The effect of conventional and PEF treatment (electric field strength: 1.1–2.8 kV cm− 1; energy density: 12.7–226 kJ/kg), frequency (5–200 Hz) and pulse number (152–300) on selected quality attributes of beef Semitendinosus (ST) was investigated. While PEF is viewed as a “non-thermal” treatment, it can induce moderate temperature rises (∆T). To eliminate any potential effect of mild temperature increases, PEF treated samples were compared to conventionally treated (water bath) samples exposed to similar temperature rises (5–35 °C) and handling conditions. Weight loss, conductivity, water holding properties and particle sizes were measured pre- and post-treatment. PEF treatment that induced a ∆T of 22 °C significantly (P < 0.05) affected weight loss of samples post treatment. Particle size analysis of the extracted myofibrils showed PEF significantly (P < 0.05) affected the myofibrils while weight loss results suggest that PEF treatment may have led to slight changes in the cell membrane leading to more water loss. However, instrumental texture was unaffected by the treatments applied.

Pulsed light (PL) and Thermosonication (TS) were applied alone or in combination using a continuous system to study their effect on Escherichia coli inactivation in apple juice. Selected quality attributes (pH, °Brix, colour (L, a, b, ΔE), non-enzymatic browning (NEBI) and antioxidant activity (TEAC)) were also evaluated pre- and post-processing. Two PL (360μs, 3Hz) treatments were selected and the juice exposed to energy dosages of 4.03J/cm2 (‘low’ (L)) and 5.1J/cm2 (‘high’ (H)) corresponding to 51.5 and 65.4J/mL, respectively. The juice was also processed by TS (24kHz, 100μm) at 40°C for 2.9min (L) or 50°C for 5min (H), corresponding to 1456 and 2531J/ml energy inputs, respectively. The effect of the resulting four energy levels and sequence (PL+TS and TS+PL) was studied. When the technologies were applied individually the maximum reduction achieved was 2.7 and 4.9logCFU/mL (for TS (H) and PL (H) respectively), while most of the combined treatments achieved reductions in the vicinity of 6logCFU/mL, showing an additive effect for both technologies when acting in combination, regardless of the sequence applied. All treatments significantly changed the colour of apple juice and the sequence in which the technologies were applied affected colour significantly (P<0.05). The energy level applied did not affect any of the measured quality attributes.

Inactivation of Escherichia coli and Listeria innocua by combinations of High Intensity Light Pulses (HILP), Ultrasound (US) and Pulsed Electric Fields (PEF) and sub-lethal concentrations of nisin (2.5mg/L) or lactic acid (500mg/L) was investigated in two different buffer systems (pH 4 for E. coli and pH 7 for L. innocua). Individually, HILP (3.3J/cm2), US (126s residence time, 500W, 40°C) and PEF (24kV/cm, 18Hz and 1μs of pulse width) did not induce a microbial reduction of greater than 2.7 or 3.6 log units, for L. innocua and E. coli, respectively. Combined treatment using HILP+PEF sufficiently inactivated E. coli without antimicrobial addition. The addition of either antimicrobial enhanced the effect of US+PEF for both E. coli and L. innocua. The addition of lactic acid enhanced the effect of HILP+US. For L. innocua the addition of nisin enhanced the effect of HILP+PEF. This confirms the potential of selected non-thermal technologies for microbial inactivation when combined with antimicrobials.

This study investigated the ability of pulsed electric fields (PEF) to inactivate a range of microorganisms in liquid media and on raw chicken meat. The susceptibilities of ten Campylobacter isolates (seven Campylobacter jejuni isolates and three Campylobacter coli isolates), Escherichia coli (ATCC 25922) and Salmonella Enteritidis (ATCC 13076) to PEF in liquid media were investigated. All Campylobacter isolates tested in liquid were susceptible to PEF treatment (65 kV/cm, 5 mu s, 500 Hz) with reductions of between 4.33 and 7.22 log(10) CFU/mL observed for the longest treatment (30 s). Significant differences in susceptibility were observed between Campylobacter isolates subjected to equivalent PEF treatments ranging from 2.41 to 5.19 log(10) CFU/mL Campylobacter isolates processed in liquid media were found to be more sensitive to PEF than E. coli and S. Enteritidis (P < 0.05). The application of PEF (3.75 and 15 kV/cm, 10 mu s, 5 Hz) to inoculated samples of raw chicken did not result in any significant reductions in total viable counts, Enterobacteriaceae, C. jejuni, E. coli or S. Enteritidis. Therefore, under the conditions used in this study. PEF technology may not be suitable as a food safety intervention measure for the control of microbial contaminants on broilers during processing although it may have potential to reduce contamination of process water (e.g. scald or spin chill water). (c) 2011 Elsevier Ltd. All rights reserved.

