Methods for determining the fermentability and predicted spirit yield of distilling malts

• Published in: Journal of the Institute of Brewing Vol. 102; no. 6; pp. 433 - 437
• Main Authors: Bringhurst, T.A, Brosnan, J.M, McInnes, B, Steele, G.M
• Format: Journal Article
• Language: English
• Published: 01.11.1996
• Subjects: malt; malting barley
• ISSN: 0046-9750; 2050-0416
• DOI: 10.1002/j.2050-0416.1996.tb00927.x

Fermentability and predicted spirit yield (PSY) are two fundamental quality parameters of distilling malt, both of which rely on empirical factors for their calculation. Experiments were carried out using modern barley varieties to assess whether these factors were still valid for use in today's distilling industry. Using the 450 g IOB mash, an average attenuation factor of 81.46 from fifty-two determinations was found which was not significantly different from the existing factor of 81.4. A novel method to calculate the attenuation factor at different alcohol strengths was demonstrated which confirmed the factor to be 81.46. The PSY factor was shown to be 6.11 for a 450 g IOB mash, calculated using methods based on predicted and actual alcohol produced. However, a high gravity mashing procedure which more closely simulated distillery conditions confirmed that the current standard factor of 6.06 was still acceptable. Results indicated that it was not necessary to change either the attenuation or PSY factors when changing from the 515 ml mash to the 450 g mash in the standard IOB Recommended Methods.