Obituary: Professor D. Donald Muir (1947–2025)

It is with much sadness we report the passing of a dear friend and colleague, Professor Donald Muir.

Donald spent his working life in dairy research at the Hannah Research Institute in Ayr, Scotland. Having completed his PhD studies under the supervision of Dr William Banks at the Flour Milling and Baking Research Association at Chorleywood, Donald then joined Willie at HRI in 1974. At that time, Willie headed up the Applied Studies Department, which later became the Food Research Division.

The remit of the Food Research Division was to exploit the scientific knowledge of lactation through devising new technologies to enhance the efficiency and competitiveness of the dairy industry. Donald became responsible for the Food Technology Section within the division.

Donald began his research at HRI working on the heat stability of milk proteins and the implication of this on the processing and functional characteristics of full cream evaporated milks, sterilised cream, milk-based powders and UHT products. He oversaw microbiological studies on the influence of raw milk quality and the effects of post-pasteurisation contamination with spoilage bacteria on the shelf life of pasteurised products. He initiated studies on cheese yield and quality.

To encourage dialogue with the UK Dairy Industry, Willie and Donald set up a Consultative Panel for Milk Utilisation in the late 1970s. The panel comprised the Technical Directors of all major UK dairy companies. With this forum for discussion, Donald's group expanded rapidly in the 1980s, fully supported by funding from the Dairy Industry.

In the early days, there was little in the way of pilot plant at HRI. Most of the practical work was carried out at the Dairy School at the then West of Scotland Agricultural College at Auchincruive. Donald set about designing and commissioning the pilot plant at HRI over the next 10 years or so, gradually building plant from laboratory scale to semi-industrial, with a capability of mimicking industrial processes for all major groups of dairy products. HRI's dairy farm provided samples for studies on the effects of seasonality of milk composition on product yield and quality. Differences in casein micelle structure and fat composition between breeds of cattle were studied in relation to processing requirements, product functionality and yield across a range of products. Microbiological studies continued with the evaluation of methodologies for extending the shelf life of dairy products with particular relevance to the microbiological safety and consumer quality. Cheese studies, initially focused on yield and quality as influenced by milk composition and processing, subsequently developed into studies on the biogenesis of cheese flavour.

Donald trained as a physical chemist. He had a natural aptitude for translating the more fundamental studies on milk chemistry in the Food Research Division to practical application. This was apparent in all his work and illustrated nicely in a project undertaken with Willie Banks in the late 1970s. A Scottish distiller approached HRI with a request for help in developing a cream liqueur. At the time cream liqueurs on the market were susceptible to a stability issue termed ‘cream plug’. Drawing on fundamental studies on alcohol stability of caseins at HRI, Donald and Willie developed a novel protocol for cream liqueur manufacture which effectively eliminated the defect. Inver House Distillers successfully launched ‘Heather Cream’, the new protocol was widely taken up by the cream liqueur industry and many projects on novel cream liqueurs were undertaken by Donald throughout his working life.

In the 1990s, Donald set up the Sensory Unit, employing a carefully screened group of taste panellists, and collaborating with statisticians from the University of Edinburgh. This allowed for sensory profiling of products across all projects. It was key to work on cheese flavour biogenesis and led to participation in many European Union funded cheese projects. Commercial work in profiling was undertaken for starter culture manufacturers, cheese producers, cream liqueur manufacturers and virtually all sectors of the dairy industry.

Throughout his time at HRI, Donald's work was greatly supported by the dairy and associated industries. The Consultative Panel for Milk Utilisation met twice yearly for more than 20 years. It was a forum for discussion of generic dairy industry issues on product quality and functionality and resulted in substantial funding for numerous projects over the years.

The Consultative Panel meeting was always followed by a day of annual leave for Donald and Willie. They would set off for a spot of salmon fishing on the River Nith, and would use this time to reflect on the previous day's discussions and to forge plans for future work. Donald enjoyed trout fishing in his local rivers; he would inevitably find a river to cast a line when on holiday with his family and liked to contribute articles on trout fishing to his favourite fishing magazines. In his spare time, he also participated in civil defence training exercises, being the Group Controller in the Warning Team (UKWMO) Group 25 at Ayr.

Donald was an active member of the Society of Dairy Technology, frequently presenting at SDT conferences and symposia. He served on the editorial board of the Journal of the Society of Dairy Technology both as a member and as editor of the journal. He undertook the role of chairman of SDT for both the Scottish Section and the main UK Society. He was delighted to receive the Gold Medal Award from the SDT. He was a Fellow of the Institute of Food Science and Technology. His work was recognised internationally, travelling extensively and presenting at conferences and symposia throughout the world. In recognition of his remarkable contribution to the scientific knowledge of dairy foods, he received the prestigious International Dairy Federation Award in 2005.

Donald was a Visiting Professor of Food Science at the University of Strathclyde and an honorary lecturer at the University of Glasgow. In 1994, on the retirement of Willie Banks, Donald became head of the Food Research Division. He had a keen sense of humour and his infectious enthusiasm, encouragement and kindness were much appreciated by his staff and students. He was much admired and respected by colleagues and associates in both industry and academia.

He was a great family man. His wife Marion, whom he met while at Chorleywood, fully supported him throughout his career. They had two daughters, Fiona and Karen, of whom he was very proud. Donald was diagnosed with Parkinson's Disease some 30 years ago. The diagnosis did not diminish his enthusiasm or capacity for work. He continued with consultancy work well into his retirement.