Thermosonication versus thermal processing of skim milk and beef slurry: Modeling the inactivation kinetics of psychrotrophic Bacillus cereus spores

Non-thermal processed foods are generally cold stored and distributed. The use of ultrasound for food preservation has attracted the interest of many research groups. In the current study, the thermosonication (TS, simultaneous ultrasound and thermal process) inactivation of psychrotrophic Bacillus cereus spores was investigated (24 kHz, 210 μm, 0.33 W/mL or W/g). First, the effectiveness of a 1.5 min TS process at 70 °C in skim milk, beef slurry, cheese slurry, and rice porridge was investigated. The TS was more effective than sole thermal treatment in reducing B. cereus spores in rice porridge, beef slurry and cheese slurry by 7, 6, and 4 fold, respectively. Then, the first-order D- and z-values for TS and thermal processing in skim milk and beef slurry, and the best model to fit TS inactivation of B. cereus spores in beef slurry were determined. The D_70 °C-values in skim milk were 2.9 min for TS and 8.6 min for the thermal treatment. And in beef slurry, values of 0.4 min for TS and 2.3 min for thermal were estimated. It was found that the Log-logistic model better described the TS spore inactivation in beef slurry. The ultrasound technology required 20–30 °C lower temperatures for the same spore inactivation, which resulted in better food quality and energy saving gains.     

Effect of high pressure homogenization on lactic acid bacteria phages and probiotic bacteria phages

To investigate the effect of high pressure homogenization on virus inactivation, phages specific for Lactobacillus delbrueckii, Lactobacillus helveticus, Streptococcus thermophilus, Lactococcus lactis, Lactobacillus paracasei and Lactobacillus plantarum were studied. The influence of pressure, number of passes, suspension medium and phage concentration were studied at 25 °C. Reductions in viability were proportional to pressure and number of passes, though the inactivation extent was phage-dependent. At 100 MPa, some bacteriophages were completely inactivated (6 log₁₀ reduction) after 3 or 5 passes, while others remained infective after 8 passes. For all phages, treatment at 60 MPa was insufficient for complete inactivation, even after 8 passes. No clear influence of suspending medium was observed. Inactivation seems to depend on phage concentration; the higher the initial load, the bigger the reduction achieved. Although these results showed that several phages studied are resistant to high-pressure homogenization, this strategy could be combined with others to control their presence in raw milk.     

Effects of high pressure treatment on indigenous enzymes in bovine milk: Reaction kinetics,inactivation and potential application

High pressure-induced inactivation of the indigenous milk enzymes alkaline phosphatase (ALP), γ-glutamyltransferase (GGT) and phosphohexoseisomerase (PHI) was studied in the pressure range 400–800 MPa at temperatures between 5 and 40 °C. With respect to pressure stability the following ranking was observed: ALP>GGT>PHI. PHI was inactivated after pressure treatment at 500 MPa and 20 °C for 10 min. In terms of reaction kinetics, inactivation of GGT followed first-order reaction kinetics in the range of 400–800 MPa whereas a reaction order of 1.5 was found for ALP. Reactivation of pressure-treated ALP was observed at low enzyme activity resulting from severe pressure treatment and 2 h storage at 35 °C. The influence of process temperature on the pressure-induced inactivation of GGT and ALP was limited in the range 5–40 °C.     

High-pressure homogenisation of raw bovine milk. Effects on fat globule size distribution and microbial inactivation

