91E-18

Ultrasound treatments and antimicrobial agents effects on Zygosaccharomyces rouxii

M. R. Arce-Garcia1, M. T. JIMÉNEZ-MUNGUIA1, E. Palou, and A. López-Malo. (1) Departamento de Ingeniería Química y Alimentos, Universidad de las Américas-Puebla, Sta. Catarina Mártir, Cholula, Puebla, 72820, Mexico

Food preservation procedures by combined methods technology may include non traditional factors such as natural antimicrobial agents and ultrasound, the success of such combinations depends on information about microbial responses. The different mode of action of the factors applied may result in an intelligent and synergistic combination.

This study presents the effect of simultaneous application of heat (45, 50 or 55°C) and low frequency ultrasound (20 kHz) at 60 or 90 μm on Zygosaccharomyces rouxii viability suspended in Sabouraud broth. The effect of selected antimicrobial agents (KS - potassium sorbate, NaB – sodium benzoate, V – vanillin, E – eugenol) concentration on the recovery media was also evaluated.

Laboratory broth was inoculated with 106 cfu/mL, heat (TT) and/or ultrasound (TTU) was applied for 5, 10 or 15 min and the yeast ability to form a colony was determined after inoculation in potato dextrose-agar formulated with aw 0.99, pH 3.5 and different antimicrobial concentrations (100, 200, 300, 400 or 500 ppm) of KS, NaB, V, or E after 10 days of incubation at 25ºC.

Zygosaccharomyces rouxiii was resistant to TT or TTU in media without antimicrobials. Increasing TTU amplitude, treatment time and antimicrobial concentration resulted in yeast inhibition. Differences in sensitivity among the antimicrobial agents were observed being more resistant to vanillin. Z. rouxii was inhibited after 5 min TTU at 45ºC and 60 μm in media containing 100 ppm of KS, NaB, or E; or at 50ºC and 60 μm with 300 ppm V. TTU applied for 15 min at 90 μm and 55ºC inhibit yeast growth when combined with 100 ppm V. TTU in combination with antimicrobials drastically reduced the intensity of heat treatments to inhibit yeast growth.

Natural and synthetic antimicrobial agents in combination with TTU treatments resulted effective for Z. rouxii inhibition, synergistic effects can be used to reduce factors intensities as a preservation technique.

Session 91E, Nonthermal Processing: Nonthermal processing of foods
2:00 PM - 5:30 PM, 2002-06-18

2002 Annual Meeting and Food Expo - Anaheim, California