Effect of mild heat pre-treatment with alkaline electrolyzed water on the efficacy of acidic electrolyzed water against Escherichia coli O157:H7 and Salmonella on Lettuce

Cut lettuce dip-inoculated with Escherichia coli O157:H7 and Salmonella was treated with alkaline electrolyzed water (AlEW) at 20°C for 5 min, and subsequently washed with acidic electrolyzed water (AcEW) at 20°C for 5 min. Pre-treatment with AlEW resulted in an approximate 1.8 log₁₀ cfu/g reduction of microbial populations, which was significantly (p⩽0.05) greater than microbial reductions resulting from other pre-treatment solutions, including distilled water and AcEW. Repeated AcEW treatment did not show a significant bacterial reduction. Mildly heated (50°C) sanitizers were compared with normal (20°C) or chilled (4°C) sanitizers for their bactericidal effect. Mildly heated AcEW and chlorinated water (200 ppm free available chlorine) with a treatment period of 1 or 5 min produced equal reductions of pathogenic bacteria of 3 log₁₀ and 4 log₁₀ cfu/g, respectively. The procedure of treating with mildly heated AlEW for 5 min, and subsequent washing with chilled (4°C) AcEW for period of 1 or 5 min resulted in 3–4 log₁₀ cfu/g reductions of both the pathogenic bacterial counts on lettuce. Extending the mild heat pre-treatment time increased the bactericidal effect more than that observed from the subsequent washing time with chilled AcEW. The appearance of the mildly heated lettuce was not deteriorated after the treatment. In this study, we have illustrated the efficacious application of AlEW as a pre-wash agent, and the effective combined use of AlEW and AcEW.     

Assessment of high intensity ultrasound for surface decontamination of salmon (S. salar), mackerel (S. scombrus), cod (G. morhua) and hake (M. merluccius) fillets,and its impact on fish quality

The effect of applying high intensity ultrasound on microbiological and quality parameters in several fish species was assessed at laboratory scale. Samples of salmon (S. salar) and mackerel (S. scombrus) as oily fish, and cod (G. morhua) and hake (M. merluccius) as white fish, were treated using an ultrasonic bath (30 kHz). Samples of each species were separated into three groups (i) untreated control (C), (ii) water immersion only (IM) and (iii) ultrasound (US) and treated for 5, 15, 25, 35 and 45 min. All physicochemical parameters were determined in samples treated for 45 min. Microbiological counts were reduced significantly (p < 0.05) after US treatment in oily fish species with reductions of up to 1.5 & 1.1 log CFU/g for psychrophilic and mesophilic viable counts (PVC & TVC) observed in salmon and mackerel respectively. Corresponding reductions in white fish species were only 0.5 log CFU/g. Lipid content did not change significantly (p > 0.05) after treatment. Significant reductions of thiobarbituric acid reactive substances (TBARS) values (C: 0.36; US: 0.18) and colour changes were observed in salmon (a* C: 12.8; US: 10.0). Moisture levels increased by 8% following US treatment in hake.     

Reduction effect of the selected chemical and physical treatments to reduce L. monocytogenes biofilms formed on lettuce and cabbage

As people shift their attention away from unhealthy foods, healthy fresh produce has become popular. However, fresh produce has contributed to many outbreaks of Listeria monocytogenes, which can form a mature biofilm within 24 h. Recent control strategies have proved ineffective in ensuring safe food production. This study focuses on L. monocytogenes biofilms formed on lettuces and cabbages using a viable plate count method and field emission electron microscopy. We investigated the reduction efficacy of treatment with 200 parts per million (ppm) chlorine, 2% each of citric, lactic, and malic acids, 32 Hz ultrasonication (US), 390 mJ/cm² ultraviolet-C (UV-C), or 750 mJ/cm² cold oxygen plasma (COP) on L. monocytogenes biofilms. Following treatment, the quality of the vegetables was analyzed with standard procedures. UV-C and COP showed the best CFU reduction, regardless of the nature of the vegetable surface, while US failed to produce any significant reduction (P > 0.05). Furthermore, chemical treatments reduced count by < 1 log colony forming unit (CFU)/cm² on lettuces, whereas a > 2 log reduction was observed on cabbages. The effect of chemical treatment largely depended on the particular vegetable, while UV-C and COP achieved high reduction regardless of the vegetable, and had no effect on quality. We, therefore, speculate that UV-C and COP show promise in overcoming L. monocytogenes biofilms on food produce.     

Effect of calcium lactate and heat-shock on texture in fresh-cut lettuce during storage

Textural and microstructural changes in fresh-cut lettuce were analysed over 12 days storage. The vegetable was treated with 120 ppm chlorine and with 15 g/L calcium lactate at room temperature (∼18–20 °C) and at 50 °C (heat-shock). Texturometer analysis showed that samples washed with calcium lactate had significantly (p > 0.05) higher crispness values than samples washed with chlorine. However the use of 50 °C treatment (heat-shock) gave better textural properties at the end of storage and significantly retarded the softening process, being in agreement with the sensorial results. Cryo-SEM micrographs showed a loss of turgor (shrinkage) of the tissue cells in the samples washed with chlorine, effect not so evident in calcium lactate treated samples. The use of heat-shock in combination with calcium lactate reduced this phenomenon better than the other two treatments. Pectin methyl esterase (PME), enzyme related to textural changes, showed higher activity in samples treated with calcium lactate at 50 °C. The combination of calcium lactate and 50 °C washing temperature maintained objective and sensorial textural properties of fresh-cut lettuce better than the calcium lactate or chlorine washing treatments at room temperature.     

Determination of the efficacy of ultrasound in combination with essential oil of oregano for the decontamination of Escherichia coli on inoculated lettuce leaves

Recent outbreaks related to fresh produce have shown that there is a need to develop new efficient and effective decontamination technologies that protect consumers' safety. Ultrasound and assisted ultrasound, i.e., the combination of ultrasound with another decontamination technology has been shown to be effective against bacteria. In this study equal surfaces of free-bacteria of Romaine lettuce were inoculated with Escherichia coli O157:H7 NCTC 12900. Leaves were then treated with an ultrasound probe system (26 kHz, 90 μm, 200 W, 14 mm Ø). Same processing time (300 s) was applied with continuous and pulsed modes of: (i) 10 s on/6 s off, (ii) 5 s on/5 s off and (iii) 2 s on/8 s off. Thus, total treatment durations were 5, 8, 10 and 25 min. Moreover, concentrations of essential oil (i.e. 0.010% v/v, 0.014% v/v. 0.018% v/v, 0.022% v/v and 0.025% v/v) of oregano were tested, operating with continuous and 2 s on/8 s off pulsed mode. The structure of treated samples was also analysed by SEM and light microscopy. Continuous ultrasound treatments led to a reduction of 2.65 ± 0.23 log CFU/cm² of E. coli on the lettuce. No significant differences were found among the tested pulsed and continuous modes. In addition no significant differences were found between injured and no-injured cells among all the applied treatments on the leaves of the lettuce. Application of the different concentrations of EO alone, at the levels mentioned previously reduced the bacteria on the surface of the lettuce. Less than 2 logs of total inactivation (on the lettuce and the treated water) were achieved when different concentrations of EO were tested alone. Assisted ultrasound enhanced the levels of microbial reduction on the surface of the lettuce at concentrations higher than 0.010% (v/v) of oregano EO. Significant differences were found at 0.018%, 0.022% and 0.025% (v/v) both in continuous and pulsed US modes when compared with samples treated only with US. Same concentrations of EO combined with continuous or pulsed mode of US reduced the level of E. coli in water below the limit of detection. When continuous or pulse mode of US was combined with 0.025% (v/v) of EO of oregano the result was synergetic. Images reported neither structural differences nor damage of the leaves among treated samples and controls. Concluding, the effectiveness of the assisted ultrasound process was dependent on the processing time rather than on the different configurations (continuous or on/off) or the total treatment duration. Furthermore, EO combined with US could work synergistically on enhancing the inactivation of the tested bacteria.     

Microbial safety considerations of flooding in primary production of leafy greens: A case study

This study evaluated the effects of a flood event, floodplain and climatic parameters on microbial contamination of leafy greens grown in the floodplains. Additionally, correlations between pathogenic bacteria and levels of indicator microorganisms have been also determined. To diagnose the microbial contamination after the flood event, sampling was carried out in weeks 1, 3, 5 and 7 after the flooding in four flooded lettuce fields. To assess the impact of flooding on the microbial contamination of leafy greens, indicator microorganisms (coliforms, Escherichia coli and Enterococcus) and pathogenic microorganisms (Salmonella spp., VTEC (E. coli O157:H7 and other verocytotoxin producing E. coli, O26, O103, O111, O145) and Listeria monocytogenes) were evaluated. Irrigation water, soil and lettuce samples showed levels of coliforms and E. coli higher than 5 and 3 log cfu/g or 100 mL, respectively when sampled 1 week after flooding. However, bacterial counts drastically declined three weeks after the flooding. Climatic conditions after flooding, particularly the solar radiation (6–8 MJ/m²), affected the survival of bacteria in the field. L. monocytogenes was not detected in lettuce samples, except for 2 samples collected 3 weeks after the flooding. The presence of Salmonella was detected in irrigation water, soil and lettuce by multiplex PCR one week after the flooding, but only 2 samples of soil and 1 sample of water were confirmed by colony isolation. Verotoxigenic E. coli was detected in soil and lettuce samples by multiplex PCR. Therefore, the implication of flood water as the source of VTEC contamination of soil and lettuce was not clear. E. coli counts in irrigation water were positively correlated with those in lettuce. A significant correlation (P < 0.005) was found between the presence of pathogens and E. coli counts, highlighting a higher probability of detection of pathogens when high levels of E. coli are found. The results obtained in the present study confirm previous knowledge which defined flooding as a main risk factor for the microbial contamination of leafy greens.     

A novel technique to improve the biodegradation efficiency of dextranase enzyme using the synergistic effects of ultrasound combined with microwave shock

The synergistic effects of ultrasound and microwave irradiation sock (US/MI-S) on hydrolysis of dextran catalytic by dextranase were studied. Ultrasound (US) treatments were performed at fixed power of 50 W/40 kHz, and the microwave irradiation shock (MI-S) was applied at different power conditions, of 10–140 W at 2450 MHz at a sock rate of 20 s/min. The hydrolysis of dextran under US/MI-S treatment was significantly higher than those performed under US, MI-S and conventional thermal incubation at all condition studied. The maximum hydrolysis rate was observed when US/MI-S (US of 50 W combined with MI-S of 60 W at a sock rate of 20 s/min for 25 min) was used in which the dextran hydrolysis increased by 171.13% compared with routine conventional heating. Results also showed that, V_max and K_M values of dextranase under US/MI-S treatment were higher than those under US, MI-S and conventional thermal incubation, which indicated that, the substrate was converted into the product at an increased rate under US/MI-S treatments. K_cat and (K_cat/K_M) values obtained under US/MI-S treatment were higher than those observed under respective conventional heating. Compared to the enzymatic reaction under US, MI-S, and conventional thermal incubation, dextranase enzymatic reaction under US/MI-S treatment showed decreases in Ea, ΔG and ΔH, however small increases in ΔS value were observed. On the other hand, CD spectra reflected that β-sheet and random coil content were decreased by the mean of the US/MI-s and US treatments and increased under MI-S treatment compared to control. However, fluorescence spectra demonstrated that, degradation rate of dextranase secondary structure was slower than that of enzyme tertiary structure. Therefore, US/MI-S treatment results in reordered secondary structure of dextranase, which was helpful for the improvement of its activity. To the best of our knowledge, this study was the first report on synergistic effects of ultrasound and microwave irradiation sock on industrial enzymes.Industrial relevanceIn order to reduce the industrial cost for the application of enzymes during the sugar manufacturing process, a synergistic effect of ultrasound and microwave irradiation sock (US/MIS) on hydrolysis of dextran catalytic by dextranase was applied. The hydrolysis of dextran under US/MI-S treatment was significantly higher than those performed under US, MI-S and conventional thermal incubation at all condition studied. The maximum hydrolysis rate was observed when US/MI-S (US of 50 W combined with MI-S of 60 W at a sock rate of 20 s/min for 25 min) was used in which the dextran hydrolysis increased by 171.13% compared with routine conventional heating. These results indicated that, the combination of ultrasound and microwave irradiation sock could be a new and innovative method for improving the dextranase activity in many industrial applications including food processing.     

Changes in quality characteristics of fresh-cut jujubes as affected by pressurized nitrogen treatment

When fresh-cut jujubes are subjected to pressurized nitrogen treatments, the nitrogen gas dissolves into water and forms clathrate hydrates which ultimately lead to restriction in water mobility. Fresh-cut jujubes were, respectively, treated with 1.0 MPa nitrogen, 1.5 MPa nitrogen, 1.9 MPa nitrogen and 1.9 MPa air for 30 min at 4 °C and without pressurized treatment(control) and then stored at 4 °C and 80 % relative humidity (RH) for 12 days. Physiological, textural, chemical, and microbial attribute were determined every 2 days. Results indicated that pressurized nitrogen treatments carried out at 1.5 MPa successfully inhibited respiration, water loss, softening, chlorophyll degradation, and color change. The treatments also significantly reduced loss of ascorbic acid and soluble solids. Treated fresh-cut jujubes carried significantly less microbial population. Thus, it was concluded that pressurized nitrogen treatment was beneficial to preserve quality of fresh-cut jujubes.     

Synergistic interaction of ultraviolet light and zinc oxide photosensitizer for enhanced microbial inactivation in simulated wash-water

Synergistic interaction of ultraviolet light (UV-A) and zinc oxide (ZnO) was investigated for enhanced inactivation of Escherichia coli BL21 and T7 bacteriophage in simulated wash-water. In the absence of organic content, UV-A (9.53 J/cm²) and 1 mM ZnO alone caused 3.9 and 0.7 log CFU/mL reductions respectively in logarithmic phase bacteria after 60 min, while a combined treatment caused 6 log CFU/mL reductions. Stationary-phase bacteria were more resistant and a combined treatment caused only 3.5 log CFU/mL reductions. Organic matter in the wash-water lowered the inactivation rates. Nevertheless, approximately 2-log reductions were observed at the highest organic load. T7 bacteriophage was not sensitive to UV-A alone. However, 1 mM photo-irradiated ZnO caused 6.00 log PFU/mL reductions after 60 min. Bacteriophage inactivation was also significantly lowered by organic matter. The reactive oxygen species generated from photo-irradiated ZnO were responsible for the microbial inactivation. UV-A irradiated ZnO is an attractive sanitation approach for fresh-produce washing.Industrial relevanceChlorine-based sanitizers that are conventionally used for washing fresh-produce suffer significant limitations including occupational hazard for workers from over-exposure to chlorine and safety hazards to the population due to formation of chlorinated organic matter. This study highlights that UV-A irradiated ZnO is a promising alternative to sanitize wash-water and fresh-produce and reduce the risk of bacterial as well as viral cross-contamination. Future studies are needed to optimize and scale-up this process for industrial use.     

High pressure carbon dioxide combined with high power ultrasound processing of dry cured ham spiked with Listeria monocytogenes

Traditionally, thermal treatments for the inactivation of Listeria monocytogenes in meat products involve undesirable changes of the product quality. In recent years, efforts have been carried out to develop alternative methods to inactivate L. monocytogenes without affecting the product quality attributes. In this context, the feasibility of combined high pressure carbon dioxide and high power ultrasound (HPCO₂ + HPU) treatment to inactivate L. monocytogenes inoculated on the surface of dry cured ham was investigated. Inactivation data were determined at 6, 8 and 12 MPa, as a function of temperature (22, 35, 45 °C) and treatment time (0.5 to 30 min), and compared to those obtained after thermal and HPCO₂ treatments.Color, pH and acidity changes of the samples after both thermal and HPCO₂ + HPU treatments were measured and compared, sensorial profile of the treated samples was evaluated by a sensory panel and shelf-life was determined by a storage study for 4 weeks at 4 °C.The results clearly revealed that HPU alone was not able to induce any microbial inactivation while HPCO₂ + HPU treatment always assured a certain level of inactivation, variable with the process temperature used: the inactivation efficiency was demonstrated higher at 35 °C rather than 22 °C and no enhancement was observed at 45 °C compared to 35 °C. Process conditions of 12 MPa, 35 °C, at 10 W for 5 min assured inactivation to undetectable level of L. monocytogenes spiked on the surface of the product with an initial concentration of about 10⁹ CFU/g. No differences were detected between acidity, pH, color and sensory attributes of the untreated and HPCO₂ + HPU treated dry cured ham surface, while slight differences were measured between the values obtained for the untreated and thermally treated samples. Additionally, the storage study demonstrated that a full microbial and quality shelf-life was assured for 4 weeks at 4 °C. The results obtained may open the doors to the application of such an innovative process at industrial level, in particular to treat ham-type or meat products.     

Inactivation of bacterial pathogens on lettuce,sprouts, and spinach using hurdle technology

Effects of chemical treatment using slightly acidic electrolyzed water (SAEW), fumaric acid (FA), or calcium oxide (CaO) and physical treatment using ultrasonication (US), micro-bubbles (MB), or ultraviolet (UV) to inactivate bacterial pathogens Listeria monocytogenes, Escherichia coli O157:H7, Staphylococcus aureus, and Salmonella spp. on lettuce, spinach, and sprouts were determined. Fresh produce inoculated with bacterial pathogens (~ 9 log CFU/mL) was immersed in distilled water (DW), SAEW, FA (0.5%), or CaO (0.2%) alone or in combination at 23 ± 2 °C for 3 min followed by treatment with US, MB for 3 min, or UV for 10 min. Effects of combined treatment on shelf-life of lettuce at 4 °C and 23 ± 2 °C were also determined in this study. Results revealed that the use of a combination of CaO + SAEW + FA + US exhibited significant reduction (p < 0.05) for bacterial pathogen on fresh produce compared to individual treatment or other combinations. CaO + SAEW + FA + US treatment exhibited highest reduction of E. coli O157:H7, S. aureus, L. monocytogenes and Salmonella spp. by 4.7, 4.9, 4.84 and 5.08 log CFU/g, respectively on lettuce as compared to spinach and sprouts. Microbial count reducing capability for combined treatment methods were ranked in the following order: SAEW + FA < CaO + SAEW + FA < CaO + SAEW + FA + US. However, introduction of US to CaO + SAEW + FA treatment resulted in little detrimental effect on the overall quality of lettuce. Moreover, CaO + SAEW + FA treatment effectively enhanced the shelf-life of lettuce stored at 4 °C and 23 ± 2 °C by about 6 days and 3 days, respectively as compared to control (DW treatment), with longer lag time (23.11 h on lettuce) for naturally occurring bacteria on fresh produce. These findings suggest that significant synergistic benefit could be obtained from combined sanitizer treatment to eliminate bacterial pathogens from fresh produce.     

Inactivation of Escherichia coli O157:H7, Salmonella and human norovirus surrogate on artificially contaminated strawberries and raspberries by water-assisted pulsed light treatment

This study investigated the inactivation of Escherichia coli O157:H7, Salmonella and murine norovirus (MNV-1), a human norovirus surrogate, on strawberries and raspberries using a water-assisted pulsed light (WPL) treatment. The effects of combinations of WPL treatment with 1% hydrogen peroxide (H₂O₂) or 100 ppm sodium dodecyl sulfate (SDS) were also evaluated. Strawberries and raspberries were inoculated with E. coli O157:H7 and treated by WPL for 5–60 s. E. coli O157:H7 on both strawberries and raspberries was significantly reduced in a time-dependent manner with 60-s WPL treatments reducing E. coli O157:H7 by 2.4 and 4.5 log CFU/g, respectively. Significantly higher reductions of E. coli O157:H7 were obtained using 60-s WPL treatment than washing with 10 ppm chlorine. Compared with washing with chlorine, SDS and H₂O₂, the combination of WPL treatment with 1% H₂O₂ for 60 s showed significantly higher efficacy by reducing E. coli O157:H7 on strawberries and raspberries by 3.3- and 5.3-log units, respectively. Similarly, Salmonella on strawberries and raspberries was inactivated by 2.8- and 4.9-log units after 60-s WPL–H₂O₂ treatments. For decontamination of MNV-1, a 60-s WPL treatment reduced the viral titers on strawberries and raspberries by 1.8- and 3.6-log units, respectively and the combination of WPL and H₂O₂ did not enhance the treatment efficiency. These results demonstrated that the WPL treatment can be a promising chemical-free alternative to chlorine washing for decontamination of berries destined for fresh-cut and frozen berry products. WPL–H₂O₂ treatment was the most effective treatment in our study for decontamination of bacterial pathogens on berries, providing an enhanced degree of microbiological safety for berries.     

Survival of Escherichia coli O157:H7 in soil and on carrots and onions grown in fields treated with contaminated manure composts or irrigation water

Many foodborne outbreaks of enterohemorrhagic Escherichia coli O157:H7 infection have been associated with the consumption of contaminated vegetables. On-farm contaminations through contaminated manure or irrigation water application were considered likely sources of the pathogen for several outbreaks. Field studies were done to determine the survival of E. coli O157:H7 on two subterranean crops (carrots and onions), and in soil fertilized with contaminated manure compost or irrigated with contaminated water. Three different types of composts, PM-5 (poultry manure compost), 338 (dairy manure compost) and NVIRO-4 (alkaline stabilized dairy manure compost), and irrigation water were inoculated with an avirulent strain of E. coli O157:H7 at 10⁷ cfu g⁻¹ and 10⁵ cfu ml⁻¹, respectively. A split-plot block design plan was used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but with contaminated irrigation water applied) and five replicates for a total of 25 plots, each measuring 1.8×4.6 m², for each crop. Composts were applied to soil as a strip at a rate of 4.5 metric tons ha⁻¹ before carrots and onions were sown. Contaminated irrigation water was sprayed once on the vegetables at the rate of 2 l per plot for this treatment 3 weeks after carrots and onions were sown. E. coli O157:H7 survived in soil samples for 154–196 days, and was detected for 74 and 168 days on onions and carrots, respectively. E. coli O157:H7 survival was greatest in soil amended with poultry compost and least in soil containing alkaline-stabilized dairy manure compost. Survival profiles of E. coli O157:H7 on vegetables and soil samples, contaminated either by application of contaminated compost or irrigation water, were similar. Hence, preharvest contamination of carrots and onions with E. coli O157:H7 for several months can occur through both contaminated manure compost and irrigation water.     

Virgin olive oil and olive fruit minor constituents as affected by irrigation management based on SWP and TDF as compared to ETc in medium-density young olive orchards (Olea europaea L. cv. Cornicabra and Morisca)

This study investigated the effect of different irrigation managements, based on the measurement of the stem water potential (SWP) and the trunk diameter fluctuations (TDF) of the olive tree, as compared to the ET-FAO methodology, with regard to the minor constituents composition of virgin olive oil (VOO) and olive fruit in two different experimental olive orchards (Olea europaea L. Cornicabra cv. and Morisca cv.). No clear relationships between the water stress integral, both seasonal and from DOY 229–277, and the oleuropein content in the drupes were found. Nevertheless, a good agreement between the content of this biophenol and the minimum SWP of the olive trees, measured from the beginning of August to the end of the irrigation season, were found (r² = 0.88–0.95 and r² = 0.90–0.95 in Cornicabra and Morisca cultivars, respectively). A lower minimum water potential corresponded therefore with a higher biophenol content in the drupe and consequently with a superior phenolic content in VOO. In both cultivars, the volatile compounds most affected by the water status of olive trees were hexanal, E-2-hexenal and hexan-1-ol, showing an inverse relationship with the water stress integral observed. Furthermore, it was observed that the irrigation scheduling based on the SWP measurement, with a threshold of ?1.2 MPa provided VOO in both cultivars with a similar phenolic and volatile composition with regard to those obtained with the FAO treatment.     

Effects on Escherichia coli inactivation and quality attributes in apple juice treated by combinations of pulsed light and thermosonication

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 (360 μs, 3 Hz) treatments were selected and the juice exposed to energy dosages of 4.03 J/cm² (‘low’ (L)) and 5.1 J/cm² (‘high’ (H)) corresponding to 51.5 and 65.4 J/mL, respectively. The juice was also processed by TS (24 kHz, 100 μm) at 40 °C for 2.9 min (L) or 50 °C for 5 min (H), corresponding to 1456 and 2531 J/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 4.9 log CFU/mL (for TS (H) and PL (H) respectively), while most of the combined treatments achieved reductions in the vicinity of 6 log CFU/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.     

Ultrasonically aided enzymatical effects on the properties and structure of mung bean starch

In this research, the effects of the high power dual-frequency ultrasound of 25 kHz + 40 kHz with α-amylase on the properties and structure of mung bean starch (MBS) were investigated. Various ultrasounds with α-amylase (5U/1 g of MBS) treatments were used: the frequency was respectively 25 kHz, 40 kHz, and 25 kHz + 40 kHz, but ultrasonic intensity was the same for each ultrasonic treatment. Both single and dual-frequency ultrasounds could promote starch hydrolysis. Brabender instrument was used to examine the viscosity of MBS. The results indicated that the ultrasound with α-amylase treatment of MBS obviously decreased the peak viscosity. The results of laser granulometry measurements showed a decrease in granular size. The decrease in peak viscosity and particle size was associated with ultrasound frequency. The scanning electric microscope (SEM) revealed that a few pores and channels were found on the starch treated with α-amylase. Furthermore, some deeper holes and more broken parts were observed on the starch sonicated with 25 kHz, 40 kHz, and 25 kHz + 40 kHz, and dual-frequency ultrasound with α-amylase had greater effects on MBS, compared to single frequency ultrasound.Industrial relevanceModified starch has excellent performance, and is widely used in food, papermaking, textile, medicine and so on. Its production method mostly used in industries is chemical method, which often causes some problems such as chemical residues and environmental pollution. In recent years, physical modification method has been paid a lot of attentions. As one of novel physical methods, ultrasound has wide applications in modified starch production. In our work, different frequency ultrasounds and enzymes were applied to the hydrolysis of mung bean starch. Their effects on the properties and structure of the starch were investigated. The experimental results and conclusion provide a useful background to the application of this novel method in starch processing industries.     

Interventions to control Salmonella contamination during poultry,cattle and pig slaughter

The fundamental principle of controlling microbial contamination during slaughter is based on sanitary and hygienic processes. Both choosing abattoir technologies and conducting individual operations should be approached with the primary goal of minimizing microbial load on the final product. Nevertheless, even when best hygienic abattoir practices are applied, complete prevention of all microbial contamination of carcasses is unachievable under commercial conditions. Therefore, in some situations it may be considered necessary to further reduce the microbial loads on carcasses through application of additional control interventions, i.e. decontamination treatments. Treatments applied on poultry carcasses or parts include water, steam and chemical solutions (e.g., lactic or acetic acid, chlorine-based compounds, cetylpyridinium chloride, and trisodium phosphate) and result in overall microbial reductions of 0.6–3.8 log units; antimicrobial activity of some chemicals (e.g., chlorine compounds) is reduced in the presence of organic material. Decontamination treatments of hides (pre-skinning) and/or cattle carcasses reduce Salmonella by < 0.7–5.1 log units. Salmonella prevalence reductions achievable by decontamination of porcine carcasses seem to be at least two-fold. Overall Salmonella reductions on final carcasses and meat can be significantly improved when multiple decontamination treatments are applied sequentially during slaughter and dressing operations. It is important to note that decontamination interventions should be validated and considered as part of a hazard analysis critical control points (HACCP)-based food safety system which is subject to verification and auditing, and they should never be used as a substitute for good sanitation and proper hygiene practices.     

Comparison of multiple chemical sanitizers for reducing Salmonella and Escherichia coli O157:H7 on spinach (Spinacia oleracea) leaves

Effectiveness of multiple chemical sanitizers on the reduction of Salmonella spp. and Escherichia coli O157:H7 on spinach was compared. Fresh spinach (Spinacia oleracea) was inoculated with a bacterial suspension containing multiple strains of rifampin-resistant Salmonella and E. coli O157:H7. Inoculated spinach leaves were treated with a water wash or water wash followed by 2% L-lactic acid at 55 °C, peroxyacetic acid (80 mg/L), calcium hypochlorite (200 mg/L), ozonated water (mg/L) or ClO₂ gas (1.2 or 2.1 mg/L). The l-lactic acid produced a 2.7 log CFU/g reduction for E. coli O157:H7 and a 2.3 log CFU/g reduction for Salmonella, statistically significant compared to water wash alone (P < 0.05), which resulted in a reduction of 0.7 log CFU/g for both pathogens. These findings indicate that 2% l-lactic acid at 55 °C may be an effective treatment for reducing pathogens on spinach leaves.     

Considerations for post-lethality treatments to reduce Listeria monocytogenes from fully cooked bologna using ambient and pressurized steam

During processing of ready-to-eat (RTE) deli meats, any secondary processing procedures such as peeling and cutting introduce the distinct possibility of cross-contamination between equipment, personnel, and food. To eliminate or reduce pathogens such as Listeria monocytogenes and ensure food safety, RTE deli meats can be pasteurized prior to or after packaging. In this study, ambient steam in-package pasteurization was compared with pressurized steam prepackaging pasteurization to reduce L. monocytogenes from fully cooked RTE bologna. The bologna (14 cm diameter×1.5 cm thickness) samples were surface-inoculated to contain about 8 log₁₀ of L. monocytogenes. To achieve 2 log reductions for L. monocytogenes, the bologna samples needed to be treated for about 10 s in pressurized steam at 131 °C or for about 2.5 min in ambient steam at 100 °C. The pasteurization time using pressurized steam treatment was about 75–90% shorter than using ambient steam treatment. Pressurized steam treatment may be integrated into a vacuum packaging unit to effectively eradicate L. monocytogenes from RTE meats just prior to sealing the retail packages to further reduce the treatment time, avoid post-treatment recontaminations by pathogens, and improve food safety without detrimentally affecting meat quality.