The series of interesting old papers reprinted under the heading "Brewing! Have things changed so much?" continues with an item first published in 1953, describing experiments in which two different types of ultrasonic equipment (an Atlas magnetostrictive oscillator with a frequency of 80000 cycles and an Ultrakust reciprocal piezoelectric system with a frequency of 1 million cycles) were suspended in the wort copper during boiling. The literature on similar experiments carried out in Europe in the early 1950s is reviewed. It is stated that ultrasonic treatment of the boiling wort improves the efficiency of extraction of bitter substances from the hops and reduces the intensity of the astringent flavour component, as well as increasing trub precipitation and facilitating the release of dissolved gases from the wort, while the treatment of sweet wort before boiling is stated to increase its sweetness and malty flavour.
Keywords : 1994