WINETECH Technical Yearbook 2021

OENOLOGY RESEARCH | AUGUST 2021

YIELD IS A PRIMARY OBJECTIVE in the industry and can be maximised by trellising systems. Besides yield per vine, synthesis and further evolution of chemical compounds may be altered by vine architecture, and this is the core subject for the current study. The aim of this study was to evaluate the influence of six different trellis systems in South African conditions. Chenin blanc vines were trained on Santorini, Ballerina, Smart Dyson, T-frame, Lyre and Stok- by-paaltjie. Grapes from two consecutive vintages (2017 and 2018) were harvested at various dates corresponding to 22-23°Brix and wine was made with the same protocol. No wood contact was used. The wines spent three months on lees before bottling and six months in the bottle before chemical and sensorial analysis. The classes of aroma compounds analysed in the wines were the ones most likely to be affected directly or indirectly by the vineyard practices, such as thiols and major volatiles, respectively. The wines were profiled by industry professionals and by an analytical panel at the Department of Viticulture and Oenology using Check-All- That-Apply (CATA) method. The profiles were evaluated to see if we could distinguish between the wines corresponding to the different trellising systems. Quality was

also assessed by industry professionals for the same reason. CHEMICAL ANALYSES A total of 25 major volatiles and three thiols were determined in the wines. The aroma compounds were evaluated as individual compounds and as classes (esters, acetates, ethyl esters, alcohols, acids, total major volatiles, and thiols). The wines from horizontal dividing or open canopy type of trellis (Lyre and T-frame) had higher concentrations of thiols and major volatiles than the rest of the systems, although comparable in practical terms. Despite some significant differences in some of the individual compounds (for example 3MHA was the highest in Lyre wines in the second season), overall differences were not apparent for either vintage. In the multivariate analysis, some of the samples corresponding to different systems clustered together; this was as a result of the similarity or dissimilarity between the systems and not due to significant variation between repeats. AROMA PROFILES CATA is a rapid sensory profiling technique, which uses a list of attributes (in the form of words or phrases), from which trained or untrained panellists can select all the descriptors they consider appropriate

Trellis effects on wine composition (PART 2: AROMA)

ASTRID BUICA, VALERIA PANZERI & HILARIA IIPINGE: South African Grape and Wine Research Institute, Department of Viticulture and Oenology, Stellenbosch University, Stellenbosch KEYWORDS: Trellising systems, wine aroma profile.

WINETECH TECHNICAL YEARBOOK 2021 | 86