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Communication

Variations in Physical and Chemical Characteristics of Terminalia catappa Nuts

by
Shahla Hosseini Bai
1,*,
Bruce Randall
1,
Repson Gama
2,
Basil Gua
3,
Doni Keli
4,
Kim Jones
5,
Brittany Elliott
6 and
Helen M. Wallace
6
1
School of Environment and Science, Griffith University, Nathan, Brisbane, QLD 4111, Australia
2
School of Science, Technology and Engineering, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia
3
Beg’s Sol Seed Technology and Supplies, Honiara, Solomon Islands
4
Solfarm Fresh, Honiara, Solomon Islands
5
Cropwatch Independent Laboratories, Wardell, NSW 2477, Australia
6
School of Biology and Environmental Science, Faculty of Science, Queensland University of Technology, Brisbane, QLD 4000, Australia
*
Author to whom correspondence should be addressed.
Horticulturae 2025, 11(5), 540; https://doi.org/10.3390/horticulturae11050540
Submission received: 27 March 2025 / Revised: 7 May 2025 / Accepted: 9 May 2025 / Published: 16 May 2025
(This article belongs to the Special Issue Wild Plant Species as Potential Horticultural Crops: An Opportunity for Farmers and Consumers—2nd Edition)
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Abstract

:
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.

