Role of Debaryomyces hansenii yeast in improving the microbial and sensory properties of Monterey cheese

Abstract

Debaryomyces hansenii yeast was grown in Malt Extract Broth medium at 30 °C for 5 days until the total count reached 5.6 ×108 colony forming units/ milliliter, Monterey cheese was made from cow's milk and adding of starter bacteria Lactococcus lactis subsp. lactis and Lactococcus lactis subsp.cremoris with D.hansenii yeast as adjunct starter in 2% for each treatment included M1 (100% starter bacteria), M2 (50% starter bacteria + 50% live D.hansenii) and M3 (50% starter bacteria + 50% dead D.hansenii),the ripening of Monterey cheese was done at 15°C and (85% relative humidity) for 56 days. The highest count of starter bacteria was 9.7 ×108 cfu/g in M1 treatment after 3 days of ripening, the lowest number of starter bacteria was 6.9 ×108 cfu/g in M2 treatment. The highest count of D.hansenii yeast was 4.3 x108 cfu/g after 3 days of ripening in M2 treatment, while the lowest count was 2.6 ×108 cfu/g in the same treatment after 56 days of ripening, no yeast was found in the treatments that had dead yeast cells, all treatments under study were decreased in the total count of coliform bacteria, Staphylococcus aureus and psychrotrophic bacteria after 14 days as they were within the standard specifications of these groups of microorganisms, Then reached to zero in the late time of ripening. M2 showed the best results of sensory evaluation in taste, flavor, textures, color and bitterness after 56 days of ripening.