The studies,
both from the University of Illinois, focused on the
oxidation-inhibiting qualities of honey - one on cooked
meat, the other on human blood. Oxidation is not good in
either case.
Oxidation of
meat degrades the flavor, but, more importantly, oxidation
of blood contributes to heart disease. Long-term consumption
of oxidized foods is implicated in aging and health problems
because oxidation proceeds through a free radical process.
Oxidation of lipoprotein (LDL) in the blood (the ‘bad’
cholesterol) is thought to play an important role in the
development of hardening of the arteries (atherosclerosis).
Increasing LDL’s resistance to oxidation is thought to
possibly delay the progression of the disease.
"Free
radicals are known to attack other molecules, such as
proteins or DNA," said principal researcher Nicki Engeseth,
professor of food chemistry at the University of Illinois.
"As a result you can get a higher incidence of
cardiovascular disease and cancer."
The idea
behind Engeseth’s research is the use of honey - a natural
source of antioxidants - in food systems to retard
oxidation, preserve flavor and color, and give consumers
fresher foods.
Previous
Engeseth work demonstrated that honey was effective at
reducing browning in sliced fruits and vegetables, which is
caused by a form of oxidation called polyphenol oxidase. So
she wondered what effect honey might have on lipid oxidation
in meat systems.
She tested
this by mixing 5 percent honey to fresh ground meat before
cooking. The classic problem with cooked refrigerated or
pre-cooked frozen meats is it develops a taste called
‘warmed-over flavor’, a loss in flavor quality caused by
lipid oxidation. Engeseth wanted to see if she could
minimize lipid oxidation by the addition of honey. Turkey,
poultry, and ham products are all complementary to honey
flavor.
"Honey is
positive for flavor in most cases, but not all," said Joseph
G. Sebranek, professor of Animal Science at Iowa State
University, and president of the American Meat Science
Association. "It works well in breakfast sausage for
instance, but probably wouldn't be too well received on
hamburgers."
Engeseth
found that adding honey to ground turkey and holding it
three days in the refrigerator significantly reduced
oxidation. Also, when measured against traditional
commercial preservatives such as butylated hydroxytoluene (BHT),
honey at a comparable concentration was much more protective
against oxidation.
Such
encouraging results lead her next to examine the ability of
honey to protect against oxidation in human blood serum.
This work, published April 6 in the Journal of Agricultural
& Food Chemistry, is the first to look at the effect of
honey on human blood.
Engeseth
collected blood samples from people working in her lab and
used honey in different concentrations from different floral
sources to see if it could protect against LDL oxidation.
"The reason
that's so important is because it's believed that LDL
oxidation is the initiating factor for atherosclerosis," she
said. "When you oxidize LDL you actually initiate plaque
deposition in the arteries. By being able to reduce the
oxidation of LDL you theoretically should be able to reduce
the incidence of plaque, or at least slow it down."
The honey
worked.
Using a
popular tool called Oxygen Radical Absorption Capacity (ORAC)
that measures total serum antioxidant activity, Engeseth
found the antioxidant capacity of honey to be equal to that
in many fruits and vegetables in its ability to counter the
degenerating activity of free radicals. "On a per gram
basis, the antioxidant capacity of fruits and vegetables, as
measured in ORAC units, is usually between .5 and 19. Of the
seven honeys we tested (acacia, buckwheat, clover, fireweed,
Hawaiian Christmas berry, soybean, and tupelo), we found a
range of 3 to 16 ORAC units," Engeseth said.
"It still is
too early to say definitively, but honey seems to have the
potential to serve as a dietary antioxidant," she said.
"Even though honey might not be consumed at the same gram
level as fruits or vegetables, the potential is there."
Interestingly, in both studies Engeseth found that
dark-colored honey, particularly buckwheat, provided more
protective antioxidant punch than lighter-colored honeys.
Engeseth examined a number of sources of buckwheat honey.
Most had ORAC values between nine and 11, although one
registered almost 17.
"So far, we
don't really know what specifically is different about
buckwheat honey, except that it's higher in phenolics,"
Engeseth said. Phenolics are compounds believed to be
produced as a result of the plant's interaction with the
environment, and seem to be the most highly correlated with
antioxidant capacity.
Follow-up
honey studies, either in progress or in the wings, should
shed more light on the exact phenolic compounds in honey and
on how effectively consumed honey prevents oxidation in the
blood of human subjects.