Non-thermal Preservation Technology Research Articles

Enhancing High-Pressure Bacterial Inactivation by Modified Atmosphere Packaging: Effect of Exposure Time and Cooked Ham Formulation

AbstractHigh-pressure processing (HPP) is a non-thermal preservation technology that can be applied as a control measure to inactivate pathogens and spoilage microorganisms once RTE meat products are packaged in a convenient format. HPP efficacy highly depends on product characteristics, but the impact of the sodium-reduced formulations and the effect of packaging atmosphere are scarcely known. The aim of the present work was to assess the effect of standard and sodium-reduced formulations from two different brands (A, B) under different packaging (vacuum and modified atmosphere packaging (MAP)) on the HPP inactivation kinetics of Listeria monocytogenes and spoilage lactic acid bacteria in cooked ham. Slices of cooked ham with standard and sodium-reduced formulations were inoculated with L. monocytogenes CTC1034 and Latilactobacillus sakei CTC746 (slime producer), packaged in vacuum and MAP (CO2:N2, 20:80), and pressurized (400 MPa/0–15 min) after 1 h (vacuum, MAP) or 24 h (MAP-exposed). Parameters of HPP inactivation kinetics were estimated by fitting the Weibull model to log reduction data. Results showed that the efficacy of HPP in sodium-reduced cooked hams tended to decrease compared to standard formulations, being the difference statistically significant for L. sakei. For L. monocytogenes, a significant enhancing effect of MAP was observed when HPP was applied just after packaging (1 h, MAP) of cooked ham of brand A. In the case of L. sakei, the inactivation by HPP was only enhanced in MAP-exposed samples. Therefore, the use of HPP as a control measure must be applied through a product-oriented approach considering the type of packaging and the time period between packaging and HPP.

Effects of Gas Composition on the Lipid Oxidation and Fatty Acid Concentration of Tilapia Fillets Treated with In-Package Atmospheric Cold Plasma.

Cold plasma (CP) is a non-thermal preservation technology that has been successfully used to decontaminate and extend the shelf life of aquatic products. However, the preservation effect of CP treatment is determined by several factors, including voltage, time, and gas compositions. Therefore, this study aimed to investigate the effects of gas composition (GasA: 10% O2, 50% N2, 40% CO2; GasB: air; GasC: 30% O2, 30% N2, 40% CO2) on the lipid oxidation of tilapia fillets treated after CP treatment. Changes in the lipid oxidation values, the percentages of fatty acids, and sensory scores were studied during 8 d of refrigerator storage. The results showed that the CP treatment significantly increased all the primary and secondary lipid oxidation values measured in this study, as well as the percentages of saturated fatty acids, but decreased the percentages of unsaturated fatty acids, especially polyunsaturated fatty acids. The lipid oxidation values were significantly increased in the GasC-CP group. After 8 d, clearly increased percentages of saturated fatty acids, a low level of major polyunsaturated fatty acids (especially linoleic (C18:2n-6)), and a decrease in the percentages of eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3) were found in GasC-CP; that is, the serious oxidation of lipids was found in the high O2 concentration group. In addition, the sensory score was also lower than that of the hypoxia CP group. Therefore, high O2 concentrations can enhance lipid oxidation and the changes in the fatty acid concentration. Controlling the O2 concentration is reasonable to limit the degree to which lipids are oxidized in tilapia after the in-package CP treatment.

Dielectric barrier discharge plasma delayed the textural hardening of bamboo shoots by regulating cell wall metabolism

Postharvest bamboo shoots may undergo a hardening process even under low-temperature storage. Dielectric barrier discharge plasma (DBDP) is a promising non-thermal preservation technology, which reportedly delays senescence and improves the texture of plants. The influences of DBDP treatment on the changes of quality attributes, cell wall components, and cell wall modifying enzymes in Lei bamboo (Phyllostachys praecox) shoots were investigated. DBDP treatment improved the shelf life, texture, and energy level while decreasing the cell membrane permeability, malondialdehyde content, and hydrogen peroxide contents of bamboo shoots. DBDP treatment obtained a higher ratio of water-soluble pectin to CDTA-soluble pectin contents as well as lower levels of cellulose and hemicellulose contents by regulating the cell wall modifying enzymes, inhibiting the self-assembly of pectin gels and cellulose-xyloglucan networks. Scanning and transmission electron microscopy showed that DBDP treatment slightly destabilized the cell wall and inhibited secondary cell wall formation. The results showed that DBDP treatment inhibited the hardening process and maintained a better texture of bamboo shoots under low-temperature storage.

