Chocolate cake: Leavening agent key to healthy profile

Using baking powder rather than baking soda in a chocolate cake mix preserves the product’s antioxidant activity and flavanol content, according to results published in the Journal of Food Science​.

However, choosing baking powder over soda produced a shorter cake and a lighter colour, wrote the researchers, led by Dr W. Jeffrey Hurst from the Hershey Company.

Flavanoids in chocolate and beyond​

The health benefits of antioxidant-rich chocolate have received much recognition in recent years, with positive findings from a number of studies impacting on consumer awareness. Chocolate manufacturers are using high cocoa content (over 70 per cent) as a means of differentiation, and cocoa has also received attention for its potential in functional food applications.

The new study by Hershey, in collaboration with scientists from Brunswick Laboratories, reports that the choice of other ingredients is vital to maintain the high flavanol and procyanidin content of cocoa, and provides key information to other formulators, not just of chocolate cakes, but other antioxidant-rich cakes.

“Beyond the loss of flavanols from cocoa-flavored foods, other flavanol-rich ingredients such as grapes, raisins, cranberries, blueberries, apples, and other fruits, and spices, such as cinnamon may suffer significant loss in their flavanol content in cakes and baked goods with high final pH,”​ wrote Dr Hurst and his co-workers.

“It is important to consider the impact of acidulants or basic leavening agents on the final pH and the impact these ingredients may have on the naturally occurring and healthful flavanol content,”​ they said.

Recipe for success​

Dr Hurst and his co-workers quantified the antioxidant activity, and the levels of total polyphenol, flavanol monomers, and their oligomers (procyanidins) in typical cocoa-containing recipes and in several commercial cake mixes. They used Hershey’s Natural Cocoa in all products.

While excellent recoveries of antioxidant activity, polyphenol, flavanol monomers, and procyanidins were observed in chocolate frosting, hot cocoa drink, and chocolate cookies, ranging ranged from 86 to over 100 per cent, the chocolate cake displayed poor recoveries, ranging from 5 to 54 per cent for antioxidant activity.

When baking soda was used as the leavening agent, the researchers noted that the pH of the mix increased, and the colour darkened. The commercially available chocolate cake mixes (which contained baking soda) were found to have high pHs, above pH 8.3, and had virtually no monomeric flavanols after baking, said the researchers.

When baking soda was replaced with baking powder, the researchers noted a reduction in the pH of the product to 6.2, and an “essentially complete retention of antioxidant activity and flavanol content”​.

“These results suggest that the effect of increased pH due to baking soda can be largely reversed by choosing the appropriate leavening acid in the form of a baking powder or by adding acidic ingredients to the recipe,”​ wrote the researchers.

“The final pH of the baked cake needs to be pH 7.5 or less for preservation of antioxidant activity and flavanol content,”​ they added.

Source: Journal of Food Science​
Published online ahead of print, doi: 10.1111/j.1750-3841.2009.01226.x
“Preservation of Cocoa Antioxidant Activity, Total Polyphenols, Flavan-3-ols, and Procyanidin Content in Foods Prepared with Cocoa Powder”​.
Authors: L. Stahl, K.B. Miller, J. Apgar, D.S. Sweigart, D.A. Stuart, N. McHale, B. Ou, M. Kondo, W.J. Hurst.