High molecular weight compounds generated by roasting barley malt are pro-oxidants in metal-catalyzed oxidations

• Type: Article in International Scientific Journal
• Date: 2016

Authors

Carvalho, DO (Author) FCUP; gendal, LH (Author) Other; Andersen, ML (Author) Other; Luis F Guido (Author) FCUP

Journal

Title: European Food Research and Technology

Vol. 242

Pages: 1545-1553

ISSN: 1438-2377

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 19 Citations

Scopus - 21 Citations

Other information

Authenticus ID: P-00K-KE9

DOI: 10.1007/s00217-016-2655-7

Abstract (EN): The roasting process and color development have been related to an increase of the antioxidant activity of roasted malts. However, roasting is also responsible for the development of high molecular compounds with a pro-oxidant effect, leading to increased levels of radicals in systems based on iron- and copper-catalyzed Fenton reactions. For this reason, the overall antioxidant and pro-oxidant properties of three malt types with different roasting degrees (pilsner, melano and black) were evaluated in a Fenton-based model beer system (5.8 % ethanol, v/v). Black malt exhibited 50 % lower radical quenching capacity compared with pale and melano malts, as determined by spin trapping and electron spin resonance detection. These differences were related to the degree of roasting and the development of high molecular weight browning compounds. High molecular weight compounds isolated from black malt wort (molecular mass in the range of 4 x 10(6) and 10(8) g mol(-1)) were responsible for an increase of radicals (approximately 40 %) in a Fenton reaction and were able to accelerate metal-catalyzed oxidation in a beer model, as shown by a decrease of almost 11 % of the dissolved oxygen. Although black malt was able to reduce the overall levels of radicals generated by the Fenton reaction, high molecular weight compounds had an opposite effect due to the reductive redox-cycling of the catalytic amounts of iron.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9