High Pressure Processing (HPP) on pre-packaged foodstuffs, solids and liquids, enables the inactivation of pathogenic and altering microorganisms.
A possible alternative to heat treatments and the use of preservative additives, with various useful applications to extend the shelf-life of products. (1) Some examples to follow.
1) HPP, High Pressure Processing. Foreword
HPP technologies – unlike heat treatments (i.e. cooking, pasteurisation) – do not utilise high temperatures but rather high hydrostatic pressures (up to 4-600 MPa, applied for time intervals typically ranging between 1.5 and 7 minutes) to achieve microbiological stability of foodstuffs (2,3). The main advantages of high pressure processes include:
-food safety. HPP technologies can inactivate pathogenic bacteria such as Listeria monocytogenes, Escherichia coli and Salmonella; (4)
-organoleptic properties. The low temperature and homogenous pressure also allow the sensory characteristics and structure of the food to be maintained. (1)
2) Treatment modalities
The products to be subjected to HPP are packed in flexible packaging (i.e. PET, polyethylene) and placed inside an autoclave that is filled with cold water.
Pressurisation of the autoclave allows pressure to be transferred to every point on the product, via the water, and ensures uniformity of treatment.
At the end of the process, which rarely lasts more than 8 minutes, the water is removed and the product is withdrawn. (3)
3) Applications in the food sector
The potential applications of HPP in the food sector are manifold (EFSA, 2022). (4) However, the costs of machinery and processes – also, and not only, in terms of energy consumption – lead to its use being limited to high-margin products.
3.1) Boneless cured ham
Cured ham is considered to be a safe product from a microbiological point of view. De-boning operations and hygienic deficiencies, however, can lead to contamination by pathogenic bacteria (i.e. Listeria monocytogenes.).
A study by the ‘Departamento de Tecnología de Alimentos’ of the University of Madrid (Pérez-Baltar et al., 2020) has shown how the application of HPP, at 600 MPa for 5 minutes, can ensure compliance with the microbiological criteria for food safety established in the EU and the USA. (5)
3.2) Plant-based foods
The application of HPP alone between 350-600 MPa can enable the elimination of Listeria m., Salmonella and E. coli in various plant-based foods. The elimination of sporigenic microorganisms (bacterial spores and moulds), on the other hand, requires the combination of HPP with heat treatment.
The application of this technology to guacamole, a fresh avocado-based condiment, is also interesting. It ensures microbiological stabilisation and prevents browning, otherwise unavoidable with exposure to heat treatment. (6)
3.3) Wines
Brettanomyces bruxellensis is a yeast that produces highly unpleasant sensory compounds in wine, able to resist sanitisation treatments and persist in cellar environments. And it is precisely to prevent its development that sulphur dioxide is often added to wines.
The use of HPP (400 MPa for just 5 seconds) on long-aged red wines, such as Cabernet Sauvignon, has been shown to completely inactivate this altering yeast. Without altering its organoleptic characteristics. (7)
3.4) Fresh cheeses
The application of HPP at 600 MPa for 5 minutes was found to eliminate the most resistant strains of Listeria monocytogenes in fresh cheeses, thus ensuring their food safety under normal distribution and storage conditions. (8)
Francesco Carlini
Footnotes
(1) Alte pressioni idrostatiche, la tecnologia destinata a diventare realtà. 19.4.17 https://tinyurl.com/3v36n6ca
(2) EFSA (2022). The efficacy and safety of high‐pressure processing of food. https://doi.org/10.2903/j.efsa.2022.7128
(3) González-Angulo M, Serment-Moreno V, Clemente-García L, Tonello C, Jaime I, Rovira J. Assessing the pressure resistance of Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enterica to high pressure processing (HPP) in citric acid model solutions for process validation. Food Res Int. 2021 Feb;140:110091. doi: 10.1016/j.foodres.2020.110091
(4) I trattamenti ad alte pressioni (HPP): cosa sono, esempi applicativi e miglior packaging impiegabile. Food & Tec. Dicembre 2018 https://tinyurl.com/29w3fvrs
(5) Aida Pérez-Baltar, Alejandro Serrano, Raquel Montiel, Margarita Medina.
Listeria monocytogenes inactivation in deboned dry-cured hams by high pressure processing. Meat Science, Volume 160, 2020, 107960. https://doi.org/10.1016/j.meatsci.2019.107960
(6) High Pressure Processing Applications in Plant Foods https://www.mdpi.com/2304-8158/11/2/223
(7) Sanelle van Wyk, Filipa V.M. Silva. High pressure inactivation of Brettanomyces bruxellensis in red wine. Food Microbiology, Volume 63, 2017, Pages 199-204. https://doi.org/10.1016/j.fm.2016.11.020
(8) K. Evert-Arriagada, A.J. Trujillo, G.G. Amador-Espejo, M.M. Hernández-Herrero. High pressure processing effect on different Listeria spp. in a commercial starter-free fresh cheese. Food Microbiology, Volume 76, 2018, Pages 481-486. https://doi.org/10.1016/j.fm.2018.07.012
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