Physicochemical and functional properties of flour from jackfruit seed for bakery applications

Introduction

Around 1.3 billion tonnes of food are wasted globally each year, and fruit by-products contribute a sizeable share [1] . Jackfruit (Artocarpus heterophyllus Lam.), the largest treeborne fruit in the world, generates considerable seed waste after the edible bulbs are consumed fresh or processed [2] . Each fruit yields 100-500 seeds that are starchy, mildly flavoured, and contain 13-17% crude protein-higher than rice, maize, or cassava [3] . Despite this nutritional promise, jackfruit seeds find limited commercial use beyond occasional boiling or roasting for snack consumption in rural households [4] . Wheat flour dominates the bakery sector, but rising wheat import costs and consumer demand for nutrient-dense, gluten-diversified products have prompted research into composite flours incorporating non-conventional sources such as legumes, tubers, and fruit seeds [5] . Jackfruit seed flour is an appealing candidate because its starch gelatinises at temperatures suitable for bread and cookie baking, and its proteins can form gels and stabilise emulsions [6] . But the practical uptake of JSF in bakeries requires a thorough understanding of its physicochemical behaviour-how it absorbs water, holds oil, foams, and emulsifies-under standardised testing protocols comparable to those used for wheat flour [7] . Earlier investigations reported proximate composition data for JSF from South Asian and Sri Lankan cultivars, yet functional-property datasets from the Surma-Kushiyara floodplainwhere the BARI Kanthal-3 cultivar is widely grown-remain scarce [8] . Processing method also matters: boiling, roasting, and simple drying each alter starch crystallinity, protein denaturation, and anti-nutrient levels differently [9] . This research therefore aimed to characterise the physicochemical and functional properties of JSF prepared by three processing routes and benchmark them against refined wheat flour, with the goal of generating data that can guide composite-flour formulations for bakery use. Refined wheat flour (Maida, local commercial brand) was purchased from a local retailer. Analytical-grade chemicals were procured from Merck (Germany) and HiMedia [10] .

Methods

Proximate composition (moisture, crude protein by Kjeldahl, crude fat by Soxhlet, crude fibre, ash, and carbohydrate by difference) was determined following AOAC methods [11] . Mineral elements (Ca, Fe, Zn, K, Mg, P) were quantified by inductively coupled plasma optical emission spectrometry (ICP-OES; PerkinElmer Optima 7300 DV) after wet digestion with HNO₃:HClO₄ (4:1). Functional properties were measured as follows: water absorption capacity (WAC) and oil absorption capacity (OAC) by the centrifugation method of Sosulski [12] ; foaming capacity (FC) and foaming stability (FS) by the whipping method; emulsion activity (EA) and emulsion stability (ES) by the method of Yasumatsu et al. [13] ; bulk density (BD) by the tapping method. Anti-nutritional factors-tannin (Folin-Denis method) and trypsin inhibitor activity (TIA; casein digestion assay)-were also determined [14] . The proximate profile of JSF differed markedly from wheat flour. Protein content of raw JSF (13.8%) was 37% higher than that of wheat flour (10.1%), while crude fibre (5.1% vs 0.4%) and ash (2.7% vs 0.5%) were several-fold higher. Fat content remained low across all JSF types (3.4-3.9%), a desirable trait for shelf stability in bakery premixes. Roasting reduced moisture to 5.8% from 8.3% in raw JSF, and boiling slightly lowered protein content to 12.9%, likely because of leaching of soluble nitrogen into the cooking water [15] . Comprehensive Interpretation JSF outperformed wheat flour in water and oil absorption, foaming, and emulsion activity regardless of processing method. Boiling was most effective at reducing antinutritional factors (tannin fell from 184.3 to 68.4 mg/100 g; TIA dropped from 9.7 to 2.3 TIU/mg), but it also leached minerals and lowered foaming capacity. Roasting offered the best balance: good functionality, lighter colour (L* = 76.8), and moderate anti-nutrient reduction. These data suggest that roasted JSF at 10-20% substitution could enrich bakery products with protein, fibre, and minerals while keeping dough handling properties within acceptable limits.

Discussion

The proximate profile of raw JSF aligns broadly with values reported by Ocloo et al. [3] for Ghanaian jackfruit seeds, although the protein content (13.8%) in the present research is slightly higher-possibly because the BARI Kanthal-3 cultivar accumulates more storage globulins during seed maturation [8] . Abedin et al. [6] noted protein values of 12. 3.9%) is an advantage for bakery flour, as it limits lipid oxidation during storage-a concern that has restricted the adoption of higher-fat seed flours such as flaxseed or sesame [16] . Among functional properties, the higher WAC of JSF (2.18-2.51 g g⁻¹) compared with wheat (1.89 g g⁻¹) is attributable to the greater proportion of hydrophilic amino acids and the open, porous starch granule structure produced during drying [7] . This elevated water uptake has practical implications: bread doughs containing JSF may require adjusted hydration levels to avoid excessive stiffness. Conversely, the higher OAC (1.62-1.84 g g⁻¹) can improve mouthfeel and flavour retention in cookies and cakes, as oil trapped within the flour matrix is released slowly during mastication [17] . The sharp reduction in trypsin inhibitor activity after boiling (76% decrease) is consistent with the heat lability of Kunitztype inhibitors widely documented in legume and seed flours [14] . Roasting achieved a moderate decrease (40%), largely through dry-heat denaturation at 120 °C. Both processing routes brought TIA well below the threshold of concern (< 5 TIU/mg) for human consumption, indicating that either can render JSF safe for inclusion in bakery formulations [18] .

Conclusion

The main contribution of this research is a side-by-side physicochemical and functional dataset for jackfruit seed flour prepared by three processing methods and benchmarked against wheat flour. JSF contains meaningfully more protein (13.8% vs 10.1%), fibre (5.1% vs 0.4%), and key minerals (Ca, Fe, K) than refined wheat flour, while its functional behaviour-particularly water and oil absorption, foaming, and emulsion activity-suits bakery processing requirements. Among the three preparation routes, roasting delivered the best combination of functional performance, colour, and anti-nutrient reduction, while boiling was more effective at eliminating trypsin inhibitors. These findings position jackfruit seed flour as a viable partial substitute (10-20%) in composite bread, cookie, and cake formulations. Open questions remain around the effect of JSF on dough rheology at higher substitution levels, its interaction with gluten during proofing, and the sensory acceptability of finished bakery products-areas that merit follow-up investigation.

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