Hayes et al. Lowest reduction 2. Roig-Sagues et al. According to these data, fat content increase enhanced the maximum temperature reached during UHPH treatment and this could have contributed to the lethal effect achieved. In addition the HPH treatments of milk is reported to enhance the release of free fatty acids due to the rupture of fatty globule membranes and the activation of lipases , and mainly short and medium chain ones, having an antimicrobial effects Lanciotti et al.
On the contrary, some Authors attributed to the fat content in milk a protective role against microbial species during the high pressure treatment performed at MPa for several cycles. Although several Authors have tested the same matrixes, and in some case the same microbial species, different inactivation results was achieved, particularly using the multi-pass approach. For example, Patrignani et al. This result, although using a different substrate and microorganism, is in agreement with the findings of Patrignani et al.
Several other authors have also found first order inactivation kinetics as a function of the number of passes Wuytack et al. These Authors attributed this behavior mainly to the physiological diversity within a microbial population and to the existence of resistant cells able to survive after repeated passes at the pressure applied.
On the other hand, it is important to take into consideration the additional effect of HPH on the antimicrobial activity of naturally occurring enzymes, such as lysozyme, lactoperoxidase system and so on. Velazquez-Estrada et al. In particular, these Authors proposed the single-pass treatment of inoculated LWE with ultra HPH at , , , and MPa, demonstrating that the level of pressure applied can influence the S.
Moreover, Panozzo et al. TABLE 2. High pressure homogenization microbial inactivation in relation to the food matrix, species and process conditions adopted. For example, Brinez et al. Kumar et al. Also Pathanibul et al. As processing pressure increased, inactivation of E. In contrast, little inactivation was observed for L. However, several authors have been demonstrated the major efficacy of HPH against Gram-negative bacteria.
On the other hand nisin is reported to be active against Gram-positive bacteria Siroli et al. Bacterial spores represent one of the major hazard in food safety due to their high resistance to most hurdles.
Thermal sterilization is the method to eliminate spores in most food applications, as it provides the highest guarantee of sterility. From a safety point of view, spores of Bacillus spp. In general, the heat resistance of spores depends on conditions such as elevated sporulation temperature, the presence of minerals and dipicolinic acid DPA , and core dehydration. The endospores are composed of a central core, which is surrounded by several protective layers. The outermost layer, the exosporium, is not present in spores of all species, and is the primary site of contact with the environment.
Between the outer and inner membrane, there is the cortex. Since the spore structure plays a major role in spore resistance, the spore inactivation in foods requires high levels of heat treatments, which can in turn have negative effects on the sensory and nutritional profile Schubert and Beaudet, ; Reineke et al.
In order to increase antimicrobial effectiveness and reduce side effects on food quality, the application of combined hurdles has also received great attention. Extensive literature indicates that the effects of combined stresses on microbial growth and survival may be additive or synergistic, when the outcome is usually significantly greater than the additive response Tapia de Daza et al.
Because of its great potential for microbial inactivation, several authors have studied the effects of HPH or UHPH, when applied individually or in combination with other mild physical or chemical stresses heat and H 2 O 2 , on the inactivation of Bacillus and Clostridium spores, whose genera, from a safety point of view, the most important species belong.
The analysis of the literature shows that the major application for HPH and UHPH regards the inactivation of spores of spoiling bacteria while the reports dealing with the inactivation of spores from pathogenic species are sporadic. These Author determined also the effects of the treatments applied on the release of DPA from the spores, since spore resistance to stresses such as temperature and pressure has been correlated to their ability to retain DPA, present in the core region of the dormant spores Setlow, ; Cortezzo et al.
The Authors outlined how the application of specific stress sequences can significantly inactivate B. The remarkable efficacy of repeated cycles at MPa suggested that dynamic high pressure, particularly applied in combination with other sub-lethal stresses, could be a useful and innovative tool for B. Among the stress conditions applied, it was observed that only the thermal shock after one HPH cycle reduced the colony count of 2.
Pinho et al. A few spores reduction 0. Therefore, although HPH be recognized as an effective method for milk pasteurization, in this specific case, HPH process is not able to guarantee the commercial sterility of milk, being necessary the association of the homogenization with another preservative method, as refrigeration.
