The color of honey: a sweetener that bee-devils food spoilage

Science News,  Sept 12, 1998  by Janet Raloff

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Most fruits and vegetables contain antioxidants. Though the average honey's ascorbic-acid equivalency, 0.8 x [10.sup.-3] [micro]eq per milligram, comes close to that of tomatoes, Berenbaum's group notes that many fruits and vegetables possess far more. Orange pulp, for instance, has 5.7 x [10.sup.-3] [micro]eq/mg, and broccoli and sweet peppers show 13.0 x [10.sup.-3] [micro]eq/mg. Dried tea, renowned for its antioxidants, can run to 220 x [10.sup.-3] [micro]eq/mg.

Moreover, Berenbaum is quick to point out, these figures may actually underestimate those foods' oxidant-quashing activity, since many of them--unlike honey--also contain large quantities of fat-soluble antioxidants such as vitamin E and carotenoids. People also tend to eat far smaller quantities of honey than they do most fruits and vegetables.

Still, she notes, per capita sugar consumption in the United States "is enormous"--roughly 150 pounds per year, according to the latest Department of Agriculture statistics. "If you were to substitute honey for all that sugar," she surmises, "the contribution of its antioxidants might become substantial."

Although the presence of antioxidants suggests that honey might be able to limit the ravages of biologically destructive agents, the proof is in the pudding, or muffins, or sausage, notes Nicki J. Engeseth, a food scientist at the University of Illinois.

In one set of experiments, she therefore added honey to fruits and vegetables that turn brown upon exposure to air. In such foods, an enzyme in the plant tissues triggers a reaction between oxygen and phenolic chemicals. The resulting browning not only makes the food unappealing but also uses up its vitamin C.

For this test, she put freshly cut apples, pears, potatoes, or yams into a blender--grinding them into a soupy homogenate--then mixed in one of six different types of honey. Though the light colored acacia honey offered no protection against browning, the darker honeys did.

Christmasberry honey retarded the browning enzyme's activity by up to 50 percent, for example. While the honey didn't match the potency of ascorbic acid or sulfites--two commercially popular antioxidants--it did lengthen the time before browning occurred.

Soy honey also greatly reduced the rate at which the foods turned brown. Indeed, it proved far more effective than the clover honeys, even though all possessed similar antioxidant ratings. This suggests, Engeseth says, that for certain applications, which antioxidants are present may be as important as their quantity.

Though buckwheat honey's high antioxidant content suggested it probably would have had the best chance of retarding enzymatic browning, "we couldn't use it," Engeseth says, because its "tarry" color would have darkened foods even in the absence of any oxidation.

In a second experiment, the group investigated honey's ability to slow the oxidation of fats. A form of food spoilage, this process turns fats rancid (SN: 2/9/85, p. 88) and may transform them into a potent risk factor for artery-clogging heart disease (SN: 5/4/85, p. 278).