Inactivation of Alicyclobacillus contaminans spores by dielectric barrier discharge plasma and its biological mechanism

Over the years, as an emerging technology, cold plasma (CP) has been widely used in the preservation of agricultural products. Alicyclobacillus spp. are spore-forming bacteria and difficult to inactivate. They adversely affect the economic value of agricultural products. Nevertheless, there are still few studies related to the inactivation of spores using CP. Herein, the inactivation effect and mechanism of dielectric barrier discharge plasma (DBDP) on Alicyclobacillus contaminans (A. contaminans) spores in phosphate-buffered saline and clarified apple juice were investigated. Plasma treatment at 75 V for 9 min achieved 99% inactivation of spores with the initial inocula of 7.13 and 5.72-log in PBS and apple juice, respectively. And the cell structure of the spores was severely disrupted leading to the leakage of the entocyte. Moreover, the surface properties of the spores were altered, making the adhesion of the spores to the hydrophobic surfaces and the stability of the bacterial suspension decreased leading to more agglomeration of the spores. Further results confirmed the intracellular homeostasis of the spores was also disrupted. Therefore, the inactivation mechanism of DBDP on spores was revealed from different perspectives, and our discoveries promote the theoretical progress in the use of plasma in food sterilization. Industrial relevanceAs an emerging nonthermal preservation technology, cold plasma has been used in food processing. In this study, we confirmed the feasibility of the inactivation of Alicyclobacillus contaminans spores in apple juice by dielectric barrier discharge plasma (DBDP) and investigated the mechanism of plasma inactivation of spores at the molecular biology level. This paper provides preliminary support for the application of low-temperature plasma in food processing such as apple juice.

Combined impact of high-pressure processing and slightly acidic electrolysed water on Listeria monocytogenes proteomes

Slightly acidic electrolysed water (SAEW) and high-pressure processing (HPP) are well-established non-thermal preservation technologies. This study investigated the deactivation mechanisms of Listeria monocytogenes by label-free quantitative proteomics analysis. Samples were treated through HPP (300 MPa for 3 min), SAEW (20 ppm available chlorine concentration), and their combinations. The KEGG pathway analysis found SAEW + HPP induced differentially expressed proteins (DEPs) associated to biofunctions of ribosomes, secondary metabolite biosynthesis, microbial metabolism in diverse environments, carbon metabolism, and biosynthesis of amino acid and aminoacyl-transfer RNA. The results showed these non-thermal treatments were able to induce the shifting of ribosome biogenesis to initiate translation in L. monocytogenes. During protein translation, the initiation stage was upregulated. However, subsequent elongation, termination, and recycling of used ribosomes were retarded. Comparing various treatments, the combination of hurdles showed greater deactivation of L. monocytogenes than any single one. The approaches developed in this study provided crucial information for minimally processing in the food industries on the application of foodborne listeriosis prevention.

Effect of microencapsulated extract of pitaya ( Hylocereus costaricensis ) peel on oxidative quality parameters of refrigerated ground pork patties subjected to UV‐C radiation

The effect of different levels of microencapsulated pitaya peel extracts (100 ppm–MPE100, 1,000 ppm–MPE1000, and 2,000 ppm–MPE2000) on the oxidative stability of refrigerated ground pork patties subjected to UV-C (0.5 J/cm2) for 10 days was investigated. Ground pitaya peel was microwave-assisted extracted utilizing different factors, and the extract with the highest polyphenol content (2.68 mg GAE/g sample) was microencapsulated and added to ground pork. MPE2000 promoted higher protection (30%) of polyunsaturated fatty acids. All extracts mitigated the increase of protein oxidation in an average value of 1.5 nmol carbonyl/mg protein; however, only MPE2000 hindered the lipid oxidation (about 44%) induced by UV-C up to sixth day. MPE2000 (ΔE = 2.65) and BHT (ΔE = 2.62) had an equal effect on preventing color changes. MPE2000 may be used as a simple and effective natural source to mitigate the adverse effects of UV-C on oxidative stability of ground pork patties. Novelty Impact Statement Ultraviolet radiation type C (UV-C) is a nonthermal preservation technology useful for extending the shelf life of foods. However, in general, UV-C doses to promote antimicrobial effect induce lipid and protein oxidation, affecting meat color, which determines quality loss and consumer rejection. Due to the toxic effects associated with the consumption of synthetic antioxidants and the increasing demand for safe and healthy products, the meat industry seeks natural alternatives capable of maintaining the oxidative stability of meat during refrigerated storage. Our study could encourage the use of microencapsulated extracts of pitaya (Hylocereus spp.) peel in irradiated pork meat at an industrial scale.

