Asparagus waste: new nutrient extraction method

By Rod Addy

- Last updated on GMT

Processors often only use the tips of asparagus, rather than the lower parts
Processors often only use the tips of asparagus, rather than the lower parts
Researchers are investigating the commercial potential of a process for extracting nutritional ingredients from asparagus waste for use in functional food products.

Asparagus has long been recognised for its nutritional benefits, particularly as a source of fibre​ and antioxidants​. One 2009 study even proposed it as a hangover cure​.

Now a new study​ published in the journal Food and Bioproducts Processing has highlighted a way to isolate and partially purify bioactive compounds including saponins, phenolics and sterols in asparagus by-product.

Many of these compounds are found in the lower portion of asparagus spears, which are often discarded during processing.

Commercialisation

“Further investigations related to stability and toxicity of ... products ... are being carried out, in order to make possible their commercialisation as functional ingredients or additives,”​ the paper states.

The patented extraction process involves hydrothermal treatment in a closed container within an industrial autoclave, using similar methods to those used in the commercial canning of plant foods.

This delivers two fractions: an aqueous functional extract containing most soluble bioactive compounds from asparagus by-product and a fibrous residue, which, after drying, constitutes bioactive fibre.

Column purification step

The process includes a column purification step, using an adsorbent polymeric resin. This allows aqueous extracts, partially purified, to be obtained and enriched in specific compounds, such as phenolics (antioxidant compounds) and saponins, which are believed to reduce ‘bad’ cholesterol.

“Both the aqueous extracts, partially purified and enriched in one of those compounds, and the bioactive fibre could be used as bioactive ingredients for designing new functional foods.”

The optimised method for the extraction of asparagus phytochemicals was found to be the treatment of asparagus by-product with water, as an extraction solvent, in a ratio of 1:2 solid:liquid (weight/volume), at 121 °C, for two hours.

Source: Food and Bioproducts Processing; available online December 2012; doi: http://dx.doi.org/10.1016/j.fbp.2012.12.004​; ‘Preparation of bioactive extracts from asparagus by-product’; authors: JM Fuentes-Alventosa; S Jaramillo-Carmona; G Rodriguez-Gutierrez; R Guillen-Bejarano; A Jimenez-Araujo; J Fernandez-Bolanos; R Rodriguez-Arcos

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