MICROBIOLOGICAL STABILIZATION AND SHELF-LIFE MODELLING OF BREWERS SPENT GRAINS THROUGH ACIDIFICATION AND ALGINATE ENCAPSULATION
Authors: Polikseni Drazho, Luljeta Pinguli, Rozana Troja and Ilirjan Malollari
Polikseni Drazho: Department of Risk Assessment, Albanian National Food Authority, Tirana, Albania.
Luljeta Pinguli: Faculty of Natural Sciences, Department of Industrial Chemistry, University of Tirana, Albania.
Rozana Troja: Faculty of Natural Sciences, Department of Industrial Chemistry, University of Tirana, Albania.
Ilirjan Malollari: Faculty of Natural Sciences, Department of Industrial Chemistry, University of Tirana, Albania.
ABSTRACT
Brewer’s Spent Grain (BSG), the primary by-product of the brewing industry, is highly susceptible to rapid spoilage due to its elevated moisture content and nutrient-rich composition. This perishable nature necessitates the application of effective stabilization strategies to extend shelf life and enable its safe and sustainable utilization in food, feed, and bioenergy sectors.
The present study aimed to evaluate the safety and shelf life of BSG intended for both human and animal consumption by investigating the influence of key physicochemical parameters, namely temperature, pH, and water activity (aw), on microbial spoilage. Additionally, innovative stabilization approaches, including acidification and alginate-based encapsulation, were explored to establish optimal microbiological stability conditions.
Fresh BSG samples were obtained from the Stefani & Co Brewery (Tirana, Albania) and subjected to microbiological analysis using Plate Count Agar (pour plate method) and Wort Agar (spread plate method). Predictive modeling of microbial degradation was performed using a bioengineering-based approach, integrating degradation kinetics with an exponential decay function to estimate shelf life under varying environmental conditions.
Acidification with food-grade acids effectively reduced the pH to 3.2–4.5, significantly inhibiting microbial growth while inducing moderate changes in soluble protein and sugar content. Furthermore, a novel stabilization technique employing sodium alginate (1.5–2%) cross-linked with CaCl₂ reduced water activity from approximately 0.96 to 0.90–0.92, resulting in a shelf-life extension of up to two weeks. The combined application of acidification and alginate treatment exhibited a synergistic effect, further enhancing microbiological stability.
The results demonstrate that simultaneous control of multiple intrinsic factors temperature, pH, and water activity is significantly more effective than the modification of a single parameter. The proposed stabilization strategies are not only technically feasible but also cost-effective, contributing to improved storage stability and reduced risks of microbial contamination and aflatoxin formation. Overall, these findings support the sustainable valorization of BSG by enabling its safe reuse in food and feed applications.
Keywords: Brewery Spent Grain, mathematical modeling, pretreatment, microbiological stabilization, shelf life, alginate treatment.