Nutritional Contents and Protein Nutritional Value of Local and Imported Soybean Tempe Flours and Their Antioxidant Activities

Abstract

The rate of population growth in Indonesia has increased rapidly, but the ability of farmers to produce foodstuffs has declined, including soybean production. Central Agency on Statistics (2013) noted that national soybean production in 2012, only amounted to 843.15 thousand tons, while the national total requirement was 2.3 million tons. To fulfill this shortage, the government should import soybean from other countries. There are many kinds of soybean products, such as tempe, tofu, tauco, soy sauce, soy milk, yuba, etc. Tempe is Indonesian traditional fermented soybean. The main problem of tempe product is its short shelf life. An alternative way to solve this problem is making tempe into flour. The objectives of this research were (1) to compare the nutritional and nonnutritional contents of local (grobogan) and imported (GMO and non-GMO) soybean tempe flours, (2) to evaluate the protein nutritional value of local (grobogan) and imported (GMO and non-GMO) soybean tempe flours, and (3) to measure antioxidant activities to DPPH radical and malonaldehyde (MDA) content in rat liver. Experimental material : local grobogan, imported GMO (Roundup Ready) and non-GMO soybean tempe flours. The research was conducted in two stages, in vitro and in vivo analysis. In vitro analysis was consists of proximate, amino acid, fatty acid, dietary fiber, total isoflavones, and vitamin E analysis. The biological assay was conducted on 25 male albino rats Sprague-Dawley as an animal model, divided into five groups, fed with imported GMO and non-GMO soybean tempe flours, local grobogan soybean tempe flours and casein as control. Parameters that used in the evaluation of protein nutritional value were protein efficiency ratio (PER), feed conversion efficiency (FCE), net protein ratio (NPR), true protein digestibility (TPD), biological value (BV), net protein utilization (NPU) and protein digestibility corrected amino acid score (PDCAAS) value. The measurement of antioxidant activity consist of DPPH antioxidant analysis and measure the MDA content in rat liver. The results showed that the nutritionals (proximate, amino acid, fatty acid, and vitamin E) and non nutritionals (dietary fiber and total isoflavones) compound of local grobogan soybean tempe flour were not much different from imported GMO and non-GMO soybean tempe flours. The evaluations of protein nutritional value showed that there were no significantly different of FCE (average 20.45%), PER (average 2.04) and NPR (average 2.80) values from all of tempe flours but lower than casein. TPD value of grobogan soybean tempe flour and non-GMO were not statistically different (average 82.62%), significantly higher than GMO soybean tempe flour (80.27%), but lower than casein (87.33%). There were no significantly different of BV (average 89.59%) and NPU (average 74.55%) values from all of samples. The PDCAAS value from local grobogan soybean tempe flour (61.82) was higher than imported GMO (52.1) and non-GMO (56.2) soybean tempe flours, but lower than casein (75.1). The scavenging activity (IC50) for DPPH radical of local grobogan soybean tempe flour was 2524.7 ppm, imported GMO was 3349.3 ppm, imported non GMO was 4049.6 ppm, while vitamin C was 5.03 ppm. MDA forming in liver showed that there was not difference (p>0.05) between grobogan (0.290 μg/g sampel), GMO (0.268 μg/g sampel), non-GMO (0.353 μg/g sampel) soybean tempe flours and casein (0.238 μg/g sampel) as control.