Abstract
The demand for nutraceutical products to maintain optimal health and prevent chronic disease continues to rise due to the high cost of healthcare. Nutraceutical products usually include plant bioactives that provide practical, safe therapeutic benefits, such as disease prevention. Some of the most influential nutraceutical products are derived from blackcurrant fruit (Ribes nigrum L.). Blackcurrants have a high anthocyanin content, which is responsible for the wide array of health benefits associated with their consumption. As such, nutraceutical products made from blackcurrants are increasingly being developed for their benefits. Although New Zealand is a major producer, there is a lack of research on the bioactive potential of New Zealand-grown cultivars, particularly regarding the potential benefits of the UV index. Moreover, the effect of unique phytochemical differences across cultivars, following standard drying methods prior to nutraceutical production, remains unclear.
This thesis aimed to investigate the role of cultivar in shaping the phytochemical composition of eight blackcurrant cultivars, and to explore how these unique profiles affect the retention of bioactive compounds after drying treatments and the bioprotective capacity during digestion. In Chapter 2, the phytochemical composition was studied using a combination of analytical techniques in fresh, freeze-dried, and oven-dried material. Chapter 3 explored how the unique phytochemical composition of the eight blackcurrant cultivars contributed to bioactive potential in oxidatively stressed Caco-2 cells, illustrating the potential health benefits.
This thesis found that total phenolic content was a major driver of total antioxidant capacity, with cultivars Rua and Kepler showing the strongest responses. Cultivars with higher anthocyanin levels, such as Ben Ard, Blackadder, Murchison, Rua and Kepler, also consistently demonstrated greater bioactive retention after drying than Hamilton, Magnus and Lb28. This trend was reinforced by in vitro digests prepared using the INFOGEST method, in which anthocyanin-rich cultivars exhibited the strongest bioprotective capacity. Across both chapters, the processing effect was apparent: freeze-drying preserved phytocompounds far more effectively than oven-drying, which caused substantial depletion in all cultivars relative to fresh material.
This thesis offers foundational insights into how blackcurrants can be optimised for nutraceutical production, both in New Zealand and internationally. As such, these findings ensure the development of sustainable, reliable products that deliver practical therapeutic benefits.