Short communication: Effect of lactose on the spray drying of Lactococcus lactis in dairy matrices.

The effects of unfavorable conditions responsible for the viability loss of Lactococcus cells during spray drying can be minimized by the application of dairy matrices as encapsulating materials. This study aimed to evaluate the use of dairy matrices with different lactose contents on the survival of Lactococcus lactis during drying and storage. The use of hydrolyzed-lactose milk resulted in notable loss of cell viability (3.90 log cycles). However, milk enriched with lactose or without fat showed better protection (viability loss between 0.26 and 1.41 log cfu/g) and greater cell survival during storage at room temperature. The enrichment of milk with lactose seems to be ideal for the drying of heat-sensitive bacteria.

Determination of ideal water activity and powder temperature after spray drying to reduce Lactococcus lactis cell viability loss.

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 (∼0.43 log cycles) was obtained in conditions of Aw = 0.198 and T°Cpowder = 52°C, which can be met by using T°Cinlet air ∼126°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.