Thermal and photochemical degradation of myoglobin pigments in relation to colour stability of sliced dry-cured Parma ham and sliced dry-cured ham produced with nitrite salt

Lipophilic and hydrophilic extracts of the red pigments from Parma ham and nitrosylated pigment of dry-cured ham produced with nitrite salt were prepared with acetone/water (75/25 v/v %) solution and aqueous phosphate buffer, respectively. The spectral characteristics differed for both the lipophilic and the hydrophilic Parma ham pigment compared with the dry-cured ham produced with nitrite salt. The red lipophilic pigment(s) extractable from Parma ham was(were) found to be very stable towards thermal degradation in acetone/water (75/25 v/v %) solution for temperatures up to 70 °C in contrast to the lipophilic pigment(s) extractable from dry-cured ham produced with nitrite salt, which was(were) found to have an energy of activation of 99 kJ/mol for thermal degradation. In contrast, quantum yields for photodegradation of the lipophilic ham pigments exposed to 366 nm (420 nm) monochromatic light were larger for Parma ham than for nitrite-cured ham [1.6×10^–5 (6.9×10^–6) versus 1.6×10^–6 (2×10^–6) mol einstein^–1] as determined for acetone/water (75/25 v/v %) solution. In agreement with these findings for the extracted lipophilic pigments, sliced Parma ham showed better colour stability than sliced dry-cured ham produced with nitrite salt, when stored in the dark at low oxygen concentration, in contrast to a faster initial discolouration for Parma ham when exposed to light, as shown for chilled storage for 35 days under retail conditions for the two products each packed at two oxygen levels (0.4 and 21%).     

Studies on the antioxidative activity of red pigments in Italian-type dry-cured ham

Aqueous phosphate buffer extracts and acetone/water extracts of pigments from Parma ham were assessed as antioxidants by (1) electron spin resonance spectroscopy using a spin probing technique to evaluate their efficiencies as scavengers of free radicals, and (2) by electrochemical measurement of oxygen depletion rate in an aqueous methyl linoleate emulsion to evaluate their efficiencies as chain-breaking antioxidant, and using both methods, compared with the effect of apomyoglobin and nitrosylmyoglobin. Aqueous phosphate extracts and acetone/water extracts of Parma ham pigment both scavenged a semi-stable nitroxide radical (Fremy's salt), and both extracts reduced the rate of oxygen consumption for lipid peroxidation (initiated by metmyoglobin) very efficiently. For apomyoglobin no antioxidative capacity was observed, and the heme moiety of the pigment(s) of Parma ham were concluded to have antioxidative properties. The more lipophilic pigment, as extracted by acetone/water, had the most significant effect, and its ability to inhibit lipid oxidation was further tested in a model food system based on cooked pork. The lipid oxidation was increasingly inhibited by increasing additions from 0.12 ppm to 0.24 ppm Parma ham pigment, and the pigment protected -tocopherol against degradation in a concentration dependent manner.     

Spectral characterisation of red pigment in Italian-type dry-cured ham. Increasing lipophilicity during processing and maturation

Spectroscopic studies of Parma ham during processing revealed a gradual transformation of muscle myoglobin, initiated by salting and continuing during ageing. Electron spin resonance spectra did, however, conclusively show that the pigment in dry-cured Parma ham at no stage is a nitrosyl complex of ferrous myoglobin as found in brine-cured ham and Spanish Serrano hams. Both near-infra red reflectance spectra of sliced ham and UV/visible absorption spectra of extract of hams, obtained with aqueous buffer or acetone, showed the presence of different red pigments at varying processing stages for both solvents. Especially, the pigment extracted with aqueous buffer exhibited unique spectral features different from those of well-known myoglobin derivatives. At the end of processing, the pigment(s) becomes less water extractable, while the fraction of red pigment(s) extractable with acetone/water (75%/25%) increases throughout the processing time up to full maturation at 18 months. The chemical identity of the 6th ligand of myoglobin could not be conclusively established, but possible candidates are discussed. The partition of the pigment(s) between pentane and acetone/water showed a strong preference for pentane, suggesting that only the heme moiety is present in the acetone/water extract, and that Parma ham pigment is gradually transformed from a myoglobin derivative into a non-protein heme complex, which was found to be thermally stable in acetone/water solution     

