Four full-time staff members of the Faculty of AgriSciences were among the 30 students in the faculty to receive their doctorates this week. They are oenologist Dr Marianne McKay, agricultural economist Dr Jan Greyling, Dr Jeanne Brand, who is an expert in the sensory qualities of wine, and wood production scientist Dr Phillip Crafford.

During the 2018 academic year (which includes December 2018 and April 2019) a total of 45 doctorates in fields of AgriSciences were awarded – a new record for the Faculty.

In all, 184 students of the Faculty of AgriSciences graduated this week. Of these, 46 successfully completed master's degree studies in different fields.

Timber as a sustainable building material

Dr Phillip Crafford is a lecturer in the Department of Forest and Wood Science. He received his PhD in Wood Product Science by comparing the environmental sustainability of certain building practices in South Africa. In particular, he found that timber and other wood-based construction generally has a far lower environmental impact than buildings that use cement, brick and steel.

“Our green building rating tools, however, do not sufficiently reflect this well documented environmental benefits of using wood," he believes.

He hopes that South African homeowners will increasingly turn to timber as the preferred green building material, as it is a renewable resource. Dr Crafford regards timber building as a way by which households can reduce their dependency on fossil fuels, and help to reduce the effects of global warming in general.

The history and politics surrounding South Africa's maize farms

Dr Jan Greyling of the Department of Agricultural Economics took a historic look at the development of South Africa's maize industry during the 20^th century. In particular, he studied how changing policies have shaped the industry.

“During the 20^th century, changes in agricultural policies had a definite influence on the production and productivity of maize farming in the country. It influenced where people decided to grow maize," he notes.

During the 1940s to 1980s, favourable policies stimulated an expansion in maize production into relatively lower yielding marginal production areas in the Western Free State and North West province.

“This spatial reallocation of production lowered productivity but investments in improving plant material, farming practices and infrastructure increased the suitability of the drier production areas," he explains. “This enabled production to remain in some of the marginal areas after the supportive policies were removed. “

The influence of smoke taint on red wines

Dr Marianne McKay of the Department of Viticulture and Oenology has been lecturing to prospective winemakers at Stellenbosch University since 2007, and has been commended for her scholarship of teaching and learning.

Given the frequency, scale and financial implications of veld fires in traditional wine regions of the Cape in recent years, the subject of her PhD in Oenology is very topical.

If wines are produced from vineyards that have withstood veld fires, grapes absorb certain compounds from the smoke, and these may cause off-odours or so-called smoke taint in the end product. Dr McKay completed a sensory study and looked at how these compounds interact to produce olfactory effects or smells in red wines.

“This sensory information helps to clarify effects on the aroma of the wine that cannot be understood if the wine is only analysed chemically," explains Dr McKay.

She hopes her findings will help winemakers decide whether to use smoke-affected grapes or not, and to increase awareness of these issues in the wine industry.

Sensory profiles of wines

Dr Jeanne Brand manages the Sensory Laboratory of the Department of Viticulture and Oenology, and regularly guides sensory tasting panels through their work.

She says because of its complexity wine is not so easy to describe. She compared four rapid methods that sensory panels commonly used to test and describe wines. She evaluated each method in terms of its cost-effectiveness and usefulness to the wine industry and for research purposes.

"It's important to choose the right wine profiling method, based on the experiment you want to do," she believes. "One must also weigh up each method's practical limitations."

Her findings highlighted two methods that in particular allow tasting panels to best distinguish between products: the CATA method and sorting.

With CATA (which stands for "check-all-that-apply") a list of attributes is provided to people who serve as judges on sensory tasting panels. They must then make their choices accordingly. With sorting, all the products are given to a tasting panel. They then sort them according to the differences and similarities between the products in terms of sensory properties such as taste and aroma.