Whole raw milk was processed using a 15 L h⁻¹ homogeniser with a high-pressure (HP) valve immediately followed by a cooling heat exchanger. The influence of homogenisation pressure (100–300 MPa) and milk inlet temperature T_in (4°C, 14°C or 24°C) on milk temperature T₂ at the HP valve outlet, on fat globule size distribution and on the reduction of the endogenous flora were investigated. The T_in values of 4–24°C led to milk temperatures of 14–33°C before the HP valve, mainly because of compression heating. High T_in and/or homogenisation pressure decreased the fat globule size. At 200 MPa, the d_4.3 diameter of fat globules decreased from 3.8±0.2 (control milk) to 0.80±0.08 μm, 0.65±0.10 or 0.37±0.07 μm at T_in=4, 14°C or 24°C, respectively. A second homogenisation pass at 200 MPa (T_in=4°C, 14°C or 24°C) further decreased d_4.3 diameters to about 0.2 μm and narrowed the size distribution. At all T_in tested, an homogenisation pressure of 300 MPa induced clusters of fat globules, easily dissociated with SDS, and probably formed by sharing protein constituents adsorbed at the fat globule surface. The total endogenous flora of raw milk was reduced by more than 1 log cycle, provided homogenisation pressure was ⩾200 MPa at T_in=24°C (T₂∼60°C), 250 MPa at T_in=14°C (T₂∼62°C), or 300 MPa at T_in=4°C (T₂∼65°C). At all T_in tested, a second pass through the HP valve (200 MPa) doubled the inactivation ratio of the total flora. Microbial patterns of raw milk were also affected; Gram-negative bacteria were less resistant than Gram-positive bacteria.     

Survival of Lipase during Manufacture of Nonfat Dry Milk

Extracellular lipases from several strains of Pseudomonas fluorescens were active against milk fat. The activity of P. fluorescens strain B52 lipase in reconstituted NDM using β-naphthyl caprylate as substrate was 70% of that found with skim milk; however, hydration of the NDM at 4°C for 12 h resulted in 85% recovery of activity. As little as .0025% (vol/vol) of P. fluorescens spent media was detected in reconstituted skim milk powder using β-naphthyl caprylate. The process of freeze-drying or spray-drying without heating had little effect on either native or P. fluorescens B52 lipase. The bacterial lipase activity was reduced by 12 to 21% and 55 to 59% in NDM treated with low heat (72°C/16 s) and high heat (110°C/2 min), respectively, while the native lipases were completely inhibited by these treatments. Both native and bacterial enzymes were stable when stored in NDM for extended periods at 20°C. In a limited study of commercial NDM samples, microbial lipase was not detected, suggesting that the quality of the raw milk was sufficiently high to restrict the presence of heat-stable lipolytic enzymes.     

Evaluation of pulsed electric field and minimal heat treatments for inactivation of pseudomonads and enhancement of milk shelf-life

Pulsed Electric Field (PEF) treatment of milk provides the opportunity to increase the shelf-life of fresh milk for distribution to distant markets. PEF treatments were evaluated in sterile (UHT) milk to determine the inactivation of added spoilage Pseudomonas isolates and the subsequent gains in microbial shelf-life (time taken to reach 10⁷ CFU mL^− 1). Little inactivation of Pseudomonas was achieved at 15 or 40 °C compared with 50 or 55 °C. The greatest inactivation (> 5 logs) was achieved by processing at 55 °C with 31 kV cm^− 1 (139.4 kJ L^− 1). Heat treatment at the application temperature without PEF treatment caused minimal inactivation of Pseudomonas (only 0.2 logs), demonstrating that the inactivation of the Pseudomonas was due to the PEF treatment rather than the heat applied to the milk. At added Pseudomonas levels of 10³ and 10⁵ CFU mL^− 1, the microbial shelf-life of PEF-treated milk was extended by at least 8 days at 4 °C compared with untreated milk. The total microbial shelf-life of the PEF-treated milk was 13 and 11 days for inoculation levels of 10³ and 10⁵ CFU mL^− 1 respectively. The results indicate that PEF treatment is useful for the reduction of pseudomonads, the major spoilage bacteria of milk.Industrial relevancePseudomonads are the major psychrotrophic spoilage microflora of refrigerated, stored HTST pasteurised milk. Long-life (UHT) products are an important component of milk sales in South-East Asia, but in recent years there has been an increasing demand for less processed milk products with extended shelf-life. The recent practice of shipping fresh bulk milk from Australia to South-East Asian countries has necessitated additional heat treatment prior to export and on arrival, to achieve the required shelf-life. Pulsed electric field treatment of HTST milk, applied alone or in combination with mild heat under optimised conditions, offers the opportunity of shelf-life extension, while limiting the reduction in quality attributes of milk associated with more severe additional heat treatments.     

Inactivation of bacteriophages by thermal and high-pressure treatment

Dairy companies commonly experience fermentation failures due to bacteriophages that are spread mainly by milk, whey or air. Heat or high-pressure treatment may potentially reduce the phage titre, but further knowledge about the inactivation kinetics is desirable. Inactivation experiments were carried out with the commonly occurring lactococcal phages P001 and P008. Phage suspensions in calcium-enriched M17-broth were heated at 55–80 °C, or high-pressure treated at up to 600 MPa. Kinetic analysis showed that the order of inactivation reaction was above 1; thus, inactivation kinetics were approximated by a non-linear regression model. The Arrhenius parameters, rate constant, k_p,T, and activation energy, E_A (for heat treatments), and the volume of activation, ΔV^# (for pressure treatments) were calculated. Both measured and calculated results indicate that phage P008 was the more heat- and pressure-resistant of the two. By combining the results from heat and pressure inactivations, a pressure–temperature diagram for phage P008 was established.     

Properties of low-fat stirred yoghurts made from high-pressure-processed skim milk

Physical properties of stirred yoghurt made from reconstituted skim milk that was high-pressure (HP)-treated at 100, 250 or 400 MPa, at 25, 70 or 90 °C, for 10 min, prior to inoculation with yoghurt cultures, were studied; portions of milk HP-treated at 25 °C were also heat-treated at 90 °C for 10 min before or after pressure treatment. Control yoghurts were made from skim milk given a heat treatment at 90 °C for 10 min. Fermentation time was not affected by treatment applied to the milk. HP treatment of skim milk at 25 °C, before or after heat treatment, gave stirred yoghurts of similar viscosities to that made from conventionally heat-treated milk. Lower viscosities were obtained when stirred yoghurts were made with milk HP-treated at elevated temperatures. A model is proposed to correlate properties of yoghurt with HP/heat-induced changes in interactions and structures of protein in the milk samples.Industrial relevanceTo meet end user expectations, the dairy industry needs to diversify its product range by tailoring specific functionalities. To meet these expectations, new processing methods such as high-pressure processing are of interest for their potential to achieve specific and/or novel functionalities and/or improve efficiencies, including reduced chemical and water use. In this paper, an investigation of the use simultaneous pressurization and heating of milk before the manufacture of stirred yoghurt is presented.     

Heat-Induced Protein Changes in Milk Processed by Vat and Continuous Heating Systems

This study investigated and compared the effects of heating system and residence times on the physicochemical properties and interactions of casein and whey proteins in heated milk. Milk was processed by vat heating (85°C for 10 to 40 min), HTST heating (98°C for .5 to 1.87 min), UHT heating (140°C for 2 to 8 s), cooled, and fractionated into casein and whey by isoelectric precipitation.β-Lactoglobulin A and B variants were partially denatured by HTST and UHT heating and totally denatured by vat heating. Increasing residence time caused significant (P<.01) increases in denaturation of both β-lactoglobulin variants in UHT and HTST heating systems and of α-lactalbumin in the vat heating system. Surface hydrophobicity and sulfhydryl content were negatively correlated with whey protein denaturation. Sodium dodecyl sulfate electrophoresis of the casein fraction of heated milk indicated the presence of a high molecular weight component that would not enter the gel. Addition of 2-mercaptoethanol to heated casein samples dissociated this component, with the concurrent appearance of β-lactoglobulin and α-lactalbumin bands. In HTST and UHT heating systems, ratio of β-lactoglobulin to κ-casein increased linearly from the complex with increasing residence time.     

