Process Intensification by Experimental Design Application to Microwave-Assisted Extraction of Phenolic Compounds from Juglans regia L.
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Microwave-assisted extraction was applied to Juglans regia L. fresh male flowers and unripe walnut seeds to evaluate the total phenolic contents of the extracts as well as the percentage of water-soluble polyphenols. The research was planned using the Design of Experiments technique to investigate the role on the extraction efficiency of different parameters, such as temperature, time and number of microwave heating cycles, together with their possible interactions. Optimization was achieved by applying a Response Surface Methodology comprising a three-factor, two-level, full-factorial Face-Centred Central Composite Design. The two input variables with a significant effect on the recovery of phenols from fresh male flowers were the extraction temperature and the number of microwave cycles. In the case of unripe walnut seeds, a linear two-factor interaction model was selected, with significant interactions occurring between temperature and time, and time and number of microwave cycles. The best experimental conditions were as follows: 100 °C, 6 min, three microwave heating cycles and 22.7 ± 0.2 mg gallic acid equivalent (GAE)/g (total phenolic content, PC); energy consumption calculations suggested slightly different conditions: 60 °C, 30 min, three microwave heating cycles and 20.7 ± 0.3 mg GAE/g (TPC).
KeywordsMicrowave-assisted extraction (MAE) DoE Juglans regia L. Phenolic compounds
The authors want to thank Dr. Sara Romeo for her support in experimental work.
Compliance with Ethical Standards
Conflict of Interest
Roberto Rosa declares that he has no conflict of interest. Lorenzo Tassi declares that he has no conflict of interest. Giulia Orteca declares that she has no conflict of interest. Monica Saladini declares that she has no conflict of interest. Carla Villa declares that she has no conflict of interest.
Paolo Veronesi declares that he has no conflict of interest. Cristina Leonelli declares that she has no conflict of interest. Erika Ferrari declares that she has no conflict of interest.
This article does not contain any studies with animals performed by any of the authors.
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