Graphical Abstract

1. Introduction

Forests are one of the major sources of food and income for many communities worldwide [1,2,3]. Forests in the tropics also provide livelihood, environmental and nutritional benefits in rural populations, although tropical trees are often poorly integrated into food systems [4]. There is growing interest in scaling up forest-sourced foods such as wild edible nuts to increase food security [1,3,5]. However, very few culinary nut species have been commercialised, and over 95% of global trade in culinary nuts consists of just five species: almond (Prunus amygdalus Batch.), walnut (Juglans regia L.), cashew (Anacardium occidentale L.), hazelnut (Corylus avellana L.) and pistachio (Pistacia vera L.) [6]. The world market for processed nuts has almost doubled in the last decade driven by consumers’ growing preference for healthy snacks [6]. New indigenous tree nut species offer the potential to improve livelihoods when traded commercially and also to increase food security in rural populations.
Canarium (Canarium indicum L.) and Brazil nuts (Bertholletia excelsa Bonpl.) are two indigenous tree nuts that have been successfully commercialised [7,8,9]. Nuts from Canarium indicum are the basis of an emerging industry that has increased income for small-scale farmers, especially women in Pacific countries [10]. Brazil nut provides approximately 40% of household income in the Amazon basin [11]. Both canarium and Brazil nuts are sourced from forests and hence help to maintain forest cover and biodiversity while producing income for smallholders [8,11]. Thus, commercialising indigenous tree nut species from forests has the potential to empower small-scale farmers in developing countries and maintain the biodiversity of forests [12,13].
Key considerations for commercialising new nuts species are kernel size and kernel recovery [14,15,16]. Kernel recovery is calculated based on the kernel recovered from the weight of the intact nut including the shell (nut in shell) [17]. Kernel-to-fruit ratio can also be used as an alternative for kernel recovery in tree selection if the kernel is extracted from the fresh fruit, rather than from the nut in shell. High kernel mass and high kernel recovery or kernel-to-fruit ratio lead to high financial returns for processors, growers and smallholder farmers [15]. Premium prices are also usually paid for large kernels, which leads to additional income for both growers and processors [15]. Kernel mass can be influenced by various factors including soil nutrient availability, management practices and environmental factors [15,17,18]. In addition, kernels are often larger close to villages, compared with those in the forests, as indigenous people have selected and domesticated nut species over centuries [19]. As a result, there can be large differences in kernel mass and kernel-to-fruit ratio throughout the geographic range of a species [14,15]. In general, trees with large kernel mass or kernel-to-fruit ratio need to be identified and propagated to commercialise a new nut crop [14,20].
Tree nuts are particularly rich in essential minerals, high in protein and contain beneficial fatty acids, antioxidants and some vitamins (i.e., A and E) [5,9,21]. Both saturated and unsaturated fatty acids are beneficial [22]. Unsaturated fatty acids, however, are more susceptible to oxidation than saturated fatty acids [5,22,23]. High unsaturated lipid concentrations may result in decreased oil stability against oxidation [23]. Lipid oxidation leads to reduced oil quality for human health and shortens the shelf life of nuts [22]. Lipid oxidation should be minimised while processing and packing nuts. The fatty acid profile can also be associated with different health benefits [21], but there is no information on the fatty acid profile for many indigenous tree nuts. The fatty acid profile is influenced by both environment and genetics [24]. There is a growing interest in including chemical composition as a selection trait in nut breeding programmes [25]. Hence, it is important to explore the fatty acid composition of tree nuts and understand the oil health benefits and oil stability to enable commercialisation.
This study examines the kernel attributes in Terminalia catappa L. (Combretaceae) collected from three Pacific countries. Terminalia catappa is a monoecious, large tropical tree that inhabits Australia, southeast Asia, Malesia, Polynesia and the Pacific Islands [26]. The tree can grow up to 40 m tall and is characterised by its drupaceous fruits, which can vary between 2.5 and 10 cm in length and approximately 2 and 4 cm in width [27]. The transition of fruit to maturity is distinguished by a change in the exterior fruit flesh colour from green to yellow and then, finally, red when fully mature or ripe [27]. This species produces flattened-obovoid seeds that are edible (hereafter referred to as ‘kernels’) and encased by an outer protective layer known as testa [27,28]. Terminalia catappa, commonly known as tropical almond, or Alite in the Solomon Islands, Natapoa in Vanuatu and Tarvola in Fiji, has been traditionally consumed throughout the Pacific and has recently been flagged for potential commercialisation [14]. In the Pacific, T. catappa usually grows within coastal areas where the soil is poor (Figure 1) [27]. This tree can play an important role in stabilising soil, as it establishes in coastal areas where the soil is highly prone to erosion [27]. This tree species commences bearing fruit when it reaches three years of age and it is also a timber tree [27].
In this study, we aimed to (1) investigate differences in fruit and kernel sizes in trees between countries; (2) determine total oil and fatty acid composition of oil; and (3) examine oil stability and potential for long shelf life using an accelerated ageing trial. It was hypothesised that there would be variations in fruit and kernel size among countries and it was also expected that the fatty acid profile of T. catappa would affect the shelf life of kernels.

2. Materials and Methods

2.1. Sample Collection and Preparation

We had 30 fruit replicates randomly collected from the canopy of each tree and 69 tree replicates within countries. In brief, the fruits of T. catappa were collected from villages located in the Solomon Islands (18 trees), Vanuatu (21 trees) and Fiji (30 trees) over 24 months between March 2017 and 2019 (Figure 2). The fruiting season of T. catappa varies across the Pacific Islands [27]. In lower latitudes, fruiting can be intermittent throughout the year [27]. Fruit production in Fiji and Vanuatu is typically highest between March and June [27]. In this study, the fruit collection aligned with the timing of fruiting; however, there were some occasions where fruit were collected at different times due to differences in fruiting patterns. The weight of individual fresh fruit was recorded using digital scales (PA4101 Pioneer Analytical Balance, OHAUS, Parsippany, NJ, USA). Traditional methods were used to crack fruit samples, where applying the force of stone hammers on either the edge or apex of the fruit revealed the kernels inside [27]. Kernels were then dried for 9 h at 40 °C to approximately 10% moisture content and weighed.