Alkaline phosphatase and microbial inactivation by pulsed electric field in bovine milk

The effects of pulsed electric field (PEF) treatments at field intensities of 25–37 kV cm^− 1 and final PEF treatment temperatures of 15 °C and 60 °C on the inactivation of alkaline phosphatase (ALP), Total Plate Count (TPC), Pseudomonas and Enterobacteriaceae counts were determined in raw skim milk. At 15 °C, PEF treatments of 28 to 37 kV cm^− 1 resulted in 24–42% inactivation in ALP activity and < 1 log reduction in TPC and Pseudomonas count, while the Enterobacteriaceae count was reduced by at least 2.1 log units to below the detection limit of 1 CFU mL^− 1. PEF treatments of 25 to 35 kV cm^− 1 at 60 °C resulted in 29–67% inactivation in ALP activity and up to 2.4 log reduction in TPC, while the Pseudomonas and Enterobacteriaceae counts were reduced by at least 5.9 and 2.1 logs, respectively, to below the detection limit of 1 CFU mL^− 1. Kinetic studies suggested that the effect of field intensity on ALP inactivation at the final PEF treatment temperature of 60 °C was more than twice that at 15 °C. A combined effect was observed between the field intensity and temperature in the inactivation of both ALP enzyme and the natural microbial flora in raw skim milk.Industrial relevanceMilk has been pasteurised to ensure its safety and extend its shelf life. However, the need for retaining heat-sensitive nutrient and sensory properties of milk has resulted in interest in the application of alternative technologies. The results of the current study suggest that PEF as a non-thermal process can be employed for the treatment of raw milk in mild temperature to achieve adequate safety and shelf life while preserving the heat-sensitive enzymes, nutrients and bioactive compounds.     

Partial renneting of pasteurised bovine milk: Casein micelle size,heat and storage stability

The effects of partial renneting at low temperature on the casein micelle (CM) size and the storage stability of milk were investigated. Low chymosin concentrations (≤ 0.03 IMCU mL^− 1) was applied to pasteurised skim milk at 4 °C and enzyme activity was terminated by thermal application at 60 °C/3 min and 85 °C/30 min, referred to as low heat (LHT) and high heat (HHT) treatment milk, respectively. The addition of rennet with concentrations of 0.01, 0.02 and 0.03 IMCU mL^− 1 for 15 min resulted in κ-casein hydrolysis of 10, 20 and 25%, respectively. Moreover, mean CM size of milk was reduced by up to 10 nm. For LHT milk, the renneted micelles appeared to be stable for up to 17 days, especially in response to the application of 0.01 IMCU mL^− 1 and at a storage temperature of 4 °C. Severe heating at 85 °C/30 min to inactivate the enzyme caused an increase in CM size.     

High-pressure and temperature effects on the inactivation of Bacillus amyloliquefaciens,alkaline phosphatase and storage stability of conjugated linoleic acid in milk

Milk rich in conjugated linoleic acid (CLA, 42 ± 3 mg g^− 1 fat) was used to evaluate the impact of high-pressure sterilization (HPS). The pressure, temperature and time needed to reduce 7-log of Bacillus amyloliquefaciens endospores were determined in the presence of nisin (4–64 mg L^− 1). In addition, the inactivation of alkaline phosphatase was evaluated. After HPS treatment, the remaining CLA and formation of hydroperoxides were monitored during storage up to 60 d at 25 °C. The addition of nisin (≥ 16 mg L^− 1) to milk significantly enhanced the inactivation of B. amyloliquefaciens (7-log reduction) after treatment at 600 MPa, 120 °C and 5 min of holding time. These conditions were selected to evaluate the impact of HPS on the CLA retention and hydroperoxides formation. Milk with the addition of nisin and treated with HPS delivered higher retention of CLA and a lower concentration of hydroperoxides compared with the UHT equivalent process (125 °C/15 s and 135 °C/10 s).Industrial relevanceHigh-pressure sterilization is a valuable alternative to produce superior quality milk products in cases where traditional thermal treatments have failed. This study evaluated the impact of processing conditions on the conjugated linoleic acid content at conditions where commercial sterilization has been achieved (7-log reduction of B. amyloliquefaciens). The outcomes of this study are considered as a step further for the development of high-pressure sterilized milk.     

