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Bridget Lysaght

Bridget Lysagt

“Dunedin really is a student city, it’s a great place to live when you’re a student.”

The opportunity to study Food Science brought Bridget to Otago. When she arrived here she was most interested in wine science but the range of options and opportunities available at the Food Science Department made her realise it was Food Science she was interested in and not just wine.

“The department is welcoming and friendly, everyone here is helpful and wants you to do well – it’s just a great atmosphere. “

Bridget received the Bee Nilson award, allowing her to return and complete an Honours year in 2014. Her project looked at the different compounds that make up the smell of hops, specifically:

  • Identifying the aromas (what do they smell like?).
  • How intense the aromas are.
  • What chemical compounds are responsible for them?

The project identified the main aroma compounds in three New Zealand hop varieties and noted the aromas that made these varieties distinct. A highlight of the project for Bridget was learning to use the range of specialist equipment required for this analysis.

Project Outline

Characterisation of aroma compounds in selected New Zealand hop varieties

Supervised by Dr Graham Eyres

Hops, the female flower cones of the hop plant (Humulus lupulus L.) are used in beer brewing to impart bitterness, odour and aroma. Currently, there is very limited knowledge on the complex chemical composition and aroma compounds that are present in recently released New Zealand hop varieties.

Gas chromatography-mass spectrometry (GC-MS) has been successfully applied for the identification and quantification of hop oil constituents. Solid phase microextraction (SPME) is the preferred preparation method because of its good extraction efficiency.

Characterisation of hop volatiles can be enhanced with concurrent chemical-sensory analysis by coupling GC-MS with GC-Olfactometry (GC-O). GC-O has been applied in numerous studies regarding beer flavour and hop aroma to analyse the sensory activity of individual components.

The present study aims to characterize the aroma compounds of selected New Zealand hop varieties. Three NZ hop varieties, ‘Nelson Sauvin’, ‘Riwaka’ and Wai-iti’ were characterised using concurrent GC-MS and GC-O analysis. SPME was used as the sample preparation method. Preliminary results indicate the characterisation of 46 compounds across the three hop varieties.