High-pressure processing treatment of beef burgers: Effect on Escherichia coli O157 inactivation evaluated by plate count and PMA-qPCR.

Propidium monoazide coupled to real time PCR (PMA-qPCR) is a novel methodology proposed for the quantification of viable bacteria in food after microbial inactivation treatments. The aim of this work was to assess the effectiveness of different pressure levels on the lethality of a pool of Escherichia coli O157 strains in beef burgers by plate count and PMA-qPCR using uidA as target gene. Also, the effect on native microbiota counts, E. coli O157 counts, and physiochemical parameters of beef burgers during storage in refrigeration and frozen conditions were assessed. The treatment at 600 MPa for 5 min was the most lethal and was selected for the evaluation of bacteria behavior under storage conditions. Native microbiota and E. coli O157 were not recovered during refrigerated and frozen storage (4°C for 7 days and -18°C for 35 days). Cooking weight loss, pH, chromatic parameters, and texture were affected by HPP. PRACTICAL APPLICATION: Practical Application: PMA-qPCR can be used as an alternative to assess microbial inactivation by different high pressure processing (HPP) conditions (pressure level, holding time and temperature) more rapidly than conventional plate counts. In addition, it has the benefit of being able to quantify viable but nonculturable bacteria from contaminated beef burgers after HPP. Moreover, this novel technique generates less pathogenic residues, which minimizes workers' exposure to human biohazards.

Physicochemical properties, degradation kinetics, and antioxidant capacity of aqueous anthocyanin-based extracts from purple carrots compared to synthetic and natural food colorants.

As a means to evaluate the potential of carrot anthocyanins as food colorants and nutraceutical agents, we investigated the physicochemical stability and antioxidant capacity of purple carrot extracts under different pH (2.5-7.0) and temperature (4-40 °C) conditions, in comparison to a commercial synthetic (E131) and a natural grape-based (GRP) colorant. During incubation, the colorants were weekly-monitored for various color parameters, concentration of anthocyanins and phenolics, and antioxidant capacity. Carrot colorants were more stable than GRP; and their thermal stability was equal (at 4 °C) or higher than that of E131 (at 25-40 °C). Carrot anthocyanins had lower degradation rate at low pH and temperature, with acylated anthocyanins (AA) being significantly more stable than non-acylated anthocyanins (NAA). Anthocyanins acylated with feruloyl and coumaroyl glycosides were the most stable carrot pigments. The higher stability of carrot colorants is likely due to their richness in AA and -to a lesser extent- copigmentation with other phenolics.

Combination of organic acids and low-dose gamma irradiation as antimicrobial treatment to inactivate Shiga toxin-producing Escherichia coli inoculated in beef trimmings: Lack of benefits in relation to single treatments.

The aim of this study was to assess the efficacy of lactic acid (LA), caprylic acid (CA), high- (HDI) and low- (LDI) dose gamma irradiation and LDI combined with LA or CA on the inactivation of a pool of Shiga toxin-producing Escherichia coli (STEC) strains inoculated on beef trimmings. The three most efficacious treatments were selected to study their effect on meat quality parameters and sensory attributes. The inoculum included five native STEC serogroups (O26, O103, O111, O145 and O157). The treatments applied were 0.5% LA, 0.04% CA, 0.5 kGy LDI, 2 kGy HDI, LDI+LA and LDI+CA. Beef trimmings were divided into two groups; one was inoculated with high (7 log CFU/g) and the other with low (1 log CFU/g) level of inoculum. Efficacy was assessed by estimating log reduction and reduction of stx- and eae-positive samples after enrichment, respectively. Results showed that treatments with organic acids alone were not effective in reducing STEC populations. For high inoculum samples, the most effective treatment was HDI followed by LDI+LA and LDI alone or combined with CA. For low inoculum samples, the most effective treatment was HDI followed by LDI alone or combined with organic acids. Concerning meat quality parameters and sensory attributes, irradiation treatments (LDI and HDI) caused minimal changes, while LDI+LA modified them significantly compared with the control. Therefore, based on our results, no benefits were observed after combining organic acids with gamma irradiation.

Inactivation of Shiga toxin-producing Escherichia coli in fresh beef by electrolytically-generated hypochlorous acid, peroxyacetic acid, lactic acid and caprylic acid.

Several studies have been conducted to verify the decontamination potential of electrolytically-generated hypochlorous acid, peroxyacetic acid, lactic acid and caprylic acid against Shiga toxin-producing Escherichia coli (STEC) in beef products. However, there is no consensus regarding their effectiveness. The aim of this study was to compare these four treatments under the same conditions and establish a ranking according to their effectiveness to inactivate STEC in fresh beef. Samples were inoculated with two levels of inoculum and rinsed for 15 s in 100 mL of antimicrobial solution treatment. Caprylic acid was the most effective treatment, followed by lactic acid and peroxyacetic acid. Electrolytically-generated hypochlorous acid had no effect. Sensory analysis showed no significant differences either in flavor or in color between samples treated with caprylic acid and reference samples. Caprylic acid appears to be an effective and viable alternative to conventional interventions frequently used for meat product decontamination.

Plum (Prunus salicina) peel and pulp microparticles as natural antioxidant additives in breast chicken patties.