Influence of ohmic heating/osmotic dehydration treatments on polyphenoloxidase inactivation,physical properties and microbial stability of apples (cv. Granny Smith)

The combined effect of ohmic heating (OH) and osmotic dehydration (OD) with vacuum impregnation (VI), on the polyphenoloxidase (PPO) inactivation, physical properties and microbial stability of apples stored at 5 °C or 10 °C was analyzed. The treatments were performed using a 65% (w/w) sucrose solution and with ohmic heating at 13 V/cm at 30 °C, 40 °C or 50 °C for 90 min. Examination of the dehydrated samples showed that the water loss and the solid gain were greater with the OD/OH and VI/OH treatments at 50 °C. PPO was completely inactivated by the OD/OH and VI/OH treatments at 50 °C. There was a correlation between the PPO activity, the color change and the browning index of the treated and stored samples; the values for these parameters were stable when PPO was inactivated. The lowest loss of firmness and color was obtained with the VI/OH treatment at 50 °C. The shelf-life of the apples treated with VI/OH at 50 °C and stored at 5 °C was extended to more than 4 weeks. Therefore, the VI/OH treatment at 50 °C was determined to be the best process for dehydrating apples.Industrial relevanceThe aim of this research was 1 to study the combined effect of ohmic heating (OH) and osmotic dehydration (OD) with vacuum impregnation (VI) on the polyphenoloxidase inactivation and microbial stability of osmotically dehydrated apples stored at either 5 °C or 10 °C. Two technologies, OH and OD were performed at 30, 40 or 50 °C with an electric field intensity of 13 V/cm and conventional heating for 90 min. The results showed a correlation between the PPO activity, the color change and the browning index of the treated and stored samples; the values were stable when PPO was inactivated. PPO was completely inactivated by the OD/OH and VI/OH treatments at 50 °C. The shelf-life of the apples treated was extended to more than 4 weeks. Under the investigated conditions, VI/OH treatment at 50 °C and stored at 5 °C may be considered the better minimal processing that preserves the fresh-like properties.     

Gel-Forming Characteristics of Milk Proteins. 1. Effect of Heat Treatment

Skim milk with or without preheating (60 to 80°C for 30 min) were acid coagulated at 60 to 80°C for 1 h with glucono-delta-lactone. Preheating below 70°C has no effect on gel firmness and water-holding capacity. When coagulated below 70°C, the gels were weak and had low water-holding capacity. When coagulated at 80°C, the gels were solid and had high water-holding capacity. Gels prepared from skim milks preheated to above 80°C had a different quality: when coagulated at less than 70°C, gel firmness increased slightly, and when coagulated at 80°C, gel firmness decreased sharply. Change in the accessibility of sulfhydryl groups in milk protein caused by heating, was also measured using Ellman's reagent. Changes in the gel-forming property of milk protein, caused by the heat treatment, were closely related to increase in available sulfhydryl groups in milk proteins, and also were related to heat denaturation of whey protein or the formation of β-lactoglobulin/κ-casein complex.     

Pressure-induced inactivation of bacteria through pressure-assisted thawing using a thermal buffer zone.

