K. Yudiono, H. Dhani
Isoflavones are bioactive compounds which are components of flavonoid compounds. Soybeans, the main ingredient of tempeh, contain these isoflavones that act as antioxidants. During the cooking process of tempeh, isoflavones become very unstable due to heat. Therefore, the boiling stage is a very important concern in the tempeh-making process. In the conventional tempeh-making method, the soybeans are boiled twice, with each boiling time carried out between 2 and 3 h after the water boils, based on a survey from tempeh SMEs. This conventional boiling time increases fuel costs, especially when processing large volumes of soybeans. This research aimed to find a boiling method with a shorter cooking time and evaluate its impact on the isoflavone content of the tempeh produced. The experiment tested boiling times of 10, 20, and 30 min for dried peeled soybeans using pressure boiling. Variables observed include the isoflavone profile and weight in the tempeh. The results from the LC-MS/MS test showed six components of tempeh isoflavones in the control treatment and after 10 min of boiling. These components were daidzein, genistein, daidzin, genistin, glycitein, and glycitin. Glycitein did not appear in the 20 and 30 min of boiling treatments, leaving only five isoflavone components in those treatments. The weight of the isoflavones for each boiling time was 180.312 mg/100 g for 10 min treatment, 211.228 mg/100 g for 20 min, 118.703 mg/100 g for 30 min, and 407.247 mg/100 g in the control treatment. The data showed that using pressure boiling in tempeh production to boil soybeans would shorten the time, but it would also accelerate the loss of isoflavone weight in the tempeh. © 2026 The Authors. Published by Rynnye Lyan Resources.
Department of Food Technology, Faculty of Agriculture, Widya Karya Catholic University, East Java, Malang, 65115, Indonesia; Department of Mechanical Engineering, Faculty of Engineering, Widya Karya Catholic University, East Java, Malang, 65115, Indonesia
