• rheological behaviour
• partcile size
• storage
• syneresis
• soy yogurt
• fortification
• brewery's spent grain

Brewery’s spent grain (BSG) is the most abundant by-product of the beer-brewing process. BSG is rich in fibre and protein and its main reuse is as an animal feed. However, because of its high nutritional value, BSG is of interest for fortification of human food products, particularly in view of its low cost and availability in large amounts. This study aims to evaluate the impact of spent grain on soy yogurt compared to a common BSG-free soy yogurt. The effect of different level addition of BSG on the physico-chemical properties (particle size distribution, syneresis, texture, and rheological behaviour) of the final product has been investigated. Changes in these physico-chemical properties during a storage period of 4 weeks have been monitored on a weekly basis. The incorporation of BSG in soy yogurt benefited the production line due to its impact in increasing the fermentation rate and supported the LAB growth. BSG-added yogurt shows an increased pH which can be a benefit for industry to use less sweetener to cover the acidity. High dietary fibre in BSG contributed to a lower syneresis, a higher shear stress and maintenance of viscosity during the storage period. Furthermore, the addition of BSG strengthened the survival level of LAB during the storage. A maximum substitution of 2% BSG is suggested to be more suitable in yogurt products due to its ability to bind water, preserve the flow behaviour and syneresis in addition to other physico-chemical properties.