18D-30

M. S. TAPIA¹, D. Bermúdez-Aguirre², A. Sánchez-Cervantes, A. Lopez-Malo⁴, F. Vergara-Balderas⁵, and J. Welti-Chanes⁴. (1) Instituto de Ciencia y Tecnología de Alimentos, Univ. Central de Venezuela, PO Box 47097, Caracas, 1041-A, Venezuela, (2) Chemical and Food Engineering, Universidad de las Américas Puebla, Santa Catarina Mártir, Cholula, Puebla, 72820, Mexico, (3) Departamento de Ingeniería Química y Alimentos, Universidad de las Américas-Puebla, Santa Catarina Mártir, Cholula, Puebla, 72820, Mexico, (4) Ingeniería Química y Alimentos, Universidad de las Américas, Puebla, Santa Catarina Mártir, Cholula, Puebla, 72820, Mexico

Fruit and vegetables products are now being processed under the concept of minimal process, with pH being a main “hurdle” for deteriorative reactions and microbial growth. In this work, the combined effect of the natural low pH of fresh mango nectar (3.6) and of untreated hot Mexican sauce (3.8) along with two storage temperatures (5 and 25ºC), on the inhibition of native flora and of inoculated E. coli was studied. Products were then sterilized and stored and the fate of inoculated E. coli was additionally investigated. Microbial populations were studied on Plate Count Agar (PCA) and on selective Eosine Methylene Blue Agar (EMB). Results showed that initial total counts of 10⁴-10⁵ CFU/g in nectar exhibited a 2 to 2.5 fold increase at both temperatures after 15 d, and E. coli was completely inhibited in 8 d (25° C) and counts of this organism had a reduction of one log cycle every 2 d (5°C) after 8 d of storage. Thermal sterilization of nectar (125° C for 15 min) eliminating competitive native flora, allowed complete inhibition of E. coli in 6 d at 25º C and 8 to 10 d at 5° C. For the untreated sauce, the initial total population of 10⁴-10⁵ (CFU/g) showed an increase of three logarithmic cycles at 25º C and no change at 5º C was observed with 15 day's storage. E. coli was totally inhibited at 6 and 10 d at 25° and 5°C respectively with no marked effect observed of the thermal sterilization of the substrate eliminating competitive flora. Results indicate that pH of the products investigated is not enough for inhibition of native flora at the evaluated temperatures, while as for E. coli, even though its total inhibition is accomplished, it is not immediate and temperature reduction seems to favor the resistance of this organism. It becomes clear that additional factors other than pH and refrigeration temperature are needed for safe minimal processed products of mango nectar and hot Mexican sauce.

Session 18D, Food Microbiology: General
2:00 PM - 5:30 PM, Sunday PM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana