The effects of tree spacing regime and tree species composition on mineral nutrient composition of cocoa beans and canarium nuts in 8-year-old cocoa plantations

The selection of shade trees with appropriate spacing is important for minimising their impact on nutrient accumulation by understorey cash crops in agroforestry systems. Cocoa trees may be intercropped with overstorey legume or non-legume shade trees. A legume tree and/or a non-legume timber tree with edible kernels (Gliricidia sepium and Canarium indicum, respectively) are used as shade trees in cocoa plantations particularly in Papua New Guinea. This study explored the nutrient concentrations of cocoa beans in response to both tree-shade species and shade-tree spacing regime. The study also investigated the extent to which C. indicum tree spacing altered the nutrient concentrations of canarium kernels. G. sepium trees in the study had a final spacing of 12 m × 12 m while the spacing regimes of either 8 m × 8 m or 8 m × 16 m used for C. indicum. The calcium (Ca) concentrations of cocoa beans did not differ significantly between plants located next to G. sepium and plants located next to C. indicum. Cocoa beans next to C. indicum trees with spacing of 8 m × 16 m had higher potassium (K) concentrations than those next to G. sepium trees. However, phosphorus (P) concentrations of cocoa beans next to C. indicum trees with spacing of 8 m × 8 m or next to G. sepium trees were significantly higher than those next to C. indicum trees with spacing of 8 m × 16 m. The K concentrations in cocoa beans and soil were not correlated nor were the P concentrations in cocoa beans and soil. Correlations between nutrients in leaves and cocoa beans, or between leaves and canarium kernels, were not strong. Our results suggest that cocoa and canarium trees can be intercropped successfully, and that they do not compete for soil nutrients. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature

A non-destructive determination of peroxide values, total nitrogen and mineral nutrients in an edible tree nut using hyperspectral imaging

Nuts are nutritionally valuable for a healthy diet but can be prone to rancidity due to their high unsaturated fat content. Nutrient content of nuts is an important component of their health benefits but measuring both rancidity and nutrient content of nuts is laborious, tedious and expensive. Hyperspectral imaging has been used to predict chemical composition of plant parts. This technique has the potential to rapidly predict chemical composition of nuts, including rancidity. Hence, this study explored to what extent hyperspectral imaging (400–1000 nm) could predict chemical components of Canarium indicum nuts. Partial least squares regression (PLSR) models were developed to predict kernel rancidity using peroxide value (PV) for two different batches of kernels, and macro- and micronutrients of kernels using the spectra of the samples obtained from hyperspectral images. The models provided acceptable prediction abilities with strong coefficients of determination (R2) and ratios of prediction to deviation (RPD) of the test set for PV, first batch (R2 = 0.72; RPD = 1.66), PV, second batch (R2 = 0.81; RPD = 2.30), total nitrogen (R2 = 0.80; RPD = 1.58), iron (R2 = 0.75; RPD = 1.46), potassium (R2 = 0.51; RPD = 0.94), magnesium (R2 = 0.81; RPD = 2.04), manganese (R2 = 0.71; RPD = 1.84), sulphur (R2 = 0.76; RPD = 1.84) and zinc (R2 = 0.62; RPD = 1.37) using selected wavelengths. This study indicated that visible-near infrared (VNIR) hyperspectral imaging has the potential to be used for prediction of chemical components of C. indicum nuts without the need for destructive analysis. This technique has potential to be used to predict chemical components in other nuts. © 2018 Elsevier B.V

Effects of roasting on kernel peroxide value, free fatty acid, fatty acid composition and crude protein content

Roasting nuts may alter their chemical composition leading to changes in their health benefits. However, the presence of testa may alleviate the negative effects of thermal treatments. Hence, this study aimed to explore the effects of roasting on kernel chemical quality and colour development of Canarium indicum and examine to what extent testa would protect kernels against damage from roasting. Roasting decreased peroxide value but increased free fatty acid, probably due to increased cell destruction and lack of enzyme inactivation, respectively. Protein content of kernels significantly decreased after roasting compared to raw kernels. However, testa-on kernels contained significantly higher protein content compared to testa-off kernels. Whilst colour development and mottling were observed in temperatures beyond 120C, roasting did not alter fatty acid compositions of kernels. The mild roasting and presence of testa in kernels can be used to enhance health benefits of kernels

Nutritional quality of almond, canarium, cashew and pistachio and their oil photooxidative stability

Daily consumption of nuts is recommended as a part of a healthy diet as they contain protein and are rich in beneficial fatty acids and essential nutrients. The nutritional qualities of nuts are affected by their fatty acid composition and other factors such as maturity. Oil oxidative stability is important to determine nut nutritional quality in terms of fatty acid composition over storage. Therefore, this study aimed to (a) assess the nutritional quality (photooxidative stability and nutrient composition) of almond, cashew, pistachio and canarium (a newly commercialised indigenous nut); and (b) explore differences in nutrient concentrations between immature and mature canarium nuts. A decrease in polyunsaturated fats after photooxidation in almond and pistachio was observed. Canarium oil did not change following photooxidation suggesting canarium may display a long shelf life when stored appropriately. Our study indicated that almond provided over 50% of the recommended daily intake for manganese whereas canarium intake provided 50% of the recommended daily intake for iron (for males). Pistachio was richer in potassium compared with other nuts and canarium was richer in boron, iron and zinc than other nut species. Mature canarium kernels were richer in boron, iron and zinc but contained less potassium than immature canarium. Therefore, the current study recommended to store kernels in dark to decrease oil photooxidation, and maturity of canarium kernels at the harvest time was important affecting nutrient concentrations of kernels. © 2018, Association of Food Scientists & Technologists (India)