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Minimising variation in aspalathin content of aqueous green rooibos extract: optimising extraction and identifying critical material attributes
Author(s) -
Miller Neil,
De Beer Dalene,
Joubert Elizabeth
Publication year - 2017
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.8370
Subject(s) - raw material , extraction (chemistry) , chemistry , water extraction , yield (engineering) , dry matter , pulp and paper industry , chromatography , mathematics , botany , materials science , biology , metallurgy , organic chemistry , engineering
BACKGROUND High levels of aspalathin, an antidiabetic dihydrochalcone, in green rooibos underpins interest in the production of a standardised extract. Elements of a quality‐by‐design approach were applied to optimise extraction conditions, aiming at the delivery of a dry matter yield ( DMY ) ≥ 160 g kg −1 and an extract with an aspalathin content ( AC ) ≥ 80 g kg −1 . RESULTS Hot water extraction parameters, namely extraction time, extraction temperature and water‐to‐plant material ratio, were optimised for DMY and aspalathin extraction efficiency ( AEE ) using Design of Experiments. Good polynomial prediction models were obtained and multiresponse desirability plots indicated 37 min, 93 °C and 23:1 as optimal conditions. Even when using 30 min and 10:1 instead for practical reasons, the target DMY and AC values could be achieved with the caveat that plant material with an AC ≥ 30 g kg −1 is used. Particle size distribution and stem content were identified as contributing to variation in the AC of raw material. CONCLUSION By setting raw material specifications in terms of AC , as well as applying practical optimum extraction conditions, 160 g kg −1 extract with an AC ≥ 80 g kg −1 could be consistently achieved from green rooibos plant material. © 2017 Society of Chemical Industry