Microbial decontamination of nuts and spices

G.G. Atungulu , Z. Pan , in Microbial Decontamination in the Food Industry, 2012

Steam pasteurization

Steam pasteurization involves heating a product to a specific temperature for a specific period of time. Hence, its most common method is called high temperature short time (HTST) treatment. The FDA has approved steam processing as an acceptable means of pasteurizing almonds. The key to steam pasteurizing almonds is in the condensation power of the steam. During pasteurization, the steam is heated to supersaturation and then allowed to condense on the cool surface of the product. One system combines steam with fluidization, then drying and cooling via a shaking mechanism. The almonds are fed into the steam pasteurizer, where superheated steam is released in a specially designed pressure area. The steam then 'fluidizes' the nuts with the assistance of the shaking mechanism via a specially designed distribution plate. It is with this condensation and consequent hot moisture that the pathogen S. Enteritidis PT30 is inactivated and the 5-log reduction occurs. The shaking and fluidization method ensures that all surfaces are exposed and treated equally. The mean free path of the steam molecule at 140   °C is 0.4   ÎĽm which is about half the diameter of the smallest cavity capable of containing Salmonella. Hence steam can quickly reach all organisms on the surface of foodstuffs and therefore incidences of the revival of the bacteria hidden in crevices are eliminated (Bari et al., 2009).

The processes of steam heating for pasteurization and sterilization are widely used and accepted worldwide. In particular, organic almonds are designated by the FDA to be pasteurized by steam, which meets the USDA Organic Program's national standards. Although the FDA-approved steam pasteurization can effectively pasteurize raw almonds, it is energy intensive and purported to increase nut moisture content which reduces nut flavor quality and structural integrity, and may need additional drying steps (Perren, 2008). Chang et al. (2010) observed that 25   s exposure of contaminated almond to steam at 143   kPa provided 5-log reduction of S. Enteritidis. The authors also noted that prolonged exposure to steam compromised product quality by increasing nut moisture content, which loosens nut skin thereby forming visible wrinkles.

Using Enterococcus faecium as a surrogate for S. Enteritidis PT30, Perren (2008) introduced the idea of controlled condensation of steam which was reported to achieve 5-log reductions in 5   min without causing any change in appearance or color of almond nuts.

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Escherichia coli O157:H7

Elaine D. Berry , James E. Wells , in Advances in Food and Nutrition Research, 2010

V Linking Preharvest and Postharvest Reduction of E. coli O157:H7

Numerous studies have demonstrated that processing practices and antimicrobial intervention procedures applied at slaughter, including hide washes, steam pasteurization, organic acid washes, hot water washes, or combinations of these treatments, substantially reduce E. coli O157:H7 from cattle carcasses (Barkocy-Gallagher et al., 2003; Bosilevac et al., 2005; Elder et al., 2000; Woerner et al., 2006a). Many of these same studies also have shown that the effectiveness of antimicrobial carcass interventions is improved by reducing the pathogen load at previous steps in the process (Arthur et al., 2004; Brichta-Harhay et al., 2008; Woerner et al., 2006a). As mentioned above, high-level fecal shedding of E. coli O157:H7 is associated with increased hide contamination, and hides are an important source of beef carcass contamination at harvest (Arthur et al., 2009; Stephens et al., 2009). Thus, it follows that pathogen reduction efforts applied throughout the animal production and processing chain should reduce the risk of E. coli O157:H7 occurrence in the final beef products.

However, recent studies suggest that any benefits of preharvest control efforts may be nullified by increases in E. coli O157:H7 infection and hide carriage of cattle that may occur during transportation and lairage. Arthur et al. (2007) found that both prevalence and levels of E. coli O157:H7 on cattle hides increased during transportation and lairage. Pulsed-field gel electrophoresis subtyping of isolates from cattle before and after transportation and from carcasses after processing revealed a large number of unique E. coli O157:H7 subtypes that were not detected at the feedlot, some of which were found in the transport trailers and many of which were likely a result of contamination from the lairage environment (Arthur et al., 2007). Subsequent work observed similar increases in E. coli O157:H7 hide prevalence from the feedlot through transport and lairage, and the pathogen was recovered from 64% of transport trailers and 60% of samples collected from the lairage environment (Arthur et al., 2008). Molecular subtyping of E. coli O157:H7 isolates indicated that cattle hide contamination that occurred in lairage accounted for a larger proportion of the hide and carcass contamination than did contamination from the feedlot (Arthur et al., 2008). Similarly, Mather et al. (2008) found that 84% of cattle at slaughter had E. coli O157 subtypes on their hides that did not match subtypes found previously on the farm of origin.