Effect of thermal buffer zone was examined on the microbial inactivation through a pressure-assisted thawing. A plastic bag of bacterial suspension enclosed with a thermal buffer zone was frozen at − 50 °C, and treated for 20 min with a pressure-assisted thawing in water of 4 °C. A reduction of 8-log cycle was obtained at 200 MPa for the stationary growth phase cells of Escherichia coli that was suspended in 1% skim milk and enclosed with wheat flour/water paste and two polytetrafluoroethylene plates. When 100% ethanol was used as a thermal buffer and the samples were pressured at 194 MPa in 1% skim milk, levels of E. coli and Listeria monocytogenes were reduced by 6-log cycle and 7-log cycle, respectively. Staphylococcus aureus decreased by 4-log cycle.Industrial relevanceThis work will contribute to new developments in the pressure processing of foods, since the use of a thermal buffer zone in pressure-assisted thawing was very effective in enhancing the level of pressure-induced microbial inactivation.     

Thermal stability of plasminogen activators and plasminogen activation in heated milk

Thermal stabilities of bovine plasminogen (PG) activators, tissue and urokinase type (t-PA and u-PA), and their impact on activation of PG, were studied after application of various heating conditions (65, 75, 85, or 90 °C for 15, 20, or 30 s), in both milk and buffer systems. Both t-PA and u-PA were thermally stable in milk heated at ⩽75 °C. However, almost half of the t-PA activity and 30% of u-PA activity was lost after heating milk at 85 °C for 30 s. A lower heat stability of both t-PA and u-PA was observed in buffer than in milk. The decrease in level of PG was more pronounced than that of active plasmin in milk heated at ⩾85 °C for 30 s; however, the residual level of PG was considerably higher than the residual level of active PL. Overall, results indicated that u-PA plays a more significant role than t-PA in the activation of PG during storage of heated milk.     

Effect of preheating and other process parameters on whey protein reactions during skim milk powder manufacture

Skim milk powder was manufactured in a milk powder plant using different preheating temperatures, concentrate heating temperatures and spray drying temperatures. Varying the preheating conditions from 70 °C for 52 s to 120 °C for 52 s had a marked effect on the denaturation of $\beta$-lactoglobulin A, $\beta$-lactoglobulin B, $\alpha$-lactalbumin, bovine serum albumin (BSA), and immunoglobulin G. In contrast, varying concentrate heating temperature (65–74 °C) and inlet/outlet air dryer temperature (200/101 °C–160/89 °C) had a minimal effect on whey protein denaturation. Most of the whey protein denaturation and association with the casein micelle occurred in the preheating section of the powder plant. Aggregation of β-lactoglobulin (β-lg) and BSA predominantly involved disulphide bonds. Although, greater than 90% of the β-lg and BSA was denatured after preheating at 120 °C for 52 s, the extent of association with the casein micelle was lower, 50% for β-lg and 75% for BSA.     

Thermal inactivation of Bacillus anthracis Sterne in irradiated ground beef heated in a water bath or cooked on commercial grills

The thermal stability of heat-shocked and non-heat-shocked spores of the virulence-attenuated Sterne strain of Bacillus anthracis was evaluated at select temperatures in irradiated, raw ground beef (25% fat) heated in a water bath or cooked using two different commercial grills. For the former, 3-g portions of inoculated ground beef were packaged in bags that were completely immersed in a temperature-controlled circulating water bath held at 65 °C (149 °F), 70 °C (158 °F), 75°(167 °F), and 80 °C (176 °F) for a predetermined length of time. For the latter, formed ground beef patties (95-g each) were inoculated with spore stock A or B of the Sterne strain and then cooked on a commercial open-flame gas grill or on a commercial clamshell electric grill to achieve target internal temperatures of either 71.1 °C (160 °F), 82.2 °C (180 °F), or 93.3 °C (200 °F). Cooking ground beef patties on commercial grills, resulted in reductions of ca. 0.8 to 3.5 log₁₀ CFU/g for spore stocks A and B of B. anthracis Sterne after heating to 71.1 °C (160 °F), 82.2 °C (180 °F), or 93.3 °C (200 °F) on either the open-flame gas grill which required ca. 9.6 min to reach the target internal temperatures or on the clamshell electric grill which required ca. 4.0 min to reach the target internal temperatures. In comparison, our data using a water bath system and heating at 65° to 80 °C predict nearly 4 log reductions in spore levels for short times, ~½ min, depending possibly on the temperature. Thus, our data suggest that models based on heating ground beef in a water bath is not a good predictor of reductions of levels of spores of B. anthracis Sterne strain that would be obtained when cooking ground beef patties on commercial grills under conditions that may be typically used by consumers and/or retail establishments. Nevertheless, our data validated that cooking ground beef patties on a commercial grill at a temperature considered to be “well-done” and a temperature (71.1 °C;160 °F) recommended by the USDA/FSIS, is effective at killing spores of B. anthracis Sterne.Industrial relevanceHeating ground beef in a water bath or cooking ground beef patties on commercial grills under conditions simulating those that are used by consumers and/or that occur in retail food service establishments is effective at killing spores of B. anthracis Sterne.     

