Exergy efficiency from staple food ingredients to body metabolism: The case of carbohydrates

Abstract

One of the methods to evaluate the efficiency in the production of foods is using exergy, the share of useful energy, and exergy analysis. In this paper, we propose a link between exergy analysis and nutrition to account for the exergy efficiency (exergy of output per exergy of input) in the metabolism of nutrients from foods in the human body. For this, we analyzed the exergy efficiency of four different chains of carbohydrate-rich products based on semi-industrial preparation processes and we included nutrient bioavailability through the use of several bioavailability indicators, including the glycemic index and protein digestibility. The least exergy efficient chain changed when not only looking at the exergy losses of the food processing chains, but also including the bioavailability and conversion of nutrients into adenosine triphosphate (ATP), the main molecule for energy storage in the body. When including only the processing chain, white bread presented the highest exergy loss, whereas the lowest values pointed to the spaghetti chain when also including metabolism both because of its preprocessing chain and its low bioavailability. In contrast, cooked potatoes were found to be an efficient source of ATP due to both a high metabolic efficiency and low process exergy losses. The carbohydrate bioavailability had a strong influence on the overall exergy efficiency of the studied cases, which shows the importance of including bioavailability aspects in the sustainability assessment of industrial food processing chains.