SHELF LIFE EXTENSION OF ARGENTINEAN WHEY CHEESE (RICOTTA) USING NATURAL ANTIMICROBIALS.

FERNANDEZ, M. VERÓNICA; JAGUS, ROSA J.; MUGLIAROLI, SANDRA L.

Las Vegas

Congreso; IFT ANNUAL MEETING AND FOOD EXPO 2012; 2012

Ricotta is a soft cheese susceptible to microbial spoilage. It is obtained fromwhey by denaturation and coagulation of water soluble milk proteins. This study aimed to investigate the effect of natural antimicrobials (nisin, alone or combined with Microgard® 300) on the shelf life extension of ricotta stored in vacuum packaging at 6-8 C. Two batches of ricotta were produced in the UBA pilot-plant, one according to standard methods (C) and one with the addition of nisin during elaboration (Np). From these productions, three additional samples were prepared: nisin added to ricotta C (N), nisin and Microgard® 300 added to C (NMg) and Microgard® 300 added to Np (NpMg). They were stored at 6-8 C in vacuum packages (O2 transmission rate of 3.000-5.000 cm3/m2dayatm). Spoilage microorganisms (psychrotrophs and coliforms) were determined during the storage of the ricotta. Moisture, fat, protein and microbiological analyses were carried out conform to standard techniques. Moisture, fat and protein content resulted 69,9%, 14,2% and 8,4%, respectively. Argentine regulations standards for cheeses with water content higher than 55% sets limits for coliforms <3,0 log UFC/g. After 18 days, coliforms in C, Np and N raised up to 5,5; 4,1; 3,0 log UFC/g respectively. It is noteworthy to mention that NpMg and NMg showed counts below the legal limits by the end of the storage. Argentine law does not set limits for psychrotrophs. According to other authors, for the present work a limit value of >105 UFC/g was taken as a failure criteria. Samples C, Np and N reached the cut-off point at 5, 8 and 14 days of storage respectively. On the other hand, NpMg and NMg showed 2,70 logUFC/g and 2,00 logUFC/g respectively after 18 days of storage. Both nisin treatments delay microbial growth, however, only natural antimicrobials combined together prevent growth by 18 days of storage.