Evaluación de la diversidad de bacterias lácticas y levaduras en quesos frescos de cabra de la Quebrada de Humahuaca

Abstract

Los objetivos de este estudio fueron identificar y caracterizar bacterias lácticas (BAL) y levaduras nativas, aisladas de quesos frescos de esta zona productora. De un total de 36 muestras sembradas en agar Sabouraud, agar MRS y M17, se obtuvieron 128 levaduras y 39 lactobacilos, los que fueron identificados fenotípicamente y evaluadas las siguientes propiedades tecnológicas: pH a la coagulación, tasa de acidificación, proteólisis en agar leche, lipólisis en agar triacetina, producción de acetoína en leche reconstituida y asimilación del citrato en agar citrato. Lb. delbruekii subsp. bulgaricus, Lb. casei subsp. pseudoplantarum, Lb. plantarum var. arabinosus, Lb. plantarum var. plantarum, Lb. casei subsp. rhamnosus, Lb. acidophilus, Lb. helveticus, Lb. fermentum, Lb. brevis var. brevis, Lactococos sp. y Enterococcus sp. fueron las bacterias lácticas identificadas. Del total de los aislamientos, 41,6% coagularon la leche en 10 horas y 33% en 5 horas. Lb. helveticus coaguló la leche a pH de 5,40 en 5 horas, hasta alcanzar un valor final de 4,16 en 24 h, mientras que Lb. delbrueckii subsp. bulgaricus y Lb. fermentum iniciaron la coagulación en 5 horas, con valores de pH iniciales de 4,81 y 4,92 hasta valores finales de 4,19 y 4,21 respectivamente. Lb. helveticus, Lb. delbrueckii subsp. bulgaricus, Lb. plantarum var. arabinosus, Lb. fermentum, Lb. casei subsp. rhamnsosus, Lb. casei subsp. pseudoplantarum, Lb. brevis var. brevis, en orden descendente, demostraron tener capacidad acidificante. Lb. fermentum y Lb. casei subsp. pseudoplantarum desarrollaron actividad proteolítica y sólo Lb. plantarum var. plantarum demostró tener actividad lipolítica. Las levaduras aisladas fueron Debaryomyces hansenii, Zygosaccharomyces rouxii, Kluyveromyces lactis, Wickerbamiela domerquiae, Dekkera bruxellensis, Candida valdiviana, Candida novakii, Dekkera bruxellensis, Candida versatilis, Candida magnoliae, Candida albicans, Pichia anómala, Dekkera anómala y Rodotorula sp. Cepas de D. hansenii, C. magnoliae, Z. rouxii,C. versatilis y K. lactis tuvieron actividad proteolítica y lipólitica, y una cepa de W. domerquiae tuvo solamente actividad proteolítica. Algunas cepas de K. lactis produjeron acetoína y D. bruxellensis y C. versatilis metabolizaron el citrato, hidrolizaron la caseína y tuvieron actividad lipolítica.

Fresh cheeses artisanal goat of the Quebrada de Humahuaca are made with raw milk, the maturation produces flavors, aromas and textures characteristic of the region. The objectives of this study were to identify and characterize lactic acid bacteria (LAB) and native yeasts isolated from fresh cheeses productive zone. A total of 36 samples seeded on agar Sabouraud agar MRS and M17, 128 yeast and 39 lactobacilli were obtained, which were phenotypically identified and evaluated the following technological properties: pH of the coagulation rate of acidification, proteolysis agar milk, lipolysis in triacetin agar, acetoin production in reconstituted milk and assimilation of citrate in citrate agar. Lb. delbruekii subsp. bulgaricus, Lb. casei subsp. pseudoplantarum, Lb. plantarum var. arabinosus, Lb. plantarum var. plantarum, Lb. casei subsp. rhamnosus, Lb. acidophilus, Lb. helveticus, Lb. fermentum, Lb. brevis var. brevis, Lactococcus sp. and Enterococcus sp. lactic acid bacteria were identified. Of all the isolates, 41.6% coagulated milk in 10 hours and 33% within 5 hours. Lb. helveticus coagulated milk to pH 5.40 in 5 hours, to a final value of 4.16 at 24 h, while Lb. delbrueckii subsp. bulgaricus and Lb. fermentum initiated coagulation in 5 hours, with initial pH values of 4.81 and 4.92 up to final values of 4.19 and 4.21 respectively. Lb. helveticus, Lb. delbrueckii subsp. bulgaricus, Lb. plantarum var. arabinosus, Lb. fermentum, Lb. casei subsp. rhamnsosus, Lb. casei subsp. pseudoplantarum, Lb. brevis var. brevis, in descending order, they were shown to have acidifying capacity. Lb. fermentum and Lb. casei subsp. pseudoplantarum developed proteolytic activity and only Lb. plantarum var. plantarum demonstrated lipolytic activity. The yeast isolates were Debaryomyces hansenii, Zygosaccharomyces rouxii, Kluyveromyces lactis, Wickerbamiela domerquiae, Dekkera bruxellensis, valdiviana Candida, Candida novakii, Dekkera bruxellensis, Candida versatilis, magnoliae Candida, Candida albicans, Pichia anomala, Dekkera anomala and Rodotorula sp. D. hansenii strains, C. magnoliae, Z. rouxii, C. versatilis and K. lactis had proteolytic and lipolytic activity, and a strain of W. domerquiae had only proteolytic activity. Some strains of K. lactis produced acetoin and D. bruxellensis and C. versatilis metabolize citrate, they hydrolyzed casein and had lipolytic activity. The results obtained in this study show that the composition of the populations of BAL and baking artisan cheeses is specific to the region. The knowledge gained from this study could be used for the production of starter cultures with specific strains of LAB and yeasts in the region for the production of fresh cheeses with specific geographical origin.