Astaxanthin Extraction from Shrimp Wastes and its Stability in 2 Model Systems

Abstract: The objective of this work was to study the stability of astaxanthin, obtained from shrimp wastes, and incorporated to 2 model systems: egg albumin protein solution and sunflower oil. Shrimp wastes were ensiled by a treatment with formic/acetic acids (4%–4% v/w wastes) and stored at 4 °C for 24 h. The pigment was extracted with organic solvents (petroleum ether:acetone:water, 15 : 75 : 10) and concentrated. The storage parameters studied were: illumination (light/dark), temperature (4/20 °C), atmosphere (air/air-free), and storage time (0, 1, 2, 3, 4, 5 wk). Results showed that total xantophylls and astaxanthin were more stable in sunflower oil than in the protein system. Total xantophylls showed more stability than astaxanthin, possibly due to the presence of other, more stable carotenoids quantified together with xantophylls. Astaxanthin concentration was significantly affected by storage time; its degradation followed a first-order reaction rate under all the studied conditions. This pigment was stable only for 17 d, even when stored in air-free flasks, under refrigeration, and in the dark. Practical Application: Shrimp catching and farming generate large amounts of polluting wastes; they can be an important source of added-value red-orange pigments. However, these pigments are highly unstable to various transformation processes and to storage conditions. This research studied the effect of storage on 2 model systems (protein and lipid) on pigment degradation.     

Industrial application of an antilisterial strain of Lactobacillus sakei as a protective culture and its effect on the sensory acceptability of cooked, sliced, vacuum-packaged meats.

The application of a protective lactic acid bacterium (LAB) during the commercial production of cooked meat products is described. The LAB, a strain of Lactobacillus sakei, was previously isolated from cooked ham and inhibited growth of Listeria monocytogenes and Escherichia coli O157:H7 in this product. L. sakei was applied to the cooked products at a concentration of 10(5)-10(6) cfu/g immediately before slicing and vacuum-packaging using a hand-operated spraying bottle. The LAB strain inhibited growth of 10(3) cfu/g of a cocktail of three rifampicin resistant mutant L. monocytogenes strains both at 8 degrees C and 4 degrees C. Consumer acceptance tests of cooked ham and of servelat sausage, a Norwegian non-fermented cooked meat sausage, showed that control and inoculated products were equally acceptable. The products were still acceptable after storage for 28 days at 4 degrees C and, after opening the packages, for a further 5 days at 4 degrees C. The findings presented here confirm that the L. sakei strain is suitable for use as a protective culture and may technically easily be implemented in the commercial production of cooked meat products.     

超高压处理抑制低温烟熏火腿中的优势腐败菌

研究尝试应用微生物菌体总RNA提取代替DNA提取,进而通过反转录-PCR( RT-PCR),结合变性梯度凝胶电泳(denaturing gradient gel electrophoresis,DGGE)技术,以期揭示超高压处理后低温烟熏火腿中腐败微生物的存活情况,探索RNA-DGGE手段判定超高压处理后微生物存活状态的可行性.分别以400 MPa和600 MPa的压力在室温(22℃)条件下,对包装后的烟熏火腿进行10 min超高压处理,未经高压处理样品作对照,于4℃冷藏条件下,贮藏1、15、30、60、90 d,直接提取样品中微生物的总RNA,对其进行RT-PCR和DGGE指纹图谱分析.DGGE指纹图谱显示,超高压处理对烟熏火腿中的优势腐败菌具有较强的抑制作用,且随压力的升高抑菌效应增强;超高压处理后烟熏火腿微生物种群结构变得单一,Weissella viridescens和Leuconostoc mesenteroides是超高压处理后烟熏火腿中的优势腐败菌.基于菌体总RNA提取的DGGE手段能够有效检测超高压处理后微生物的存活状况,揭示超高压对低温烟熏火腿中优势腐败微生物的抑菌效果.     