Also Amador Espejo et al. These Authors provided important evidence of the suitability of UHPH technology for the inactivation of spores in high numbers, leading to the possibility of obtaining commercially sterile milk. Because of the great interest within the food industry in aldehydes, ketones, esters as natural antimicrobial compounds Burt, ; Patrignani et al. In general, the approaches used are aimed to destabilize the microbial outer membranes of Gram-negative bacteria or to modify the chemical structure of the enzyme.
For example, Ibrahim et al. These modifications generate an amphitropic protein able to spread the cytoplasmic membrane Vannini et al. Peptic digestion or heat treatment are reported to augment the antimicrobial activity of lactoferrin. In this perspective, several authors tried to modify the enzyme structure, and consequently its activity, by using HPH in order to increase food safety. On the other hand the effect of HPH on naturally occurring food enzymes involved also in shelf-life, ripening and functionality of several matrices has been demonstrated Kheadr et al.
From a safety point of view, Vannini et al. The enzyme addition enhanced the immediate pressure efficacy on almost all the considered species as indicated by their instantaneous viability loss following the treatment. Moreover, the combination of the enzyme and HPH significantly affected the recovery and growth dynamics of the considered species.
Although L. Iucci et al. Their antimicrobial activities were tested on L. Particularly, the highest immediate inactivation values were recorded when L. Although to a lesser extent than HPH treatment the heat treatments applied also were able to increase the antimicrobial activity of lysozyme. The Author suggested that the large supramolecular structure is disrupted under pressure, allowing the components to move freely and become independent of the original structure.
Interactions can reform when the pressure instantaneously decreases but the original structure is not reformed because of the independent movements of the components. Patrignani et al. In fact, dynamic pressure is reported to enhance antimicrobial activity of lysozyme and lactoferrin, probably due to the change of the exposure of hydrophobic regions Iucci et al.
Also Velazquez-Estrada et al. The critical evaluation of the available literature data has showed the great potential of HPH for microbial inactivation and food safety purpose. Since several Authors have been tested its potentialities in vitro and real systems, demonstrating its different ability for pathogenic species inactivation in relation to the strains considered, the food matrix and technological procedures adopted.
However, until the introduction of new valve design and ultra high pressure homogenizers, able to reach pressures of MPa, this technology was implemented in food industry only for fat globule reduction, for juice treatment and emulsion creation. The introduction of these new variables have opened new field in food sector, also for food decontamination and permitting to replace or minimize the traditional thermal treatments generally applied for the safety purposes. The new main applications regard the treatment of milk for consumption or dairy product manufacture , fruit and vegetable juice, vegetable milks, and food component such as enzymes obtaining more stable and safer products without detrimental effects on quality properties.
In fact, in the most of the cases, the literature data have underlined an improvement of the sensory and nutritional properties and stability of the HPH and UHPH treated products. The replacement of traditional thermal treatment can represent an advantage for the industry since this HPH is a cold technology with a lower impact on the environment, more sustainable, saving energy, time and additional costs. Moreover the literature data have demonstrated that HPH, when applied to the milk for cheesemaking, can increase the cheese yield, reduce the cheese hydrolytic patterns, reducing the costs for ripening.
Moreover, another important improvement of the state of the art was done for the inactivation of resistant endospores, which still represent a great challenge for food industry. The literature data have pointed out that the combination of UHPH and several chemico-physical hurdles can be regarded as tool for spore inactivation especially for milk based products. Further improve of food safety and functional properties could be achieved exploiting the well recognized dynamic pressure potential to obtain nanoparticles of antimicrobial molecules or functional ingredients.
However, also in this case the reduction of thermal treatment can represent an advantage for food industry and contribute to the maintenance of the quality and nutritional properties of foods. However, although the achieved aims, UHPH has not been yet implemented in food industry since conventional and ultra homogenizer do not guarantee by themselves the sterilization and, subsequently, packaging of foods in aseptic conditions is needed. This results in a great disadvantage for food industry because it limits the implementation of this technology in food process as full alternative to thermal treatment.
