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Stabilized phycocyanin in sugar solutions

IP.com Disclosure Number: IPCOM000248903D
Publication Date: 2017-Jan-20
Document File: 4 page(s) / 154K

Publishing Venue

The IP.com Prior Art Database

Abstract

The blue color of spirulina comes from phycocyanins which are protein-chromophore complexes. If protein unfolding can be prevented the interactions between the chromophore and the protein remain, this results in stable color. Present approach was to stabilize the protein structure and the interaction between the chromophore and the protein, by removing the effect of water on the protein structure. We found that the unfolding of proteins (observed as color loss) can be reduced by dissolving the protein in very highly concentrated sugar solutions.

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Stabilized phycocyanin in sugar solutions

Introduction

Where does the color come from?

The blue color of spirulina comes from phycocyanins (Figure 1) which are protein-chromophore

complexes. The chromophore is a tetrapyrrole and is covalently bound to the protein, by a

thioether bond. Apart from the thioether bond the chromophore interacts with the protein by

hydrogen bonding which results in favorable conformation of the chromophore, which in turn

results in strong blue color. Any changes to this protein-chromophore interaction usually lead to

loss of color.

Figure 1. Phycocyanin 3D structure, 6 monomers aggregated to form a hexamer. Chromophores

are displayed in color.

Figure 2. Structure of the chromophore.

What leads to loss of color?

Proteins are very dynamic molecules where their structure is influenced by pH, temperature,

interaction with other molecules and presence of phase boundaries. Therefore any color complex

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that relies on specific protein structure for the correct color will be very difficult to stabilize.

Furthermore the color can also be lost by oxidation of the chromophore. Our major challenge was

to stabilize the color during pasteurization at 90°C. At this high temperature the protein unfolds

leading to substantial loss of color.

In order to solve this problem, we decided to focus on stabilizing the color in a beverage syrup

which is delivered as a syrup to end consumer for sodastream® or in a soda dispenser. This way

the long term stability of the color in the final beverage is not an issue because the beverage is

consumed right away. Therefore, the main requirements for this project is that the color needs to

be stable during pasteurization.

Protein structure in water

The water has substantial influence on protein structure and plays a large role in protein

unfolding. The water structure around a protein can influence the 3D structure of the protein by

influencing the internal hydrogen bonding of the protein (Berns and McClements 1998). It is

known that sugars can influence the structure of water and that this is dependent on the type and

concentration of sugar (Gharsallaoui et al. 2008). However the influence of sugar on protein

structure is not predictable.

Our approach was to add increasing amount of sugar to the phycocyanin in order to stabilize the

protein and thus increase stability of the blue color during storage and heating.

Prior art

WO 2015/090697 describes how phycocyanin can be stabilized by hydrolyzing the phycocyanin

with chemicals or enzymes and then complexed with polyphenols, resulting in stable color at pH

below 4, during heating to 90°C and storage in presence of intense light.

Materials and Methods

The following materials where used: Phycocyanin (trade name Linablue HGI, manufacturer DIC

Japan), Tannic acid (Sigma Aldrich), Glucose, Trehalose, fructose, glycerol and glucose syrups.

Phycocyanin was dissolved in a solution containing sugars (0-65% w/w) at pH 6. Tannic acid-

phycocyanin co...