Natural Antimicrobials Combined with Ultrasound Treatments to Enhance Quality Parameters and Safety of Unpasteurized Strawberry Juice

ABSTRACT The search for novel non-thermal preservation technologies is continuously growing, as traditional thermal processing may have undesirable effects on sensory and nutritional properties of fruit juices. Therefore, the aims of this study were to find the ultrasound, pomegranate extract and geraniol levels that simultaneously optimize different quality parameters of strawberry juice after 14 days of refrigerated storage (5°C) and evaluate the performance of the optimal combination of these treatmentsto control a contamination with Escherichia coli O157:H7. Response surface methodology was applied for optimization study where geraniol was applied at 0, 0.15 and 0.30 μL/mL; pomegranate extract, at 0, 180 and 360 μg/mL; and ultrasound treatments were performed at 40 kHz during 0, 15, and 30 min. The optimum combination resulted in 0.15 μL/mL of geraniol, 360 μg/mL of pomegranate extract and 30 min of ultrasound. This treatment was able to significantly reduce microbial counts, with a low impact on sensory attributes, while improving the antioxidant capacity of the product compared tountreated juice samples. Also, it allows reducing the contamination with E. coli to undetectable values. Thus, the optimized treatment resulted adequate for extending the shelf-life as well as increasing the safety of strawberry juice.

Study of apple juice preservation by filtration through silica microparticles functionalised with essential oil components

Novel non-thermal preservation technologies are needed given consumers' demand for minimally processed high quality food products with a long shelf life. In this work, novel filtering materials based on silica microparticles functionalized with essential oil components (eugenol and vanillin) were applied as an alternative preservation method for apple juice. After confirming the immobilisation of the antimicrobial compounds on particles' surface, the capacity of the filtration system to pasteurise apple juice inoculated with Escherichia coli was proven (a reduction of at least 5-log). The influence of filtration on the physico-chemical (pH, acidity, soluble solids, colour) and microbiological (mesophilic, psychrophilic and mould and yeast) parameters of fresh apple juice was evaluated throughout refrigerated storage, as well as the potential leaching of the immobilised bioactive compounds. The results showed the capability of the functionalised particles to completely remove the native flora of fresh apple juice and to preserve the product's microbial stability throughout the study period (>120 days). Filtering juice through the eugenol-functionalised particles did not strongly affect the physico-chemical properties, except for the colour attribute. The use of immobilised vanillin significantly affected some product characteristics, probably due to the partial release of compounds to the food matrix. Therefore, the immobilisation methodology should be optimised before applying this support to a real scenario. Nevertheless, the immobilisation of these bioactive compounds on silica microparticles allowed filtration technology to be developed as a promising alternative to existing pasteurisation technologies to provide microbial stable and quality acceptable food products.

Sublethal Injury and Viable but Non-culturable (VBNC) State in Microorganisms During Preservation of Food and Biological Materials by Non-thermal Processes.

The viable but non-culturable (VBNC) state, as well as sublethal injury of microorganisms pose a distinct threat to food safety, as the use of traditional, culture-based microbiological analyses might lead to an underestimation or a misinterpretation of the product’s microbial status and recovery phenomena of microorganisms may occur. For thermal treatments, a large amount of data and experience is available and processes are designed accordingly. In case of innovative inactivation treatments, however, there are still several open points with relevance for the investigation of inactivation mechanisms as well as for the application and validation of the preservation processes. Thus, this paper presents a comprehensive compilation of non-thermal preservation technologies, i.e., high hydrostatic pressure (HHP), pulsed electric fields (PEFs), pulsed light (PL), and ultraviolet (UV) radiation, as well as cold plasma (CP) treatments. The basic technological principles and the cellular and molecular mechanisms of action are described. Based on this, appropriate analytical methods are outlined, i.e., direct viable count, staining, and molecular biological methods, in order to enable the differentiation between viable and dead cells, as well as the possible occurrence of an intermediate state. Finally, further research needs are outlined.