In contrast, Fegan et al. (2009) did not observe increases in either prevalence or levels of E. coli O157 in feces or on hides as a result of transportation and lairage. E. coli O157 prevalence in feces were similar at the feedlot (18%) and after slaughter (12%), and hide prevalence decreased from 31% at the feedlot to 4% after transportation and lairage. Subtyping isolates by pulsed-field gel electrophoresis showed that all E. coli O157 from hides and feces at slaughter were of the same subtype as those collected at the feedlot. Minihan et al. (2003) did not examine hides, but also did not see an increase in E. coli O157 fecal shedding by cattle as a result of transportation and lairage. Reicks et al. (2007) found E. coli O157:H7 on less than 2% of feedlot cattle hides both before and after shipping.

Risk factors for E. coli O157:H7 hide contamination during transportation and lairage included holding cattle in E. coli O157:H7 positive lairage pens, holding cattle in feces-contaminated pens, and transportation for distances greater than 160.9   km (Dewell et al., 2008). Mather et al. (2008) identified transport to the processing plant by a commercial hauler, as opposed to the farmer, as a risk factor for cross-contamination of cattle hides. Odds of preevisceration carcasses being positive for E. coli O157:H7 were higher within truckloads of cattle containing at least one animal with fecal E. coli O157:H7, and were particularly high when at least one high-level shedding animal was within the truckload (Fox et al., 2008b).

While not in full agreement, results of the cited studies indicate that E. coli O157:H7 prevalence or numbers in and on cattle during transportation or in lairage can increase as a result of contact with one another, or with contaminated feces, transport trailers, or holding pens at lairage. These observations suggest that preservation of E. coli O157:H7 reduction benefits achieved on the feedlot or farm by preharvest control strategies would require the wide adoption and practice of these procedures, and that interventions are needed to limit cattle contamination with this pathogen during transportation and lairage.

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Advances in food surface pasteurisation by thermal methods

G. Purnell , C. James , in Microbial Decontamination in the Food Industry, 2012

8.3.2 Atmospheric steam

Atmospheric steam pasteurisation of meat

A successful steam process, in terms of industrial application, has been that developed in the United States by FMC Frigoscandia; the Steam Pasteurisation System (SPS) for red meat (Fig. 8.1). Studies on this commercially available system for treating red-meat carcasses have been conducted and published by Kansas State University (Nutsch et al., 1997; Phebus et al., 1997). Significant reductions, in the order of 3.5 log units for specific bacteria, have been reported. The full commercial system (SPS 400 Steam Pasteurisation System) consists of a three-stage cabinet. Washed carcasses pass through an air-drying stage to remove residual water from the carcass, before an enclosed steam-treatment stage that may be followed by spray-cooling.

Fig. 8.1. Beef carcass immediately after treatment in an atmospheric steam cabinet in commercial operation.

A modified version of this system has been evaluated in a UK red-meat abattoir. In this work a 90   °C for 10   s treatment was favoured, producing reductions in inoculated Enterobacteriaceae of up to 3 log CFU cm−2 on treated beef carcasses (Eveleigh, 2000). However, a noticeable colour change to treated carcasses was apparent, resulting in this treatment not being adopted by the UK red-meat industry. The same equipment was evaluated by Whyte et al. (2003) on poultry carcasses. Conditions similar to those used to treat beef carcasses commercially in the United States (90   °C for 12   s) were found to produce statistically insignificant reductions in APCs, Enterobacteriaceae and thermophilic campylobacters. Increasing the treatment time to 24   s decreased cell population by 0.75, 0.69 and 1.3 log CFU g−1, respectively. However, visible damage to the outer skin tissue was found.

Studies at the University of Bristol (Corry et al., 2007), using bespoke pilot equipment (Fig. 8.2), have compared both atmospheric steam and hot water treatments for use on poultry carcasses under both laboratory and commercial conditions. In experimental studies, whole chicken carcasses, inoculated with Campylobacter jejuni and Escherichia coli K12, were treated with steam at atmospheric pressure for up to 20   s in a pilot-scale cabinet (and with hot water in a pilot immersion system for 20–30   s at 75 and 80   °C). In steam, numbers of C. jejuni were reduced by ~   1.8 log CFU cm−2 in 10   s and 3.3 log CFU cm−2 in 20   s. Corresponding reductions in numbers of E. coli K12 were 1.7 and 2.8 log CFU cm−2. However, the 20   s treatments caused the skin to shrink and change colour. The optimum treatment for maximum effect on C. jejuni and E. coli, least skin shrinkage and change of colour was concluded to be 10–12   s. Trials in a commercial poultry plant using naturally contaminated carcasses compared treatments for 10   s in steam with 20   s in hot water at 80   °C. The appearance of the treated carcasses was assessed visually at intervals until the end of shelf-life, and checks made for pseudomonas, Enterobacteriaceae and campylobacters on breast skin. Initial levels of Campylobacter spp. were low (~   1 log CFU cm−2) and variable, but reductions (similar for steam and hot water) of about 2 log cycles were obtained for the other two groups. Numbers of campylobacters were reduced, but not eliminated. Visual assessment indicated that the hot water treatment caused less change in appearance than the steam treatment. Carcasses produced using either treatment could be used for production of 'skin-off' portions. It was considered that changes to appearance of skin-on carcasses or portions would be acceptable to many consumers.

