Development of chickpea tempeh using Rhizopus oryzae for dysphagia diet: Effect of fermentation time and heat treatment

Patients with dysphagia must manage their health with an appropriate diet. Chickpea tempeh is a nutritious source of carbohydrates and proteins, but its texture modification is necessary to suit varying severities of dysphagia, according to the International Dysphagia Diet Standardization Initiative (IDDSI) Framework. This study assessed the effects of fermentation time and heat treatment for development of tempeh classified as IDDSI level 6. The physicochemical and structural properties of tempeh were investigated, with a focus on biological changes during fermentation. Tempeh was prepared by grinding chickpeas to particle size of 3.50 ± 0.22 mm and fermenting for 24, 36, 48, 60, and 72 h using Rhizopus oryzae. During fermentation, the biological properties of tempeh changed, resulting in more white mold mycelia (cake) and the release of amylase and protease enzymes. Before cooking, tempeh exhibited increased hardness and brittleness by cake, as well as pH, total soluble solids, and DPPH increased by enzymetic activity. Fungal enzymes and heat treatment (175 °C) changed the rough and aggregated microstructure and molecular structure of chickpeas, as confirmed by scanning electron microscopy and Fourier transform infrared spectroscopy. The texture of cooked tempeh became softer and less brittle by fermentation time, attributed to weakening of cake bonds and enzymatic softening of chickpeas. IDDSI Framework results classified 24 and 36 h fermentation as level 7, and 48, 60, and 72 h fermentation as level 6. Tempeh with modified texture by heat treatment and controlled fermentation time may contribute to the improved health of patients with dysphagia.