Executive Summary: Compounds from Vegetable Waste, Part 1

Summary of Project and Key Findings:
A protocol for recovering phenolic phytochemicals from apple was used to determine if it can be adapted to vegetables, i.e. carrots and onions. The goal was to develop an integrated processing approach based on novel, low cost combinations of existing, proven technologies that will extract a greater range of ingredients, likely to include fibre (soluble/ insoluble), phenolic phytochemicals, proteins, and minerals. We received the onion waste stream from the onion producer later than expected, which delayed the trials. The carrot pomace did not arrive so we had to create our own pomace in the lab using a small bench top fruit juicer.

Small scale extraction trials were carried out using a combination of equipment and operational conditions to isolate polyphenols, fibre and other compounds from carrot and onion by-products. Analyses of samples were carried out to determine the amount of extracted material from the various extraction steps. This includes total phenolics, proteins, dietary fibre, sugars and minerals.

Preliminary results show that higher yields of polyphenolics were obtained with higher temperature and lower pH. It is expected that higher temperature will enhance the solubility of phenolics and lower the viscosity, hence, achieving better diffusivity and mass transfer that will increase the yields. The low pH will enhances the protonation of phenolic compounds rendering them more hydrophobic and thus increasing their yield in the final product. Most of the samples were extracted using water (aqueous) as a solvent and one sample was extracted with ethanol for comparison.

The resin adsorption method was used to separate and concentrate the phenolic from the other non-phenolic compounds, such as sugars and fibres. The resin used in the trial was di-vinyl-benzene adsorbent resin. It was found that significant amount of phenolics have been extracted using water at moderate temperatures and low pH. The high amount of phenolics retained by the resin indicates that we have chosen an appropriate resin that could also be used for the proposed scale up trials.

High performance liquid chromatography (HPLC) analysis will be carried out on some of the samples to identify and quantify the phenolics across a few of the processing steps; mainly on the samples before and after the adsorption step in order to perform a mass balance to estimate the yield from the use of our extraction protocol.

It was possible to recover minerals during the first phase of the extraction process, however, low amounts of soluble fibre and proteins were recovered in the eluate.

The recovery of very low amounts of proteins and soluble fibre from the various extraction steps means that further work is required to optimise the process to provide full recovery of these components. The small scale extraction process we implemented in this project was smaller than the pilot scale process we usually use in our facility and this may have contributed to the low recovery rates of some of the components.