Commercial high pressure processing of ham and other sliced meat products at Esteban Espuña, S.A.
Abstract:
The chapter covers the evolution of high pressure processing technology for commercial applications, particularly for the treatment of sliced cooked ham at 400 MPa, and for the treatment of dry cured ham and Tapas products with next generation high pressure equipment at 600 MPa. The characteristics of the high pressure equipment, the treatment of specific products and their intrinsic physico-chemical properties, and the benefits from a commercial viewpoint will be presented in detail.
2.1 Introduction
During the slicing and packaging processes of sliced meat products, the products inevitably suffer from some type of microbiological recontamination. The growth of microorganisms present from this recontamination can limit the safe preservation and shelf-life of these products. Such preservation problems typically have only moderate impact on dry, cured, sliced products; however, they are a more serious concern for products with high water activities, high pH, and that contain virtually no competing bacterial flora capable of hindering the proliferation of spoilage microorganisms. These problems in the preservation of sliced heat-treated products are a particular hindrance for sliced cooked ham in terms of their commercialization and marketability. The main problems identified involve the presence and growth of Lactobacilli that cause the progressive acidification of the product and limit the product shelf-life to a relatively short period.
In view of these problems, some corrective actions were taken to maximize safety and freshness during product shelf-life, such as employing logistics procedures that avoided intermediate warehouses and reducing the expiration dates for sliced cooked products (and sliced cooked ham in particular). However, these changes were insufficient to improve the taste of the cooked ham near the end of its commercial shelf-life, and there was an increase in returns of expired product. Several studies between 1990 and 1997 attempted to resolve these issues for cooked ham. Thermal pasteurization of the cooked, sliced ham in its final packaging was found to be an effective method for enhancing microbiological stability of the product.
Heat pasteurization processes work with cooked products and they cannot be used with dry cured products. In these cases, heat pasteurization compromises the organoleptic and sensory characteristics (texture, flavor, color, etc.) of the products. Even with cooked products, thermal pasteurization unavoidably causes the release of juices, protein, and fat from the product, which adversely effects product appearance. These liquids accumulate in the package and have an undesired effect on texture, juiciness, color, etc. An absorbent interleaver was developed in order to absorb excess liquid and improve the presentation of the thermally pasteurized products. While the interleaver improved product appearance, it was not a commercially acceptable solution, because the products became too dry and developed a tough texture during their shelf-life.
High pressure processing (HPP) is an emerging nonthermal food processing technology in which the food is subjected to high hydrostatic pressures (200–700 MPa) by a non-compressible fluid (usually water) at generally moderate temperatures (usually significantly below 100 °C). HPP has been applied in the food industry since 1992, when the first products treated by HPP were marketed in Japan. By the end of 1995, seven companies were marketing commercial HPP- treated products, such as jam, fruit juice, sauces, rice wine, and rice cake (Hayashi, 1997). By 1996, HPP technology was gaining prominence in the food industry because of its advantages for inactivating microorganisms and enzymes at ambient or relatively low temperatures with less adverse affect on the flavor, color and nutritional constituents of foods compared to thermal-only processes (Hoover et al., 1989; Mertens and Knorr, 1992; Cheftel, 1995; Cheftel and Culioli, 1997). In general, HPP tends not to destroy the covalent bonds between atoms of the constituent molecules, as the energy used during the treatment is relatively low, and the process affects hydrogen bonds and ionic and hydrophobic interactions in macromolecules. Accordingly, HPP treatments are effective against microorganisms and enzymes to ensure food safety and shelf-life stability, respectively, but HPP is less aggressive than heat so that the product tends to retain much of the flavor, texture, nutrients, and quality attributes of the product pre-processing.
In assessing alternatives to heat pasteurization of sliced meat products, Esteban Espuña, S.A. decided to explore the potential use of HPP. In October 1996, pilot tests were conducted in Nantes (France) using HPP treatments up to 400 MPa on various sliced meat products (cooked and cured) to determine the effects of HPP on reducing microorganisms, inhibiting microbial growth after treatment, and on the organoleptic characteristics (such as appearance, texture, color, syneresis, etc.) of the products. HPP treatments of cooked products at 400 MPa significantly reduced microbial population levels, but the HPP treatments at 400 MPa were less effective for inactivating microorganisms with dry, cured products. Results of these pilot tests were encouraging for the application of HPP technology to preserve sliced cooked meat products, to maintain safety and product freshness until the end of their commercial shelf-life, and also to overcome problems induced by thermal pasteurization processes.