2.2. Oil Extraction and Chemical Analyses

The 30 kernels collected from each tree were randomly assigned into 5 replicates per tree, with each replicate containing 6 kernels. Kernels of each replicate were pooled and crushed using a mortar and pestle. The crushed kernels were added to Pentane (45–50 mL) and stirred for 45 min using a magnetic stirrer followed by centrifuging at 2600 rpm for 6 min. The procedure was repeated to ensure kernel oil was fully extracted. The Pentane was then evaporated a Bucci Rotovac (BÜCHI Labortechnik AG, Flawil, Switzerland). The weight of oil was recorded and kept in sealed vials at 4 °C for fatty acid composition analysis. A PerkinElmer Clarus 580 GC coupled to a SQ 8S MS (PerkinElmer, Waltham, MA, USA) was used to measure the fatty acid composition of the oil samples, following the same conditions as described in Bai et al. [5]. In summary, an Elite-5MS (30 m × 0.25 mm × 0.25 μm) column was used, with helium carrier gas at a constant flow of 1.0 mL/min set to a temperature programme of 50 °C for 0.5 min, ramping at 10 °C/min until 300 °C and holding for 1.0 min [5]. Masses ranging from 40 to 400 (m/z) and from 3.1 to 26.5 min at 70 eV were analysed.

2.3. Oil Stability Using Accelerated Ageing

Terminalia catappa fruit were sourced from Vanuatu for this part of our experiment. Approximately 60 fruit were collected from three trees. Kernels were manually extracted from fruits as described above and then dried for 17 h at 45 °C to a moisture content of 1.5%. All kernels were pooled and mixed and then randomly divided into three replicates. Each replicate contained approximately 20 g of the kernel and was sealed in an aluminium foil pouch of 14 cm × 8 cm and incubated at 45 °C for 21 days. Hexanal concentration was measured at day 0 (initial), after 7, 14 and 21 days following the incubation commencement. Approximately 40 mL gas of headspace at each day of sample collection was extracted using a syringe and analysed for hexanal concentration using the e-nose, OdourScan®, developed by Next Instruments [29].

2.4. Calculations

The kernel-to-fruit ratio (%) was calculated as (weight of individual kernel/individual fruit) × 100. Oil content was calculated as (mass of oil × 100)/mass of kernel. Total unsaturated fatty acids (TUS) were calculated as the sum of C16:1 cis (palmitoleic acid), C18:2 (linoleic acid), C18:1 cis (oleic acid), C18:1 trans (elaidic acid) and C20:1 (eicosenoic acid). Total saturated fatty acids (TS) were calculated as the sum of C14:0 (myristic acid), C16:0 (palmitic acid), C18:0 (stearic acid), C20:0 (arachidic acid) and C22:0 (behenic acid).

2.5. Statistical Analyses

All data met the assumptions of normality. We compared differences across countries in kernel attributes including fruit mass, kernel mass, kernel-to-fruit, ratio (%) and total oil and fatty acid composition using a one-way ANOVA followed by Tukey’s test at p < 0.05. The differences in hexanal concentrations among sampling days were examined using a one-way ANOVA followed by Tukey’s test at p < 0.05. Finally, two principal component analyses (PCA) were implemented to (a) visualise how fatty acid compositions, including C16:1, C18:2, C18:1 cis, C20:1, C14:0, C16:0, C18:0, C20:0 and C22:0, were distributed based on the countries and (b) show the extent to which kernel characteristics of fruit mass, kernel mass, kernel-to-fruit weight ratio, total oil content, total saturated fatty acids and total unsaturated fatty acids would vary among three countries. We calculated eigenvalues, percentages of variance and cumulative percentages of variance of PCA scores for fatty acid compositions and kernel characteristics. We explored relationships between different fatty acids using Pearson’s correlation. We also explored correlations between different kernel characteristics using Pearson’s correlation. We explored relationships between fatty acids and kernel characteristics using Pearson’s correlation, with a 2-tailed significance test. The SPSS version 24 (IBM Corp, Chicago, IL, USA) was used to perform all data analyses.