The application of sonication and thermosonication (53 ± 1 °C) was investigated as potential methods for reducing numbers of Campylobacter, enterobacteriaceae and total viable counts (TVC) on raw poultry. Sonication equipment included a high-intensity unit (HI) and a low-intensity unit (LI), which produced 20,000 and 20 W/L, respectively. The susceptibility of ten Campylobacter isolates in liquid media to thermosonication treatment was also investigated to determine whether differences between isolates existed. All Campylobacter strains were susceptible to thermosonication in the HI unit with inactivations ranging from 2.97–4.15 log10 CFU/mL. Campylobacter jejuni was more susceptible to thermosonication than to thermal or sonication treatment with mean inactivations of 4.72, 1.45 and 3.17 log10 CFU/mL, respectively. Following 16 min thermal, sonication and thermosonication treatments of broiler skin pieces in the HI unit, no viable Campylobacter or enterobacteriaceae were detected and TVC were reduced by 1.93, 1.34 and 2.49 log10 CFU/g, respectively. Thermosonication treatment in the LI unit reduced enterobacteriaceae and TVC populations by 2.74 and 1.69 log10 CFU/g, respectively. Thermosonication treatment was generally more effective against Campylobacter in liquid matrices in comparison to inoculated poultry products.

The application of crust freezing (CF) applied as a stand-alone treatment or in combination with ultraviolet (UV) light for reducing the level of artificially inoculated Campylobacter jejuni on raw chicken was investigated. CF air temperatures of -5, -15 and -27 °C (±3 °C) with freezing times of 70, 15 and 6 min, respectively, were used. The level of C. jejuni on chicken was also examined following subsequent refrigerated (0-4 °C) storage at 3 and 7 days. All CF treatments resulted in significant reductions compared to untreated controls (P < 0.05). Although combining CF with UV also resulted in significant reductions for C. jejuni, the combined treatments were generally no more effective than treatment by CF alone. Overall, the color of chicken drumsticks was not affected by CF treatments (P ≥ 0.05). In general, CF resulted in increased drip loss (P < 0.05), which increased over storage time and was greater at higher CF temperatures. The current study indicates that CF has potential for reducing the levels of C. jejuni by between 0.5 and 1.5 log(10) CFU/g and impacts minimally on the color of treated skin.

A blend of orange and carrot juice was processed by three selected treatments combining pulsed electric fields (PEF) (24 kV/cm, 18 Hz, 93 mu s), ultraviolet light (UV) (10.6 J/cm(2)) or high intensity light pulses (HILP) (3.3 J/cm(2)), in each case, with manothermosonication (MTS) technology (400 kPa, 35 degrees C, 1000W, 20 kHz). Treatment effects on selected physicochemical and sensory properties of the juice were evaluated. No significant changes were found in non-enzymatic browning (NEBI) or antioxidant activity compared to an untreated control. However, the treatments increased all the Hunter Lab colour values, while total phenolics were significantly decreased. Each combination achieved on average 78% inactivation of pectin methyl esterase (PME). Sensory analysis showed that the colour of the product processed by hurdle combinations was preferred to that of a pasteurised sample (72 degrees C, 26 s), while the flavour was adversely affected by all of the non-thermal treatments. Panellists did not perceive differences in the odour, sweetness or acidity of the product. Results indicate that, under the current experimental conditions, the application of the selected combinations of non-thermal technologies resulted in a product in which certain quality attributes were somewhat inferior to those of a lightly pasteurised control juice. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

