| Congresso Brasileiro de Microbiologia 2023 | Resumo: 305-2 | ||||
Resumo:ABSTRACT
The food industry extensively utilizes dehydrated lactic acid bacteria (LAB) starter cultures for various applications, including fermented milk, vegetables, and meat. Currently, freeze-drying is the most used reference technology for drying LAB, which offers high survival rates over extended periods. However, this method involves long drying times and substantial energy consumption, resulting in high production costs. To address these challenges, researchers have increasingly explored spray drying as a promising alternative to replace freeze-drying. Therefore, this study aimed to define the operational parameters capable of achieving a balance between the cell viability loss and the energy cost of spray drying process. Lactococcus lactis subsp. lactis Q1C2, isolated from artisanal cheese in the Brazilian Amazon region, was used as the model bacterium. To obtain the cell concentrate, a drying medium was first prepared with 200 g of whole milk powder dispersed in 250 g of sterile distilled water (final solid content of 45 °Brix) heated to 85 °C for 1 h and then refrigerated until the temperature reached 40 °C. Then, L. lactis subsp. lactis Q1C2 was inoculated to reach a concentration of 2.8 x 1010 cfu/g. The cell concentrate at 40 °C was injected into a pilot scale spray dryer model MSDi 1.0 (Labmaq do Brasil, São Paulo, Brazil) at varied flow rates (Fconcentrate = 0.24, 0.48 and 0.72 kg/h) and inlet air temperature (T ºCinlet air = 115, 130, 145 and 160 ºC). Two independent repetitions were performed and the powders were storage in covered tubes by aluminum foil and vacuum packed at 4 and 25 °C for 120 days. Cell concentrate, powders immediately after drying (0 days) and during storage time (15, 30 and 120 days), were subjected to microbial analysis to define cell viability by microdroplet assay. The moisture content and Aw analyses were performed to define the efficiency parameters by thermodynamic characterization. The cell viability was significantly influenced by both the outlet temperature (T ºCair outlet) and powder temperature (T ºCpowder), while Aw did not show a significant impact. The best results were obtained when the cell viability losses were below 0.47 log cfu/g during storage time. The ideal conditions to produce bacteria through spray drying with high energy efficiency and lower adhesion rate were at 130-145 ºC/0.72 kg.h. For mantain cell viability, the ideal operating parameter was at 115 ºC/0.72 kg.h. In addition, the powders storage temperature had significant influence on the viability rates; at 4 ºC reduced slower, while at 25 ºC higher cell viability loss was observed during storage time. From the perspective of cost to maintain cell viability, the lowest temperature applied was the most favorable operational parameter for production, regardless of flow rates. However, these parameters led to a significant adhesion rate, causing income losses. Hence, it is crucial to carefully select the best condition to optimize the process, as the ideal spray drying conditions can ensure maximum cell viability at the lowest energy cost.
Palavras-chave: cell viability, dehydrated lactic acid bacteria, energy efficiency, operational parameters Agência de fomento:CAPES (Financial code 001), CNPq and FAPEMIG | |||||