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ABSTRA ABSTRA ABSTRA ABSTRA ABSTRACT CT CT CT CT: R : R : R : R : Response sur esponse sur esponse sur esponse sur esponse surface methodology was used to study the effect of antibr face methodology was used to study the effect of antibr face methodology was used to study the effect of antibr face methodology was used to study the effect of antibr face methodology was used to study the effect of antibro o o o owning agents (4-hexylr wning agents (4-hexylr wning agents (4-hexylr wning agents (4-hexylr wning agents (4-hexylresor esor esor esor esorcici-ci-cicinol, glutathione, N-acetylcysteine, and ascorbic acid) and storage time (14 d) on the color of minimally pro-nol, glutathione, N-acetylcysteine, and ascorbic acid) and storage time (14 d) on the color of minimally pro-nol, glutathione, N-acetylcysteine, and ascorbic acid) and storage time (14 d) on the color of minimally pro-nol, glutathione, N-acetylcysteine, and ascorbic acid) and storage time (14 d) on the color of minimally pronol, glutathione, N-acetylcysteine, and ascorbic acid) and storage time (14 d) on the color of minimally processed Fuji apples. The selected color parameters were cessed Fuji apples. The selected color parameters were cessed Fuji apples. The selected color parameters were cessed Fuji apples. The selected color parameters were cessed Fuji apples. The selected color parameters were L

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High-intensity pulsed electric fields (HIPEF) can be used as a nonthermal preservation method that is believed to enhance the effect of nisin on microorganisms such as Staphylococcus aureus. The survival of S. aureus inoculated into skim milk and treated with nisin, with HIPEF, or with a combination of nisin-HIPEF was evaluated. Nisin dose, milk pH, and HIPEF treatment time were the controlled variables that were set up at 20 to 150 ppm, pH 5.0 to 6.8, and 240 to 2,400 micros, respectively. HIPEF strength and pulse width were kept constant at 35 kV/cm and 4 micros, respectively. No reduction in S. aureus concentration was observed in skim milk at its natural pH after treatment with nisin, but 1.1 log units were recovered after 90 min of treatment at pH 5.0 with 150 ppm nisin. A reduction in viable S. aureus counts of 0.3 and 1.0 log unit in skim milk treated with HIPEF at its natural pH was observed at 240 and 2,400 micros, respectively. The nisin-HIPEF treatment design was based on a response surface methodology. The combined effect of nisin and HIPEF was clearly synergistic. However, synergism depended on pH. A maximum microbial inactivation of 6.0 log units was observed at pH 6.8, 20 ppm nisin, and 2,400 micros of HIPEF treatment time, whereas a reduction of over 4.5 log units was achieved when pH, nisin concentration, and HIPEF treatment times were set at 5.0, 150 ppm, and 240 micros, respectively.

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The effectiveness of malic acid in combination with physicochemical quality stabilizing compounds to inactivate Listeria monocytogenes, Salmonella Enteritidis and Escherichia coli O157:H7 inoculated in fresh-cut "Fuji" apples packaged in air and stored at 5C was evaluated. Apple pieces were immersed for 1 min in solutions containing 1% w/v N-acetyl-L-cysteine, 1% w/v glutathione and 1% w/v calcium lactate with and without 2.5% w/v D-L malic acid to control apple browning, softening and reduce the populations of pathogenic microorganisms. Fresh-cut apples dipped in each solution were then inoculated with L. monocytogenes, S. Enteritidis or E. coli O157:H7. The use of malic acid in combination with physicochemical quality stabilizing compounds caused more than 5 log 10 cfu/g of L. monocytogenes, S. Enteritidis and E. coli O157:H7 counts. The results obtained in this work pointed out the potential use of malic acid in combination with physicochemical quality stabilizing compounds as a good alternative for safety assurance of fresh-cut apples. PRACTICAL APPLICATIONSThe use of organic acids such as malic acid, as well as physicochemical quality stabilizing compounds such as N-acetyl-L-cysteine, glutathione and 1 Corresponding

Staphylococcus aureus is an important milk-related pathogen that is inactivated by high-intensity pulsed electric fields (HIPEF). In this study, inactivation of Staph. aureus suspended in milk by HIPEF was studied using a response surface methodology, in which electric field intensity, pulse number, pulse width, pulse polarity, and the fat content of milk were the controlled variables. It was found that the fat content of milk did not significantly affect the microbial inactivation of Staph. aureus. A maximum value of 4.5 log reductions was obtained by applying 150 bipolar pulses of 8 mus each at 35 kV/cm. Bipolar pulses were more effective than those applied in the monopolar mode. An increase in electric field intensity, pulse number, or pulse width resulted in a drop in the survival fraction of Staph. aureus. Pulse widths close to 6.7 micros lead to greater microbial death with a minimum number of applied pulses. At a constant treatment time, a greater number of shorter pulses achieved better inactivation than those treatments performed at a lower number of longer pulses. The combined action of pulse number and electric field intensity followed a similar pattern, indicating that the same fraction of microbial death can be reached with different combinations of the variables. The behavior and relationship among the electrical variables suggest that the energy input of HIPEF processing might be optimized without decreasing the microbial death.

Among nonthermal treatments, high-intensity pulsed electric field (HIPEF) has received special attention on account of its potential use in treating liquid foods and its feasible application in continuous-flow processing. Improving the food quality of milk and dairy products with HIPEF processing may be a relevant consideration in product development research. However, the future implementation of HIPEF equipment on an industrial scale may require more studies into the effects of the process parameters on the shelf-life of milk, the optimization of the HIPEF process with specific emphasis on the degree of microbial inactivation and energy consumption, more accurate design of the HIPEF equipment used for milk processing and a sensorial and nutritive evaluation of the treated product.