The combination of novel, non-thermal technologies for preservation purposes is a recent trend in food processing research. The objectives of the current study were (i) to optimise PEF or MTS treatment conditions which would achieve a maximum reduction of up to 3 log cycles of Listeria innocua in a milk based smoothie, when these technologies were applied individually, and (ii) to investigate possible additive or synergistic effects of the combined technologies. Microbiological analysis was performed by inoculating the smoothie with L. innocua and enumerating populations pre- and post-processing. All technologies applied within combinations significantly reduced L. innocua in the smoothie, when compared to untreated controls (p ≤ 0.0001). The sequence in which the MTS and PEF were applied was found to have a significant impact on the level of microbial reduction achieved (p ≤ 0.05). The sequence of MTS followed by PEF was the most effective in inactivating L. innocua achieving a mean reduction of 5.6 log cfu/ml, thereby exceeding the 5 log cycles minimum requirement specified by the United States Food and Drug Administration (US FDA). Significantly (p ≤ 0.05) lower reductions of 4.2 log cfu/ml were achieved when the PEF + MTS sequence combination was applied. The combination of MTS + PEF achieved inactivation comparable to thermally treated samples (p > 0.05). This study has shown the combination MTS + PEF is a promising hurdle preservation approach to control undesirable microorganisms in milk based smoothie beverages.

Campylobacter is an important cause of human gastroenteritis worldwide. Chicken meat is frequently contaminated with this organism and is considered to be a significant source of infection. It has been predicted that lowering the numbers of Campylobacter on chicken meat can reduce the risk to public health. The aims of the current study were to investigate the susceptibility of Campylobacter to high intensity near ultraviolet/visible (NUV–vis) 395±5nm light and to examine its potential for the microbiological decontamination of raw chicken and contact surfaces. Exposure of Campylobacter jejuni and Campylobacter coli to NUV–vis light of irradiances was assessed at three distances (3, 12 and 23cm) from the light source for up to 10min, corresponding to doses of 0.06 to 18J/cm2. Overall, levels of inactivation in liquid and on raw chicken improved with longer exposure times and shorter distances from the light source. Reductions of more than 7log10CFU/mL were achieved for Campylobacter isolates in liquid following 2min exposure at 3cm. Exposure of skinless chicken fillet to NUV–vis light for 1 or 5min at 3cm distance reduced C. jejuni by 2.21 and 2.62log10CFU/g, respectively. Increasing the treatment time to 10min did not significantly increase the level of inactivation. In general, NUV–vis light treatment did not affect the colour of raw chicken. Excluding treatments which resulted in excessive heating (>50°C) of chicken skin, a maximum reduction of 0.95log10CFU/g was achieved for C. jejuni following 10min exposure to NUV–vis light at 12cm (P<0.05). For Enterobacteriaceae and total viable counts, significant reductions were achieved only on chicken fillet samples. Light treatments were significantly effective for decontaminating contact surfaces as there were no C. jejuni recovered from stainless steel or cutting board surfaces after NUV–vis light treatments from an initial inoculum of 2–4log10CFU/cm2 (P<0.05). The current study demonstrates potential for the use of NUV–vis light for the inactivation of Campylobacter spp. in liquids, on raw chicken and contact surfaces. The incorporation of this technology could be implemented in a commercial processing plant at various stages, for example to decontaminate carcasses during air chilling. It could also be applied at critical stages within the plant to control microbial contamination on equipment surfaces.

Non-thermal technologies such as UV irradiation can offer advantages for minimal processing of transparent beverages. In this study, reconstituted apple juice was exposed to UV light in a continuous laboratory scale system at energy dosages ranging from 2.66 to 53.10 J/cm2 by changing the exposure time. Treated juices were then evaluated for microbial inactivation and selected physical and chemical attributes. Product quality was further assessed by sensory evaluation using a 30-member consumer panel. Microbiological analysis was performed by inoculating apple juice with Escherichia coli K12 and Listeria innocua and microbial numbers were counted pre- and post-processing. UV energy levels did not affect pH, °Brix, or total phenols content, but decreased non-enzymatic browning (p < 0.01) and antioxidant capacity (p < 0.05) compared to unprocessed juice. A colour-lightening effect was noted with increasing energy dose. All UV treatments applied (2.66 J/cm2 and above) resulted in a reduction below the detection level (<1 log cfu/ml) for both E. coli and L. innocua in apple juice. Sensory evaluation showed that samples treated with energy dosages up to 10.62 J/cm2 were comparable to the control in terms of acceptability, though higher dosages produced adverse effects in terms of flavour and colour. Based on these results, UV treatment with low energy dosages could represent a valid alternative to thermal processing to eliminate pathogenic microorganisms while maintaining quality in reconstituted apple juice.

