Factors affecting extraction and encapsulation of bioactive compounds and aroma in pandan Pandanus amaryllifolius leaves

Abstract

The pandan leaf is a rich source of chlorophyll. In its natural state chlorophyll is unstable. It becomes extremely labile on exposure to acid or heat, breaking down into derivatives of olive brown coloration. Chlorophyll analogues, in which Zn is substituted for Mg, are more stable. This study optimized conditions for Zn-chlorophyll complex formation were 300 ppm zinc chloride at pH 5 and 110 °C for 15 min. The chlorophyll derivatives obtained included Zn-pheophytin a, b and Zn-pyropheophytin a, b. These analogues are green in color, like native chlorophyll, but more stable to acid and high temperature. The Zn-chlorophyll derivatives also show greater antioxidant properties than native chlorophyll. Subsequently, a hydrolytic enzyme was used to extract the derivatives. The commercial enzyme pectinase (Pectinex® Ultra SP-L, activity 10292 PGU/mL) assisted in the extraction process and an experimental design using response surface methodology (RSM) was utilized to further optimize the yield. The optimum conditions were 2.3−2.5% (v/w) Pectinex® Ultra SP-L, 240−260 min incubation time and extraction repeated twice. Under the optimum conditions, the extraction yields of green chlorophyll and antioxidant activity were increased 17.3 and 1.9 fold, respectively, over non-enzymatic treatment. From Zn-chlorophyll powder production by spray drying method, three different wall material types, gum arabic (GA), maltodextrin (MD) and OSA-modified starch (MS), were studied based on their physicochemical properties and the stability of encapsulated powder. It was found that the process with 30% (w/w) OSA-modified starch proved best for chlorophyll powder production. Under this optimum condition was obtained the highest of green coloration, chlorophyll content and antioxidant activity of the product. Decay of Zn-chlorophyll derivatives GA, MD and MS displayed first-order kinetics with rate constants (k) of 2.1 x 10⁻³, 1.8 x 10⁻³ and 1.5 x 10⁻³ day⁻¹, respectively and the half-life value (t1/2) of 330, 385 and 462 days, respectively. Chlorophyll powders proved to remain unchanged over a wide range of pH and temperature, validating their potential use as coloring additive in food product. The obtained chlorophyll powder contained 2-acetyl-1-pyrroline, the characteristic flavor of pandan leaves. The zinc content of the product was found to be within regulation limit set by the FDA. Collectively, the results support the potential for using natural green colorants in the food industry.