ANGIOTENSIN CONVERTING ENZYME INHIBITOR ACTIVITY OF THE SOYBEAN TEMPEH PROTEIN AS FUNCTIONAL FOOD

Tempeh is an Indonesia's indigenous fermented food that is widely preferred by the community. Fermented food has functional food as an antihypertensive by angiotensin-converting enzyme (ACE) inhibitor. This study was aimed to measure protein activity of tempeh as ACE inhibitor. Soybean was fermented using Rhizopus sp. with various fermentation times of 0, 6, 12, 18, 24, 30, 36, 42 and 48 hours. Protein extraction was performed at the isoelectric point, the degree of hydrolysis was considered as trichloroacetic-dissolved nitrogen. The best fermentation time was determined by the degree of hydrolysis (DH) and protein content. Protein extract was fractionated by using an ultra membrane with 3 kDa cut of. Proximate analysis was performed by the AOAC method. The measurement of an ACE inhibitor was based on the formation of hippurate acid-H-Histidyl-L-leucine (HHL). Results of this study revealed that the lipid content of tempeh was lower than that of soybean while the water content of tempeh was higher than soybean. The best fermentation time was found at 24 hours. Protein content was 236.31 ppm and DH was 36.03%. The best fraction that was able to inhibit ACE was a fraction below 3 kDa with an inhibitory capability of 67.43%. Protein of tempeh contained proline, valine, isoleucine, histidine, teonine, tyrosine, leucine, aspartic acid, lysine, glycine, arginine, alanine, phenylalanine, glutamic acid, serine and methionine. This study concludes that tempeh was able to inhibit ACE by in vitro and is potentially continued to in vivo examination, thus tempeh can be claimed as a functional food.