The non-thermal technologies High Intensity Light Pulses (HILP) and Thermosonication (TS) were applied alone and in combination to study their effect on Escherichia coli inactivation in orange juice. Two different energy settings were chosen in the current study, 'Low' (L) and 'High' (H), being the combinations applied: HILP(L) (4.03 J/cm(2)), HILP(H) (5.1 J/cm(2)), TS(L) (2.8 min residence time at 40 °C) and TS(H) (5 min residence time at 50 °C). Both the individual technologies and their combinations (HILP&TS and TS&HILP) were studied. Results showed inactivation ranging from 1.10 (TS(H)) to 2.42 (HILP(H)) log cfu/ml for the hurdles when applied individually and from 2.5 (HILP(L)&TS(H)) to 3.93 (HILP(H)&TS(L)) log cfu/ml for the combined treatments. Similar reductions in E. coli populations were achieved in orange juice by all treatment combinations irrespective of the sequence in which they were applied.

The combination of novel, non-thermal technologies for preservation purposes is a recent trend in food processing research. In the present study, non-thermal hurdles such as ultraviolet light (UV) (5.3 J/cm2), high intensity light pulses (HILP) (3.3 J/cm2), pulsed electric fields (PEF) (34 kV/cm, 18 Hz, 93 μs) or manothermosonication (MTS) (4 bar, 43 °C, 750 W, 20 kHz) were examined. The objective was to establish the potential of these technologies, applied individually or in paired sequences, to inactivate Escherichia coli and Pichia fermentans inoculated in a fresh blend of apple and cranberry juice. The shelf-life evaluation of selected non-thermally treated samples was conducted over 35 days and compared to pasteurised samples and untreated juices. All treatments applied individually significantly reduced (1.8–6.0 log cfu/ml) microbial counts compared to the untreated sample (p < 0.01). Furthermore, UV treatment produced significantly greater inactivation (p < 0.05) for E. coli compared to P. fermentans. Combinations of non-thermal hurdles consisting of UV or HILP followed by either PEF or MTS resulted in comparable reductions for both microorganisms (p ≥ 0.05) to those observed in thermally pasteurised samples (approx. 6 log cfu/ml). Thermally pasteurised samples had a shelf life exceeding 35 days, while that of UV + PEF and HILP + PEF-treated samples was 14 and 21 days, respectively. These results indicate that combinations of these non-thermal technologies could successfully reduce levels of E. coli and P. fermentans in apple and cranberry juice, although optimisation is required in order to further extend shelf life.

A blend of apple and cranberry juice was processed by a combination of a light-based technology (ultraviolet light (UV) (5.3J/cm2) or high intensity light pulses (HILP) (3.3J/cm2) in combination with pulsed electric fields (PEF) (34kV/cm, 18Hz, 93μs) or manothermosonication (MTS) (5bar, 43°C, 750W, 20kHz). Selected physical and chemical attributes were evaluated pre- and post-processing, and the sensory attributes of non-thermally treated samples were compared to conventional pasteurisation (26s, 72°C). No significant changes were found in non-enzymatic browning, total phenolics and antioxidant activity of the juices. UV+PEF and HILP+PEF treatments did not affect the colour of the product and HILP+PEF processing retained more monomeric anthocyanins than any other combined treatment. Sensory analysis showed that UV+PEF and HILP+PEF combinations did not impact on odour and flavour of the juice, while combinations that included MTS adversely affected those attributes.

