Study of Yellow Root {Arcangelisia flava Merr) as A Natural Food Additive with Antimicrobial and Acidity-stabilizing Effects in the Production Process of Palm Sugar

摘要

Fermentation by several types of microorganisms was considered as one of several factors causing quality degradation of the palm sap used for production of palm sugar. During harvesting period, pH value of the palm sap gradually decreasing from 6.5 to approximately 4.5. In order to avoid the rapid fermentation, traditionally, the local community uses a material made by mixing small pieces of heartwood of jack tree {Artocarpus heterophyllus) with slaked lime (calcium hydroxide) solution. However, the safety of this material if consumed by the human is still unclear. Consumption of food containing high concentration of slaked lime may cause several organ dysfunctions such as liver, kidney, also heart and cardiovascular diseases. Therefore, this study was aimed to investigate an alternative material substituting the traditional one by examining the antimicrobial and acidity-stabilizing effects of Yellow Root {Arcangelisia flava Merr) extract. Antimicrobial activity of the water extract was evaluated through a disc-diffusion method using three microorganisms, Salmonella typhii, Staphylococcus aureus, and Trichophyton rubrum. In addition, toxicity test was also performed using BSLT (brine shrimp lethality test). Water extract of A. flava exhibited a positive respond against Salmonella typhii, Staphylococcus aureus, and Trichophyton rubrum with inhibition zones of 19.35, 16.98, and 19.78 mm, respectively at application level of 2% (v/v). Furthermore, this extract also showed an ability to stabilize the acidity of fresh palm sap (pH 5.8-6.5) due to fermentation mechanism during harvesting and storing. The ability of the extract to stabilize the acid level may be caused by the presence of its active compounds such as alkaloid, tannin, and saponin. The glucosides of those compounds may inhibit the hydrolysis of disaccharide such as sucrose becomes its monosaccharides. Those compounds may also deactivate enzyme invertase secreted by the microbes which can increase the acid level. From the toxicity test, water extract of A. flava was considered as a natural product with no toxicity. Therefore, water extract of A. flava can be utilized as a safe natural food additive, especially in the production of palm sugar.