Indigenous yeast as starter cultures for cheese production

Abstract

The demand for functional foods with probiotic microorganisms is currently growing considerably. However, there is a difficulty for the food industries to incorporate the probiotic into the food because each microorganism has a physiological requirement. Therefore, the food to which it will be incorporated must meet this requirement. Among the probiotics already sold, most are bacteria, with only one yeast being recognized. The objective of this work was to evaluate the probiotic and technological potential of Kluyveromyces lactis B10 and Torulaspora delbrueckii B14 yeasts isolated from Canastra cheese processing and to evaluate their use as starter cultures in cheese. Resistance to the gastrointestinal tract was assessed by passage through the gastrointestinal tract under simulated conditions. Others such as self-aggregation, hydrophobicity, pathogen inhibition and β-galactosidase production were performed. The technological characterization was performed through the evaluation of yeast survival capacity at different NaCl concentrations (2.5, 5 and 10%) and at different temperatures (4 and 40 ºC) for 21 days. The yeasts were evaluated as single and mixed starter cultures in cheese production. The cheeses were analyzed via HPLC and GC-MS. After the passage through the simulated gastrointestinal tract, T. delbrueckii B14 and K. lactis B10 yeasts presented viability above 80%, self-aggregation rates above 90% and yield of 0.35 U/g and 0.53 U/g of β-galactosidase, respectively. Both yeasts presented survival when exposed to different NaCl concentrations and at 4 ºC, but when exposed to 40 ºC T. delbrueckii B14 yeast did not survive, and K. lactis B10 survived only in the first 7 days of evaluation. The lactose present in the cheeses was partially or completely consumed, showing that both yeasts have the capacity to degrade lactose. A total of 38 volatile compounds were found, 6 acids, 9 alcohols, 14 esters, 3 aldehydes and 6 others. Among the acids, isocaproic, hexanoic, decanoic and butanoic were the most abundant in all cheeses. The alcohols found in higher concentrations were 2,3-butanediol, phenethyl alcohol, isoamyl alcohol and isobutanol. And isoamyl acetate and phenethyl acetate esters were the most abundant in all cheeses. The results show that K. lactis B10 and T. delbrueckii B14 yeasts are resistant to passage through the gastrointestinal tract and that they can be used in the production of cheese as starter cultures, with the production of volatile aromatic compounds that help improve the final product quality.