Fig. 8.2. Batch pilot-scale steam pasteurisation unit used for scientific evaluation of steam treatment of poultry carcasses.

Most studies on the utilisation of atmospheric steam have aimed to develop processes that produce a substantial reduction in microbial numbers, but do not result in substantial cooking of the product. Avens et al. (2002) determined the treatment conditions necessary for a total thermal destruction of microbes (end count of <   10   CFU   cm−2), irrespective of damage. For atmospheric steam (96–98   °C), a 3   min treatment was required to reduce natural contamination of retail carcasses from 104 to <   6   CFU   cm−2. This treatment substantially cooked all the samples.

Atmospheric steam pasteurisation of seafood

Atmospheric steam treatments have been shown to have potential for treating fish, specifically catfish (Balá et al., 1999) and salmon (Bremer et al., 2002). Atmospheric steam pasteurisation of fish has been demonstrated by Balá et al. (1999) to have potential in reducing skin microflora on deheaded and eviscerated whole catfish. A food steamer was used and samples treated for 30, 60, 90 and 120   s in conditions ranging between 90 and 98   °C. Results indicated that as steam treatment duration increased, so did microbial reductions. Initial reductions in total, coliform and psychrotrophic counts caused by the steam treatments were maintained during storage. Steam treatment for 120   s reduced total, coliform and psychrotrophic counts (compared with untreated controls) by 2.3, 3.5 and 3.4 log10 CFU cm−2 after 4   days of storage at 4   °C. The effect of such treatment on sensory characteristics was not discussed; however, it was noted that exposed muscle surfaces were discoloured and that the skin developed a white film after heating.

Bremer et al. (2002) describe trials on steam pasteurisation of gutted and defined whole salmon using bespoke treatment equipment. The fish was hung by a jaw hook and a reservoir of steam initially at approximately 8   bar was released onto and into the carcass. Fish were inoculated with L. monocytogenes at 4–5 log CFU/fish, and after an 8   s treatment, no L. monocytogenes could be recovered. In-plant trials conducted with naturally occurring organisms showed longer treatments were necessary, but nevertheless, 7 of 10 fish treated for 8   s and all 10 fish treated for 11   s showed no recoverable L. monocytogenes.

Atmospheric steam pasteurisation of produce

Atmospheric steam treatments before storage have been successfully used to control microorganisms on carrots (Afek et al., 1999; Gan-Mor et al., 2011), potato (Afek et al., 1999), sugarcane (Singh et al., 1987), sweet potato (Afek and Orenstein, 2003) and even lettuce (Martin-Diana et al., 2007). Steaming of produce has also been shown to perform functional operations such as improving the red colour of litchi peels (Kaiser et al., 1995), raising the levels of ascorbic acid and vitamins in broccoli (Petersen, 1993), and to change evaporation levels in mandarin oranges (Lin et al., 1992). It is also used to aid peeling of a wide range of agricultural produce.

A 3   s atmospheric steam treatment (product temperature ~   90   °C) before packaging reduced the proportion of decayed carrots from 23% to 2% after 60   days storage at 0.5   °C followed by 7   days at 20   °C (Afek et al, 1999). When carrots were inoculated with spoilage fungi, percentages of decay, after similar periods of storage and shelf-life, were 5% for steam-treated carrot and 65% for the non-treated controls.

Gan-Mor et al. (2011) assessed steam jets for the reduction of the plant pathogen Sclerotinia sclerotiorum. Carrots were rotated on a roller conveyer as they passed below steam jets combined with electric steam drying elements and heat reflectors. The aim of the rotation was to give steam coverage onto all surfaces and this was monitored by thermal imaging equipment. After water cooling (4   °C, 10   min), carrots were subjected to 0, 2, 3 and 4   s steam treatments attaining mean surface temperatures of 57   °C, and maximal temperatures of 65   °C for 0.3   s. Carrots not water-cooled before steam pasteurisation were not of a marketable quality, whereas those water-cooled did not possess significantly different crispness, sweetness, bitterness and overall eating quality scores to non-pasteurised carrots. A 3   s treatment gave the best overall compromise treatment with almost no colour change, a slight reduction in sprouting and a 60% reduction in soft rot after storage over non-pasteurised products. Similar benefits were seen for sweet potato storage (Afek and Orenstein, 2003) where a 3   s atmospheric steam treatment reduced the proportion of decay in cured sweet potatoes from 32% to 3% after 5   months of storage and in non-cured sweet potatoes from 86% to 14%.

