(1) Background: The oil stability of tree nuts during storage can be influenced by storage conditions such as temperature, humidity, and moisture concentration. However, few studies have assessed how the presence of testa and shell affects the oil stability of tree nuts during storage. We aimed to determine how storage conditions affect oil stability in almond and canarium, in particular, the presence of testa and storage time of nut-in-shell (NIS). (2) Methods: We measured peroxide value (PV), free fatty acid (FFA) and hexanal concentrations of almond and canarium (blanched vs. kernel-in-testa) stored at 45 °C for 24 days. We also measured PV, FFA and fatty acid composition of canarium samples at days 0 and 140 stored as NIS under ambient conditions. (3) Results: The presence of testa in almond and canarium decreased hexanal and PV concentrations at day 24 of incubation. Canarium PV and FFA concentrations increased over 140 days of storage in the shell compared to day 0. However, both PV and FFA concentrations remained within the acceptable threshold during storage. No changes in fatty acid composition were found during NIS storage. (4) Conclusions: Testa and shell could act as a natural coating, slowing down oxidation rates. Hence, long-term storage on nuts in testa or nuts in shell are recommended for tree nuts.

Food security remains one of the most critical global challenges of the 21st century. Traditional tree crops domesticated by indigenous people have the potential to increase food security and improve the livelihoods of smallholders in developing countries. However, the nut characteristics of many traditional tree crop species in the tropics are poorly understood. In particular, physical and chemical characteristics are important to explore when selecting trees to commercialise. Three species, Barringtonia procera, B. edulis, and B. nova-hiberniae, have a long history of traditional use and domestication in Pacific Island countries. The aim of this study was to explore the physical and chemical characteristics of Barringtonia spp. in three Pacific countries: Solomon Islands, Vanuatu, and Fiji. There were significant differences in kernel weight, oil concentration, and fatty acid concentration among the countries. The kernel weight was significantly higher in Solomon Islands compared with those in Vanuatu and Fiji (9.65 g, 7.61 g, and 5.64 g, respectively). Average kernel weight in Fiji was well above 3 g, which indicated that processing could be commercially viable. The total oil concentration was significantly higher in Vanuatu and Solomon Islands than Fiji, with average concentrations of 38.96% in Solomon Islands, 47.11% in Vanuatu, and 26.20% in Fiji. Barringtonia spp. exhibited high concentrations of unsaturated fatty acids, similar to other tropical nuts, which suggests that it may be a potential healthy oil for human consumption. Notably, kernel size, oil concentration, and fatty acid composition varied geographically, potentially due to climatic differences and historical seed transfer. Our study demonstrated the potential of Barringtonia to be commercialised to enhance food and nutrition security and provide a guide for cultivar selection.

Indigenous forest foods have great potential to diversify cropping systems and increase food security and the resilience of food systems to climate change. Underutilised indigenous tree nuts in particular can provide health benefits to local communities and improve livelihoods when commercialised. However, for many tree nut species, there is little knowledge of important kernel characteristics. Kernel size and oil composition are important factors for commercialisation and health benefits, respectively. We assessed kernel attributes of Terminalia catappa L. (Combretaceae), a traditional forest food in the Pacific, in the Solomon Islands, Vanuatu and Fiji. We assessed kernel mass and kernel-to-fruit mass ratio, explored the fatty acid profile of oil, and oil stability against oxidation using accelerated ageing at 45 °C for 21 days. The largest kernels were found in the Solomon Islands with an average mass of 1.66 g. Similarly, kernel-to-fruit mass ratios were higher in the Solomon Islands and Vanuatu than in Fiji. Terminalia catappa contained higher concentrations of unsaturated fatty acids than saturated fatty acids. Among the unsaturated fatty acids, oleic acid and linoleic acid were the two most abundant. Kernels incubated at 45 °C exhibited significantly higher hexanal concentrations on day 7 compared to those on day 0 of incubation. This rapid oil oxidation may be associated with high unsaturated fatty acid concentrations in kernels. These findings may have implications for oil shelf life. Our study suggests T. catappa trees from the Solomon Islands exhibit desirable kernel characteristics that make them suitable for selection and commercialization. The commercialization of an underutilised forest food tree like T. catappa will enhance food and nutrition security for local communities.