UV light was investigated for the decontamination of raw chicken, associated packaging, and contact surfaces. The UV susceptibilities of a number of Campylobacter isolates (seven Campylobacter jejuni isolates and three Campylobacter coli isolates), Escherichia coli ATCC 25922, and Salmonella enterica serovar Enteritidis ATCC 10376 in liquid media were also investigated. From an initial level of 7 log CFU/ml, no viable Campylobacter cells were detected following exposure to the most intense UV dose (0.192 J/cm(2)) in liquid media (skim milk subjected to ultrahigh-temperature treatment and diluted 1:4 with maximum recovery diluent). Maximum reductions of 4.8 and 6.2 log CFU/ml were achieved for E. coli and serovar Enteritidis, respectively, in liquid media. Considerable differences in susceptibilities were found between the Campylobacter isolates examined, with variations of up to 4 log CFU/ml being observed. UV treatment of raw chicken fillet (0.192 J/cm(2)) reduced C. jejuni, E. coli, serovar Enteritidis, total viable counts, and Enterobacteriaceae by 0.76, 0.98, 1.34, 1.76, and 1.29 log CFU/g, respectively. Following UV treatment of packaging and surface materials, reductions of up to 3.97, 4.50, and 4.20 log CFU/cm(2) were obtained for C. jejuni, E. coli, and serovar Enteritidis, respectively (P < 0.05). Overall, the color of UV-treated chicken was not significantly affected (P ≥ 0.05). The findings of this study indicate that Campylobacter is susceptible to UV technology and that differences in sensitivities exist between investigated isolates. Overall, UV could be used for improving the microbiological quality of raw chicken and for decontaminating associated packaging and surface materials.

The influence of cell design on the uniformity of batch ohmic heating of a solid foodstuff was examined. Various ways of minimising heat loss from the cell surface including insulation or providing supplementary heat via a heating belt or panel were assessed but discarded in favour of housing the cell in a hot air cabinet maintained at 80 °C and eliminating the surrounding cell body. Various electrode materials and designs were evaluated prior to opting in favour of platinised titanium electrodes of minimal practicable thickness (1 mm). The final system developed involved the use of a combined ohmic/convection heating with the food stuff contained in a plastic casing pressurised between two spring-loaded electrodes. Under optimised conditions a maximum overall temperature variation of 12.1 °C within the product was achieved after 150 s which was reduced to 8.6 °C after 3 min standing time.

High Intensity Light Pulses (HILP) represent an emerging processing technology which uses short (100-400 μs) light pulses (200-1100 nm) for product decontamination. In this study, model and real foods of differing transparencies (maximum recovery diluent (MRD), apple and orange juices and milk) were exposed to HILP in a batch system for 0, 2, 4 or 8 s at a frequency of 3 Hz. After treatment, inactivation of Escherichia coli or Listeria innocua was evaluated in pre-inoculated samples. Sensory and other quality attributes (colour, pH, Brix, titratable acidity, non-enzymatic browning, total phenols and antioxidant capacity (TEAC)) were assessed in apple juice. Microbial kill decreased with decreasing transparency of the medium. In apple juice (the most transparent beverage) E. coli decreased by 2.65 and 4.5 after exposure times of 2 or 4 s, respectively. No cell recovery was observed after 48 h storage at 4°C. No significant differences were observed in quality parameters, excepting TEAC and flavour score, where 8 s exposure caused a significant decrease (p<0.05). Based on these results, HILP with short exposure times could represent a potential alternative to thermal processing to eliminate undesirable microorganisms, while maintaining product quality, in transparent fruit juices.

This study aimed to develop radio frequency (RF) pilot-scale protocols for tempering beef meat blends (4kg blocks) to achieve average temperatures between −2 and −5°C. Post-tempering temperature distribution in these blocks was compared to products tempered by conventional methods. The optimum RF power–time combination for tempering lean and 50:50 lean:fat mixtures to the target range was 500W for 11min which produced respective means of −3.6°C (s.d. 1.1) and −3.4°C (s.d. 1.5). In contrast, 400W for 11min was optimum for fat (mean −4.9°C, s.d. 2.1). This study shows the principal advantages of RF over conventional tempering as an approximate 30 fold tempering time reduction and a greater uniformity of end point temperature distribution under the conditions employed. Furthermore, power consumption was reduced approximately ninefold with RF compared to conventional tempering. More uniform temperature distribution was achieved in samples that were comminuted to a greater extent.

