Impact of steaming as a processing technique on the nutritional, health-promoting, and functionality of spekboom (Portulacaria afra) plant properties

The study of processing wild edible succulent plants such as the spekboom (Portulacaria afra) as a nutritional and functional food source is crucial for improving food security, combating malnutrition, and promoting dietary diversity. This study evaluated the effect of steaming, a traditional food processing method on enhancing the nutritional and functional properties of the spekboom plant leaves. Fresh leaves were steamed at 100 °C for 4 min, blended into a pulp, frozen, freeze-dried, and milled into a powder. The resulting powder was analysed for its nutritional composition, health-promoting, and functional properties. The results indicated that steaming significantly improved the nutritional profile, increasing fibre content by 14.07% and protein by 12.06%. Phytochemical levels were also enhanced, with total phenolic content reaching 15.14 mg GAE/g and total flavonoid content 15.52 mg/QE/g. Antioxidant activity increased markedly, as shown by 2,2-azinobis-(3-ethylbenzthiazolin-6-sulphonic acid) (26.73 mM TE/g) and ferric reducing antioxidant power (FRAP) (95.72 μmol TE/g). Gas chromatography–mass spectrometry analysis revealed increased average peak areas of several amino acid metabolites following steaming. Functional properties were also enhanced, with water and oil absorption capacities increasing 6–10 g/g. Additionally, pasting properties showed a higher peak and final viscosities, suggesting improved gel strength and stability. Overall, steaming enhanced the nutritional quality, functional characteristics, and potential health benefits of spekboom. These findings highlight the value of processing wild edible succulent plants to improve their suitability and appeal as nutrient-rich ingredients human diet consumption.