Natural antioxidants as food and beverage ingredients - Natural Food Additives, Ingredients and Flavourings - page 105

antioxidants like BHA and BHT were used to protect industrial polymers against
oxidation prior to their introduction to the world of foods and have been in the
human diet for only a relatively short time. The introduction of synthetic
antioxidants requires extensive safety testing, which is not the case with natural
antioxidants.
A major advantage in using natural antioxidants is the less restrictive limitations
on usage levels for these materials. The use of natural antioxidant systems is
generally limited by the degree of fl avor, color or cost that can be tolerated to give
maximal performance. On the other hand, regulations do limit the usage level of
synthetic antioxidants such as BHA, BHT, tert -butylhydroquinone (TBHQ) and
EDTA in each type of food application. When synthetic antioxidants used at their
regulatory maximum limit fail to deliver the required level of protection,
combinations of natural and synthetic antioxidants can be used to provide the
needed performance levels, while still taking advantage of the cost savings that a
base level of synthetics provide. Moreover, synergistic effects have been
occasionally reported between synthetic and natural antioxidants (rosemary in
combination of BHA or BHT) (Romano et al. 2009).
The use of natural antioxidants seems to have its own set of disadvantages and
limitations - a major one being effectiveness. On the molecular level, natural
antioxidants can be as potent as their synthetic antioxidants, but active components
usually exist amongst other extract constituents that are not active in managing
oxidation, resulting in a need to use much higher levels of the overall extract
in order to deliver the required amount of antioxidant active ingredient to the
system. As mentioned earlier, when the natural antioxidant is used at a high
level, the fl avor, aroma and color of the food can potentially be impacted
unacceptably. Higher cost also becomes a factor at high dosage, since natural
antioxidants come from botanical sources with limited availability and are
generally more expensive.

5.3.1 Phenolics
Phenolics constitute a large group of phytochemicals having in common the same
functional group, but belonging to very different chemical classes such as phenolic
acids (rosmarinic and carnosic acid), hydroxybenzoic acids (vanillic acid),
hydroxycinnamic acids (ferulic and chlorogenic acid), fl avonoids (quercetin,
catechin and rutin), anthocyanins (delphinidin), tannins (procyanidin, ellagic acid
and tannic acid), lignans (sesaminol, seco-isolariciresinol), stilbenes (resveratol),
coumarins ( o -coumarine) and essential oils (carvacrol, eugenol) (Pokorný 2007).
Therefore, the bioactive compound that needs to be isolated from the spice is the
determining criteria for the type of solvent, spice to solvent ratio and extraction
technique that needs to be used. Crude extracts can be further purifi ed by
fractionation, solvent partitioning, recrystallization, or defl avorization and
decolorization. From a mechanistic perspective, the extraction parameters are also
infl uenced by the desired properties such as metal chelating potential, radical
scavenging activity, polarity and certainly extraction yield.

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