Treatments involving pulsed electric fields (PEF) in combination with high intensity light pulses (HILP) were applied to reconstituted apple juice in a continuous system using a 2 x 4 factorial design, with sequence and energy levels as main factors. Two PEF field strengths (24 kV/cm or 34 kV/cm) were selected (treatment time 89 mu s each) corresponding to "high" (H) and a "low" (L) energy inputs (261.9 and 130.5 J/ml, respectively). Juice was also pumped through a HILP system (pulse length 360 mu s, frequency 3 Hz) and exposed to energy dosages of 5.1 J/cm(2) (H) or 4.0 J/cm(2) (L) corresponding to 65.4 and 51.5 J/ml, respectively. Microbiological analysis was performed by inoculating juice with Escherichia coli 1(12 and counting microbial populations pre- and post-processing. Selected physical and chemical quality attributes were compared with those of unprocessed controls. A sensory evaluation was conducted using 31 untrained panellists and the products compared to thermally processed juice (94 degrees C for 26 s). With the exception of HILP (H) and PEF (L), all combinations achieved the minimum microbial reduction of 5 log units required by the FDA. The results obtained for PEF (L) followed by either HILP (Lot H) suggest a synergistic effect on microbial inactivation. In general, the quality attributes were not affected by the chosen treatments and sensory evaluation revealed that the HILP(L)/PEF(L) combination was the most acceptable of the selected non-thermal treatments.Industrial Relevance: Heat remains the dominant microbial/enzyme inactivation technique though its impact on food quality is often at odds with increased consumer demand for minimally processed (MP) products. The reduction in intrinsic preservation in MP products raises new safety and stability risks and a major trend is the combination of inhibitory techniques to effectively preserve without the extreme use of a single technique (i.e. hurdle technology). PEF and HILP are emerging nonthermal/mild-heat technologies which have antimicrobial capabilities when applied alone or in combination with other physicochemical hurdles. Only a limited amount of work has focused on combinations of emerging technologies. As consumers have less reservations about physical (vs. chemical) preservation treatments, the objective of this paper is to assess if novel combinations of these emerging physical hurdles achieves the twin goals of food safety and quality in apple juice. This will involve assessing whether these combinations are effective vs. selected microorganisms un-/mildly heated products. In addition the nutritional/sensory quality of these MP products will be compared to untreated products. (C) 2011 Elsevier Ltd. All rights reserved.

The combination of pulsed electric fields (PEF) and bacteriocins in a hurdle approach has been reported to enhance microbial inactivation. This study investigates the preservation of orange juice using PEF in combination with nisin (2.5ppm), natamycin (10ppm), benzoic acid (BA; 100ppm), or lactic acid, (LA; 500ppm). Pichia fermentans, a spoilage yeast frequently isolated from orange juice, Escherichia coli k12 or Listeria innocua were inoculated into sterile orange juice (OJ) with, and without, added preservatives. The antimicrobial activity over time was evaluated relative to an untreated control. The effect of PEF treatment (40kV/cm, 100μs; max temperature 56°C) was assessed on its own, and in combination with each antimicrobial.

Cylindrical cores of beef semitendinosus (500g) were cooked in a combined ohmic/convection heating system to low (72 degrees C, LTLT) and high (95 degrees C, HTST) target end-point temperatures. A control was also cooked to an end-point temperature of 72 degrees C at the coldest point. Microbial challenge studies on a model meat matrix confirmed product safety. Hunter L-values showed that ohmically heated meat had significantly (p<0.05) lighter surface-colours (63.05 (LTLT) and 62.26 (HTST)) relative to the control (56.85). No significant texture differences (p>/=0.05) were suggested by Warner-Bratzler peak load values (34.09, 36.37 vs. 35.19N). Cook loss was significantly (p<0.05) lower for LTLT samples (29.3%) compared to the other meats (36.3 and 33.8%). Sensory studies largely confirmed these observations. Cook values were lower for LTLT (3.05) while HTST and the control were more comparable (6.09 and 7.71, respectively). These results demonstrate considerable potential for this application of ohmic heating for whole meats.