RESUMO
Spray drying presents a promising technology for preserving bacteria despite a low survival rate of heat-sensitive cultures when subjected to the drying process. The aim of this study was to determine the ideal powder parameters [water activity (Aw) and temperature (T°Cpowder)] needed to produce dehydrated Lactococcus lactis ssp. lactis with a high viability after drying. Cell concentrates injected into a spray dryer using varying cell concentrate flow rates (Fconcentrate = 0.3 to 1.0 kg/h), inlet air temperatures (T°Cinlet air = 115 to 160°C), and outlet air temperatures (T°Coutlet air = 70 to 115°C) resulted in powders with different values of Aw and T°Cpowder, and levels of cell viability loss. Lower cell viability reduction (â¼0.43 log cycles) was obtained in conditions of Aw = 0.198 and T°Cpowder = 52°C, which can be met by using T°Cinlet air â¼126°C and T°Coutlet air = 88.9°C regardless of Fconcentrate values. After 60 d of storage at room temperature, cell population varied from 7.0 × 105 to 1.1 × 108 cfu/g. The initial powder Aw had no influence on cell death rate, but T°Cpowder influence was observed. The approach adopted in this study can be applied to other bacteria or spray dryer equipment to determine optimal drying conditions.
Assuntos
Técnicas Bacteriológicas/métodos , Dessecação , Lactococcus lactis/fisiologia , Água/análise , Pós/análise , TemperaturaRESUMO
Marajó cheese made with raw buffalo milk in the Amazon region of Brazil can be considered a good source of wild lactic acid bacteria strains with unexplored and promising characteristics. The aim of this study was to develop a potential probiotic starter culture for industrial applications using freeze drying and spray drying. A decrease in the survival rates of freeze-dried samples compared with spray-dried samples was noted. The spray-dried cultures remained approximately 109 cfu·g-1, whereas the freeze-dried samples showed 107 cfu·g-1 after 60 d of storage at 4°C. All of the spray-dried samples showed a greater ability to decrease the pH in 10% skim milk over 24 h compared with the freeze-dried samples. The spray-dried samples showed a greater resistance to acidic conditions and to the presence of bile salts. In addition, under heat stress conditions, reduction was under 2 log cycles in all samples. Although the survival rate was similar among the evaluated samples after drying, the technological performance for skim milk showed some differences. This study may direct further investigations into how to preserve lactic acid bacteria probiotics to produce spray-dried starters that have a high number of viable cells that can then be used for industrial applications in a cost-effective way.