Tree nuts are rich in nutrients, and global production and consumption have doubled during the last decade. However, nuts have a range of quality defects that must be detected and removed during post-harvest processing. Tree nuts can develop hidden internal discoloration, and current sorting methods are prone to subjectivity and human error. Therefore, non-destructive, real-time methods to evaluate internal nut quality are needed. This study explored the potential for VNIR (400–1000 nm) hyperspectral imaging to classify brown center disorder in macadamias. This study compared the accuracy of classifiers developed using images of kernels imaged in face-up and face-down orientations. Classification accuracy was excellent using face-up (>97.9%) and face-down (>94%) images using ensemble and linear discriminate models before and after wavelength selection. Combining images to form a pooled dataset also provided high accuracy (>90%) using artificial neural network and support vector machine models. Overall, HSI has great potential for commercial application in nut processing to detect internal brown centers using images of the outside kernel surface in the VNIR range. This technology will allow rapid and non-destructive evaluation of intact nut products that can then be marketed as a high-quality, defect-free product, compared with traditional methods that rely heavily on representative sub-sampling.

(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.

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.