Effects of spirulina powder on the physicochemical and volatile properties of rice balls

This study compared the quality of rice balls prepared with different concentrations of spirulina powder (0%, 1%, 3%, 5%, and 7%) and investigated their nutritional composition, color parameters, hardness, water distribution, and fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and gas chromatography-ion mobility spectrometry (GC-IMS) findings. Spirulina significantly improved the nutritional value of rice balls, with the protein content increasing by 38.37%. With increasing spirulina concentrations, the L* and W values of rice balls decreased, causing a green appearance with progressively intensified color, whereas the hardness increased significantly. Low-field nuclear magnetic resonance (LF-NMR) findings revealed that low spirulina concentrations (1%–5%) increased the proportion of bound water and decreased that of free water, whereas at 7% concentration, T 22 increased and the proportion of free water rebounded, indicating a reduced water-binding capacity of the system. The FTIR and XRD results indicated that spirulina altered the short-range molecular order and long-range crystalline structure of starch. Furthermore, R 1049/1022 and the relative crystallinity increased by 17.53% and 18.5%, respectively, with increasing spirulina concentrations, indicating that spirulina accelerated short-term starch retrogradation. SEM observations further indicated that spirulina addition disrupted the continuous starch matrix, resulting in enlarged pores and an increased pore number. GC-IMS identified 52 volatile compounds, and spirulina significantly altered both the composition and relative abundance of aroma-active compounds. These data provide a theoretical basis for developing nutrient-enriched rice-based products.