Tropical fruit seed starches structure-function insights for high value applications

Tropical fruit seeds, often discarded as waste, constitute 20-40% of the total fruit's mass and represent an untapped, sustainable source of starch with distinctive functional properties. The primary objective of this study was to evaluate the physicochemical, morphological, structural, thermal, functional, and rheological characteristics of starches isolated from guama (G), huaya (H), mango (M), and rambutan (R) seeds, aiming to bridge the knowledge gap of these underutilized resources and explore their viability as alternatives to conventional starches. Starches from tropical fruit seeds were isolated by aqueous extraction and characterized using X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, functional assays (swelling power, solubility, gel firmness), and rheological analysis. Key findings revealed amylose content ranging from 12.6% (H starch) to 34.8% (M starch) and granule sizes from 3.2 μm (H starch) to 18.7 μm (G starch). G starch displayed superior crystallinity (32.5%), gelatinization temperature (78.4 °C), and swelling power (18.5 g/g), while M starch exhibited low gelatinization parameters (63.2 °C; 8.3 J/g) and stable paste clarity, suitable for edible films. R starch formed robust gels (38.6 g/cm²) with pronounced retrogradation, and H starch showed high initial clarity, which is appropriate for the production of short-term coatings. Rheological analysis confirmed that amylose-rich starches (M and R starches) promote retrogradation, whereas amylopectin-rich starches (H starch) confer shear stability. These findings highlight the diverse properties of non-conventional starches from tropical fruit seeds, positioning them as sustainable substitutes for conventional sources in food, pharmaceutical and industrial sectors, thereby promoting waste valorization, circular bioeconomy, and environmental sustainability.