Antimicrobial and antioxidant effects of combined high pressure processing and sage in beef burgers during prolonged chilled storage

Abstract The combined effect of sage (0.3 and 0.6%) and high pressure processing (HPP) [300 MPa (10 min, 9.9 °C) and 600 MPa (10 min, 10.2 °C)] on the antimicrobial and antioxidant characteristics of beef burgers during prolonged chilled storage (60 days) was analysed. Sage powder showed antioxidant and antimicrobial activities, but the addition of sage powder to burgers had no apparent effect on antimicrobial activity; however, antioxidant activity was detected as measured by TBARS, hexanal and photochemiluminescence (PCL). In general, lipid oxidation increased in all samples during storage. HPP at 600 MPa had no effect on lipid oxidation but caused mesophilic and psychrotrophic counts to remain close to the detection limit for at least 6 days. Significant correlations were found between lipid oxidation measured by TBARS and PCL and between TBARS with hexanal over the storage period. Sage had no detrimental effects on sensory attributes of burgers. Industrial relevance Sage is an aromatic plant with excellent antimicrobial and antioxidant properties. High pressure processing (HPP) is an efficient non-thermal preservation technology. As far as the authors are aware, very few studies have holistically addressed the question of stability (microbial spoilage and oxidation of lipids) of traditionally-prepared burgers as affected by HPP and addition of a natural plant. This paper examines the possible application of both treatments so as to obtain beef burgers with suitable oxidative and microbiological stability over prolonged chilled storage without this affecting sensory attributes.

Polypropylene-based packaging materials for shelf-life enhancement of yellow corn (Zea mays) kernels: Effects on lutein, aflatoxin content, sensory, and nutritional profiles

Yellow corn (Zea mays) kernels were packaged in unilamellar polypropylene (PP), bilamellar PP/PET (polyethylene terephthalate), and trilamellar PP/PET/Al (aluminium foil) composite and stored at ambient conditions (23 ± 2 °C, 80% RH) for the extension of their shelf-lives. Lutein content, aflatoxin content, sensory, physicochemical, phytochemical, and nutritional properties were adjudged. X-ray diffraction, thermogravimetric-differential thermal analyses, differential scanning calorimetry, and percentage opacity of the three packaging composites revealed that among the three combinations investigated, PP/PET/Al composite possessed highest crystallinity, thermal stability, and percentage opacity, thereby exhibiting improved barrier properties against moisture, gas, and light. These attributes led to enhanced carotenogenesis and minimal aflatoxin content, conferring highest shelf-life of 90 days to the trilamellate packaged corn kernels, compared to PP- and PP/PET-packaged samples (60 days). Sensory, physicochemical, phytochemical, and nutritional profiles were also best retained in the same compared to PP- and PP/PET-packaged and control corn grits. Practical applications Corn is one of the major cereal crops consumed worldwide. Besides its nutritive value, it is also a good source of the nutraceutical “lutein.” Therefore, to meet the demand of the food processing industries and consumers, the grains must be preserved well. The current approach of application of non-thermal preservation technology viz. “packaging” (using commercially viable, flexible packaging materials) could well preserve lutein as well as sensory attributes, phytochemical properties and nutritional constituents of the corn grits, when stored at ambient conditions (23 ± 2 °C, 80% RH).

Influence of pulsed electric field processing on the quality of fruit juice beverages sweetened with Stevia rebaudiana

A fruit juice-stevia beverage was processed using pulsed electric fields (PEF), a non-thermal preservation technology, with the purpose of investigating the feasibility of PEF for bioactive compounds and steviol glycosides enhancement and its impact on physicochemical properties. Variable ranges of response surface methodology were 20–40kV/cm (electric field strength), 100–360μs (treatment time) and 0–2.5% (w/v) stevia. After PEF, ascorbic acid was retained by more than 74%. Some of the analyzed PEF treatments resulted in an enhancement of total anthocyanins and carotenoids. The best results for rebaudioside A/stevioside ratio were obtained when PEF was applied at 30kV/cm for 230μs. Hydroxymethylfurfural content and total color differences were maximum at the highest electric field strength assayed (40kV/cm). PEF conducted at 21kV/cm during 360μs with 2.5% stevia led to the beverage with the greatest content in bioactive compounds and sweetening properties with minimal color changes.

