17A-9 |
|
N. GUTIÉRREZ-MÉNDEZ, M. G. Gastelum-Franco, B. J. Rodriguez-Terrazas, and G. V. Nevárez-Moorillón. Food Science and Technology Graduate Program, Universidad Autónoma de Chihuahua, P.O.Box 1542-C, Chihuahua, 31170 The development of dairy products that contain probiotics bacteria has taken great importance, because of the benefits attributed to those bacteria. It has also been demonstrated that probiotics bacteria have the capacity to inhibit bacterial pathogens by the production of diverse metabolits. Chihuahua cheese is frequently involved in contamination problems by pathogenic bacteria like Escherichia coli and Staphylococcus aureus . The aim of this project was to evaluate the use a probiotic co-culture to reduce contamination by Staphylococcus aureus and Escherichia coli , during the production and storage of Chihuahua cheese, as well as the survival of probiotics bacteria. Chihuahua cheese was produced according to the traditional method, but Lactobacillus acidophilus and Lactobacillus casei (log 5 UFC/ml each) were used as a co-culture. The cheese was also intentionally contaminated with S. aureus and E. coli . (log 4 UFC/g each); then vacuum packed and stored at 24ºC and 6ºC. Counts of E. coli, S. aureus and both Lactobacillus were done during 60 days of storage. Results showed a reduction of 3 log cycles on E. coli and 4 on S. aureus after the first 15 days of storage at 24ºC. L. acidophilus remained at log4 UFC/g and L. casei at log6 UFC/g after 60 days. When cheese was stored at 6ºC E. coli counts were reduced by 3 log cycles only after 60 days of storage, and S. aureus counts did not decreased at that time. L. casei counts remained at log5 UFC/g and L. acidophilus was reduced to log3 UFC/g. Our results demonstrate that the use of a co-culture of probiotic bacteria during Chihuahua cheese production, can signifcantly reduce the growth of E. coli and S. aureus at 24ºC. Nevertheless, the number of probiotic bacteria, specially of L. acidophilus were not enough after storage to consider the product a probiotic food.
Session 17A, Dairy Foods: Cheese and microbiology
|