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Category Archives: HHP
Research – Effect of High Hydrostatic Pressure Processing on the Microbiological Quality and Bacterial Diversity of Sous-Vide-Cooked Cod
High hydrostatic pressure (HP) is a promising method to improve the microbiological quality of sous-vide foods. Monitoring the composition and behavior of the microbial communities in foods is of most importance for the production of high-quality and safe products. High-throughput sequencing (HTS) provides advanced approaches to determine food’s microbial community composition and structure. The aim of the present study was to determine the impact of different HP treatments on the microbial load and bacterial diversity of sous-vide Atlantic cod. Sous-vide cooking at 57.1 °C for 30 min followed by HP treatment at 500 MPa for 8 min reduced viable cell counts (total aerobic mesophiles) in the cod samples below detectable levels for 45 days of storage under refrigeration. In a second trial with cod cooked sous-vide at 52 °C for 20 min followed by HP treatments at 300 or 600 MPa (with HP treatment temperatures of 22 °C or 50 °C for 4 or 8 min, depending on treatment), only the treatments at 600 MPa delayed bacterial growth for at least 30 days under refrigeration. The optimal HP conditions to improve the microbiological quality of sous-vide cod cooked at low temperatures were obtained at 600 MPa for 4 min at a pressurization temperature of 50 °C. Bacterial diversity was studied in cod cooked sous-vide at 52 °C for 20 min by HTS. In the absence of HP treatment, Proteobacteria was the main bacterial group. A succession of Pseudomonadaceae (Pseudomonas) and Enterobacteriaceae was observed during storage. Firmicutes had low relative abundances and were represented mainly by Anoxybacillus (early storage) and Carnobacterium (late storage). The HP-treated sous-vide cod showed the greatest differences from controls during late storage, with Aerococcus and Enterococcus as predominant groups (depending on the HP conditions). The application of HTS provided new insights on the diversity and dynamics of the bacterial communities of sous-vide cod, revealing the presence of bacterial genera not previously described in this food, such as Anoxybacillus. The significance of Anoxybacillus as a contaminant of seafoods should be further investigated.
Research – The effectiveness and safety of high pressure food treatment
Definition and applicable regulations
High pressure treatment (HPP), also known as “high pressure hydrostatic treatment (HHP)” or “ultra pressure treatment (UHP)”, is a non-thermal (<45 °C) food preservation technology that inactivates forms vegetative pathogens and spoilage microorganisms – does not inactivate bacterial spores – using high pressures with minimal effects on taste, texture, appearance or nutritional value.
High pressure treatment is not specifically regulated within the EU, however, according to Regulation (EC) 852/2004 regarding the hygiene of food products, HPP is considered a processing. Any relevant food safety legislation is applicable to HPP ─hygiene requirements, microbiological criteria, food contact materials, traceability and labeling requirements. The guidance document on the application of certain provisions of Regulation (EC) 852/2004 introduces, in section 9.6, clarifications on the implementation of the HPP.
The European Food Safety Authority (EFSA) was asked to issue a scientific opinion on the efficacy (reduction of foodborne pathogen levels) and food safety of HPP. Specifically, the terms of reference of the mandate required: to provide an overview of the foods to which the HPP is or could be applied, together with the processing conditions; list the intrinsic and extrinsic factors that may influence the effectiveness of HPP; and assess the potential chemical and microbiological risks to food safety of HPP-treated foods compared to untreated foods or foods that are routinely applied in order to increase their microbiological food safety.An evaluation of the use of HPP was also requested for two specific purposes: as an alternative to the pasteurization and ultra high temperature (UHT) treatment of raw milk and raw colostrum; and for the control of Listeria monocytogenes in ready-to-eat foods. Quality aspects and organoleptic properties were beyond the scope of this mandate.
Type of food treated and processing conditions
Virtually all types of food can be treated with HPP. However, foods that contain trapped air (eg, bread, cakes, whole and freshly cut fruits and vegetables) are not suitable for HPP because their porous structure will be adversely affected. Low-moisture foods, such as powdered products and nuts, are not usually treated with this technology due to low microbial inactivation when the water content is less than 40%.
