Abstract
Over the last twenty years, Réunion Island has experienced a dietary change marked by a decline in the consumption of starchy foods and plant-based products, in favor of foods rich in animal proteins, refined sugars and ultra-processed products. This dietary transition is alarming, with a worrying rise in the prevalence of overweight and obesity. This public health situation calls for a diversification of local eating habits towards healthier food products. The sweet potato root is particularly rich in fibers and micronutrients such as phenolics compounds, carotenoids (in orange-fleshed varieties) or anthocyanins (in violet-fleshed varieties). Starch, a major component, makes it a food of interest for slow carbohydrate intake. This root is a promising option to reintroduce plant-based foods into the diets of Reunion's inhabitants. Its agronomic characteristics are also advantageous as it can be grown in a variety of climatic conditions, including drought, and its production yields are high.This thesis is part of a program for the promotion of locally produced sweet potatoes. The aim of this thesis was twofold. First, it aimed to characterize the diversity in composition of a panel of cultivars grown in reunion Island, for their morphotype and root composition. Secondly, the objective was to explore the impact of processing that involved a lactic acid fermentation step and a cooking step (boiling, steaming, baking), on content and bioavailability of bioactive compounds. Lactic acid fermentation is an ancestral sustainable process, which increases food stability and modulates both sensory properties and composition of foods. Cooking of sweet potato root is required to gelatinize starch and obtain a pleasant texture. Thus, the aim of the present study was therefore to identify which of the processes applied to sweet potatoes guarantee the best nutritional qualities, taking into account inter-cultivar diversity. This approach led to the recommendation of cultivars, among those that are available in library,which presented the best nutritional benefits. A detailed profile of bioactive compounds of nutritional interest was established, regarding their content and bioavailability, as a consequence of each processing step applied and in which order. Steaming, followed by a step of lactic acid fermentation, is the process leading to the best stability of bioactive compounds (phenolic compounds, carotenoids and anthocyanins). On the opposite, lactic acid fermentation applied first is in most cases detrimental to bioactive compound content. This thesis resulted in recommendations for the choice of cultivars and processing methods for the regional food transformation sector. It contributes to rehabilitate sweet potato consumption in Reunion Island diets, by highlighting its nutritional benefits and optimizing its processing.