Grapevine cation and anion transfer : a perspective from the soil to wine chemical and sensory properties

Muller, Katharina (2017-03)

Thesis (MScAgric)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: Soil salinity and sodicity occurs mostly in arid and semiarid environments. Saline soils contain high concentrations of soluble salts like sodium chloride (NaCl) in the solum or regolith of the soil. Sodic soils are defined as having a high concentration of sodium ions compared to other cations on the soil particle surface. Grapevines are known to be moderately sensitive to salinity. Both soil salinity and sodicity have an adverse effect on plant growth, whether directly or indirectly. Soil salinity and sodicity have a deleterious effect on the grapevine’s physiological responses, including yield reduction, decrease in shoot growth and increase in cation and anion concentrations in the fruit and final wine, and may also affect the biochemical pathways, consequently leading to toxicities, deficiencies and mineral imbalances in the grapevine. The most important cations associated with salinity are Na+, Ca2+ and Mg2+, whereas the most important anions are Cl-, SO42- and HCO3-. These ions may occur naturally in the soil, however they are more commonly added to the soil through irrigation or may be exacerbated through persistent droughts. Cation and anion analysis in the leaves, the petioles and grape components is essential for the prevention of the negating effects these cations and anions have on grapevine physiology, the grape juice, the final wine product and the export feasibility. The OIV (Oeno 6/91) resolution in regard to sodium states that “When wine contains excess sodium (excess sodium is equal to the content of sodium ions less the content of chloride ions expressed as sodium), it is generally less than 60 mg/L, a limit which may be exceeded in exceptional cases…”. The limit in South Africa is 100 mg/L Na content. As a result of these restrictions, some wines are rejected from the export market. High concentrations NaCl also has an effect on the sensorial quality of wine, and may as a result be described as flat, dull, soap, seawater-like and saline. In this study, soil salinity and sodicity occurrences were investigated on two farms, Farm A Chenin blanc and Farm B Chenin blanc and Pinotage in the Paardeberg area. These plots were divided into ‘high’ and ‘low vigour’ according to salinity and sodicity levels. Soil analysis was conducted at three depths to confirm the presence of high cation and anion concentrations in the soil. Meso-climate loggers were installed on both farms in order to analyse the climatic effects on the grapevine. Vegetative and reproductive measurements were conducted including trunk circumference measurements, shoot measurements, destructive leaf area measurements, berry sampling and harvest measurements. Investigations were also conducted on the effects of high cation and anion concentrations in the soil, different grapevine parts (leaves, petioles and canes), grape berry parts (juice, homogenised, skin and sediment) and in the subsequent wines. In addition to this, the effects of these cation and anion concentrations on grapevine growth, wine composition and the sensorial profile of the wines were also determined The study aimed to provide insight into the positive and negative aspects of possible soil cation and anion transfer to the grapevine, grape juice and wine. Soil samples confirmed the presence of salinity/sodicity in the plots. This had an adverse effect on the growth as well as yield per vine. Shoot, petiole and leaf analysis showed high concentrations of sodium, reaching values greater than 1500 mg/kg. The juice cation and anion analysis showed high levels of sodium for some plots, however chloride levels in the leaves, petioles, grape juice and wines were found to be below harmful limits. There were differences between juice, sediment, skin and homogenised sample analysis, confirming that the sediment contained the highest cation and anion content. Descriptive sensory analysis showed no significant differences in terms of their saltiness, however some wines exhibited significant differences between aroma and taste descriptors. The high salt content in the wine may have had a positive effect on the taste of the wine. At low salt concentrations wines may appear to be sweeter, or less bitter. This study showed that high saline or sodic soils had an effect on the grapevine growth, specifically the trunk circumference, shoot growth and leaf area. The different cation and anion concentrations found in the shoots, leaves and petioles showed that some cations and anions were translocated from the soil to the grapevine parts. The grape juice obtained from the grapes also showed high levels of certain cations, however the juice sediment analysis exhibited the highest concentrations of cations compared to the skins, the homogenised and juice samples. The sensory analysis showed that at certain concentrations, wine aroma and taste could be affected positively or negatively, however this was dependent on the concentrations of the cation and anions.

