The enzyme laccase was used to cross-link specific groups present in beet pectin, which could then be electrostatically deposited onto the surfaces of protein-coated droplets, and offer food formulators new opportunities, according to the research published in the journal Food Hydrocolloids.
"We believe that mimicking biochemical processes prevalent in nature (such as enzymatic cross-linking of pectin) allows one to rationally design novel functional performance into commercial emulsified products," wrote Francois Littoz, D. Julian McClements from the Department of Food Science at the University of Massachusetts.
"We should note that as well as improving the stability of emulsified lipids in food products during their production, transport, storage, and consumption, this approach may also prove useful for controlling the digestibility of lipids in vivo since the ability of digestive enzymes at accessing encapsulated lipids may be altered by the presence of a cross-linked interfacial layer," they added.
Emulsions are applied to a range of food products, including salad dressings, beverages, dips, sauces, desserts, and yoghurts.
Littoz and McClements prepared emulsions containing 0.1 weight per cent corn oil, 0.05 weight per cent beta-lactoglobulin (Davisco Foods), and 0.02 weight per cent beet pectin (Herbstreith and Fox KG) at pH 7.
The pH was then lowered to 4.5 to promote the electrostatic deposition of the pectin, and laccase was then added to promote cross-linking of the adsorbed beet pectin molecules.
The technique was shown to work, with stable emulsions formed.
"Our results suggest that the beet pectin layer remains attached to the droplet surfaces when the pH is raised from 4.5 to 7.0, even though it would normally be expected to become detached because of the electrostatic repulsion between the anionic pectin and anionic protein-coated droplets at pH 7," they stated.
The Amherst, Massachusetts-based researchers also report a higher stability to salt for the emulsions containing lipid droplets coated by beta-lactoglobulin and cross-linked beet pectin than for emulsions containing lipid droplets coated only by beta-lactoglobulin. This attributes to the adsorbed pectin's ability to reduce agglomeration by increasing the repulsive and decreasing the attractive interactions between the droplets.
"These results suggest that emulsions with improved functional performance can be prepared using a bio-mimetic approach that utilizes enzymes to cross-link adsorbed biopolymers," they concluded.
Source: Food Hydrocolloids
Published online ahead of print, doi: 10.1016/j.foodhyd.2007.06.009
"Bio-mimetic approach to improving emulsion stability: Cross-linking adsorbed beet pectin layers using laccase"
Authors: Francois Littoz, David Julian McClements