Effect and mechanism of steam explosion combined with enzymatic method on improving the texture of areca nut

Areca nut texture can be improved using steam explosion and enzymatic hydrolysis technologies. In this study, a systematic investigation was conducted to clarify the effects of steam explosion–enzymatic hydrolysis on areca nut texture. Textural attributes were examined with microstructure, functional properties, and composition, with an emphasis on lignin structural evolution. A comparison was also performed on a standalone steam explosion and a combined steam explosion–enzymatic hydrolysis. The results demonstrated that better performance was achieved in the steam explosion with enzymatic treatment, particularly with the more uniform color, the low surface wrinkles, and the smoother and flatter morphology. By contrast, steam explosion treatment alone lightened the color of areca nut, surface wrinkles, and the pericarp structure, leading to partial exposure of fibers. In textural properties, the raw areca nut exhibited the highest hardness and chewiness, but the lowest springiness. With steam explosion with enzymatic treatment, the hardness and chewiness significantly decreased by 30% and 8.44%, respectively, while the springiness dramatically increased by 111.4%. The texture indicated that the softer fibrous structure of the product was enhanced oral compliance with low chewing resistance. In terms of functional properties, the raw areca nut showed relatively low water-holding capacity, water swelling, and oil-holding capacity. Steam explosion treatment alone significantly enhanced water- and oil-holding capacity by 15.21% and 29.94%, respectively. The best functional performance was achieved in steam explosion with enzymatic treatment. All three functional indicators were further enhanced, where water-holding capacity, oil-holding capacity, and water swelling capacity increased by 27.38%, 91.62%, and 12.37%, respectively. Scanning electron microscopy observations revealed that the raw areca nut shared a dense cellular structure. After steam explosion treatment alone, cell walls were ruptured with the high porosity. Following the steam explosion with enzymatic treatment, there was even more loose cellular structure, while the cell wall ion was disrupted substantially. With respect to composition, steam explosion treatment alone resulted in minimal lignin, glucan, and xylan content, whereas, the total sugar content increased significantly. After steam explosion with enzymatic treatment, the chemical components decreased significantly, except for the increasing total sugar content. Gel permeation chromatography analysis indicated that steam explosion treatment alone increased the weight-average molecular weight and polydispersity index of lignin, whereas steam explosion with enzymatic treatment was reduced both Mw and PDI. Fourier-transform infrared spectroscopy confirmed that its aromatic structure remained intact after different treatments. Molecular weight distribution was primarily altered to disrupt the polymerization state. Interunit linkages were cleaved to maintain the phenylpropanoid skeleton. Moderate lignin modification was avoided to prevent excessive degradation for product integrity after structure weakening. In conclusion, the steam explosion and enzymatic hydrolysis were combined to synergistically dismantle the dense fibrous architecture of areca nut under physical and biochemical actions. While optimal lignin modification was simultaneously induced to improve the texture, hydration behavior, and overall quality. Thereby, the finding can provide the robust theoretical support and a practical technical reference to advance processing in the areca nut industry.