Physicochemical and microbiological assessment of Nypa fruticans sap collected in Sarawak, Malaysia

Abstract

Nipa sap is a sweet and translucent beverage that originated from nipa palm (Nypa fruticans) tree. In Sarawak, nipa sap become raw material for nipa sugar or locally known as gula apong. However, nipa sap undergoes natural fermentation that alters the properties of nipa sap including taste, aroma and quality. Fermented nipa sap is whitish colour with an unpleasant aroma and taste, which makes it unacceptable for consumption. Hence, it is no longer suitable to make nipa sugar. This study aimed to determine the physicochemical and microbiological changes of nipa palm sap from fresh to fermented. The nipa sap was allowed to undergo natural fermentation at room temperature for 56 days. Samples were collected every 24 hrs for the first week and once a week in the subsequent week. The selected physiochemical qualities were analysed using high-performance liquid chromatography (HPLC) whereas the microbial content was analysed using spread plating. Fresh nipa sap showed the highest load of sugar (334.2±12 g/L) with sucrose as the main sugar found (231.5±4.3 g/L), followed by fructose (42.1±1.2 g/L), and glucose (29.7±3.2 g/L). Fresh nipa sap also possessed the lowest load of ethanol (0.08±0.03 g/L), lactic acid (1.09±0.06 g/L), and acetic acid (0.05±0.01 g/L) as well as microbial and yeast concentration. Later, ethanol started to accumulate on day 4 (9.80±0.1 g/L) and the highest peak was on day 21 (19.1±2.01 g/L). The microbial concentration changed as well, affecting the quality of nipa sap. As nipa sap plays such an important role in the lifestyle of people in Sarawak, this study provides a better understanding of the microbiology and biochemistry of its fermentation process. Hence, proper planning for handling fresh nipa sap should be considered to ensure the quality of value-added product production.