2006 Volume 39 Issue 9 Pages 956-962
Wastes discharged from beer breweries are mainly composed of malt and hop. The nutritional value of malt is quite high and, consequently, it is recycled as feed for domestic animals; however, the nutritional value of hop as feed is not so high. A new utilization method for hop waste is therefore required. In this experiment, it is found that Procyanidin, a polymer composed of catechins, is abundantly contained in hop bract part and hop itself. This research deals with the extraction of total polyphenols, catechin, and procyanidin from hop bract part under various extraction conditions. When ethanol was used as the extract solvent, about 30% of the total extracted polyphenols was procyanidin, showing that ethanol has the highest selectivity for procyanidin. The extraction of all polyphenols, catechin, and procyanidin was conducted in about 10 min at a temperature of 293–333 K and with horizontal shaking at 130 rpm. The amount of each polyphenol extracted increased with increasing temperature. The total amount of catechin extracted reached a maximum at an extraction temperature of 333 K. Compared with tea, more polyphenols were shown to be contained in the hop bract part. A continuous extraction process for collection of the polyphenols contained in the hop bract part using a modified mixer-settler extractor device is described and the fundamental performance of the presented extractor was examined.
