Functional and microbiological properties of spirulina soybean tempeh flour modified by heat-moisture treatment and annealing

Spirulina, known for its high protein content, can be developed into tempeh and further processed into flour for bakery products. However, the direct use of spirulina-tempeh flour as a premix presents challenges, particularly in achieving stable volume and texture. This study aimed to determine the most effective modification method for improving the characteristics of spirulina-tempeh flour. Accordingly, two modification techniques were applied: Heat-Moisture Treatment (HMT) and annealing. Following this, statistical analysis was conducted using one-way Analysis of Variance (ANOVA) with Duncan's Multiple Range Test (DMRT) (p < 0.05), and the De Garmo method was used to identify the best treatment. Overall, the results revealed that HMT was the most effective method in enhancing flour properties. In particular, the HMT-modified flour exhibited the following values: moisture content 4.82% db, fat content 27.63% db, Ash Content (AC) 2.35% db, protein content 41.40% db, Water Absorption Capacity (WAC) 1.93 g/g db, Oil Absorption Capacity (OAC) 0.38 g/g db, syneresis 77.49% db, swelling volume 4.85 mL/g db, solubility 0.20% db, antioxidant activity (IC₅₀) 49.998 ppm, starch content 1.903% db, and amylose content 0.007% db. Meanwhile, microbiological properties further indicated a Standard Plate Count (SPC) of 2.74 × 10⁴ CFU/g. In conclusion, HMT effectively improved the functional, physicochemical, and microbial characteristics of spirulina-tempeh flour, making it more suitable for use in bakery products.