3. Results

The average fruit mass was significantly higher in Vanuatu (33.72 g) than in the Solomon Islands (29.21 g) and Fiji (7.97 g) (Table 1). The smallest fruit mass was found in Fiji. Kernel mass was on average 1.66 g in the Solomon Islands, significantly higher than samples from Vanuatu and Fiji (Table 1). The average kernel mass in Vanuatu was also significantly higher than in Fiji (Table 1). The average kernel-to-fruit ratio (%) was greater in both the Solomon Islands and Vanuatu compared with that of Fiji (Table 1).
Kernels from the Solomon Islands exhibited significantly higher total oil content compared to those from Vanuatu (Table 1). Kernels from Fiji contained significantly higher unsaturated fatty acid concentrations than those from the Solomon Islands and Vanuatu (Table 1). Across all countries, the predominant fatty acids identified were palmitic acid (C16:0), linoleic acid (C18:2) and oleic acid (C18:1Cis) (Table 2).
We identified a strong negative correlation between the two predominant fatty acid concentrations found in T. catappa kernels: palmitic acid (C16:0) and linoleic acid (C18:2) (r = −0.76) (Supplementary Table S1). Positive correlations were found between fruit mass and kernel mass (r = 0.70) and between total saturated fatty acids (TS%) and total unsaturated fatty acids (TUS%) (r = 0.50) (Supplementary Table S2). Notably, palmitic acid (C16:0) exhibited significant positive correlations with kernel characteristics including kernel mass (r = 0.28) and kernel-to-fruit weight (r = 0.28) (Supplementary Table S3). In contrast, linoleic acid (C18:2) was negatively correlated with kernel mass (r = −0.43) and kernel-to-fruit weight (r = −0.44).
We found no distinct clustering in the fatty acid compositions of the countries, with PCA1 explaining 35.4% of the total variance and PCA2 explaining 57.7% of the total variance (Figure 3a). Two principal components (i.e., PC1 and PC2) with eigenvalues of 4.85 and 1.52, respectively, were extracted (a in Table 3). Palmitoleic acid (C16:1), arachidic acid (C20:0), myristic acid (C14:0) and behenic acid (C22:0) had strong positive loadings of 0.93, 0.90 and 0.81, respectively, on PCA1 (Table 3). The predominant fatty acids in T. catappa kernels—oleic acid (C18:1 cis), palmitic acid (C16:0) and linoleic acid (C18:2)—had strong negative loadings of −0.66, −0.83 and −0.75 in PCA 1, PCA2 and PCA3, respectively (a in Table 3). Kernel characteristics between the Solomon Islands and Fiji did not overlap and the two principal components of PCA1 and PCA2 explained 45.4% and 21.8% of total variance, respectively (Figure 3b). Two principal components (i.e., PCA1 and PCA2) with eigenvalues of 2.85 and 1.16, respectively, were extracted (b in Table 3). Kernel mass, total saturated fatty acids and fruit mass had strong positive loadings of 0.82, 0.56 and 0.72 on PCA1. Kernel-to-fruit weight had a positive loading of 0.91 on PCA2, and total oil had a positive loading of 0.86 on PCA3 (b in Table 3).
Hexanal concentrations initially measured at 30.2 ppm increased to 142.9 ppm after 21 days of incubation (Table 4). Moreover, hexanal concentrations on day 7 were significantly higher than on day 0 (Table 4).

