Impact of Non-Starch Polysaccharides and Protein on Mash Viscosity: A Comparative Study of Hard and Soft Wheat in Irish Whiskey Production

The viscosity of wheat mash is a critical parameter in Irish whiskey production, directly influencing mashing efficiency and lautering. Elevated viscosity can result in operational issues such as mash thickening, reduced pumpability, and equipment fouling. This study investigates the role of Non-Starch Polysaccharides (NSP)—specifically Water Extractable Arabinoxylans (WEAX) and β-glucans—on the viscosity of mash produced from hard and soft wheat at various mashing stages. Additionally, the relationship between protein content and viscosity is analysed to understand its role in mash processing challenges. A time-point study was conducted to measure viscosity, NSP levels, and protein content at different stages of mashing for both hard and soft wheat. Statistical analysis using the Generalised Linear Model (GLM) demonstrated a significant positive relationship between β-glucan and viscosity in soft wheat, whereas WEAX had an inverse relationship with viscosity for soft wheat. NSP did not show any statistically significant effect on the viscosity of hard wheat. Protein content, on the other hand, had a highly significant inverse relationship with viscosity in both hard and soft wheat. Despite lower β-glucan and WEAX extraction levels in hard wheat, its viscosity remained consistently higher than that of soft wheat, suggesting that the molecular weight of the extracted NSP, rather than their concentration alone, may play a critical role in influencing mash rheology. The findings of this study are important in balancing the NSP and protein levels to control viscosity in wheat-based whiskey production, providing key insights to enhance grain-based whiskey production.