Microencapsulação por spray drying de leveduras epifíticas do café para inoculação no processo fermentativo

Abstract

The yeasts commercialization in the liquid form is not indicated in the long term as the cells lose viability. In addition, there is a risk of contamination and higher costs with transport and refrigerated storage. Thus, an alternative is spray drying. This technique can be used continuously and quickly, allowing high production rates with low operating costs. That said, the objective of this work was to evaluate the effectiveness of microencapsulation by spray drying to promote the drying and coating of three epiphytic coffee yeasts: Saccharomyces cerevisiae CCMA0543, Torulaspora delbrueckii CCMA0684 and Meyerozyma caribbica CCMA1738. The work was divided into three steps. The first step was evaluating of the cell viability of microencapsulated yeasts in a laboratory-scale spray dryer. The yeasts (109 CFU mL−1) were microencapsulated separately with maltodextrin (15%), maltodextrin (15%) with sucrose (2%), or maltose (2%). The results showed that cell viability varied between 94.06 and 97.97%. After six months, both yeasts stored at 7 °C and 25 °C showed 107 and 102 CFU mL−1, respectively. This step showed that it was possible to microencapsulate the epiphytic coffee yeasts by spray drying. Maltodextrin was efficient as a wall material. The second step evaluated the effect of operational parameters on the drying process to obtain microencapsulated yeasts in a larger-scale spray dryer. The wall material concentration and the drying air inlet temperature were investigated using the Central Rotational Composite Design (DCCR). Then, the fermentative performance of microencapsulated yeasts was evaluated in a coffee peel and pulp media. The yeasts reached cell viability and drying yields above 90 and 50%, respectively. Whey powder maintained the cell viability of the three yeasts over 90 days of storage at room temperature (25°C) and was selected as wall material for the three yeasts. M. caribbica was more sensitive to spray drying and less resistant to storage. Some differences were found in the fermentation, but the microencapsulated yeasts maintained their biotechnological characteristics. Finally, the third step compared the fermentative performances of liquid and microencapsulated yeasts in coffee fermented by self-induced anaerobiosis (SIAF). After 180 h of fermentation in the natural process, microencapsulated T. delbrueckii (MT) (7.97x107 cells/g) presented a larger population than liquid T. delbrueckii (FT) (1.76x107 cells/g). The state of the yeast influenced the concentration of organic and volatile compounds. Coffees inoculated with microencapsulated S. cerevisiae (MS) showed dominant notes of fruitiness, caramel, and nuts in natural processing. In the pulped coffee, the coffees inoculated with MT presented caramel, honey, and nuts. Considering the analyzed parameters, the most suitable yeasts for natural and pulped processing would be MS and MT, respectively. In conclusion, spray drying microencapsulated yeasts were metabolically active and may be considered with commercial potential, especially for coffee producers interested in using starter cultures during SIAF.