Significant changes occur in phenolic profiles, antioxidant activity during chocolate processing.

Studies have shown that phenolic compounds are present in cocoa and chocolate at significant levels, even greater than those found in tea and wine. Nowadays, there is much interest in phenolics because of their antioxidant activity. However, polyphenols are very sensitive to many processing conditions. Certain processing conditions can cause significant losses of both phenolic compounds and their antioxidant activity.

Chocolate manufacturing involves many processing steps that can affect those compounds. Scientists from Turkey attempted to evaluate the losses and changes that occur in cocoa products in terms of their phenolic compounds and antioxidant activity during chocolate production. They found that significant changes occur in phenolic profiles during the alkalization of cocoa and chocolate. This makes it necessary to optimize processing conditions and maintain the antioxidant activity of the compounds, so that consumers can benefit from the product.

The researchers examined cocoa nib, natural and alkaline cocoa powder, milk chocolate and bitter chocolate for their phenolic content and antioxidant activity. The products were all sourced from a chocolate processing plant in Turkey. The scientists analyzed the materials' total flavonoid content, total phenolic content and phenolic profiles. In addition, antioxidant activity was determined by using the 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and diphenylpicryl-hdrazyl (DPPH) radical scavenging activity methods.

The investigators statistically evaluated significant differences that were found in the data obtained for each sample. The total phenolic content for the samples was in the range of 10.8 to 32.5 mg of catechin per gram. The total phenolics and total flavonoid content were the highest in cocoa nib and natural cocoa. Alkalized cocoa had a significantly lower phenolic content and antioxidant activity than did the natural cocoa.

The bitter and milk chocolates had differences in their DPPH radical scavenging activity. In natural cocoa nib and powder, procyanidins and cyanidin glucosides were the abundant phenolics. In the alkalized cocoa and chocolate samples, there were more gallocatechins and fewer procyanidins.

Further information. Dilek Boyacioglu, Istanbul Technical University, Food Engineering Department, Ayazaga Campus, 34469 Maslak Istanbul, Turkey; phone: [phone]; fax: [phone]; email: [e-mail].