The study, published in Food Chemistry, investigated how varying extraction conditions impacted the yield and chemical properties of pectin recovered from waste cocoa husks.
Led by Wee-Sim Choo from Monash University Sunway Campus, Malaysia, the researchers noted that commercial pectins - which widely used as gelling agents in the food, pharmaceutical and cosmetic industries - are extracted mainly from by-products from the food industry, including citrus peel, apple pomace and to a smaller extent, sugar beet pulp.
"One way to utilise cocoa husks is that it could be used as a source of pectin," noted the researchers- who found that the highest yield of pectin (7.62%) was obtained using a citric acid recovery process.
Choo and colleagues noted that there are generally two commercial types of pectin: high methoxyl (HM) pectin and low methoxyl (LM) pectins. These different forms of pectin have different physicochemical characteristics and thus different applications, they said.
The team used a variety of extraction conditions to investigate the effect of temperature, extraction time and substrate–extractant ratio on pectin recovery from the cocoa husk by-products.
Pectin was extracted from cocoa husks using water, citric acid at pH 2.5 or 4.0, or hydrochloric acid at pH 2.5 or 4.0.
The team reported that temperature, extraction time and substrate–extractant ratio all affected yield, uronic acid content, the degree of methylation (DM) and the degree of acetylation (DA) of the extracted pectins.
Yield and uronic acid content of the extracted pectins ranged from 3.38–7.62% to 31.19–65.20%, respectively - while the DM and DA of the extracted pectins ranged from 7.17–57.86% and 1.01–3.48%, respectively, said the authors.
The pectin obtained from cocoa husks was mainly LM pectin, however the team noted that this depended on the nature and pH of extractant used: "Water and hydrochloric acid produced pectin with a smaller DM range in which all were LM pectin," said the team. "Conversely, citric acid produced pectin with a wider DM range in which it can be of LM or HM pectin, depending on the extraction conditions."
The Malaysian researchers reported that the highest yield of pectin (7.62%) was recovered using citric acid - at pH 2.5 [1:25 (w/v)] at 95 °C for 3.0 h. The highest uronic acid content (65.20%) in the pectin was obtained using water [1:25 (w/v)] at 95 °C for 3.0 h.
Source: Food Chemistry
Volume 141, Issue 4, Pages 3752–3758, doi: 10.1016/j.foodchem.2013.06.097
"Effect of extraction conditions on the yield and chemical properties of pectin from cocoa husks"
Authors:Siew-Yin Chan, Wee-Sim Choo