Chemistry Reference
In-Depth Information
products' (MRPs) organoleptic notes that characterize baked, broiled and
roasted foods, MRPs cause nutritional variations, one of which is the appearance
of antioxidant activity.
Numerous studies have demonstrated the antioxidant effectiveness of MRP
either during food processing, or in model systems. Devshand and De
Muelenaere (1996) assessed the effect of reducing sugars and available lysine
during extrusion by determining the antioxidant activity of the extracted lipids
and found that MRP are a source of antioxidants. In a review by Namiki, several
examples of MRP antioxidant contribution were reported in actual foods such as
processed cereals, cookie dough and powdered milk (Namiki, 1988).
The antioxidant capacity of MRP was also evaluated in model systems such
as heated soybean oil and pregelatinized starch containing a Maillard reaction
reducing agent and amino acid, where the extent of browning correlated with the
antioxidant protection (Mastrocola and Munari, 2000).
Although the antioxidant effects of MRP have been confirmed in a multitude
of studies, the mechanism of action is not well defined. It could be related to
radical scavenging activity, or metal chelating potential (or both) or to the ability
of some of the intermediates to act as reductases. The specific compounds
responsible for the activity have not been isolated nor identified due to the
complexity of the Maillard cascade of reactions (Reische et al., 2008).
12.6 What can we learn from the plastics industry?
The types of plastics now on the market were made possible only through the
development and use of antioxidants. Without them, polymers we rely on would
not have the properties necessary to fill the many applications we now take for
granted. Just as with foods, antioxidants of various kinds and functions protect
polymers during their synthesis, processing, fabrication and long-term use. Both
polymers and foods are subject to oxidation during preparation processes that
can involve exposure to heating, shear, light and metals. Both polymers and
foods suffer oxidation during ambient storage or use. The mechanism of
oxidation of these two materials share many features in common, including a
radical chain mechanism, free radical intermediates, and types and actions of
initiators. Just as polymer antioxidants function and are classed as primary and
secondary antioxidants, chelators, quenchers, and so on, so too are food
antioxidants. Table 12.6 lists representative examples of various types of anti-
oxidants for polymers and foods. There are many empty spaces in the column
for food antioxidants, where no known representatives of a given chemical class
exist. It is one purpose of this chapter to highlight these gaps and encourage
researchers to search for naturally occurring substances from GRAS plants that
have the appropriate chemical functionality to fill these gaps and provide new
and better ways of stabilizing foods. Powerful combinations of antioxidants
(including primary, secondary, chelators, quenchers, and carbon radical
scavengers) have transformed the plastics industry ± each component of which
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