According to the data collected through a questionnaire in food operators, the relative importance between the types of food that are currently treated with HPP is as follows:
- High – Cooked meat products (including sliced, hot dog , etc.) ready-to-eat, raw-cured meat products (fermented or dried); acidic fruit and vegetable juices, guacamole and ready-to-eat pre-cooked meals.
- Medium – Fruit purees, moist salads (pH <5), and other spreads (eg, hummus, pesto); crustaceans, shellfish, molluscs and derived products; baby food.
- Low : fish and fishery products; milk, raw milk and pasteurized cheese, processed cheese in sauce or spread and dairy products (except cheese).
In the industrial context, to inactivate microorganisms, pressures of between 400 and 600 MPa are applied, for 1.5 to 6 minutes. The water used as a pressure transmission fluid for HPP is often pre-cooled to 4-8 °C.
Typically, products (liquid, semi-solid and solid foods) are packaged in flexible plastic materials prior to HPP to prevent recontamination of the product after HPP. Equipment for processing liquids in bulk before packaging is also available, but is currently rarely used.
Intrinsic and extrinsic factors of food that influence the effectiveness of high pressure treatment
According to EFSA’s scientific opinion, the main intrinsic factors in food that influence the effectiveness of HPP in terms of reducing vegetative microorganisms are water activity (a w ) and pH. Microbial inactivation increases with high values of a w and low pH values. Carbohydrates, proteins and lipids have a protective effect on microorganisms, which reduces microbial reduction. The main extrinsic factors are pressure and target pressure retention time. The type of microorganism, the taxonomic unit and the strain and the physiological state of the microorganisms to be inactivated also affect the effectiveness of the HPP.
The efficacy of HPP in different food matrices is variable due to the interactions between specific intrinsic factors, which makes it difficult to predict the efficacy of HPP in a complex food matrix.
EFSA recommends that the interactions of the different components be considered in the planning of the assessment of the impact of intrinsic factors on the effectiveness of PPPs and that validation studies be performed on actual food matrices.
Possible chemical and microbiological hazards associated with high pressure treatment
Food HPP poses no additional microbiological risk to food safety (eg, spore activation, induction of sublethal cell damage, conversion of normal form of prions to amyloid forms, and induction of virulence, gene expression for toxins and cross-resistance to other stresses) compared to other treatments commonly applied to these foods (eg, thermal pasteurization).
EFSA has also assessed the risk associated with mycotoxins and chemical processing contaminants by establishing that PPH-treated foods do not present a higher risk compared to conventionally treated foods.
HPP does not generate additional chemical food safety hazards from food contact materials compared to foods treated under similar temperature and weather conditions without HPP.
High pressure treatment as an alternative to pasteurization of milk
When raw milk, colostrum, dairy products or colostrum products are subjected to a heat treatment, such as pasteurisation or ultra-high temperature (UHT) treatment, the treatment must comply with the conditions laid down in the Regulation (CE) 853/2004. According to this Regulation, if pasteurization is used for these products, food operators must ensure that the following specifications are met: a high temperature for a short period of time (at least 72 ° C for 15 seconds), a low temperature for a long period of time (at least 63 °C for 30 minutes), or any other combination of temperature and time conditions to obtain an equivalent effect.
There is a growing interest in the use of HPP as an alternative treatment to pasteurization and UHT because it is expected to maintain properties closer to those of raw milk and colostrum.
According to the data collected and evaluated by EFSA, it was determined that HPP could not achieve logarithmic reductions (log 10 ) equivalent to those achieved by thermal pasteurization of milk (more than 10 log 10 ) or by UHT (log 10). more than 12 log 10 ). However, HPP conditions could be identified to achieve reductions equivalent to those recommended by international agencies as benchmarks of performance criteria for pasteurization (eg, reductions of 5, 6, 7, and 8 log 10 ). ).From the mathematical models obtained, several examples are provided of the minimum requirements (combination of pressure and time) of the HPP that, with a high certainty, would allow to reach the different criteria of operation.