Effect of cooking bag and netting packaging on the quality of pork ham during water cooking

As a preliminary test for combining water cooking with vacuum cooling in soup of pork ham, three package treatments were designed to study the effect of cooking bag and netting on the quality of water cooked ham, i.e. ham cooked with a cooking bag and without a cooking bag (single netting and double netting). For treatments without a cooking bag, the results indicated that there was no significant superiority of ham cooked with double netting compared with ham cooked with single netting on the processing efficiency and quality characteristics. Although the hams cooked with a bag performed better in some chemical retentions and pigment, the water contents were significantly lower than those hams cooked in single netting (P<0.05), and there was a higher shrinkage tendency compared with the hams cooked without a bag. For the processing characteristics and texture properties of pork ham, there were no significant differences observed among the treatments with and without a cooking bag in terms of the combined effect of cooking and cooling (P>0.05). By considering the safety, convenience, cost, and the recovery effect on the quality changes of ham during vacuum cooling in soup, cooking with single netting is a better choice for future research.     

Influence of NaCl content and cooling rate on outgrowth of Clostridium perfringens spores in cooked ham and beef

The effect of NaCl concentration and cooling rate on the ability of Clostridium perfringens to grow from spore inocula was studied with the use of a process that simulates the industrial cooking and cooling of smoked boneless ham and beef roasts. NaCl was added to ground cooked hams A and B (which were commercially obtained) to obtain levels of 2.4, 3.1, 3.6, and 4.1% (wt/wt) and 2.8, 3.3, 3.8, and 4.3% (wt/wt), respectively, and to raw ground beef to obtain levels of 0, 1, 2, 3, and 4% (wt/wt). Ham C, a specially formulated, commercially prepared product, was supplemented with NaCl to obtain levels of 2.0, 2.5, 3.0, and 3.5%. The samples were inoculated with a three-strain mixture of C. perfringens spores to obtain concentrations of ca. 3 log10 CFU/g. Portions of meat (5 g each) were spread into thin layers (1 to 2 mm) in plastic bags, vacuum packaged, and stored at -40 degrees C. Thawed samples were heated at 75 degrees C for 20 min and subsequently cooled in a programmed water bath from 54.4 to < or = 8.5 degrees C in 15, 18, or 21 h. For the enumeration of C. perfringens, samples were plated on tryptose-sulfite-cycloserine agar and incubated in an anaerobic chamber at 37 degrees C for 48 h. Population densities for cooked ham and beef increased as cooling time increased, and NaCl exerted a strong inhibitory effect on the germination and outgrowth of C. perfringens. For beef, while 3% NaCl completely arrested growth, pathogen numbers increased by > or = 3, 5, and 5 log10 CFU/g in 15, 18, and 21 h, respectively, when the NaCl level was <2%. C. perfringens did not grow during cooling for 15, 18, or 21 h in ham samples containing > or = 3.1% NaCl. Results obtained in this study suggest that a 15-h cooling time for cooked ham, which is normally formulated to contain >2% NaCl, would yield an acceptable product (with an increase of <1 log10 CFU/g in the C. perfringens count); however, for beef containing <2% NaCl, C. perfringens populations may reach levels high enough to cause illness.     