AFRIKAANSE OPSOMMING: Grond met hoë vlakke wit- of swartbrak kom hoofsaaklik in droë en halfdor omgewings voor. Brak gronde bevat hoë konsentrasies oplosbare soute soos natriumchloried (NaCl) in die solum of regoliet van die grond. Gronde met swartbrak is gronde met ’n hoë konsentrasie natriumione in vergelyking met ander katione op die oppervlak van die grondpartikels. Wingerde is daarvoor bekend dat hulle matig gevoelig is vir brak. Beide wit- of swartbrak het ’n nadelige effek op plantegroei, hetsy direk of indirek. Brak grond het ook ’n skadelike effek op die wingerdstok se fisiologiese response, insluitend ’n afname in opbrengs, ’n afname in lootgroei en ’n toename in katioon- en anioonkonsentrasies in die vrugte en die finale wyn, en kan ook die biochemiese paaie affekteer en gevolglik lei tot oormaat, tekorte en mineraal wanbalanse in die wingerdstok. Die belangrikste katione wat verband hou met brak is Na+, Ca2+ en Mg2+, terwyl die belangrikste anione Cl-,SO42- en HCO3- is. Hierdie ione kan natuurlik in die grond voorkom, hoewel hulle meer algemeen by die grond gevoeg word deur besproeiing of vererger kan word deur aanhoudende droogte. Katioon- en anioon-analises van die blare, die blaarstele en die druifkomponente is noodsaaklik vir die voorkoming van die negatiewe effekte van hierdie katione en anione op wingerdstokfisiologie, die druiwesap, die finale wynproduk en die moontlikheid vir uitvoer. Die OIV (Oeno 6/91) resolusie met betrekking tot natrium sê dat wanneer wyn ’n oormaat natrium bevat (’n oormaat is gelyk aan die inhoud van natrium-ione minus die inhoud van chloried-ione uitgedruk as natrium), dit gewoonlik minder is as 60 mg/L, ’n perk wat in buitengewone omstandige oorskry mag word. Die perk in Suid-Afrika is 100 mg/L Na+ inhoud. As gevolg van hierdie perke word sekere wyne op die uitvoermark afgekeur. Hoë NaCl konsentrasies het ’n effek op die sensoriese kwaliteit van wyn en kan veroorsaak dat die wyn as pap, eentonig, seepagtig, seewateragtig en sout beskryf word. In hierdie studie is voorvalle van wit- en swartbrak in die grond op twee plase in die Paardeberg-omgewing ondersoek – Plaas A se Chenin blanc en Plaas B se Chenin blanc en Pinotage. Hierdie liggings is verdeel in ‘hoë’ en ‘lae groeikrag’ op grond van die vlakke van brak waargeneem. Grondanalises is op drie dieptes gedoen om die teenwoordigheid van hoë konsentrasies van katione en anione in die grond te bevestig. Meso-klimaat sensors is op albei plase geïnstalleer om die klimaatseffekte op die wingerdstokke te analiseer. Vegetatiewe en reproduktiewe metings is geneem, insluitend stam-omtrek, lootmetings, destruktiewe blaaroppervlakmetings, monsters van korrels en oesmetings. Ondersoeke is ook gedoen na die effekte van hoë katioon- en anioonkonsentrasies in die grond, in verskillende dele van die stok (blare, blaarstele en winterlote), in dele van die druiwekorrel (sap, gehomogeniseer, dop en afsaksel) en in die gevolglike wyne. Daarbenewens is die effekte van hierdie katioon- en anioonkonsentrasies op wingerdgroei, wynsamestelling en die sensoriese profiel van die wyne bepaal. Die doel van die studie was om insig te verskaf in die positiewe en negatiewe aspekte van die moontlike oordrag van katione en anione vanuit die grond na die wingerdstok, druiwesap en wyn. Grondmonsters het die teenwoordigheid van sout/natrium in die persele bevestig. Dít het ’n nadelige effek op die groei sowel as opbrengs per stok gehad. Loot-, blaarsteel- en blaar-analises het hoë konsentrasies natrium aangedui, met vlakke van tot hoër as 1 500 mg/kg. Die analise van katione en anione in die sap het hoë vlakke natrium vir sommige persele getoon, hoewel die vlakke in die blare, blaarstele, druiwesap en wyne gevind is om onder skadelike perke te wees. Daar was verskille tussen die analises van die sap, sediment, dop en gehomogeniseerde monsters, wat bevestig het dat die sediment die hoogste inhoud van katione en anione bevat het. Beskrywende sensoriese analise het egter geen noemenswaardige verskille in terme van hulle southeid getoon nie, hoewel sommige wyne aansienlike verskille tussen aroma- en smaakbeskrywers vertoon het. Die hoë soutgehalte van die wyn het moontlik ’n positiewe effek op die smaak daarvan gehad. Teen lae soutkonsentrasies kan wyn soeter, of ten minste minder bitter, voorkom. Hierdie studie het getoon dat gronde met hoë vlakke van sout of sout-natrium brakheid ’n effek het op wingerdgroei, veral op stamomtrek, lootgroei en blaaroppervlak. Die verskillende katioon- en anioonkonsentrasies in die lote, blare en blaarstele het gewys dat sommige katione en anione vanaf die grond na die wingerddele vervoer is. Die sap afkomstig van die druiwe het ook hoë vlakke van sekere katione getoon, hoewel die afsaksel-analises die hoogste konsentrasies van katione in vergelyking met die doppe, en die gehomogeniseerde en sapmonsters vertoon het. Die sensoriese analises het getoon dat, by sekere konsentrasies, wynaroma en -smaak positief of negatief beïnvloed kon word, maar dit was afhanklik van die konsentrasies katione en anione.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101089
This item appears in the following collections: