Resistance of phages lytic to pathogenic Escherichia coli to sanitisers used by the food industry and in home settings

Phages are potentially useful as antimicrobial agents in food‐processing environments, provided they can remain active upon extended storage and in the presence of sanitisers. Survival of six phages lytic against enteropathogenic (EPEC) and shiga‐toxigenic (STEC) Escherichia coli strains was assessed upon storage at 4 °C, ?20 °C and ?70 °C in phosphate‐buffered‐saline (PBS) and Tris‐magnesium‐gelatine buffer (TMG) for up to 1 year. The phages were also exposed to ethanol, sodium hypochlorite, peracetic acid, quaternary ammonium chloride (biocide A), hydrogen peroxide/peracetic acid/peroctanoic acid (biocide B), p‐toluensulfonchloroamide (biocide D) and alkaline chloride foam (biocide C). Plaque‐forming units remained unchanged when the phages were stored at 4 °C in both buffers tested, but decreased by 3.5 and 5.7 log₁₀ PFU when stored in PBS at ?20 and ?70 °C, respectively. Moreover, TMG seems to be the most protective suspension medium with decreasing temperature because a 1?log₁₀ PFU reduction was observed at ?20 and ?70 °C. Incubation in 100% ethanol for 24 h reduced plaque counts only by 2.5 log₁₀ PFU. In 10 ppm of sodium hypochlorite and in biocide B (0.13%), the counts decreased by ~5 and ~6 log₁₀ PFU after 15 min. Finally, biocide A and D reduced counts by 4 and 2–4 log₁₀ PFU after 30 min and 8 h of incubation, respectively. Phages were completely inactivated only by peracetic acid and biocides C and E. Therefore, the phages evaluated might be potentially applied together with classical sanitisers such as ethanol and industrial biocides A, B and D, in disinfection programs against pathogenic STEC and EPEC strains.     

Coliphage as pressure surrogates for enteric viruses in foods

In this study the potential of using selected bacteriophages as pressure surrogates for hepatitis A virus (HAV) and Aichi virus (AiV) was investigated. The coliphages included, T₄, MS2, Qβ, λ imm 434, λ cI 857 and λ cI 857A. T₄ displayed similar pressure responses as HAV and was chosen for further study. The most pressure-resistant phage, MS2, was selected as a possible surrogate to estimate AiV inactivation by high pressure processing (HPP). HAV, AiV and their selected bacteriophage surrogates were treated at a range of pressures and times in three different media. All four were treated in phosphate-buffered saline (PBS), artificial seawater (ASW) or oyster slurry (OS) at 250, 400 or 500 MPa for 1, 5 or 10 min at 20 °C. While T₄ had similar pressure resistance to HAV under conditions of high (500 MPa) and lower pressure (250 MPa), inactivation trends were very different following treatment at 400 MPa and when the viruses were suspended in OS. MS2 showed similar resistance as AiV but at ambient treatment temperatures only. The highest levels of inactivation of MS2 were achieved at 60 °C and 500 MPa. AiV was eliminated at 60 °C for 5 min at ambient pressure, but > 3 log survived exposure to 60 °C at 500 MPa. This degree of protection by pressure may be important in determining the mechanisms of pressure and heat resistances in other viruses.Industrial relevanceGreater knowledge of the responses of viruses and their surrogates to high pressure will aid in the validation of new high pressure-processed food that may be at risk to contamination from HAV or other enteric viruses.     

Comparison of hydrostatic and hydrodynamic pressure to inactivate foodborne viruses

The effect of high hydrostatic pressure (HPP) and hydrodynamic pressure (HDP), in combination with chemical treatments, was evaluated for inactivation of foodborne viruses and non-pathogenic surrogates in a pork sausage product. Sausages were immersed in distilled water, 100-ppm EDTA, or 2% lactoferrin, and then inoculated with feline calicivirus (FCV), hepatitis A virus (HAV) or bacteriophage (MS2, phiX174, or T₄). Each piece was packaged individually and subjected to pressure by either HDP, HPP (500 MPa, 5 min, 4 °C), or control (no pressure). On sausages immersed in water, HPP and HDP significantly (P < 0.05) reduced titers of FCV by 2.89 and 2.70 log₁₀ TCID₅₀/ml, and HAV by log₁₀ 3.23 and 1.10, respectively, when compared to non-pressure-treated controls. Titers of T₄ (1.48 and 1.10 log₁₀ PFU/g) and MS2 (1.46 and 0.96 log₁₀ PFU/g) were also significantly reduced by HPP and HDP treatments, respectively, in combination with water. Inoculation of viruses and bacteriophage on a meat product may have protected viruses from complete inactivation by pressure treatments.

Industrial relevance

This is the first study to directly compare hydrostatic and hydrodynamic pressure technologies to inactivate microorganisms. This is also the first study to examine the inactivation of viruses and bacteriophages by pressure technology in a deli meat product. This study shows that viruses attached to meat surfaces may be protected from complete inactivation by hydrostatic and hydrodynamic pressure treatments, and these findings require more investigation into the survival of viruses in deli meat products.     

Development of a spray-dried conjugated whey protein hydrolysate powder with entrapped probiotics

Bifidobacterium animalis ssp. lactis ATCC27536 and Lactobacillus acidophilus ATCC4356 were encapsulated in a conjugated whey protein hydrolysate (WPH10) through spray drying. Probiotic cultures were added at the ratio of 1:1 into the conjugated WPH10 solution at a spiking level of about 10 log₁₀ cfu/mL. The mixture was spray dried in a Niro drier with inlet and outlet temperatures of 200°C and 90°C, respectively. The final dried product was determined for cell viability and further stored for 16 wk at 25°, 4°, and ?18°C to monitor viability and functionality. Micro images showed the presence of link bridges in non-conjugated WPH10, whereas, in the case of conjugated WPH10, round particles with pores were observed. The mean probiotic counts before and after spray drying were 10.59 log₁₀ cfu/mL and 8.98 log₁₀ cfu/g, respectively, indicating good retention of viability after spray drying. The solubility and wetting time of the WPH10-maltodextrin (MD) encapsulated probiotic powder were 91.03% and 47 min, whereas for WPH10, the solubility and wetting time were 82.03% and 53 min, respectively. At the end of storage period, the counts were 7.18 log₁₀ cfu/g at 4°C and 7.87 log₁₀ cfu/g at ?18°C, whereas at 25°C the counts were significantly reduced, to 3.97 log₁₀ cfu/g. The solubility of WPH-MD powder was 82.36%, 83.1%, and 81.19% at ?18°C, 4°C, and 25°C, respectively, and wetting times were 61 min, 60 min, and 63 min at ?18°C, 4°C, and 25°C, respectively. By contrast, for WPH10 powder, the solubility significantly reduced to 69.41%, 69.97%, and 68.99% at ?18°C, 4°C, and 25°C, and wetting times increased to 71 min, 70 min, and 72 min at ?18°C, 4°C, and 25°C, respectively. The conjugated WPH10 is thus demonstrated as a promising carrier for probiotics and can be further used as an ingredient for developing functional foods, to harness their enhanced functionality and health benefits derived from both WPH and probiotics.     

Combined high pressure and heat treatment effectively disintegrates spore membranes and inactivates Alicyclobacillus acidoterrestris spores in acidic fruit juice beverage

The commercial potential of high pressure and thermal processing (HPTP) was investigated against Alicyclobacillus acidoterrestris spores in commercial acidic apple juice beverage and in acidified and neutral potassium buffers. With starting spore counts prior to treatments being 6.5 and 7.2 log₁₀ respectively for strains AJA 66 (D_90°C 15.4 min) and ATCC 49025 (D_90°C 8.5 min), HPTP at 600 MPa at 80 °C for 3 min provided an optimal treatment with spore viability reduced below the detection limit for both strains. HPTP at 80 °C for 1 min and HPTP at 70 °C for 3 min achieved 4.1–4.5 log₁₀ CFU/mL reduction. HPTP at 70 °C for 1 min reduced the number of viable spores by 2.0–2.5-log₁₀ CFU/mL. Flow cytometry revealed the presence of membrane-compromised spores among culturable spores following HPTP and heat alone treatments at different temperatures. Electron microscopy clearly showed the efficiency of HPTP with crushed or hollow spores predominating after treatments. No correlation between HPTP susceptibility and genetic diversity was observed for two genotypes of A. acidoterrestris spores. The treatment combination provides a promising option for industrial utility since it requires lower heat and processing time.     

Thermal inactivation of Salmonella on chicken wings cooked in domestic convection and air fryer ovens

Chicken wings are among the most popular poultry products for home and foodservice consumption. Poultry products must be handled and cooked safely to decrease the risk of foodborne salmonellosis for consumers. This study aims to validate the use of domestic appliances (convection and air fryer ovens) for the thermal inactivation of Salmonella on chicken wings. Wings (n = 3, 46.5 ± 4.3 g) were inoculated with a five-strain cocktail of Salmonella (ca. 8 log₁₀ CFU/wing) and cooked in a convection oven (179.4°C) or an air fryer (176, 190, or 204°C) for 2, 5, 10, 15, 20, 22, or 25 min. Thermocouples recorded temperature profiles of wings and appliances. Salmonella counts were determined on XLD agar for rinsates (100 ml/sample), and rinsates were enriched to recover bacteria below the limit of quantification. The recommended internal cooking temperature (73.8°C) was achieved after a range of 7.5 to 8.5 min in both appliances. Salmonella counts were reduced by 6.5 log₁₀ CFU/wing when this temperature was achieved. Cumulative lethality (F-value) calculations predicted a 9-log reduction after 7.0 to 8.1 min of cooking. However, sample enrichments tested positive for Salmonella for all cooking times below 22 min. Ultimately, cooking at the temperature–time combinations recommended by manufacturers and online recipes helped achieve complete microbial elimination in both appliances. This study contributes to the validation of home cooking methods to ensure consumer safety.     

Enhanced inactivation of pectin methyl esterase in orange juice using modified supercritical carbon dioxide treatment

The aim of the study is to quantify the effect of ethanol addition and exposure surface on the inactivation of pectin methyl esterase (PME), a juice clarifying enzyme, in orange juice using supercritical carbon dioxide (SC‐CO₂). Addition of ethanol to the SC‐CO₂ at 2% (v/v) caused greater inactivation than SC‐CO₂ alone, with a maximum reduction of PME activity of 97% at 30 MPa and 40 °C for 60 min. As the surface area to volume ratio was increased, the rate of inactivation of PME increased. Analysis of first‐order reaction kinetic data revealed that D values were greatly influenced by ethanol addition and agitation. With the addition of 2% ethanol, the D value reduced by half, that is, 56 min from 109 min. With impeller agitation of the sample at 1100 ± 100 rpm, the D value for PME was further reduced to 43 and 30 min without and with ethanol, respectively. The activity of PME treated with SC‐CO₂ remained unchanged after 14 days of storage at 4 °C. Treatment did not significantly change pH or colour, but did significantly increase the cloud values of the juice, resulting in a cloud stabilised juice with similar qualities to fresh juice.     

High pressure thermal processing of pears: Effect on endogenous enzyme activity and related quality attributes

The effect of high pressure-thermal (HPT) processing (600 MPa, 20–100 °C) on the activity of pear enzymes and related quality attributes was investigated. HPT processing at 20 °C for 5 min resulted in 32%, 74% and 51% residual activities of polyphenol oxidase (PPO), peroxidase (POD) and pectin methylesterase (PME), respectively. Increasing processing temperature to 40 and 60 °C reduced the level of PPO and POD inactivation, with the maximum residual activities of 64% and 123%, respectively observed after 3-min treatments at 40 and 60 °C. Overall, HPT at 20 to 60 °C had minimal effect on quality, although enzymatic browning was observed upon air exposure. HPT at 80 to 100 °C caused almost complete inactivation of PPO and POD with 90% and 92% inactivation respectively after 3-min processing at 100 °C, which reduced browning upon air exposure. Nevertheless, the lowest texture retention of 22% was observed under this condition.Industrial relevanceThe study examined the effects of combined high pressure thermal processing on quality related pear enzymes and related instrumental quality attributes such as colour and texture. The study enabled identification of processing regimes for enzyme inactivation and quality retention. The excellent quality retention following HPP at 20 to 40 °C makes this condition suitable for ‘fresh-like’ small portion products for immediate consumption after unpacking that do not require complete PPO and POD inactivation. On the other hand, the almost complete inactivation of oxidative enzymes PPO and POD at 100 °C makes this condition more appropriate for the production of bulk products for food service applications or pureed ingredients for baby food, or pear pieces for yoghurt, that require PPO inhibition but not necessarily high firmness retention.     

Destruction of Salmonella enteritidis inoculated in liquid whole egg by high hydrostatic pressure: comparative study in selective and non-selective media

The destruction of Salmonella enteritidis inoculated in liquid whole egg at approximately 10⁷−10⁸cfu ml^−lwas studied under combinations of pressure (350 and 450 MPa), temperature (50, 20, 2 and −15°C) and time (5, 10, 15 min and cycles of 5+5 and 5+5+5 min). One non-selective medium (tryptone soy agar) and two selective media (brilliant green agar and salmonella-shigella) were used to evaluate viability of S. enteritidis after pressurization. The inactivation rate increased with pressure and exposure time, being minimal at 350 MPa and −15°C for 5 min (over 1 log₁₀of reduction) and reaching total inactivation (8 log₁₀of reduction) in several treatments at 50°C. Treatments in cycles showed greater effectiveness than continuous treatments of the same total time. The effect of pressure was enhanced by elevated temperatures. The higher counts were obtained in the non-selective medium, indicating the presence of injured cells after pressure treatment. D -values obtained for two temperatures (2 and 20°C) and different times (0–60 min) under controlled pressure (400 MPa) showed that microbial inactivation followed a first-order kinetics with a decimal reduction time evaluated in tryptone soy agar medium of 9·5 min at 2°C and 8·8 min at 20°C.     

Dairy bacteriophages isolated from whey powder: Thermal inactivation and kinetic characterisation

Fifty three bacteriophages of three lactic acid bacteria species (i.e., Lactococcus lactis, Leuconostoc pseudomesenteroides, Streptococcus thermophilus) isolated from whey powders and whey powder formulations, were tested for their thermal stability. Complete inactivation of Ln. pseudomesenteroides and S. thermophilus phages required 1 min heating at 85 °C and 90 °C, respectively. L. lactis phages exhibited the highest heat resistance and 16% of them were still detectable after heat treatment at 95 °C for 1 min. The most thermo-resistant phages of L. lactis (P956), Ln. pseudomesenteroides (P973) and S. thermophilus (P1008) were selected to determinate their kinetic parameters and lines of equal effects for 9-log inactivation. High D-values of 105 min (phage P956), 74 min (P973) and 25 min (P1008) were determined for thermal treatments at 75 °C, confirming previous findings that pasteurisation conditions are insufficient for adequate inactivation of thermo-resistant dairy phages.     

Impact of enzyme inactivation conditions during the generation of whey protein hydrolysates on their physicochemical and bioactive properties

The thermal inactivation conditions (75 °C × 35 min, 80 °C × 10 min, 85 °C × 5 min and 90 °C × 5 min) for Protamex? following bovine whey protein concentrate (WPC) hydrolysis was studied with the view to limiting WPC hydrolysate (WPH) aggregation while maintaining bioactivity. A decrease in the amount of large WPH aggregates formed was observed at inactivation temperatures ≤85 °C. However, the WPC appeared to be more hydrolysed on heating at 75 °C × 35 min, as Protamex? was active for longer under these heating conditions. Significantly (P < 0.05), higher WPH antioxidant (oxygen radical absorbance capacity – ORAC) activity was obtained on inactivation at temperatures ≤80 °C. In contrast, the dipeptidyl peptidase IV (DPP‐IV) inhibitory properties of all WPH samples were similar (P > 0.05). A reduction in thermal treatment from 90 °C × 5 min to 85 °C × 5 min was sufficient to decrease the amount of large aggregates formed in the hydrolysate without altering its bioactive properties.     

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.     

Combined effects of contact insecticides and 50 °C temperature on Sitophilus oryzae (L.) (Coleoptera: Curculionidae) in wheat grain

The effects of the insecticides deltamethrin, bifenthrin, thiamethoxam, spinosad and abamectin were tested in the laboratory in combination with extreme temperature of 50 °C to discover potential improvements of existing pest management programmes for Sitophilus oryzae (L.) control. Adults were released into wheat grain treated with three insecticide doses ranging 0.125–1.0 mg/kg and exposed to 50±1 °C temperature at the intervals of 0, 65, 75 and 85 min, and direct and combined effects were determined after 1, 2, 7 and 14 days of exposure/recovery at 25±1 °C and 60 ± 5% r. h., as well as impact on F₁ progeny production/reduction PR (%) after 8 weeks.The results showed that the mortality of S. oryzae adults increased with exposure/recovery duration more than under the activity of each insecticide alone and its interaction with extreme temperature. After 14 days, all three rates of deltamethrin (0.125–0.5 mg/kg), the two higher rates of bifenthrin (0.25 and 0.5 mg/kg) and the highest rates of abamectin (0.5 mg/kg) and thiamethoxam (1.0 mg/kg) caused maximum adult mortality (100%) and PR (100%) after weevil exposure to 50 °C already after the interval of 65 min, while spinosad had the same effect after 75 and 85 min, which effectiveness was 1.25–20 times higher than the activities of the insecticides and 50 °C temperature alone, considering all trial variants. The lowest rate of bifenthrin (0.125 mg/kg) was found after 65 min activity in combination with exposure to 50 °C, and especially spinosad (0.25 mg/kg) after 65 and 75 min, to have stimulated progeny production 17, 33 and 236%, respectively, while deltametrin showed 100% effectiveness against S. oryzae in all combinations of wheat grain treatment at 50 °C temperature, including the dose 0.125 mg/kg.     

Destruction of Salmonella Enteriditis inoculated onto raw almonds by high hydrostatic pressure

The effects of continuous (50,000, 60,000 and 70,000 psi with holding times of 5 and 10 min) and discontinuous (oscillatory) (six cycles at 60,000 psi with a holding time of 20 s) high hydrostatic pressure (HHP) treatments on the viability of two Salmonella Enteriditis strains (FDA and PT30) inoculated onto raw almonds were evaluated at 25, 50, and 55 °C. Complete inactivation of the S. Enteriditis was achieved in 0.1% peptone water after continuous pressurization at 60,000 psi and 25 °C for 5 min. Continuous pressurization of raw almonds inoculated with S. Enteriditis at 60,000 psi and 50 °C for 5 min resulted in less than a log reduction (log₁₀ 0.83) of vegetative cells. The decimal reduction time using the continuous pressurization parameters was determined to be 9.78 min. A discontinuous process consisting of six cycles of pressurization at 60,000 psi and 50 °C for 20 s provided greater than a one log reduction (log₁₀ 1.27 for FDA and log₁₀ 1.16 for PT30) of the S. Enteriditis concentration. The low water activity (a_w) of the almonds was found to impart baroprotective attributes on the S. Enteriditis cells. When the almonds were directly suspended in water and then pressurized, a log₁₀ reduction of 3.37 was achieved. HHP of certain dry foods appears to be feasible if the food is directly suspended in the pressurizing medium (water).     

Grape seed extract for foodborne virus reduction on produce

Grape seed extract (GSE) is reported to have antibacterial properties with few current studies on antiviral activity. Recently, we reported the effects of GSE against foodborne viral surrogates in vitro. This study evaluated the application of GSE (commercial Gravinol-S) against hepatitis A virus (HAV) and human norovirus surrogates, feline calicivirus (FCV-F9) and murine norovirus (MNV-1), on model produce. Washed and air-dried lettuce (3 × 3 cm²) and jalapeno peppers (25–30 g) were inoculated with FCV-F9, MNV-1, or HAV at high (∼7 log₁₀ PFU/ml) or low (∼5 log₁₀ PFU/ml) titers, and treated with 0.25, 0.5, 1 mg/ml GSE or water for 30 s to 5 min. Treatments were stopped/diluted with cell-culture media containing 10% heat-inactivated fetal bovine serum and evaluated using plaque assays. At high titers, FCV-F9 was reduced by 2.33, 2.58, and 2.71 log₁₀ PFU on lettuce; and 2.20, 2.74, and 3.05 log₁₀ PFU on peppers after 1 min using 0.25, 0.50, and 1 mg/ml GSE, respectively. Low FCV-F9 titers could not be detected after 1 min at all three GSE concentrations. Low titer MNV-1 was reduced by 0.2–0.3 log₁₀ PFU on lettuce and 0.8 log₁₀ PFU on peppers, without reduction of high titer. GSE at 0.25–1 mg/ml after 1 min caused 0.7–1.1 and 1–1.3 log₁₀ PFU reduction for high and low HAV titers, respectively on both commodities. Instrumental color analysis showed no significant differences between treated and untreated produce. GSE shows potential for foodborne viral reduction on produce as part of hurdle technologies.     

Effect of Air-Drying Conditions on Physico-chemical Properties of Osmotically Pre-treated Pomegranate Seeds

The drying of pomegranate seeds was investigated at 40 °C, 50 °C and 60 °C with air velocity of 2 m/s. Prior to drying, seeds were osmodehydrated in 55 °Brix sucrose solution for 20 min at 50 °C. The drying kinetics and the effects of osmotic dehydration (OD) and air-drying temperature on antioxidant capacity, total phenolics, colour and texture were determined. Analysis of variance revealed that OD and air-drying temperature have a significant influence on the quality of seeds. Both anthocyanin and total phenolic contents decreased when air-drying temperature increased. The radical diphenylpicril-hydrazyl activity showed the lowest antioxidant activity at 60 °C. Both chromatic parameters (L*, C* and h°) and browning index were affected by drying temperatures, which contributed to the discolouring of seeds. The final product has 22%, 20% and 16% of moisture; 0.630, 0.478 and 0.414 of a _w; 151, 141 and 134 mg gallic acid equivalent/100 g fresh matter (FM) of total phenolics; 40, 24, 20 mg/100 g FM of anthocyanins and 46%, 39% and 31% of antioxidant activity, for drying temperatures of 40 °C, 50 °C and 60 °C, respectively. In view of these results, the temperature of 40 °C is recommended as it has the lowest impact on the quality parameters of the seeds. Differential scanning calorimetry data provided complementary information on the mobility changes of water during drying. Glass transition temperature (Tg′) depends on moisture content and as consequence, on drying conditions. In fact, Tg′ of seeds dried at 60 °C (Tg′ = −21 °C) was higher than those dried at 50 °C (Tg′ = −28 °C) or 40 °C (Tg′ = −31 °C) and osmodehydrated seeds (Tg′ = −34 °C). During OD and drying process, the texture of seeds changed. The thickness of seeds shrank by 55% at 60 °C.     

Thermal and chemical inactivation of Lactobacillus virulent bacteriophage

The effect of thermal treatments and several biocides on the viability of Lactobacillus virulent phage P1 was evaluated. Times to achieve 99% inactivation (T₉₉) of phage at different treatment conditions were calculated. The thermal treatments applied were 63, 72, and 90°C in 3 suspension media (de Man, Rogosa, Sharpe broth, reconstituted skim milk, and Tris magnesium gelatin buffer). Phage P1 was completely inactivated in 5 and 10 min at 90 and 72°C, respectively; however, reconstituted skim milk provided better thermal protection at 63°C. When phage P1 was treated with various biocides, 800 mg/L of sodium hypochlorite was required for total inactivation (～7.3 log reduction) within 60 min, whereas treatment with 100% ethanol resulted in only a ～4.7 log reduction, and 100% isopropanol resulted in a 5.2-log reduction. Peracetic acid (peroxyacetic acid) at the highest concentration used (0.45%) resulted in only a ～4.-log reduction of phage within 60 min. The results of this study provide additional information on effective treatments for the eradication of potential phage infections in dairy plants.     

Effects of plasma-activated water on microbial growth and storage quality of fresh-cut apple

Fresh-cut ‘Fuji’ apples were immersed for 5 min in plasma-activated water (PAW) generated, by plasma generated with sinusoidal voltages at 7.0 kHz with amplitudes of 6 kV, 8 kV, and 10 kV, designated PAW-6, PAW-8, and PAW-10, respectively. The control group was soaked in distilled water for 5 min instead of PAW. The results indicated that the growth of bacteria, molds, and yeasts was inhibited by PAW treatments during storage at 4 ± 1 °C, especially the microbial inactivation with PAW-8, which was the most efficient. PAW-8 reduced the microbial counts by 1.05 log₁₀CFU g⁻¹, 0.64 log₁₀CFU g⁻¹, 1.04 log₁₀CFU g⁻¹ and 0.86 log₁₀CFU g⁻¹ for aerobic bacteria (aerobic plate counts), molds, yeasts and coliforms on day 12, respectively. In addition, the bacterial counts of fresh-cut apples treated with PAW were <5 log₁₀CFU g⁻¹, which did not exceed to the existing China Shanghai local standard (DB 31/2012–2013) during 12 days of storage. PAW treatments reduced superficial browning of fresh-cut apples without affecting their firmness and titratable acidity. In addition, no significant change was observed in antioxidant content and radical scavenging activity between the PAW-treated and control groups. It is suggested that PAW is a promising method for preservation of fresh-cut fruits and vegetables, which is usually beneficial to the quality maintenance of fresh-cut fruits and vegetables during storage.     

Pasteurization of carrot juice by combining UV-C and mild heat: Impact on shelf-life and quality compared to conventional thermal treatment

The combination of UV-C radiation and mild heat (UV-H) treatment is a promising strategy for synergistically increasing microbial inactivation in low UV-transmitting juices. In this research, we explored the suitability of UV-H treatment in carrot juice pasteurization and its impact on juice quality during shelf-life compared to that of thermal pasteurization. UV-H treatment at 60 °C (3.92 J/mL, 3.6 min) enabled reductions of over 5 log₁₀ cycles in the reference pathogens and a significant reduction in spoilage yeasts, bacteria, and bacterial spores. The activity of pectin methylesterase and polyphenol oxidase was reduced by UV-H treatment to levels close to those of low-temperature pasteurization (60 °C/18.1 min). The native population of total aerobic bacteria, lactic acid bacteria, and yeasts and molds of UV-H-treated juice remained undetectable during 29 days of cold storage. Furthermore, viscosity, cloud stability, and the color of fresh juice were better preserved by UV-H treatment than by thermal pasteurization throughout storage.Industrial relevanceThis study demonstrates that UV-H treatment is a beneficial alternative to conventional thermal processing in carrot juice pasteurization, since appropriate inactivation levels of pathogenic and spoilage microorganisms can be reached while better preserving the quality attributes of fresh juice throughout its shelf-life.     

Application of statistical process control,sampling, and validation for producing Listeria monocytogenes-free chicken leg quarters processed in steam followed by impingement cooking

Chicken leg quarters (180–230 g) were processed for 4 min in steam at 99°C and then in an air impingement oven for 24 min at an oven temperature of 232°C, an air velocity of 2 m/s, and a humidity of 60%. The cooked chicken leg quarters were sampled to measure for the end-point internal temperatures. Sampling size in each subgroup for the internal temperature measurements was determined based on a normal distribution at a confidence level of 95%. The process mean, range, and standard deviation at 95% confidence level were 73.9°C, 1.8°C, and 0.9°C, respectively, for the internal temperatures of the cooked chicken leg quarters. The process lethality was validated for up to 7  log₁₀ cfu/g reductions of Listeria monocytogenes in the cooked chicken leg quarters and verified by an inoculation study in which the chicken leg quarters were injected with 0.1 ml of the culture per cm² of the product surface area to contain 7–8 log₁₀ cfu/g of L. monocytogenes. This paper provided an approach for process control, sampling, and validation to reduce pathogens in fully cooked poultry products.