The other 26 students in the Faculty of AgriSciences who also received their doctorates on 2 April were:

• Dr Adrian Adams (Soil Science) - Lipid humification by soil clays

• Dr Abiodun Alawode (Wood Product Science) - Properties and potential use of Irvingia gabonensis and Irvingia wombolu kernel extracts as an eco-friendly wood adhesive
• Dr Francois Bekker (Entomology) - Spatio-temporal analyses of fruit fly populations in selected areas of the Western Cape
• Dr Richard Bwala (Aquaculture) - Development of a cost-effective system of ovoviviparous low-salinity production of Artemia nauplii as live food for the larvae of the African catfish (Clarias gariepinus: Burchell, 1822)
• Dr Chad Cheney (Conservation Ecology) - An evidence base of improving management effectiveness of alien plants in protected areas: relationships of scale, efficiency and strategy
• Dr Obert Chikwanha (Animal Science) - Feed supplement and meat preservative potential of red grape (Vitis vinifera) pomace in lamb production
• Dr Glynnis Cook (Genetics) Characterization of citrus tristeza virus variants and their influence on symptom expression in grapefruit
• Dr Gerida de Groot (Food Science) - Genotyping South African wheat cultivars for hardness alleles
• Dr Marcela Espinaze (Conservation Ecology) - Parasites of African penguins: diversity, ecology and effect on hosts
• Dr Chantelle Human (Food Science) - The physicochemical properties and stability of aspalathinin micro- and nanoencapsulated green rooibos extract formulations
• Dr Zaharan Hussein (Food Science) - Bruise damage susceptibility of pomegranates and impacts on fruit quality
• Dr Imke Kritzinger (Horticultural Science) - Postharvest moisture loss in Japanese plums
• Dr Linda Bandile Luvuno (Conservation Ecology) - Understanding social-ecological regime shifts: the case of woody encroachment
• Dr Francis Munalula (Wood Product Science) - The growth response of selected Zambian hardwood species to changing climatic conditions
• Dr Ziyanda Mpetile (Animal Science) - The genetics of ovine resistance to gastrointestinal nematodes
• Dr Megan North (Animal Science) - The potential of quercetin to improve performance and meat quality in rabbits
• Dr Maria Shipandeni (Animal Science) - Modulation of starch digestion for productive performance in dairy cows
• Dr Leigh Steyn (Entomology) - The development of a management strategy for the control of the Cape grapevine leafminer, Holocacista capensis (Lepidoptera: Heliozelidae) in South African's table grape vineyards
• Dr Vernon Steyn (Entomology) -Integrated management of false codling moth, Thaumatotibia leucotreta, on stone fruit and table grapes
• Dr Etienne Terblanche (Viticulture) - The impact of grape ripeness level on the berry and wine composition and potential wine style of Vitis vinifera L. cv. Pinotage
• Dr Michaela van den Honert (Food Science) - Antibiotic resistance prevalence in livestock and wildlife species in South Africa
• Dr Nadia van der Colff (Wine Biotechnology) - Exploring consumers' risk perception in wine retail decision-making: insights for Chenin blanc
• Dr Julia van Schalkwyk (Conservation Ecology) - Beta-diversity across different scales in the Cape Floristic Region: how well does a biosphere reserve capture this invertebrate diversity
• Dr Gideon van Zyl (Plant Pathology) - The use of Adjuvants to improve fungicide spray deposition and control of Alternaria brown spot in citrus
• Dr Haile Wale (Forest Science) - Pattern and dynamics of remnant dry Afromontane forests: A case study in Northwestern Ethiopia
• Dr Liesl Wiese (Soil Science) - Mapping soil organic carbon stocks by combining NIR spectroscopy and stochastic vertical distribution models: A case study in the Mvoti River catchment, KZN, South Africa

Photo caption:
The four staff members of the Faculty of AgriSciences are Dr Phillip Crafford, Dr Jan Greyling, Dr Marianne McKay and Dr Jeanne Brand.
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Group picture caption:

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​From left to right: 1 row (stair): Abiodun Alawole, Maria Shipandeni, Obert Chikwanha, Imke Kritzinger, Haile Wale, Francis Manulula.
2nd row (stair): Zaharan Hussein, Marcela Espinaze Pardo.
3rd row (stair): Chad Cheney, Ziyanda Mpetile, Linda Luvuno, Leigh Steyn, Gerard Bekker, Gerida de Groot.
4th row (trap): Philip Crafford, Megan North, Michaela van den Honert, Vernon Steyn, Jan Greyling

Behind: Marianne McKay and Jean Brand

 Absent during photo shoot: Adrian Adams, Richard Bwala, Glynnis Cook, Chantelle Human, Ziyanda Mpetile, Nadia van der Colff, Julia van Schalkwyk, Johannes van Zyl and Liesl Wiese​​