FP and RL put in writing this review together consulting the available literature, patents on the topic and trying to investigate several aspects on high pressure homogenization and safety.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Amador Espejo, G. Food Microbiol 44, — Google Scholar. Bernkop-Schnurch, A. Synthesis and evaluation of lysozyme derivates exhibiting an enhanced antimicrobial action. Betoret, E. Strategies to improve food functionality: structure-property relationships on high pressures homogenization, vacuum impregnation and drying technologies.
Trends Food Sci. Bevilacqua, A. Effects of high-pressure homogenization on the survival of Alicyclobacillus acidoterrestris in a laboratory medium. High-pressure homogenisation and benzoate to control Alicyclobacillus acidoterrestris : a possible way?
Food Sci. Effects of the high pressure of homogenization on some spoiling microorganisms, representative of fruit juice microflora, inoculated in saline solution. Brinez, W. Inactivation by ultra high-pressure homogenization of Escherichia coli strains inoculated into orange juice.
Food Prot. Inactivation of Listeria innocua in milk and orange juice by ultrahigh-pressure homogenization. Food Protect. Inactivation of Staphylococcus spp. Food Control 10, — Burns, B. Probiotic crescenza cheese containing Lactobacillus casei and Lactobacillus acidophilus manufactured with high pressure-homogenized milk.
Dairy Sci. Burns, P. Potential of high pressure homogenisation on probiotic Caciotta cheese quality and functionality. Foods 13, — Burt, S. Essential oils: their antibacterial properties and potential applications in foods. Food Microbiol. Effect of high pressure homogenization applied individually or in combination with other mild physical or chemical stresses on Bacillus cereus and Bacillus subtilis spore viability.
Food Control 20, — Chen, W. Inactivation of Alicyclobacillus acidoterrestris using high pressure homogenization and dimethyl dicarbonate.
Cortezzo, D. Analysis of the action of compounds that inhibit the germination of spores of Bacillus species. Diels, A. High-pressure homogenization as a non-thermal technique for the inactivation of microorganisms. Moderate temperatures affect Escherichia coli inactivation by high-pressure homogenization only through fluid viscosity.
Inactivation of Escherichia coli by high-pressure homogenisation is influenced by fluid viscosity but not by water activity and product composition. Modelling inactivation of Staphylococcus aureus and Yersinia enterocolitica by high-pressure homogenisation at different temperatures.
One the the added benefits of many homogenization techniques is the destruction of pathogens within a sample. There are several kinds of homogenizers mechanical, high pressure and ultrasonic , each using one or more specific types of force. As a by-product of the processing method each force facilitates, many homogenizers render samples with varying levels of sterility. For instance, high pressure homogenizers can effectively kill microorganisms in food samples.
Other homogenizers that produce high levels of heat most mechanical homogenizers can kill various pathogens, as well, but the accompanying heat frequently degrades the overall sample.
Finally, the purpose of most homogenizers is to mix substances well. Reducing the size of the particles in a substance allows it to more readily and easily combine with the particles of another substance. The two-stage homogenizer permits precise control of the homogenization process. The analyzer can be placed at each milk plant to provide real-time feedback on the homogenization process.
This allows for optimization of the final product, cost savings by eliminating overprocessing of the material and out-of spec material, and evaluation of the homogenizer itself for wear or breakage.
The distribution below is the result of measurement of whole raw, unhomogenized milk with the LA particle size analyzer. The distribution shows the large fat globules prior to homogenization. The ratio and size of fat globules to casein is such that the caseins are not seen in whole milk. Particle Size of Raw Milk.
This distribution is of whole homogenized milk. This is a stable distribution of the milk emulsion. The LA monitors this size reduction very well. Particle Size of Whole Milk. This represents the caseins which now show up in the distribution, due to the removal of the fat globules. This results in the protein appearing as a second mode. Since non-fat milk lacks the emulsified fat globules the distribution is made up primarily of the protein caseins.
The remaining distribution is just the proteins. Particle Size of Nonfat Milk. The main goal of homogenization is to break up the large fat globules and create a stable emulsion that has an increased shelf life, a better taste, and improved mouth feel. The LA is an excellent tool to monitor this process.
0コメント