The grading classification for Styrax sumatrana resins based on physico chemical characteristics using two-step cluster analysis

Abstract

Non timber forest management of styrax resin has become the main community livelihood in the Tapanuli region, North Sumatra, Indonesia. However, thousands of tons of incense resin produced have not been graded simply and inaccurately. The resin grading has been determined visually based on shape, size, and color. This is a disadvantage regarding the important value of this commodity is its chemical content. The objectives of the study were (a) to investigate the physico chemical properties of styrax resin based on current local grading, and (b) to develop a new grading classification of Sumatran incense (Styrax sumatrana) resin. A completely random design was carried out to determine the physico chemical properties of styrax from six incense grade traded. The results showed that the current quality grading affects the physico chemical properties of the resin. The first grade contains the best physico chemical properties, conversely the sixth is the lowest among others. Isolated cinnamic acid from various grades produces different levels of purity. The highest balsamic acid content and purity were derived from the highest quality incense (current local Grade I) while the lowest was contained by Grade VI. A two-step cluster analysis was performed to identify an accurate classification of resin grade according to both numerical and categorical attributes. Clustering algorithms with the two-step method worked efficiently and determined the optimal number of clusters, four grade incense profiles. The most important grade contains higher balsamic content and purity, lower impurities, ash content, melting point, and moisture content. Ash content and impurities were the most important predictor for differentiating each segment. The information obtained is expected to facilitate more accurate and honest resin quality grading application for farmers and traders.