4. Discussion

There were significant differences in kernel mass among the three countries. Kernel mass is considered one of the more important factors in tree selection [13,30,31]. Nuts with larger kernels increase financial returns to farmers and processors when commercialised [13,32]. We found an 80% difference between the weight of the largest (Solomon Islands) and smallest (Fiji) kernels. Therefore, farmers from Fiji would need to process five nuts more for every nut collected in the Solomon Islands to obtain the same kernel return. Canarium indicum has been recently commercialised in the Pacific [10,33]. The recommended kernel mass for C. indicum is at least 3 g to make this nut economically viable [15]. The average kernel mass of T. catappa was less than 3 g, although some were very close to 3 g. Hence, the commercialisation of nuts should focus on selecting trees with large kernels, as processing fruits with small kernels is not likely to be economically viable [10,15].
Kernel-to-fruit mass of T. catappa also differed significantly among the three countries. In general, high kernel recovery (kernel mass to nut-in-shell mass) or kernel-to-fruit mass is sought for tree selection [31,34]. These characteristics may be weighted for tree selection but other traits are also important for nut selection. For example, some macadamia nuts with high kernel recovery have thin shells and, hence, are susceptible to pests [31,34]. Soil nutrient availability is another factor in kernel recovery and yield [35]. In macadamia, boron spray has increased kernel recovery and yield [35]. Therefore, it is important to understand pest tolerances and nutrient needs of trees that have high kernel recovery values before tree selection is undertaken.
We observed rapid oil oxidation in T. catappa, perhaps because of the higher total unsaturated fatty acid than saturated fatty acid concentrations [5,22,23]. The concentration of oleic acid and linoleic acid is another driving factor affecting oil stability. Oleic acid is a monounsaturated fatty acid, but linoleic acid is a polyunsaturated fatty acid. Polyunsaturated fatty acids possess higher double-bond carbons in the molecular structure than those of monosaturated fatty acids and hence are less stable against oxidation [22,36]. Therefore, higher oleic acid concentrations than linoleic acid concentrations can increase oil stability [22,23]. Oleic acid concentrations were higher than linoleic acid concentrations in T. catappa. We had sourced kernels for the accelerated ageing from Vanuatu where oleic acid concentrations varied between 27% and 41%. However, we also observed the highest oleic acid concentrations in Fiji (at 50%) and the smallest oleic acid concentrations in the Solomon Islands (at 22%). Hence, our observation of rapid oil oxidation might imply a shortened shelf life of this nut under elevated temperatures. In the current study, the fast oxidation occurred under high temperatures; hence, low storage temperatures may prolong the shelf life of the oil.
The fatty acid composition of the T. catappa was very close to other tropical nuts including Barringtonia procera (Miers) R. Knuth and C. indicum [5,9,37]. Our results imply that T. catappa contains oil with beneficial fatty acids when consumed as food [5]. Terminalia catappa is rich in oleic acid and linoleic acid, and both of these unsaturated fatty acids are known to confer health benefits in other culinary nuts [5,38]. These fatty acids are known to be protective against several cardiovascular diseases [39], which are an increasingly significant public health concern in Pacific Island nations [40]. It should also be noted that T. catappa had higher palmitic acid concentrations than the majority of culinary nuts [5]. Palmitic acid has been found to be a dominant saturated fatty acid in another tropical nut, C. indicum [5]. Culinary nuts, which have beneficial fatty acids and antioxidants, may offer potential benefits in mitigating the risk of cardiovascular disease when consumed instead of processed alternatives [41].
Variations in the physical and chemical properties of T. catappa nuts were found. Fruit mass showed the highest variation in Vanuatu. Interestingly, the large variation in fruit mass was not translated into the kernel mass variation because there were no significant differences in average kernel mass between the Solomon Islands and Vanuatu where their stand errors were overlapping. Many factors drive interpopulation variability in plants [42]. Generally, there are common factors that drive the kernel variations in interpopulation such as the origin of the nuts, environmental conditions, pollination, soil properties, nutrient availability and genetics [14,17,43,44,45]. In a related study on this species, there was significant variability between trees within each country in kernel mass [14]. Variation in kernel properties is common in tree nuts and is often reported between trees of different genotypes, and even within a single genotype [14,15]. For example, self-pollinated macadamia nuts are smaller than cross-pollinated nuts from the same maternal genotype, and self- and cross-pollinated nuts have different chemical compositions [46]. All three countries were also in locations that did not share similar tropical climatic conditions. As a result, a lack of seasonal alignment on some occasions existed in our dataset, which might partly play a part in increasing variation among countries. It should also be noted that we found that some characteristics, such as fatty acid compositions, did not significantly vary from one country to another. It is very common in the Pacific countries that a plant like T. catappa has been intensively selected for domestication by villagers and seeds may have been transferred from one country to another over centuries [27]. For example, this species has even been naturalised in countries such as Brazil and those in the Caribbean and East Africa [27]. Similarities found between countries in terms of fatty acid composition could be the result of selection.

