problem reaching technological berry composition recommended in literature. Thus, the hypothesis was that the technological composition of grape cultivars necessary for wine production is a problem in cold weather conditions. The aim of this thesis was to find out the effect of cultivar characteristics and spring cover on the technological parameters of grapes (soluble solids, organic acids, juice pH and sugar/acid ratio). The experiment was carried out in 2019 on open field conditions at the EMÜ Rõhu Experimental Station vineyard in Tartu County. In the cultivar comparison experiment the variants: `Hasansky Sladky`, `Zilga` and `Rondo` were studied. In the spring cover study the experimental variants were: `Hasansky Sladky` and `Zilga` both without the spring cover and with the cover were studied. In 3rd of May right after crown thinning the frost cloth (50 g/m², white) that was used as a spring cover was installed on the side of the plants. The frost cloth was removed after flowering on the 26th of June. The soluble solids content of the cultivars ranged from 15 to 19 ºBrix. `Rondo` had the lowest soluble solids content, only 15 °Brix. From the labrusca-type grapes in the experiment `Zilga` did not reach the recommended soluble solids content for red wine (17...18 ºBrix), but `Hasansky Sladky` exceeded the recommended soluble solids content. Spring cover increased the soluble solids content of `Zilga` to 18 ºBrix. Spring cover had no significant impact on `Hasansky Sladky`. Organic acid content of the cultivars was 0.59-0.98 g/100g. Highest acid content was found in the cultivar `Hasansky Sladky`. Organic acid content of `Hasansky Sladky` was significantly impacted by the usage of spring cloth, it was reduced by 0.12 g/100g. The sugar/acid ratio ranged from 16...27 and `Zilga` had the highest sugar/acid ratio. The usage of spring cover did not significantly impact the sugar/acid ratio of `Zilga`. Cultivar `Hasansky Sladky` results were significantly different, spring cover had a positive impact on it. Cultivar characteristics did not impact the experiment´s berry juice pH, in all cultivars it was 3.6. In both cultivars pH increased significantly after the usage of spring covers. In the cultivar `Zilga` spring cloth increased the juice pH to 3.72 and in the cultivar `Hasansky Sladky` pH increased to 3.68. The results of the trial year show that achieving the technological composition suitable for red wine is a problem in cold weather conditions. All cultivars used in the experiment had problematic technological parameters. However the harvested grapes are suitable for making rose sparkling wine with low alcohol content. Lastly, it can be concluded that the spring cover had an impact on berries technological maturity