Effect of high pressure treatment on microbial populations of sliced vacuum-packed cooked ham

In this study, culture-dependent and culture-independent approaches were used to reveal the microbial diversity and dynamic changes occurring in sliced vacuum-packed cooked ham after high pressure processing (HPP, 400MPa or 600MPa for 10min at 22°C) during refrigerated storage over 90days. Direct extraction of genome DNA and total RNA from meat samples, followed by PCR-denaturing gradient gel electrophoresis (DGGE) and RT-PCR-DGGE on 16S rDNA V3 region, was performed to define the structure of the bacterial populations and active species in pressurized cooked ham. Results showed that HPP affected differently the various species detected. The predominant spoilage organisms of cooked ham, such as Lactobacillus sakei and Lactobacillus curvatus, were found to be very sensitive to pressure as they were unable to be detected in HPP samples at any time during refrigerated storage. Weissella viridescens and Leuconostoc mesenteroides survived HPP at 600MPa for 10min at 22°C and were responsible for the final spoilage. An RNA-based DGGE approach clearly has potential for the analysis of active species that have survived in pressurized cooked ham. High pressure processing at 400 or 600MPa for 10min at room temperature (22°C) has a powerful inhibitory effect on the major spoilage bacteria of sliced vacuum-packed cooked ham. High pressure treatment may lead to reduced microbial diversity and improve the products' safety.     

Determination of Critical Oxygen Level in Packages for Cooked Sliced Ham to Prevent Color Fading During Illuminated Retail Display

ABSTRACT:  The effect of packages with different oxygen transmission rates (OTR), different gas-to-product-volume (GP) ratios, and various levels of residual oxygen after packaging on the color stability of cooked ham exposed to commercial retail light conditions was studied. Sliced cooked ham was packaged in thermoformed packages with OTR of 0.04 and  0.06 mL O₂/pkg × 24 h  and GP ratios of 2.6 and 4.1. After packaging, the packages were additionally divided into groups with 4 levels of residual oxygen ranging from 0.09% to 0.46%. The packaged ham was stored in darkness at 4 °C up to 33 d, and during the storage period samples were withdrawn and exposed to light for 2 d before instrumental and visual color evaluation. In order to maintain an acceptable color of this particular ham product when exposed to typical retail light conditions, the highest acceptable level of oxygen in the headspace of the packages was 0.15% oxygen at the time of illumination. This threshold level was independent of the storage time before light exposure. A residual oxygen level of below 0.15% just after packaging combined with the package with the lowest OTR  (0.04 mL O₂/pkg × 24 h)  and the lowest GP ratio (2.6) was the optimal condition for maintaining the color of the tested ham product throughout the entire storage period.     

Use of antimicrobial biodegradable packaging to control Listeria monocytogenes during storage of cooked ham

The antimicrobial effect against L. monocytogenes of biodegradable films (alginate, zein and polyvinyl alcohol) containing enterocins was investigated. Survival of the pathogen was studied by means of challenge tests performed at 6 degrees C during 8 and 29 days, for air-packed and vacuum-packed sliced cooked ham, respectively. Air packaging was tested with two concentrations of enterocins (200 and 2000 AU/cm2). Control air-packed cooked ham showed an increase of L. monocytogenes from 10(4) to 10(7) CFU/g after 8 days. By contrast, packaging with antimicrobial films effectively slowed down the pathogen's growth, leading to final counts lower than in control lots. Air-packaging with alginate films containing 2000 AU/cm2 of enterocins effectively controlled L. monocytogenes for 8 days. An increase of only 1 log unit was observed in zein and polyvinyl alcohol lots at the same enterocin concentration. Vacuum packaging with films containing enterocins (2000 AU/cm2) also delayed the growth of the pathogen. No increase from inoculated levels was observed during 15 days in antimicrobial alginate films. After 29 days of storage, the lowest counts were obtained in samples packed with zein and alginate films containing enterocins, as well as with zein control films. The most effective treatment for controlling L. monocytogenes during 6 degrees C storage was vacuum-packaging of sliced cooked ham with alginate films containing 2000 AU/cm2 of enterocins. From the results obtained it can concluded that antimicrobial packaging can improve the safety of sliced cooked ham by delaying and reducing the growth of L. monocytogenes.     