Esteban Espuña, S.A. considered HPP an exciting opportunity for offering consumers traditional meat products featuring improved quality and enhanced microbial safety during the shelf-life of the product. The successful marketing of HPP-treated fruit products (various fruit products in Japan, avocado products in the US, and various fruit juices in France, Portugal, and the UK) helped create a positive market outlook among global consumers toward foods preserved with HPP that encouraged Espuña to invest in HPP technology as a marketable alternative to thermal pasteurization for sliced, cooked meat products. Several important factors went into the company making this decision. First, HPP would potentially improve product quality of the cooked meat products and help the company gain market advantage over the competition. Second, being the first sliced meat company to exploit HPP technology while it was undergoing further development would help the company gain significant experience with this technology prior to its competitors. Third, the company also believed equipment manufacturing companies would eventually develop industrial equipment capable of carrying out treatments at the higher pressures needed for cured products (they comprise the main product base of Espuña), and prior experience with HPP technology would then be advantageous. Fourth, the use of high pressure would also provide the company with more potential opportunity for developing new products with HPP.
2.2 High pressure processing (HPP) equipment
2.2.1 400 MPa HPP equipment (Fig. 2.1)
In July, 1997, Esteban Espuña, S.A. bought a prototype horizontal configuration high pressure machine with a capacity of 320 L and maximum working pressure of 400 MPa. The company’s production design flows and HACCP system established in the plant suggested that a horizontal system had clear advantages over vertical configuration equipment to avoid the cross-contamination of treated and untreated products. The horizontal configuration requires loading at one end of the machine and unloading at the other end. This separation between the treated and the untreated products helps avoid cross-contamination.
Working conditions
Treated product = sliced cooked ham. Maximum operating pressure = 400 MPa, pressurization hold time = 10 min, maximum water temperature = 15 °C, production = 120 kg/cycle, cycles per day = 30, and total cycles performed (1998–2008) = 59 000.
Laboratory and pilot-scale research for sliced meat products
Laboratory and pilot-scale research for sliced meat products (cooked ham, dry cured ham, and bacon) determined the following:
• the optimal working parameters of high pressure, temperature, and processing time
• the effectiveness of the HPP treatment on the inactivation of pathogens of interest in each sliced meat product
• the shelf-life of each HPP-treated sliced meat product
• The texture and organoleptic characteristics of the HPP-treated meat products
• the appropriateness of the HPP treatment for each sliced meat product.
2.2.2 Major operational challenges with the equipment
Since the first high pressure unit installed at Esteban Espuña, S.A. was a prototype, Espuña had to collaborate with the equipment supplier continuously for the first years of operation to resolve any operational issues, such as maintenance costs and equipment repairs, finding suitable baskets for product placement, and defining the drying process of products after HPP treatments.
Maintenance costs and equipment and repairs
The original pumping system of the prototype did not function properly due to problems with the multiplier seals of the high pressure pumps. The nature of the construction material is important to prevent wear of the seals (gaskets). The first alternative pumping system provided significant improvements, but the problems were not resolved. Different suppliers of multipliers were contacted until the correct equipment for the high pressure pumps was found. Another major problem was detected in the wear of the joints. A large number of different joints were tested in order to find materials capable of withstanding the high pressures of the equipment. The discharge valves still suffer significant wear during operation and must be replaced frequently.
Baskets for product placement
The design of the baskets for placing product inside the high pressure vessel is crucial, since they determine the amount of product treatable per cycle. They need to be made of a durable material that does not damage the coating material of the interior of the pipe body as they slide during loading and unloading. It is also important that water drains out of them quickly for rapid processing throughput and to conveniently facilitate its recovery. The original baskets were made of perforated metal that allowed the water to drain quickly, but the metal rapidly eroded the coating material of the interior of the pipe body. Special hard plastic baskets had to be developed to solve these problems.
Drying the products
After HPP of the pre-packaged products, the product is removed from the high pressure vessel and it is covered with water. Cold drying equipment was purchased and implemented under a standard operating procedure. This cold drying process prepares the packaged product for labelling and packing, while also ensuring that the product maintains quality (compared to the effects of heat).
2.2.3 600 MPa HPP equipment (Fig. 2.2)
As mentioned above, high pressure treatments at 400 MPa tend not to significantly reduce pathogens and their concomitant risks in dry cured products, and higher pressure capabilities are need for ensuring the safety of these products. The 600 MPa high pressure equipment has a capacity of 318 L and a horizontal configuration to avoid post-processing cross-contamination of treated products.
Dimensions
Length = 4.5 m, internal diameter = 300 mm, external diameter = 806 mm, and volume = 218 L.