Heat resistance of Lactobacillus paracasei isolated from semi-hard cheese made of pasteurised milk

Nine strains of non-starter Lactobacillus paracasei isolated from semi-hard cheese made of pasteurised milk were selected for their anticlostridial activity. Resistance to thermisation (60 °C, 5 min) and pasteurisation (73 °C, 15 s) was investigated using a submerged-coil apparatus. MRS broth-grown cultures of all nine strains survived thermisation in buffer. The level of resistance to thermisation was strain dependent and lower for freshly grown cells (stationary phase cells) than for resting cells (freshly grown cells kept diluted 10-fold in MRS broth at 17 °C for 6 days). None of the nine Lb. paracasei strains survived or recovered after pasteurisation in buffer when grown in MRS broth, while seven of the nine strains survived pasteurisation in UHT whole milk when grown in milk. Identity of the strains was successfully confirmed during the experiments using repetitive-PCR analysis. The potential of Lb. paracasei strains to survive pasteurisation of cheese milk was demonstrated.     

Hard surfaces decontamination of enteropathogenic and Shiga toxin-producing Escherichia coli using bacteriophages

Three Myoviridae phages (DT1, DT5 and DT6) specific for pathogenic Escherichia coli were studied, either individually or as cocktails, for their lytic activity on in vitro challenge tests. Also, cocktail ability to reduce artificial contamination on hard surfaces (glass coverslips and stainless steel coupons) by three pathogenic Escherichia coli strains (EPEC920, non-O157 STEC ARG4827 and O157:H7 STEC464) was tested. Assays of phage stability during refrigerated storage showed that the three phages evaluated retained a high viability after two months at 4 °C. Challenge tests showed high reductions in viable cells, of up to 6.4 log CFU ml^− 1, for all tested strains at 37 °C. Efficiency was somewhat lower at 4 °C, though biocontrol levels were still good, reaching values of up to 3.8 log CFU ml^− 1. Considering only results obtained at 37 °C, phage cocktails produced the highest reduction in most cases. Treatments with phage cocktails produced complete inactivation (ca. 5–6 log CFU ml^− 1) of EPEC920 and O157:H7 STEC464 on glass coverslips, and of EPEC920, non-O157 STEC ARG4827 and O157:H7 STEC464 on stainless steel coupons, at both temperatures (4 °C and 37 °C) and multiplicity of infection (ca. 10³ and 10⁷) tested. However, some strains not detected at 3 h were sometimes detected at 24 h, and inactivation of non-O157 STEC ARG4827 on glass coverslips was never accomplished; viable cell reductions in all these cases ranged from 1.2 to 5.4 log CFU ml^− 1. Our results suggest that lytic phages, either individually or as a cocktail, may be useful for reducing contamination on hard materials used in food processing surfaces. To our knowledge, this is the first study focused on the use of bacteriophages to reduce contamination of food processing surfaces by EPEC and non-O157 STEC strains.