Valorisation of brewers’ spent grain in a soy yogurt product

Beatrice Sella

Master's thesis

Abstract:

Brewery’s spent grain (BSG) is the most abundant by-product generated from the beer-brewing process. BSG is rich in fibre and protein and, to date, the main use for the elimination of this by-product has been as an animal feed. However, because of its high nutritional value (such as the content of bioactive phenolic compounds with antioxidant activity), BSG is of interest for application and fortification of human food products, particularly in view of its low cost and availability in large amounts. The study examines soy yogurt and aims to evaluate the impact of spent grain on soy yogurt compared to a common BSG-free soy yogurt. The effect of spent grains addition (at different levels) on the physico-chemical properties (particle size distribution, syneresis, texture, and rheological behaviour) of the final product has been investigated. Changes in the aforementioned physico-chemical properties during a storage period of 4 weeks have been monitored on a weekly basis. In fact, the incorporation of BSG in soy yogurt benefited the production line due to its impact in increasing the fermentation rate and supported the Lactic Acid Bacteria (LAB) growth. BSG-added yogurt allowed the LAB growth and increased the pH which can be a benefit for industry to use less sweetener to cover the acidity. The presence of high dietary fibre in BSG contributed to a lower syneresis, a higher shear stress and maintenance of viscosity at certain levels of addition during the storage period. Furthermore, the addition of BSG at certain levels 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 preserve the flow behaviour and syneresis in addition to other physical properties. In general, syneresis decreases with increasing BSG levels. The results demonstrate BSG's capacity to bind water, maintaining yogurt's flow characteristics and consistency.

Keywords

a, b, c

Language used: English

Date on which the thesis was submitted / produced: 18. 2. 2024

Thesis defence

• Date of defence: 21. 2. 2024
• Supervisor: Ing. Iveta Klojdová, Ph.D.
• Reader: Andrea Serra, Bc., externi

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Master programme:
Sustainable Agriculture and Food Security