Working conditions
Treated products = dry cured meats. Maximum operating pressure = 600 MPa, pressurization hold time = 5–10 min (depending on product), maximum water temperature = 15 °C, production = 110 kg/cycle, cycles per day = 38, total cycles performed (2005–2008) = 34 500.
Laboratory and pilot-scale research for dry cured meat products
Between 2000 and 2005, internal laboratory and pilot-scale studies were undertaken to assess the effectiveness of 600 MPa treatment for dry cured products (especially for sliced cured ham) using pilot-scale equipment. The most noteworthy investigations are listed below:
• Determining the effects of HPP at 600 MPa on the microbiology, bio-equivalence, biochemical properties, and bioavailability of nutrients; and determining the mutagenic activity of vacuum-packed sliced meat products: cooked ham, dry cured pork ham, and marinated beef loin (Grèbol, 2002; Garriga et al., 2004; Garcìa Regueiro et al., 2002).
• Evaluating the inactivation kinetics of L. monocytogenes by HPP (unpublished results). Personal communication of research carried out by SSICA-Stazione Sperimentale per l’Industria delle Conserve Alimentari, Parma, Italia for Esteban Espuña, S.A. For related reference, see Gola et al. (2003).
• Modeling, designing, and optimizing a high pressure-assisted freezing process in food (Arnau et al., 2003).
• Evaluating the application of HPP for dry-cured ham to improve texture, flavor, and safety (Serra et al., 2007a; 2007b).
• Determining the efficiency of HPP at 600 MPa to inactivate pathogens of concern in different meat products (Jofré et al., 2009).
• Developing new products treated by high pressure (internal research).
The main results from this research work were:
• HPP at 600 MPa and 31°C (88°F) for 6 min to treat sliced, vacuum-packed dry cured ham samples caused a reduction of at least 2-log cycles of spoilage microorganisms, maintained low levels of survivors during the storage period at refrigerated temperatures, contributed to retaining organoleptic attributes and freshness during prolonged storage periods (investigated up to 120 days), and helped prevent off-flavors, sour taste, and gas formation (Garriga et al., 2002).
• Enterobacteriaceae and Escherichia coli were below the detection limit in all HPP-treated and untreated samples (Garriga et al., 2004).
• Bioequivalence analysis concluded that HPP-treated (600 MPa for 10 min at 31°C) vacuum-packed, cooked ham and dry cured ham were substantially equivalent to their untreated counterparts (Garcìa Regueiro et al., 2002).
• Showed that an HPP treatment at 600 MPa and 25 °C for at least 7.5 min was sufficient to obtain 5 decimal reductions of strains of L. monocytogenes isolated from raw ham with water activity (aw) = 0.90 (unpublished results). Personal communication of research carried out by SSICA-Stazione Sperimentale per l’Industria delle Conserve Alimentari, Parma (Italy) for Esteban Espuña, S.A. For related reference, see Gola et al. (2003).
• HPP treatments at 600 MPa and 31°C for 6 min reduced > 2-log cycles of Salmonella spp. and L. monocytogenes in dry cured products (for more information, see Jofrè et al., 2009).
• Toxicological evaluation of both HPP-treated and untreated cooked ham and dry cured ham were carried out using an in vitro Ames test (Maron and Ames, 1983) in order to compare the potential mutagenicity. All extracts obtained from the samples were shown to be ineffective as mutation-inducing agents in the experimental conditions.
2.3 Commercialized HPP-treated food products
The specific objectives of Esteban Espuña, S.A. were to achieve successful commercialization and marketing of the HPP-treated meat products, sliced cooked ham in particular, by assuring product freshness until the end of its best-before date, and ensuring food safety by reducing health risks associated with pathogenic microorganisms. In 1998, Esteban Espuña, S.A. pioneered the use of HPP for meat products when it began marketing sliced cooked ham (Fig. 2.3).
Fig. 2.3 Commercial sliced cook ham product (aw > 0.95) treated with HPP (400 MPa, 10 min, 15 °C) and labeled ‘Product pasteurized by high pressure: it keeps fresh until it is consumed’.
In mid-2002, the company launched the first phase of its range of tapas products developed with the use of HPP technology (Fig. 2.4). Tapas are mini pork sausages made with Spanish paprika and marinated diced pork that are heat-and-serve products for consumer convenience.
Fig. 2.4 An example of the ‘Tapas al minute’ range: Pinchitos a las finas hierbas - diced pork marinated with Spanish herbs (aw > 0.95) and treated with HPP after packaging (400 MPa and 10 min or 600 MPa and 5 min).
