Investigating the potential of Portulacaria afra (spekboom) leaves as a sustainable food source

Indigenous plants could contribute to sustaining and improving the current food system in South Africa. This study determined the morphological and physicochemical properties of raw and cooked (baked, stir-fried, steamed and blanched) P. afra leaves. Additionally, a survey was conducted to collect exploratory data on consumer knowledge and awareness of P. afra leaves as a food source, and willingness to incorporate them into their diets. Cooking resulted in a lighter green cooked product with a less firm texture. The water activity (0.93–0.95) and moisture content (84.86–92.89%) of P. afra leaves were similar to most fresh green leafy vegetables. P. afra has a low pH (≤ 3.5) and low titratable acidity (< 0.094), classifying it as a high-acid food. The ascorbic acid content of the leaves increased by 18.23–32.02% upon cooking. Cooking significantly reduced (p < 0.05) the viscosity of the P. afra leaf extract, which also showed a non-Newtonian, pseudoplastic (shear-thinning) behaviour. Survey results revealed a limited consumer awareness of P. afra as a food source. The majority of respondents had little to no knowledge of the use (62.5%), health benefits (67.5%), and flavour profile (66.6%) of P. afra leaves. Despite this, a majority of the respondents indicated a willingness to include, eat, and purchase P. afra leaves. This indicates a need for increased information dissemination on its health benefits, uses as a food source and potential dietary inclusion. P. afra leaves can be consumed after cooking, stored and used similarly to other fresh green leafy vegetables.