5. Conclusions

This study identified trees from the Solomon Islands have the largest kernels and kernel-to-fruit ratio. As a result, trees from the Solomon Islands could be selected for tree breeding and commercialisation. In all locations, T. catappa had higher total unsaturated fatty acid concentrations than saturated fatty acid concentrations, which might facilitate rapid oil oxidation. However, high total unsaturated fatty acid concentrations indicate potential health benefits for this tree nut. Our study suggests T. catappa could improve food security and provide health benefits to local communities, and select populations with large kernels and high kernel-to-fruit ratios could be targeted for commercialisation.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/horticulturae11050540/s1, Table S1: Correlation matrix of fatty acids present in Terminalia catappa kernels; Table S2: Correlation matrix for the variables of fruit mass, kernel mass, kernel-to-fruit weight (%), total oil (%), total saturated fatty acid (TS) and total unsaturated fatty acid (TUS) of Terminalia catappa; Table S3: Correlation matrix between variables of fruit mass, kernel mass, kernel-to-fruit weight (%) and fatty acids present in Terminalia catappa kernels (n = 275); Tables S4 and S5: Supplementary Data for Tables.

Author Contributions

Conceptualisation, S.H.B. and H.M.W.; methodology, S.H.B.; validation, S.H.B., B.R., R.G., B.G., D.K., K.J., B.E. and H.M.W.; formal analysis, S.H.B.; data curation, S.H.B., B.R., R.G., B.G., D.K., K.J. and H.M.W.; writing—original draft preparation, S.H.B.; writing—review and editing, S.H.B., B.R., R.G., B.G., D.K., K.J., B.E. and H.M.W.; visualisation, S.H.B. and B.E.; supervision, S.H.B.; funding acquisition, S.H.B. and H.M.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Australian Centre for International Agricultural Research, project numbers: FST-2014-067, FST-2017-038 and FST-2022-124.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Materials. Further inquiries can be directed to the corresponding author(s).

