Meeting the global protein supply requirements of a growing and ageing population.

Human dietary patterns are a major cause of environmental transformation, with agriculture occupying ~ 50% of global land space, while food production itself is responsible for ~ 30% of all greenhouse gas emissions and 70% of freshwater use. Furthermore, the global population is also growing, such that by 2050, it is estimated to exceed ~ 9 billion. While most of this expansion in population is expected to occur in developing countries, in high-income countries there are also predicted changes in demographics, with major increases in the number of older people. There is a growing consensus that older people have a greater requirement for protein. With a larger and older population, global needs for protein are set to increase. This paper summarises the conclusions from a Rank Prize funded colloquium evaluating novel strategies to meet this increasing global protein need.

A single-enzyme system for starch digestibility screening and its relevance to understanding and predicting the glycaemic index of food products.

There is currently great interest in increasing provisions of healthier carbohydrate foods, particularly those that possess a low Glycaemic Index (GI) when measured in vivo. The metabolic response to many starch-rich foods is driven largely by differences in the rate and extent of starch amylolysis. Enzyme-kinetic parameters obtained from high-throughput in vitro amylolysis assays therefore have potential for rapid prediction of GI for starch-rich foods. The aim of this study was to evaluate the usefulness of a starch digestibility screening method and resulting enzyme-kinetic parameters in comparing and predicting the GI of a range of carbohydrate-rich foods. Starch-rich foods (n = 20) with GI ranging from 36 to 81 were digested by porcine pancreatic α-amylase for 90 min under a fixed enzyme-substrate ratio (4 U/10 mg starch) at 37 °C on a rotary mixer. Starch digestion progress was determined by quantification of reducing sugar concentration in aliquots collected throughout the incubation. Indices of starch digestibility (C20, C60, C90, HI, C∞, and k) were obtained and compared with GI values. Digestibility curves revealed differences in the starch amylolysis for the broad range of foods tested. In vitro starch digestibility indices were significantly correlated (p < 0.01) with GI, with the exception of the rate constant, k. Out of all the indices tested, C90 and C∞ were the most strongly correlated with in vivo rankings for GI of matched food products (Tb = 0.596, p < 0.001 and Tb = 0.599, p < 0.01, respectively), however the digestibility plots obtained for some of the more slowly digested foods were linear over 90 min meaning that C∞ and k could not be obtained from first order kinetic analysis. C90 was most strongly correlated with the absolute GI values (r = 0.724, p < 0.001). Overall starch digestibility profiles reflected differences in starch amylolysis for food with varying GI, and C90 provided the best indication of absolute and relative GI values across all product categories. The in vitro starch digestibility screening method shows potential for rapid prediction of GI values and is recommended for early stage food product development and for mechanistic studies.