The headspace flavor compounds of orange juice were isolated by solid-phase microextraction (SPME) fiber coated with 100 μm of poly(dimethylsiloxane) and separated by gas chromatography. The effects of the orange juice temperature from 25 to 80 °C and the adsorption time from 5 to 40 min on the equilibrium of flavor compounds between the SPME coating and the orange juice indicated that the equilibrium time decreased as the sample temperature increased. The equilibrium of the flavor compounds between the SPME coating and the orange juice required 30 min at 40 °C or 20 min at 60 °C. The amount of orange flavor compounds adsorbed by SPME coating decreased as the orange juice temperature increased from 25 to 80 °C. The resolution of the gas chromatogram increased as the inside diameter of the injection port liner decreased from 1 to 0.75 mm. The concentrations of ethyl butyrate, octanal, decanal, α-pinene, and limonene in orange juice were 0.4, 1.1, 1.0, 1.4, and 254 ppm, respectively. The coefficients of variation for the analyses of ethyl butyrate, octanal, decanal, α-pinene, and limonene ranged from 4.4% for 0.4 ppm ethyl butyrate to 1.6% for 254 ppm limonene. Keywords: Headspace; SPME-GC; flavor analysis; orange flavor

The effect of high voltage pulsed electric field (PEF) treatment on Escherichia coli O157:H7 and generic E. coli 8739 in apple juice was investigated. Fresh apple juice samples inoculated with E. coli O157:H7 and E. coli 8739 were treated by PEF with selected parameters including electric field strength, treatment time, and treatment temperature. Samples were exposed to bipolar pulses with electric field strengths of 30, 26, 22, and 18 kV/cm and total treatment times of 172, 144, 115, and 86 micros. A 5-log reduction in both cultures was determined by a standard nonselective medium spread plate laboratory procedure. Treatment temperature was kept below 35 degrees C. Results showed no difference in the sensitivities of E. coli O157:H7 and E. coli 8739 against PEF treatment. PEF is a promising technology for the inactivation of E. coli O157:H7 and E. coli 8739 in apple juice.

In this study, pulsed electric field (PEF) treatment of beer, effectiveness of PEF treatment on microbial inactivation, effects of PEF treatment on sensory properties, and detection of electrode material migration were explored. Beer samples were treated by PEF for the inactivation of natural flora and inoculated cultures of Saccaromyces uvarum, Rhodotorula rubra, Lactobacillus plantarum, Pediococcus damnosus, and Bacillus subtilis. Inactivation induced by the PEF treatment was 0.5, 4.1, 4.3, 4.7, 5.8, and 4.8 log 10 colonyforming units/mL in the above microorganisms, respectively (P < 0.05). There was a significant increase in the amount of Cr, Zn, Fe, and Mn ions in the beer samples after PEF treatment (P < 0.05) leading to a statistically significant degradation in flavor and mouth feel. Further studies are needed to optimize electrode materials and PEF treatment to minimize or eliminate this degradation.

A group of selected enzymes were subjected to continuous pulsed electric field (PEF) treatments to evaluate the inactivation effect of PEF. For a treatment time of 126 s, 51.7% and 83.8% of pepsin was inactivated at 37.0 kV/cm and 41.8 kV/cm, respectively. Enzyme activity of polyphenol oxidase decreased 38.2% when treated at 33.6 kV/cm for 126 s. Enzyme activity decreased 18.1% and 4.0% for peroxidase treated at 34.9 kV/cm and chymotrypsin treated at 34.2 kV/cm, respectively. No significant change in lysozyme activity was observed after PEF from 0 to 38 kV/cm for 126 s. Both PEF and the induced heat contributed to the observed inactivation effect, depending on the properties of enzymes and test conditions.

To investigate influences of pulsed electric field (PEF) on bovine IgG immunoactivity, soymilk enriched with hyperimmunized dairy milk protein concentrate was subjected to PEF and thermal treatments. Thermal treatment at 78.8 °C for 120 s inactivated 5.1 logs in natural flora and resulted in 86% decrease in IgG activity PEF at 41 kV/cm for 54 s inactivated 5.3 logs of natural flora and resulted in no significant change (P > 0.05) in bovine IgG activity. Specific antigen-binding activity of bovine IgG against Salmonella enteritidis showed parallel correlation with the measurement of IgG concentration. No further significant change in IgG immunoactivity was observed during a 10-wk storage at 4 °C in PEF-, thermally-, or un-treated samples.