Acknowledgments

This work was only possible with the support provided in-country to collect samples by the Secretariat of the South Pacific (Fiji), Lapita Café and Department of Forestry (Vanuatu), SolFresh and Beg’s Sol Seed Technology and Supplies (Solomon Islands). We thank Peter Brooks for his help in the analysis of the oil samples for FAME. We acknowledge John Oakeshott and Paitia Negalevu of the Secretariat of Pacific Community, Suva, Fiji.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Horticulturae 11 00540 g001
Figure 1. (a) Terminalia catappa trees occurring in the coastal areas of Solomon Islands, (b) ripe fruit and (c) kernels of T. catappa (photo credit: (a,b) Bruce Randall and (c) Brittany Elliott).
Figure 1. (a) Terminalia catappa trees occurring in the coastal areas of Solomon Islands, (b) ripe fruit and (c) kernels of T. catappa (photo credit: (a,b) Bruce Randall and (c) Brittany Elliott).
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Figure 2. Terminalia catappa trees occurring in the coastal areas of Solomon Islands, Vanuatu and Fiji. This map was produced using the free and open-source software, QGIS v 3.36.2, and ESRI base map layer (World Imagery (Clarity) Beta).
Figure 2. Terminalia catappa trees occurring in the coastal areas of Solomon Islands, Vanuatu and Fiji. This map was produced using the free and open-source software, QGIS v 3.36.2, and ESRI base map layer (World Imagery (Clarity) Beta).
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Figure 3. Principal component analyses (PCA) showing the clustering of Terminalia catappa based on (a) fatty acid composition and (b) kernel characteristics per country of origin: Solomon Islands (open blue rectangular), Vanuatu (open red triangular) and Fiji (open green circle).
Figure 3. Principal component analyses (PCA) showing the clustering of Terminalia catappa based on (a) fatty acid composition and (b) kernel characteristics per country of origin: Solomon Islands (open blue rectangular), Vanuatu (open red triangular) and Fiji (open green circle).
Horticulturae 11 00540 g003
Table 1. Differences in fruit mass, kernel mass, kernel-to-fruit weight (%), total oil (%), total saturated fatty acid (TS) and total unsaturated fatty acid (TUS) of Terminalia catappa at the country level. Different lower-case letters indicate significant differences among countries at p < 0.05 (Tukey’s HSD).
Table 1. Differences in fruit mass, kernel mass, kernel-to-fruit weight (%), total oil (%), total saturated fatty acid (TS) and total unsaturated fatty acid (TUS) of Terminalia catappa at the country level. Different lower-case letters indicate significant differences among countries at p < 0.05 (Tukey’s HSD).
Solomon IslandsVanuatuFiji
Fruit mass (g)
Mean ± SE29.21 ± 0.52 b33.72 ± 0.90 a7.97 ± 0.17 c
N418486746
Minimum10.175.902.60
Maximum67.49142.1935.00
Kernel mass (g)
Mean ± SE1.66 ± 0.04 a1.58 ± 0.03 b0.33 ± 0.01 c
N416486746
Minimum0.100.050.01
Maximum3.933.940.82
Kernel-to-fruit weight (%)
Mean ± SE5.64 ± 0.10 a5.61 ± 0.13 a4.75 ± 0.09 b
N416486746
Minimum0.280.350.12
Maximum15.5315.2811.13
Total oil (%)
Mean ± SE59.37 ± 1.08 a55.34 ± 1.21 b56.86 ± 0.30 ab
N85105150
Minimum46.2728.2147.32
Maximum77.5584.1965.56
TS (%)
Mean ± SE46.04 ± 0.55 a44.30 ± 0.37 b38.60 ± 0.28 c
N68.0090.00150.00
Minimum36.9232.8631.96
Maximum64.6552.1145.99
TUS (%)
Mean ± SE54.44 ± 0.52 c55.70 ± 0.37 b61.40 ± 0.27 a
N68.0090.00150.00
Minimum49.3347.8954.01
Maximum68.5567.1468.04
Table 2. Descriptive statistics (mean ± standard error) of Terminalia catappa for fatty acid compositions collected from Solomon Islands (n = 68), Vanuatu (n = 90) and Fiji (n = 150).
Table 2. Descriptive statistics (mean ± standard error) of Terminalia catappa for fatty acid compositions collected from Solomon Islands (n = 68), Vanuatu (n = 90) and Fiji (n = 150).
Solomon IslandsVanuatuFiji
C14:0 (myristic)0.04 ± 0.0010.03 ± 0.0020.02 ± 0.001
C16:0 (palmitic)40.37 ± 0.57039.86 ± 0.35434.16 ± 0.255
C18:0 (stearic)5.22 ± 0.0684.28 ± 0.0794.29 ± 0.061
C20:0 (arachidic)0.35 ± 0.0140.11 ± 0.0030.11 ± 0.002
C22:0 (behenic)0.06 ± 0.0040.03 ± 0.002 0.03 ± 0.001
C16:1 (palmitoleic)0.26 ± 0.0120.08 ± 0.0030.06 ± 0.001
C18:2 (linoleic)23.81 ± 0.41120.31 ± 0.38820.83 ± 0.337
C18:1 cis (oleic)29.73 ± 0.48534.9 ± 0.34340.15 ± 0.326
C18:1 trans (elaidic)0.61 ± 0.0150.37 ± 0.0340.33 ± 0.006
C20:1 (eicosenoic)0.04 ± 0.0030.03 ± 0.0020.03 ± 0.001
Table 3. Principal component analyses (PCA) values of Terminalia catappa: (a) fatty acid composition and (b) kernel characteristics.
Table 3. Principal component analyses (PCA) values of Terminalia catappa: (a) fatty acid composition and (b) kernel characteristics.
(a) Fatty Acid Compositions(b) Kernel Characteristics *
PCA1PCA2PCA3PCA1PCA2PCA3
Eigenvalues4.851.521.182.851.161.07
Percentages of variance35.4422.3217.8745.4921.4918.10
Cumulative percentages of variance35.4457.7775.6445.4966.9885.09
C16:1 (palmitoleic)0.900.030.01
C20:0 (arachidic)0.900.11−0.04
C14:0 (myristic)0.81−0.110.18
C22:0 (behenic)0.810.340.15
C18:1 cis (oleic)−0.670.630.27
C18:1 trans (elaidic)0.650.150.41
C20:1 (eicosenoic)0.600.500.21
C18:0 (stearic)0.58−0.14−0.34
C16:0 (palmitic)0.31−0.830.40
C18:2 (linoleic)0.510.11−0.75
Fruit mass (g) 0.72−0.190.39
Kernel mass (g) 0.820.3950.19
Kernel-to-fruit weight (%) 0.260.91−0.27
Total oil (%) −0.020.180.86
TS (%) 0.89−0.24−0.20
TUS (%) −0.890.230.20
* Kernel characteristics included fruit mass, kernel mass, kernel-to-fruit weight ratio, total oil content, total saturated fatty acids and total unsaturated fatty acids.
Table 4. Hexanal concentrations (mean ± standard error) of Terminalia catappa over 21 days of incubation at 45 °C. Different lower-case letters indicate significant differences between incubation days at p < 0.05 (Tukey’s HSD).
Table 4. Hexanal concentrations (mean ± standard error) of Terminalia catappa over 21 days of incubation at 45 °C. Different lower-case letters indicate significant differences between incubation days at p < 0.05 (Tukey’s HSD).
Incubation Period (Days)
Day 0Day 7Day 14Day 21
Hexanal Concentration (ppm) 30.20 ± 6.67 c97.59 ± 5.67 b132.27 ± 9.17 ab142.99 ± 12.51 a
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MDPI and ACS Style

