Quality and safety of Sterculia murex, a scientifically unknown nut from Southern Africa

Sterculia murex, the wild Lowveld chestnut, is an indigenous tree from southern Africa. In South Africa, this tree has a very restricted distribution in eastern Mpumalanga. The tree is identified by its distinctive flowers and spiky fruits, and is also known for its oily and sweet-tasting seeds. Although the seeds are consumed by local communities, no data is available on the safety and commercial value of the nuts. This paper is the first published report on the safety and composition of S. murex nuts since the unpublished report by Wehmeyer in 1986. The microbiological analysis confirms the minimal presence of microorganisms in the raw material but no contamination or mycotoxins were observed after roasting. Due to the high water content (9.99%), a drying of ten days at 35 °C was found to be required in order to obtain a suitable product for roasting. The nuts were found to contain 14% protein, with a high percentage of glutamic acid, aspartic acid, arginine, leucine and glycine, and 16% oil. The roasted nuts possess phenolics with a good antioxidant activity and can be considered as a fairly good source of selenium, copper, calcium and iron. The sensory evaluation highlights the aftertaste of the roasted nuts. Therefore, the roasted nuts are best incorporated as an ingredient into breakfast cereals mixes or snacks and energy bars to take advantage of its good nutritive food value.