Fiber microparticles (MPCs) separately obtained from peel and pulp of Japanese plum residues contained co-extracted ß-carotene, lutein, and α- and γ-tocopherols, as well as polyphenols (cyanidins, quercetin derivatives, pentameric proanthocyanidins). Peel and pulp MPCs were then separately evaluated as natural antioxidant additives (2.0% w/w level) in raw breast chicken patty, susceptible to oxidation. Their effect on technological properties was also analyzed. MPCs reduced in 50% the formation of thiobarbituric acid reactive substances (TBARS) in raw patties during 10-days storage at 4.0°C. Ferric reducing power (FRAP) was 77-157% higher in MPCs-added patties, especially with peel MPCs, being then attributed to the antioxidants supplied by these MPCs. It can be also associated to the highest α- and γ-tocopherol levels found in the peel MPCs-added patties, which remained high after cooking as well. Also, higher pectin and low lignin contents of pulp MPCs determined greater hydration, stabilized the cyanidins and, hence, the red color transferred to raw patties, and increased springiness of cooked patties. Plum peel and pulp MPCs are efficient additives for chicken meat products.

Effect of high-pressure treatment on hard cheese proteolysis.

The application of high hydrostatic pressure (HHP) treatment has been proposed to reduce the ripening time of cheese via modifications in the enzymatic activities or the substrate reactivity. Investigations on the effect of HHP on cheese proteolysis have been undertaken with either encouraging results or little effect according to the treatment conditions and the type of cheese, but information concerning the effect of HHP on the ripening of hard cooked cheese is still lacking. In this report, we describe the effect of HHP treatment on Reggianito cheese proteolysis. For that purpose, 1-d-old miniature cheeses (5.5-cm diameter and 6-cm height) were treated at 100 or 400MPa and 20°C for 5 or 10min, and control cheeses in the trial were not pressurized. All cheeses were ripened at 12°C during 90d. The HHP did not affect gross composition of the cheeses, but microbial load changed, especially because the starter culture count was significantly lower at the beginning of the ripening of the cheeses treated at 400MPa than in controls and cheeses treated at 100MPa. Cheeses treated at 400MPa for 10min had significantly higher plasmin activity than did the others; the residual coagulant activity was not affected by HHP. Proteolysis assessment showed that most severe treatments (400MPa) also resulted in cheeses with increased breakdown of αS1- and ß-CN. In addition, nitrogen content in soluble fractions was significantly higher in cheeses treated at 400MPa, as well as soluble peptides and free AA production. Peptide profiles and individual and total content of free AA in 60-d-old treated cheese were as high as in fully ripened control cheeses (90d). Holding time had an effect only on pH-4.6-soluble nitrogen fraction and plasmin activity; cheese treated for 10min showed higher values than those treated for 5min, at both levels of pressure assayed. We concluded that HHP treatments at 400MPa applied 1d after cheesemaking increased the rate of proteolysis, leading to an acceleration of the ripening process in Reggianito Argentino cheese, whereas 100-MPa treatments did not lead to significant changes.

High pressure treatments combined with sodium lactate to inactivate Escherichia coli O157:H7 and spoilage microbiota in cured beef carpaccio.

High-pressure treatments (400 and 600 MPa) combined with the addition of sodium lactate (1 and 3%) were tested to reduce Escherichia coli O157:H7 (STEC O157) and spoilage microbiota contamination in a manufactured cured beef carpaccio in fresh or frozen conditions. Counts of spoilage microorganisms and STEC O157 were also examined during the curing step to prepare the carpaccio. STEC O157 counts remained almost unchanged through the curing process performed at 1 ± 1 °C for 12 days, with a small decrease in samples with 3% of sodium lactate. High-pressure treatments at 600 MPa for 5 min achieved an immediate reduction of up to 2 logarithmic units of STEC O157 in frozen carpaccio, and up to 1.19 log in fresh condition. Counts of spoilage bacteria diminished below detection limits in fresh or frozen carpaccio added with sodium lactate by the application of 400 and 600 MPa. Maximum injury on STEC O157 cells was observed at 600 MPa in carpaccio in fresh condition without added sodium lactate. Lethality of high-pressure treatments on STEC O157 was enhanced in frozen carpaccio, while the addition of sodium lactate at 3% reduced the lethality on STEC O157 in frozen samples, and the degree of injury in fresh carpaccio.

Conventional freezing plus high pressure-low temperature treatment: Physical properties, microbial quality and storage stability of beef meat.

Meat high-hydrostatic pressure treatment causes severe decolouration, preventing its commercialisation due to consumer rejection. Novel procedures involving product freezing plus low-temperature pressure processing are here investigated. Room temperature (20°C) pressurisation (650MPa/10min) and air blast freezing (-30°C) are compared to air blast freezing plus high pressure at subzero temperature (-35°C) in terms of drip loss, expressible moisture, shear force, colour, microbial quality and storage stability of fresh and salt-added beef samples (Longissimus dorsi muscle). The latter treatment induced solid water transitions among ice phases. Fresh beef high pressure treatment (650MPa/20°C/10min) increased significantly expressible moisture while it decreased in pressurised (650MPa/-35°C/10min) frozen beef. Salt addition reduced high pressure-induced water loss. Treatments studied did not change fresh or salt-added samples shear force. Frozen beef pressurised at low temperature showed L, a and b values after thawing close to fresh samples. However, these samples in frozen state, presented chromatic parameters similar to unfrozen beef pressurised at room temperature. Apparently, freezing protects meat against pressure colour deterioration, fresh colour being recovered after thawing. High pressure processing (20°C or -35°C) was very effective reducing aerobic total (2-log(10) cycles) and lactic acid bacteria counts (2.4-log(10) cycles), in fresh and salt-added samples. Frozen+pressurised beef stored at -18°C during 45 days recovered its original colour after thawing, similarly to just-treated samples while their counts remain below detection limits during storage.