Under the most stringent industrially used HPP conditions (600 MPa for 6 minutes), reductions of 5 log 10 for Mycobacterium bovis , 8 log 10 for Shiga toxin-producing Escherichia coli (ECTS or STEC),Listeria monocytogenes , Salmonella spp . and Campylobacter spp. , and 6 log 10 for Staphyloccoccus aureus .
According to EFSA, no data were found on the impact of HPP on the reduction of Brucella melitensis and tick-borne encephalitis virus (TBEV) and therefore no conclusions could be drawn for these. dangers.
EFSA evaluated several milk and colostrum compounds to determine their suitability as indicators of HPP efficacy, including the endogenous alkaline milk phosphatase enzyme (ALP) – widely used to verify the proper thermal pasteurization of milk. γ-glutamyltransferase (GGT), xanthine oxidase (XoX), β-lactoglobulin (β-Lg) or lactoferrin (LF).
In view of the available evidence, EFSA concludes that none of the evaluated indicators can currently be proposed as an appropriate indicator for use under the commercially viable technological conditions of HPP applied to industry (400 and 600 MPa for 1.5-6 minutes) and recommends further in-depth studies to determine the suitability of such compounds as indicators of HPP efficacy.
Efficacy of high pressure treatment for the control of Listeria monocytogenes in ready-to-eat foods
The most relevant foods associated with human listeriosis in the EU that are also relevant to be treated with HPP to increase microbiological food safety include ready-to-eat cooked meat products, soft and semi-soft cheeses, fresh cheeses and smoked or marinated fish. .
For ready-to-eat cooked meat products, the minimum requirements (combinations of pressure and retention time) were derived, which would achieve reductions of 1 to 5 log 10 for L. monocytogenes . For the other types of ready-to-eat foods relevant to listeriosis, the high uncertainty of the data did not allow the establishment of generic minimum HPP conditions, so specific validation studies are required for each specific product.
Salmonella spp. and E. coli were identified as the most relevant additional hazards, apart from L. monocytogenes, in ready-to-eat foods associated with human listeriosis. In the foods mentioned, these pathogens ( Salmonella and E. coli ) are generally more sensitive to HPP than L. monocytogenes and are thought to be inactivated to a similar or greater extent.
According to the EFSA report, further studies on the inactivation by HPP of L. monocytogenes and other pathogenic bacteria relevant to ready-to-eat foods, such as smoked fish, marinated fish, soft and semi-soft cheese, would be needed to establish the generic minimum requirements for HPP to ensure the safety of these foods.
Research – High Hydrostatic Pressure Treatment Ensures the Microbiological Safety of Human Milk Including Bacillus cereus and Preservation of Bioactive Proteins Including Lipase and Immuno-Proteins: A Narrative Review
Breast milk is the nutritional reference for the child and especially for the preterm infant. Breast milk is better than donated breast milk (DHM), but if breast milk is not available, DHM is distributed by the Human Milk Bank (HMB). Raw Human Milk is better than HMB milk, but it may contain dangerous germs, so it is usually milk pasteurized by a Holder treatment (62.5 °C 30 min). However, Holder does not destroy all germs, and in particular, in 7% to 14%, the spores of Bacillus cereus are found, and it also destroys the microbiota, lipase BSSL and immune proteins. Another technique, High-Temperature Short Time (HTST 72 °C, 5–15 s), has been tried, which is imperfect, does not destroy Bacillus cereus, but degrades the lipase and partially the immune proteins. Therefore, techniques that do not treat by temperature have been proposed. For more than 25 years, high hydrostatic pressure has been tried with pressures from 100 to 800 MPa. Pressures above 400 MPa can alter the immune proteins without destroying the Bacillus cereus. We propose a High Hydrostatic Pressure (HHP) with four pressure cycles ranging from 50–150 MPa to promote Bacillus cereus germination and a 350 MPa Pressure that destroys 106 Bacillus cereus and retains 80–100% of lipase, lysozyme, lactoferrin and 64% of IgAs. Other HHP techniques are being tested. We propose a literature review of these techniques. View Full-Text