Reuterin,lactoperoxidase, lactoferrin and high hydrostatic pressure treatments on the characteristics of cooked ham

The effect of reuterin, lactoperoxidase system (LPS) and lactoferrin (LF) combined with high hydrostatic pressure (HHP) on the characteristics of sliced cooked ham during 35 days at 4 and 10 °C were investigated. Reuterin and LPS inhibited the growth of total microorganisms during 35 days at 4 and 10 °C, whereas a regrowth at 10 °C was observed when HHP was applied. Combined treatments kept total viable counts below 1.5 log cfu/g after 35 days at 10 °C. Regarding the effect of treatments on colour of cooked ham, LPS alone or in combination with HHP slightly affected L*, a* and b* values, but these changes tended to attenuate during storage. Likely, slight differences were registered in shear strength values among control and treated cooked ham. The accumulation of volatile compounds was reduced in cooked ham treated with LPS and LF in combination with HHP, even under abuse temperature conditions (10 °C).Industrial relevanceLPS applied in combination with HHP was the most effective treatment at reducing the growth of total microorganisms in refrigerated cooked ham with minor changes in its characteristics. The antimicrobial activity of such combined treatment against food-borne pathogens, which has also been reported in RTE foods, points to its usefulness to assure a safe product of sensory characteristics similar to those of untreated cooked ham.     

Growth characteristics of Listeria monocytogenes as affected by a native microflora in cooked ham under refrigerated and temperature abuse conditions

This study examined the growth characteristics of Listeria monocytogenes as affected by a native microflora in cooked ham at refrigerated and abuse temperatures. A five-strain mixture of L. monocytogenes and a native microflora, consisting of Brochothrix spp., isolated from cooked meat were inoculated alone (monocultured) or co-inoculated (co-cultured) onto cooked ham slices. The growth characteristics, lag phase duration (LPD, h), growth rate (GR, log₁₀ cfu/h), and maximum population density (MPD, log₁₀ cfu/g), of L. monocytogenes and the native microflora in vacuum-packed ham slices stored at 4, 6, 8, 10, and 12 °C for up to 5 weeks were determined. At 4-12 °C, the LPDs of co-cultured L. monocytogenes were not significantly different from those of monocultured L. monocytogenes in ham, indicating the LPDs of L. monocytogenes at 4-12 °C were not influenced by the presence of the native microflora. At 4-8 °C, the GRs of co-cultured L. monocytogenes (0.0114-0.0130 log₁₀ cfu/h) were statistically but marginally lower than those of monocultured L. monocytogenes (0.0132-0.0145 log₁₀ cfu/h), indicating the GRs of L. monocytogenes at 4-8 °C were reduced by the presence of the native microflora. The GRs of L. monocytogenes were reduced by 8-7% with the presence of the native microflora at 4-8 °C, whereas there was less influence of the native microflora on the GRs of L. monocytogenes at 10 and 12 °C. The MPDs of L. monocytogenes at 4-8 °C were also reduced by the presence of the native microflora. Data from this study provide additional information regarding the growth suppression of L. monocytogenes by the native microflora for assessing the survival and growth of L. monocytogenes in ready-to-eat meat products.     

巴马火腿红色色素的研究进展

综述了巴马火腿红色色素研究的最新进展。巴马火腿在腌制时不添加硝酸盐或亚硝酸盐 ,经过长期的加工过程 ,巴马火腿肉具有稳定的红色。巴马火腿的红色色素与添加硝酸盐或亚硝酸盐腌制的普通火腿的红色色素具有不同的吸收光谱、颜色稳定性和抗氧化性。根据巴马火腿红色色素的吸收光谱、荧光光谱、高压液相色谱和高分辨率电喷雾电离质谱 ,证实了巴马火腿的红色色素是锌 原卟啉IX。     

Efficacy of pulsed light for shelf-life extension and inactivation of Listeria monocytogenes on ready-to-eat cooked meat products