2.3.1 Effect of high pressure on high water activity products (aw > 0.95)
As mentioned above, slicing and packaging operations take place after cooking, and preventing cross-contamination from occurring at these points is critical with regard to determining the shelf-life and safety of the products. Under good hygiene/manufacturing practices, the levels of pathogenic and spoilage microorganisms in the products are very low. Because of the high water activity (aw > 0.95) of cooked ham, lactic acid bacteria on the ham coming mainly from cross-contamination during slicing and packaging can quickly grow to 108 CFU/g in untreated products (Fig. 2.5).
Fig. 2.5 Lactic acid bacteria evolution during commercial shelf-life. HPP treatments significantly reduce the population levels and growth of Lactobacilli, which compromise the taste, flavor, and shelf-life of cooked packaged meat products.
The pressurized product shows a significant delay in the growth of spoilage microorganisms compared to the untreated product, thereby also contributing to maintaining the sensorial freshness for at least 60 days after treatment (Garriga et al., 2002; Jofré et al., 2009). Bioequivalence and sensorial tests also show that HPP induces no differences in biochemical properties, aroma, flavor, color, and texture compared to untreated samples (Garriga et al., 2004; García Regueiro et al., 2002). Thus, HPP treatments produced a commercial packaged cooked sliced ham product (Fig. 2.3) and tapas products (Fig. 2.4) that retain their fresh taste for 60 days (the best-before date) and has widespread consumer appeal (Grébol, 2002).
2.3.2 Effect of HPP on lower water activity (aw < 0.92) products
Dried cured products (sausage, cured ham, etc.) are products that are generally microbiologically very stable, with the proliferation of spoilage microorganisms limited by the relatively low water activity values of the products (Feiner, 2006). The main concern with these products is ensuring the absence of pathogens, especially Salmonella spp. and L. monocytogenes. European law requires the absence of Salmonella in 25 g of product, and allows only < 100 cfu/g L. monocytogenes (Commission Regulation EC, 2005). Positive analysis above their respective limits for either of these pathogens means the product involved must be recalled, which results in economic losses and negative publicity for the company.
High pressure treatments with 400 MPa do not significantly reduce these pathogens and their concomitant risks in dry cured products. HPP treatments at 600 MPa and 31°C for 6 min reduces > 2-log cycles of Salmonella spp. and L. monocytogenes in dry cured products (Jofré et al., 2009). HPP treatments at 600 MPa and 25 °C for at least 7.5 min effected the inactivation of 5 decimal reductions of strains of L. monocytogenes isolated from raw ham with aw = 0.90 (unpublished results). For related references see Gola et al. (2003). Enterobacteriaceae and Escherichia coli were below the detection limit in all HPP-treated and untreated samples (Garriga et al., 2004). Additionally, bioequivalence analysis of vacuum-packed HPP-treated (600 MPa and 31°C for 10 min) cooked ham and dry cured ham were essentially equivalent to their untreated counterparts (García Regueiro et al., 2002).
2.4 Treatment costs
The main costs involved in the use of HPP for applications relating to food preservation are the initial capital investment, routine operating costs and maintenance, and subsequent amortization costs. Maintenance costs depend on the reliability of each component in the equipment, and higher pressures tend to cause more wear of the components. The use of higher pressures reduces treatment times and increases production capacity, and these factors help to recover incurred financial costs. The cost per kg of HPP-treated products using the commercial equipment (600 MPa) is half the cost per kg of treated product in the prototype (400 MPa) (see Table 2.1).
2.5 Conclusions
After ten years of operating HPP equipment for food preservation for successfully commercialized meat products, we draw the following conclusions based on our cumulative experience:
• The application of HPP was commercially successful for traditional meat products (sliced cooked ham), and its availability also facilitated the development of commercially successful new products, such as the ‘Minute Tapas’ range of products.
• HPP treatments at 600 MPa for 6 min. is an efficient method to delay the growth of spoilage microorganisms in packaged sliced cooked ham and dry cured ham (Garriga et al., 2002).
• HPP at 600 MPa for 6 min. significantly reduces the safety risks associated with Salmonella and L. moncytogenes in packaged sliced cooked ham and dry cured ham (Garriga et al., 2002).
• The use of HPP allows us to sell value-added high-quality (high organoleptic attributed and reduced microbial risks) premium products to certain customers with specific standards and a willingness to purchase premium products at premium prices.
