Effects of Seed Germination on Physicochemical and Bioactive Compounds Characteristics of Velvet Bean Tempe

Abstract

Indonesia, known as the largest tempe-producing country globally with approximately 160,000 producers, faces a challenge in meeting the demand for tempe due to insufficient local soybean supply. To address this issue, Indonesia has been compelled to import significant quantities of soybeans, reaching 1.68 million tons in 2020, which escalated by 47.78% to 2.49 million tons in 2021. This study aims to scientifically investigate the impact of velvet bean seed germination on the physicochemical characteristics and bioactive components of velvet bean tempe. The research methodology involved quantitative analysis to obtain reliable results. The preliminary analysis established that the optimal velvet bean tempe fermentation time was 48 hours. Following germination, the physical properties of velvet bean sprouts exhibited an increase in weight accompanied by a reduction in bulk density and absolute density. Furthermore, the germination treatment resulted in decreased brightness, saturation, whiteness, and pH values, while simultaneously increasing the hardness of the tempe. Chemical analysis demonstrated that germination of velvet bean seeds led to an elevation in moisture content and a decrease in carbohydrate content within the produced tempe. Additionally, bioactive component analysis revealed that the germination treatment contributed to a reduction in total phenol content from 52.46 to 36.30 mg AAE/100g, antioxidant capacity from 132.80 to 66.90 mg GAE/100g, and GABA content from 54.20 to 21.50 mg/100g in the tempe. These findings provide valuable scientific insights into alternative ingredient utilisation and production processes optimisation of velvet bean tempe.

Germination effects on the physicochemical properties and sensory profiles of velvet bean (Mucuna pruriens) and soybean tempe

“…The materials used in this study were Genetically Modified Organism (GMO) soybeans (Sb&B Food Inc., Casselton, United States), and velvet bean seeds purchased from PT. Nagari Bumi Asri (Yogyakarta, Indonesia) with a chemical composition that can be seen in our previous study (3), Raprima ® tempe starter (Bandung, Indonesia), and polypropylene plastic as tempe packaging. Moreover, the materials used for analysis consisted of reagents for proximate analysis, 1-diphenyl-2-picrylhydrazyl (DPPH), ascorbic acid, Folin-Ciocalteu, and gallic acid from Sigma-Aldrich (United States).…”

“…These enzymes facilitate the conversion of polyphenolic compounds into quinone group compounds, contributing to the seeds’ dark colour ( 24 ). In addition, according to Astawan et al ( 3 ), the reduced lightness observed in germinated velvet bean and soybean tempe is caused by the high concentration of amino acids in the seeds that result from the germination process. When the seeds undergo heating or boiling during tempe production, these amino acids undergo non-enzymatic browning, such as the Maillard reaction.…”

“…Tempe also contains various bioactive compounds, such as isoflavones which act as an antioxidant. The fermentation process converts glycone isoflavones (in soybean) into aglycone isoflavones (in tempe), which are easier to digest by the human body ( 3 ).…”

“…In soy-based tempe, the germination of soybean seeds had proven to decrease the hardness value and firmness of the resulting tempe ( 12 ). Meanwhile, germination of velvet bean reduced antioxidant capacity, total phenol, and GABA content, but increased the protein content in the resulted velvet bean tempe ( 3 ).…”