Effects of Thermal and High-pressure Treatments on the Microbiological, Nutritional and Sensory Quality of a Multi-fruit Smoothie

Fruit juices have become an important product for the healthy food world. In the last 5 years, the sales of industrial juices treated by non-thermal preservation technologies such as high-pressure processing (HPP) have strongly increased. In the present study, the effect of the application of two stabilization treatments, mild heating (MH; 80 °C for 7 min) and high-pressure processing (HPP; 350 MPa for 5 min), on multi-fruit smoothies was compared on a wide range of quality parameters immediately after treatment and during a refrigerated storage of 21 days. From the physico-chemical and instrumental colour point of view, immediately after treatment, HPP smoothies were more similar to the fresh product than those treated by MH. During storage, the colour of MH smoothies was more stable although HPP ones showed lower browning index and viscosity more similar to the untreated product. Additionally, HPP provided smoothies with better sensory properties and higher nutritional quality than MH. In general, HPP smoothies were more similar to the untreated product. However, HPP smoothies kept a residual enzyme activity which is likely to limit the shelf life of this multi-fruit smoothie.

Effects of Electrical Pretreatments on the Yield and Quality Characteristics of Red Bell Pepper Puree

AbstractElectrical treatments, which are among the nonthermal preservation technologies, have been gaining importance with the changes in the preferences of consumers who want high quality foods. In this study, electroplasmolysis (EP) as a pretreatment and microwave (MW) heating as an alternative to traditional heating were used in the production of red pepper puree in order to increase the puree yield and improve the quality characteristics of the puree. The red pepper purees were treated by EP, conventional heating (CH) as the control and also combinations of treatments (EP + MW, EP + CH). The EP application was optimized using response surface methodology. The optimum conditions were found as a voltage gradient of 143 V/cm and a treatment time of 60 s. At this optimum point, the yield was found to be 76.3%. In the combination of the EP and MW groups, the yield increased by 7.56% compared with the control group. The pectin and vitamin C contents increased after the pretreatments when compared to the control group.Practical ApplicationsElectrical treatments are used as an alternative to traditional food processing techniques. Electroplasmolysis (EP) application provides an increased permeability of the plant tissues. This benefit can be used in the production of fruit and vegetable juice or puree. Yield is so important especially on the industrial scale. EP and microwave applications increased the yield and also the quality of the red bell pepper puree, and as a result, these methods are useful for food processing technology.

Intense light pulses upset the sensory quality of meat products

Intense light pulses (ILP) is a promising non-thermal preservation technology. Few data are reported about the impact of the treatment on sensory quality of meat and meat products. Evaluation of the impact of ILP on sensory quality of meat products was performed using five different types of meat products: cooked ham, Parisian sausage, Parma ham, fermented sausage and bacon. All the samples were treated with 1 and 5 light pulses (pulse duration of 300 μs and pulse intensity of 3.4 J/cm2) at a rate of one pulse per 2 seconds. Changes in the sensory quality induced by intense light pulses were different and depended on type of meat product and ILP dose applied. The results for cooked meat products are not promising because ILP significantly deteriorated their sensory quality. Dry-cured meat product, Parma ham and bacon, showed greater sensory resistance to the impact of ILP than examined cooked meat products. Fermented sausage was least affected by ILP of all the meat products investigated. Pulsed light lightened cooked ham after the higher treatment was applied while the lightness of Parisian sausage remained unaffected by the treatment. The a* value significantly decreased only after the 5-pulses treatment in Parma ham, fermented sausage and bacon while the b* value changed significantly (increased) only in bacon.

Nonthermal Food Processing Alternatives and Their Effects on Taste and Flavor Compounds of Beverages

Food drinks are normally processed to increase their shelf-life and facilitate distribution before consumption. Thermal pasteurization is quite efficient in preventing microbial spoilage of many types of beverages, but the applied heat may also cause undesirable biochemical and nutritious changes that may affect sensory attributes of the final product. Alternative methods of pasteurization that do not include direct heat have been investigated in order to obtain products safe for consumption, but with sensory attributes maintained as unchanged as possible. Food scientists interested in nonthermal food preservation technologies have claimed that such methods of preserving foods are equally efficient in microbial inactivation as compared with conventional thermal means of food processing. Researchers in the nonthermal food preservation area also affirm that alternative preservation technologies will not affect, as much as thermal processes, nutritional and sensory attributes of processed foods. This article reviews research in nonthermal food preservation, focusing on effects of processing of food drinks such as fruit juices and dairy products. Analytical techniques used to identify volatile flavor-aroma compounds will be reviewed and comparative effects for both thermal and nonthermal preservation technologies will be discussed.