Hosseini Bai, S.; Randall, B.; Gama, R.; Gua, B.; Keli, D.; Jones, K.; Elliott, B.; Wallace, H.M. Variations in Physical and Chemical Characteristics of Terminalia catappa Nuts. Horticulturae 2025, 11, 540. https://doi.org/10.3390/horticulturae11050540

AMA Style

Hosseini Bai S, Randall B, Gama R, Gua B, Keli D, Jones K, Elliott B, Wallace HM. Variations in Physical and Chemical Characteristics of Terminalia catappa Nuts. Horticulturae. 2025; 11(5):540. https://doi.org/10.3390/horticulturae11050540

Chicago/Turabian Style

Hosseini Bai, Shahla, Bruce Randall, Repson Gama, Basil Gua, Doni Keli, Kim Jones, Brittany Elliott, and Helen M. Wallace. 2025. "Variations in Physical and Chemical Characteristics of Terminalia catappa Nuts" Horticulturae 11, no. 5: 540. https://doi.org/10.3390/horticulturae11050540

APA Style

Hosseini Bai, S., Randall, B., Gama, R., Gua, B., Keli, D., Jones, K., Elliott, B., & Wallace, H. M. (2025). Variations in Physical and Chemical Characteristics of Terminalia catappa Nuts. Horticulturae, 11(5), 540. https://doi.org/10.3390/horticulturae11050540

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