Comparisons between Conventional and Microwave-Assisted Extraction of Natural Colorant From Mesocarp and Exocarp of Cocus Nucifera

Abstract

This study aimed at exploring the feasibility of using the mesocarp and exocarp of Cocus nucifera as a natural colorant using microwave-assisted extraction in which often regarded as a waste materials. The effects of microwave power and heating time on the yield of colorant, pH and colour determination were investigated. The highest colorant yield in mesocarp and exocarp was found to be 6.0% (8 min of extraction at 100 W) and 6.8% (12 min of extraction at 300W), respectively. While the control, extraction of colorant by conventional method (90 min at 90 º C), showed a percentage of 5.2% (mesocarp) and 3.6% (exocarp) yield of colorant. Meanwhile, pH of all extracts fluctuated throughout the experiment. The results proved that heating time and microwave power slightly affected the pH of all samples due to pH being inconsistent throughout the experiment. In colour determination, lightness (L*) was slightly decreased for all samples which extracted at all microwave power which indicated that the longer the heating time the darker colour was extracted. Overall, the colour of exocarp was darker than mesocarp extract due to L*, c* and h* values were lower than the mexocarp extract. The utilization of microwave-assisted extraction has significant improvement in the extraction of natural colorant compared to traditional boiling method. In fact, application of microwave irradiation method proved to be a rapid and improved technique for natural colorant extraction and extensively reduced the extraction time.

Phytochemical Properties and Antimicrobial Activity of Natural Colorant Extracted from Mesocarp and Exocarp of Cocos nucifera

“…About 10 g of each mesocarp and exocarp samples were transferred into a conical flask containing 200 ml of 0.1 M sodium hydroxide (ratio of 1:20). The mixtures were then heated in a microwave (Samsung, Korea) at 300W for 2 minutes [15]. After microwave heating, the mixtures were allowed to be cooled to room temperature before filtered using filter paper (150 mm) (CHM, Germany).…”

Optimization of Natural Dye Extraction from Coconut Husk

“…Also, among all the samples studied, the combination of mesocarp and exocarp resulted in the highest values of TPC (1.73±1.99 mg GAE/g; p<0.05), TFC (2.24±0.04 mg QE/g; p<0.05) and TTC (0.23±0.01 mg TE/g) and they were significantly different from every other sample (Figure 2). In a study conducted by Rodiah et al (2018) which assessed the polyphenolic contents of mesocarp and endocarp of coconuts, the authors found that the mesocarp had a TPC value (32.24 mg GAE/g) and it was significantly higher than the TPC value of the exocarp (8.63 mg GAE/g). However, the authors did not assess the TPC values of the combination of mesocarp and exocarp.…”

“…The coconut husk consists of the endocarp, mesocarp, and exocarp which make up about 30-35% of the whole coconut (Tan et al, 2007). It is estimated that 5280 kg of dry coconut husk is produced per hectare every year which is significant and (Rodiah et al, 2018) there is a dire need to find a way to manage the waste. One approach is to add value to the waste by utilizing the coconut husk as a natural dye.…”