2.6 Company information
Esteban Espuña, S.A. was founded in 1947 and manufactures meat products from its headquarters in Olot, the capital of the Garrotxa region (in the north of Catalunya, Spain). Over the years the company has combined traditional and modern production methods to provide a variety of high quality meat products. In 1989 Esteban Espuña, S.A. launched its sliced meat product range, with the aim of offering its customers innovative, convenient products. This new product range caused a sales increase which motivated the construction of an entirely new slicing plant after only four years. In 1998, Esteban Espuña, S.A. pioneered the use of high pressure in the meat products industry by marketing sliced cooked meat products. The commercial success of these products has led to additional commercial successes with the development of innovative new products, such as their range of tapas products also treated with HPP.
2.7 References
Arnau, J., Gou, P., Monfort, J.M., Sanz, P.D., Molina-García, A.D., Otero, L., Fernández, P.P., Guamis, B., Espuña, X., Grèbol, N., Masoliver, P., Gassiot, M., Yuste, J., Quevedo, J., Procedimiento para la protectión y estabilización del color de carnes y productos elaborados de carne, frescos, marinados o parcialmente deshidratados, tratados por alta presión’, 2003. [Spanish application number: 200300734.].
Cheftel, J.C. Review: High-pressure, microbial inactivation and food preservation. Food Science and Technology, International. 1995; 1:75–90.
Cheftel, J.C., Culioli, J. Effects of high pressure on meat: A review. Meat Science. 1997; 46:211–236.
Commission Regulation (Ec) No 2073/2005 of 15 November 2005 on microbiological criteria for foodstuffs.
Feiner, G. Introduction to the microbiology of meat and meat products. In: Meat products handbook: Practical science and technology. Cambridge: Woodhead Publishing Limited; 2006.
García Regueiro, J.A., Sárraga, M.C., Hortós, M., Díaz, I., Valero, A., Rius, M.A. Bioequivalence of meat products treated with high pressure processing. available at http://hdl.handle.net/2072/4750, 2002.
Garriga, M., Aymerich, T., Hugas, M. Effect of high pressure processing on the microbiology of skin-vacuum packaged sliced meat products: cooked pork ham, dry cured pork ham and marinated beef loin. available at http://hdl.handle.net/2072/4686, 2002.
Garriga, M., Grèbol, N., Aymerich, M.T., Monfort, J.M., Hugas, M. Microbial inactivation after high-pressure processing at 600 MPa in commercial meat products over its shelf life. Innovative Food Science and Emerging Technologies. 2004; 5:451–457.
Gola, S., Frustoli, M., Rovere, P., Miglioli, L. Inattivazione di Listeria monocitogenes in prosciutto crudo trattato con la pressione idrostatica. Industria Conserve. 2003; 78:441–449.
Grèbol, N. Commercial use of high hydrostatic pressure in sliced cooked ham in Spain. In: Hayashi R., ed. Trends in high pressure bioscience and technology. Amsterdam: Elsevier Science; 2002:385–388.
Hayashi, R. High-pressure bioscience and biotechnology in Japan. In: Heremans K., ed. High Pressure Research in the Biosciences and Biotechnology. Leuven: Leuven University Press; 1997:1–4.
Hoover, D.G., Metrick, A.M., Papineau, A.M., Farlas, D.-F., Knorr, D. Biological effects of high hydrostatic pressure on food microorganisms. Food Technology. 1989; 43:99–107.
Jofré, A., Aymerich, T., Grèbol, N., Garriga, M. Efficiency of high hydrostatic pressure at 600 MPa against food-borne microorganisms by challenge tests on convenience meat products. Lwt-Food Science and Technology. 2009; 42:924–928.
Maron, D., Ames, B.N. Revised methods for the Salmonella mutagenicity test. Mutation Res.. 1983; 113:173–215.
Mertens, B., Knorr, D. Developments of non-thermal processes for food preservation. Food Technology. 1992; 46:126–133.
Serra, X., Ságarra, C., Grèbol, N., Guàrdia, M.D., Guerrero, L., Gou, P., Masoliver, P., Gassiot, M., Monfort, J.M., Arnau, J. High pressure applied to frozen ham at different process stages. 1. Effect on the final physicochemical parameters and on the antioxidant and proteolytic enzyme activities of dry-cured ham. Meat Science. 2007; 75:12–20.
Serra, X., Grèbol, N., Guàrdia, M.D., Guerrero, L., Gou, P., Masoliver, P., Gassiot, M., Ságarra, C., Monfort, J.M., Arnau, J. High pressure applied to frozen ham at different process stages. 2. The effect on the sensory attributes and on the colour characteristics of dry-cured ham. Meat Science. 2007; 75:21–28.