Pulsed light (PL) was tested for its utility to improve the microbial quality and safety of ready-to-eat cooked meat products. Vacuum-packaged ham and bologna slices were superficially inoculated with Listeria monocytogenes and treated with 0.7, 2.1, 4.2 and 8.4 J/cm². PL treatment at 8.4 J/cm² reduced L. monocytogenes by 1.78 cfu/cm² in cooked ham and by 1.11 cfu/cm² in bologna. The effect of PL on lipid oxidation and sensory properties was also investigated. The 2-thiobarbituric acid values were very low and chromaticity parameters were within the normal values reported for cooked meat products. PL at 8.4 J/cm² did not affect the sensory quality of cooked ham, while treatments above 2.1 J/cm² negatively influenced the sensory properties of bologna. The combination of PL and vacuum packaging provided ham with an additional shelf-life extension of 30 days compared with only vacuum packaging. The shelf-life of bologna was not extended by PL.

Industrial relevance

The efficacy of pulsed light for the decontamination of surfaces offers excellent possibilities to ensure food safety and to extend shelf-life of ready-to-eat (RTE) products. The results of this study indicate that Listeria monocytogenes can be reduced by approximately 2 log cfu/cm² in RTE cooked ham and 1 log cfu/cm² in bologna using a fluence of 8.4 J/cm². This dose does not affect the sensory properties of ham and triples its shelf-life when compared with conventional RTE products. On the contrary, fluences above 2.1 J/cm² are not suitable for the treatment of bologna since sensory quality is modified.     

诺邓火腿红色素的分离纯化及结构鉴定

为探究诺邓火腿红色素化学本质,采用75%丙酮溶液提取,结合C₁₈固相萃取小柱进行分离纯化,通过紫外-可见光光谱(ultraviolet spectroscopy,UV-Vis)、荧光光谱、超高效液相色谱-串联质谱(ultra-high performance liquid chromatography-tandem mass spectrometry,UPLC-MS/MS)、傅里叶变换红外光谱(Fourier transform infrared,FTIR)和核磁共振(nuclear magnetic resonance,NMR)共同表征诺邓火腿红色素的化学结构。结果表明：在UV-Vis中416 nm处有1个强吸收峰,546 nm和584 nm处有2个弱对称吸收峰,符合金属卟啉特征;以420 nm激发,红色素在590 nm处有1个强荧光发射峰,644 nm处有1个弱荧光发射峰,与Zn-原卟啉IX(Zn protoporphyrin IX,ZnPP)标准品比对后高度重合,表明卟啉环中的金属离子是锌离子;在UPLC-MS/MS的正离子(m/z 625.177 9[M+...     

Effects of Lactic Acid on the Growth Characteristics of Listeria monocytogenes on Cooked Ham Surfaces

The surfaces of ready-to-eat meats are susceptible to postprocessing contamination by Listeria monocytogenes. This study examined and modeled the growth characteristics of L. monocytogenes on cooked ham treated with lactic acid solutions (LA). Cooked ham was inoculated with L. monocytogenes (ca. 10(3) CFU/g), immersed in 0, 0.5, 0.75, 1.0, 1.25, 1.5, and 2.0% LA for 30 min, vacuum packaged, and stored at 4, 8, 12, and 16°C. LA immersion resulted in <0.7 log CFU/g immediate reduction of L. monocytogenes on ham surfaces, indicating the immersion alone was not sufficient for reducing L. monocytogenes. During storage, no growth of L. monocytogenes occurred on ham treated with 1.5% LA at 4 and 8°C and with 2% LA at all storage temperatures. LA treatments extended the lag-phase duration (LPD) of L. monocytogenes and reduced the growth rate (GR) from 0.21 log CFU/day in untreated ham to 0.13 to 0.06 log CFU/day on ham treated with 0.5 to 1.25% LA at 4°C, whereas the GR was reduced from 0.57 log CFU/day to 0.40 to 0.12 log CFU/day at 8°C. A significant extension of the LPD and reduction of the GR of L. monocytogenes occurred on ham treated with >1.25% LA. The LPD and GR as a function of LA concentration and storage temperature can be satisfactorily described by a polynomial or expanded square-root model. Results from this study indicate that immersion treatments with >1.5% LA for 30 min may be used to control the growth of L. monocytogenes on cooked meat, and the models would be useful for selecting LA immersion treatments for meat products to achieve desired product safety.     