High Pressure Treatment Effect on Physicochemical and Nutritional Properties of Fluid Foods During Storage: A Review

Abstract: Consumers demand foods that are easy to consume and that are of high nutritional and sensory quality. Therefore, they appreciate the similarity of minimally processed products to fresh products. In recent years, the food industry has shown increased interest in nonthermal preservation technologies, because they provide products of proven quality and can be an alternative to traditional thermal methods, thus increasing added value. This review examines the effects of high pressure processing (HPP) on the nutritional and physicochemical parameters of fluid foods. While some general trends can be observed, the effects of HPP differ not only according to treatment intensity, but also according to the food matrix, suggesting that each matrix should be studied separately.

Effects of UV-C Light Processing on Some Quality Characteristics of Grape Juices

White and red grape juices (GJs) were subjected to ultraviolet C (UV-C) light as a non-thermal preservation technology using a coiled tube UV-C reactor with nine lamps. The effects of UV-C light on microbial (total aerobic count and yeast and mould count) and some chemical quality characteristics (total phenolics, antioxidant capacity, anthocyanin and polymeric colour, etc.) of white and red GJs were investigated. The results were compared with control (untreated) and heat-treated juice samples. Single-pass UV-C treatment (12.6 J/mL) of white and red GJs resulted in 3.51 and 3.59 log reductions in total aerobic count and, 2.71 and 2.89 log reductions in yeast and mould counts, respectively. The microbial loads of both GJs were completely eliminated after two passes through the reactor (25.2 J/mL). After UV-C and heat treatments, there were no significant changes in antioxidant capacity, total phenolics, titratable acidity, soluble solids and pH of white and red GJs (P > 0.05). The losses in monomeric anthocyanins were 6.1% and 8.7% after UV-C treatment of 12.6 and 25.2 J/mL doses, respectively. However, anthocyanin level of red GJ was significantly affected by the heat treatment with an 11.8% loss (P < 0.05). The percent polymeric colour of the red GJ with heat treatment was significantly higher compared to the colour with the UV-C treatment.

Development of resistance in Cronobacter sakazakii ATCC 29544 to thermal and nonthermal processes after exposure to stressing environmental conditions

The objective was to study the response of Cronobacter sakazakii ATCC 29544 cells to heat, pulsed electric fields (PEF), ultrasound under pressure (Manosonication, MS) and ultraviolet light (UV-C) treatments after exposure to different sublethal stresses that may be encountered in food-processing environments. Cronobacter sakazakii stationary growth-phase cells (30°C, 24h) were exposed to acid (pH 4·5, 1h), alkaline (pH 9·0, 1h), osmotic (5% NaCl, 1h), oxidative (0·5mmoll(-1) H(2) O(2), 1h), heat (47·5°C, 1h) and cold (4°C, 4h) stress conditions and subjected to the subsequent challenges: heat (60°C), PEF (25kVcm(-1) , 35°C), MS (117μm, 200kPa, 35°C) and UV-C light (88·55mWcm(-2), 25°C) treatments. The inactivation kinetics of C. sakazakii by the different technologies did not change after exposure to any of the stresses. The combinations of sublethal stress and lethal treatment that were protective were: heat shock-heat, heat shock-PEF and acid pH-PEF. Conversely, the alkaline shock sensitized the cells to heat and UV-C treatments, the osmotic shock to heat treatments and the oxidative shock to UV-C treatments. The maximum adaptive response was observed when heat-shocked cells were subjected to a heat treatment, increasing the time to inactivate 99·9% of the population by 1·6 times. Cronobacter sakazakii resistance to thermal and nonthermal preservation technologies can increase or decrease as a consequence of previous exposure to stressing conditions. The results help in understanding the physiology of the resistance of this emerging pathogen to traditional and novel preservation technologies.

Influence of high pressure homogenization (HPH) on the structural stability of an egg/dairy emulsion

Abstract High pressure homogenization (HPH) is a novel non-thermal preservation technology, which can improve the microbiological quality of products without affecting their stability. The main objective of this paper is to study the influence of different HPH treatments on the structure of a sauce (an egg/dairy emulsion), in order to obtain the higher physicochemical stability. The oil-in-water emulsion was stable up to 100 MPa with the oil droplets surrounded by several layers of natural emulsifiers. Critical pressures, between 150 and 250 MPa, produced a destabilization of the emulsion thus causing a separation of phases. A coalescence phenomenon progressively occurred when pressure increased. This phenomenon was due to the loss of the natural emulsifier barrier. Changes on the electrophoretic pattern were also observed at high pressure levels, showing an insolubilization of proteins. Lipid fraction was observed to be chemically stable after the HPH treatment.