Riddet Institute science features on 2019 Massey University Deans List

“Research work reported here is not only of exceptional nature and of great importance but also has been carried out very intelligently and ingeniously”, states the examiner’s report on Dr Arup Nag’s PhD thesis. Dr Nag, a Riddet Institute research officer and former Massey University PhD student is delighted to have been selected to appear on the 2019 Massey University Dean’s List of Exceptional Theses.

The Dean’s List of Exceptional Theses published each year, is a small selection of PhD research that examiners consider to be of exceptional quality and in the top 10% of work in the scientific field. It is an outstanding honour. Dr Nag joins three former Riddet Institute students who have also received this accolade: Dr Anwesha Sakar (now Associate Professor of Food Science at the University of Leeds, UK) and Dr Carlene Stark, both in 2010 with Dr Devastotra Poddar in 2016.

Dr Nag’s thesis is entitled “Studies on the stability of probiotic bacteria during long term storage” and he completed his PhD working part time at the Institute. A PhD was a natural progression to develop his skills and expertise, as he was employed as a researcher in the same scientific area.

Dr Nag explains “Bacteria are consumed in many products – in capsules, in milk drinks or in tablets for probiotic supplements for example – and they are stabilized within the product. This means the bacteria go into an inert state or coma, where they are alive, but their biological activity is temporarily halted. The bacteria will gradually die off over time. That is the challenge, to stabilize them so that they can be stored, even at room temperature, for longer periods. When consumed, the bacteria revive. Probiotic milk drinks have a shelf life of about a week in the refrigerator for this reason. A suitable stabilization technique must be used if the manufacturer wants to ensure that even after one year a powdered product contains live probiotics.”

“My project was about stabilising the bacteria in a way to provide a longer shelf life – 1-2 years depending on the storage temperature. I tested novel techniques, mild processing that was not harmful to the bacteria. I discovered the mechanism and the science behind the stabilization process. The crucial part of the process is the protecting agents that help to maintain bacterial structure and prevent deformation. I used a new preservation technique (fluidized bed drying) and found it gives better results and is less expensive than the standard industrial process.”

Dr Nag began his PhD research in 2014, following his Master of Food Technology in 2009, both  at Massey University. His PhD examiners were highly complementary not only about his research thesis but the fact that the science is currently being commercialised. “The study is highly significant and unique in its approach. Overall, it is an excellent piece of original work of an outstanding nature and has been successful in achieving its objectives. The work not only adds to the advancement of technology and knowledge in the field of stability of bacteria undergoing long term storage. But may also revolutionize the industrial production and use of shelf stable probiotic foods,” say the examiners. Dr Nag is currently managing the handover of the technology as it transfers to a manufacturing environment, where it is being marketed as “ProBioLifeTM” .The wider project has resulted in two more PhD projects, patents and is now subject to the commercialisation contract.

Dr Nag says being part of the innovation process has been important to him “I never expected to receive this honour, it is very rewarding. After so many years, we are finally about to commercialise the technology. I will be visiting a factory soon and helping to manufacture a real product. I am managing the hand over project to transfer the expertise. The loop is finally being completed”, he says. While the process Dr Nag and his wider team have designed, is very different from the standard process used in the food industry, they are hopeful of a shift to the new technology. “If we can show that the product is superior, then I am optimistic it will be adopted gradually,” says Dr Nag.

Dr Nag was supervised by Distinguished Professor Harjinder Singh (Riddet Institute), Dr Abby Thompson (Food HQ), Dr Rachel Anderson (AgResearch), Dr Derek Haisman (Riddet Institute) and Dr Pat Janssen (Massey University).

2022 © Riddet Institute