Red Pigment of Parma Ham and Bacterial Influence on its Formation

The red pigment of Parma ham was compared with the myoglobin derivatives present in meat and meat products. Spectral patterns of 75% acetone extracts and electron spin resonance spectra from Parma ham differed from those of the myoglobin derivatives. Staphylococci isolated from Parma ham generated red myoglobin derivative from metmyoglobin. Model fermented sausage prepared by inoculation with the isolates developed a more desirable red color without nitrite or nitrate treatment. The red pigment of Parma ham and the model sausage appeared to be the same myoglobin derivative. The reddening of Parma ham is probably caused by the action of bacteria.     

Co-culture experiments demonstrate the usefulness of Lactobacillus sakei 10A to prolong the shelf-life of a model cooked ham

This study investigated the usefulness of two selected lactic acid bacteria, Lactobacillus sakei subsp. carnosus (10A) and the lactocin S producing L. sakei 148 (LS5), to extend the shelf-life of cooked meat products. The interaction between these potential protective cultures and the spoilage organisms, Leuconostoc mesenteroides (LM4) and Brochothrix thermosphacta (BT1), were examined in co-culture studies on a model cooked ham product at 7 degrees C under vacuum packaged conditions. Furthermore, the influence of the glucose content of the model cooked ham on the interaction phenomena was investigated. When artificially contaminating the model cooked ham with BT1 at 10(2) cfu/g in combination with 10A at 10(5) cfu/g, the growth of BT1 was significantly slower compared to a simultaneous mono-culture experiment. In a similar experiment with LM4, LM4 reached a level of 10(7) cfu/g +/-14 days later when LM4 grew together with 10A compared to its growth in mono-culture. The lactocin S producing LS5 did not demonstrate an inhibitory action towards LM4 or BT1 and is therefore not useful as protective culture on cooked meat products. The glucose level of the model cooked ham had no influence on the observed antagonistic interactions of 10A towards LM4 or BT1, indicating that the action of the biopreservative 10A in cooked meat products is independent of the substrate glucose.     

High-pressure processing and antimicrobial biodegradable packaging to control Listeria monocytogenes during storage of cooked ham

The efficiency of combining high-pressure processing (HPP) and active packaging technologies to control Listeria monocytogenes growth during the shelf life of artificially inoculated cooked ham was assessed. Three lots of cooked ham were prepared: control, packaging with alginate films, and packaging with antimicrobial alginate films containing enterocins. After packaging, half of the samples were pressurized. Sliced cooked ham stored at 6 degrees C experienced a quick growth of L. monocytogenes. Both antimicrobial packaging and pressurization delayed the growth of the pathogen. However, at 6 degrees C the combination of antimicrobial packaging and HPP was necessary to achieve a reduction of inoculated levels without recovery during 60 days of storage. Further storage at 6 degrees C of pressurized antimicrobial packed cooked ham resulted in L. monocytogenes levels below the detection limit (day 90). On the other hand, storage at 1 degrees C controlled the growth of the pathogen until day 39 in non-pressurized ham, while antimicrobial packaging and storage at 1 degrees C exerted a bacteriostatic effect for 60 days. All HPP lots stored at 1 degrees C led to counts <100CFU/g at day 60. Similar results were observed when combining both technologies. After a cold chain break no growth of L. monocytogenes was observed in pressurized ham packed with antimicrobial films, showing the efficiency of combining both technologies.