Juice processing effects on quality of Aronia pomace – A resource for colour extraction

Michael Vagiri & Martin Jensen Aarhus University, Department of Food Science, Kirstinebjergvej 10, DK-5792, Årslev, Denmark

AARHUS UNIVERSITY

ultra sonic bath for 20 min. The extracts were then centrifuged for 10 min and analyzed with HPLC-DAD to separate and quantify monomeric anthocyanins. Total monomeric anthocyanins were determi-ned with a spectrophotometer using the pH differential method. Yields of juice and pomace, as well as anthocyanin retention during processing of berries to juice were also determined.

Results

- Pre-heating of the mash prior to and during processing increased juice yield (Fig. 2).

- Following pressing, anthocyanins were retained in higher concentration in the pomace (Fig. 3), than in the juice.

- Anthocyanin levels in the pomace were affected mostly by enzyme treatment followed by maceration temperature (Fig. 4).

- Cold pressing frozen berries without enzyme addition gave the highest concentrations of anthocyanins in the pomace (Fig. 4)

- Although cyanidin-3-galactoside and cyanidin-3-arabinoside were sensitive to processing treatments, their quantitative distribution did not change and were the most abundant compounds (Fig. 4).

Conclusions

In conclusion, juice processing factors had a significant and opposite effect on the yield of juice and pomace, and on the con-centration of anthocyanins. Since Aronia pomace is a rich source of anthocyanins, as found in this study, the pomace may be useful in value-added applications for the recovery of natural pigments as opposed to just disposing the pomace as waste or animal feed.

Introduction

Anthocyanins are well known natural red colourants, with potential applica-tion in colouring of food products. Berry fruits are well documented among the widely recognized sources of anthocyanins. For instance, black cho-keberries (Aronia melanocarpa (Michx.) Elliot) are a rich source of anthocyanins, and its pomace–a byproduct of juice processing could be efficiently used for extraction of natural colours for the food industry.

Aim

In this study, we evaluated how the quality of Aronia pomace varies depending on the methods used in juice processing (in the range from low to high intensity), and what quality of the colour extract can be obtained from pomace.

Materials & Methods

An overview of the juice processing scheme is shown in Fig. 1.Fully ripe berries from the cultivar A. melanocarpa ‘Viking’ were harvested at the Department of Food Science, Aarhus University, Denmark.

The pomace samples were ground and three replicates for each sample were extracted with 15 mL of acidified methanol (MeoH:HCL, 99:1 v/v) using

Figure 1. A schematic representation of Aronia juice processing.

Figure 3. Retention of total monomeric anthocyanins (mg cya-glu/100 g FW) during processing of frozen berries to juice and pomace using different processing treatments.

Figure 4. Concentration of monomeric anthocyanins (mg/100 g FW) in Aronia pomace using different processing treatments.

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mic

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Tel:

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Figure 2. Stacked bar graph depicting the juice (white bars) and pomace (grey bars) yields (%) obtained after different processing treatments.

Acknowledgements.

The study was performed as a part of the project COLARO funded by GUDP, Danish Ministry of Environment and Food.