Whilst many of the produce items treated with steam have been relatively robust, steam pasteurisation of more delicate items such as lettuce has also been assessed (Martin-Diana et al, 2007). Pre-cooled (4   °C) lettuces were subjected to a 10   s blanching steam spray at about 100   °C, then water-cooled at ~   25   °C for 1   min with agitation, and finally dried for 5   min using an automatic salad spinner. These were compared to a conventional chorine wash. Steam-treated lettuces showed improved browning and textural properties over the standard chlorine rinse techniques. Both treatments showed similar microbial profiles, sensory panel scores for fresh appearance and acceptability (although outer wrapped leaves were removed after treatments). However, both groups of samples were deemed fit for consumption at the end of a 10-day storage period. The steam treatment was found to have a negative effect in nutrient levels.

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On-line physical methods for decontaminating poultry meat

C. James , in Food Safety Control in the Poultry Industry, 2005

17.2.2 Atmospheric steam

The most successful steam process yet, in terms of industrial application, has been that developed in the USA by FMC Frigoscandia, the Steam Pasteurisation System (SPS) for red meat, using atmospheric steam. Studies on this com- mercially-available system for treating red-meat carcasses have been conducted and published by Kansas State University (Nutsch et al., 1997; Phebus et al., 1997). Significant reductions, of the order of 3.5 log units for specific bacteria, have been reported. The full commercial system (SPS 400 Steam Pasteurisation System) consists of a three-stage cabinet. Washed carcasses pass through an air- drying stage to remove residual water from the carcass, before an enclosed steam-treatment stage that is followed by spray-cooling.

A modified version of this system has been evaluated in a UK red-meat abattoir, and Whyte et al. (2003) carried out a series of trials on poultry carcasses. Conditions similar to those used to treat beef carcasses commercially in the USA (90 °C for 12   sec) were found to produce statistically insignificant reductions in aerobic plate counts (APCs), Enterobacteriaceae and thermophilic campylobacters. Increasing the treatment time to 24   sec decreased counts by 0.75, 0.69 and 1.3 log cfu per g, respectively. However, visible damage to the outer skin tissue was found.

The effects of various steam treatments on the appearance, shelf-life and microbiological quality of chicken portions have been investigated at the University of Bristol (James et al., 2000). Application of steam at atmospheric pressure (100 °C for 10   sec) on naturally-contaminated chicken breast portions resulted in a 1.65 log cfu per cm2 reduction in TVC. However, in comparison with untreated controls, this treatment did not extend the shelf-life. Steam treatment for up to 10   sec on chicken portions inoculated with a nalidixic acid- resistant strain of Escherichia coli serotype 080 resulted in a maximum reduction of 1.90 log cfu per cm2. Overall, results indicated that significant reductions in microbial counts could be achieved for chicken meat using steam. However, the reductions were less than would be expected from the time-temperature cycles used. Further studies (Corry et al., 2003) have continued, as part of a project funded by the UK Food Standards Agency, to devise practical methods that will reduce numbers of campylobacters and salmonellas on raw poultry carcasses and portions, without producing unacceptable changes in appearance or texture. Investigations have been carried out using a mixture of C. jejuni and E. coli K12 (a surrogate for Salmonella), inoculated onto the breast skin of carcasses. Atmospheric steam-treatments reduced numbers of C. jejuni by about 1.5 log units in 10   sec, 2.5 log units in 12   sec and 3.5 log units in 20   sec. However, they also caused the skin to shrink and change colour. The optimum treatment for maximum effect on C. jejuni, least skin shrinkage and change of colour was concluded to be 12   sec. This work has shown that survival of the test strains of C. jejuni and E. coli K12 is similar, although campylobacters are usually considered to be more sensitive to heating and drying than either salmonellas or E. coli. Comparison of the heat-resistance of the test strain of C. jejuni with other strains of C. jejuni and C. coli indicated that the test strain was of average resistance.

Most researchers have aimed to develop processes that produce a substantial reduction in microbial numbers, but do not result in substantial cooking of the product. Avens et al. (2002) determined the treatment conditions necessary for a total thermal destruction of microbes (end count of   <   10 aerobic microbes per cm2), irrespective of damage. For atmospheric steam (96–98 °C), a 3   min treatment was required to reduce natural contamination of retail carcasses from 104  cfu per cm2 to <   6. This treatment substantially cooked all the samples.

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Harvest processes for meat

Steven M. Lonergan , ... Dennis N. Marple , in The Science of Animal Growth and Meat Technology (Second Edition), 2019

Heating Steps (Hot Water or Steam Pasteurization)

Not surprisingly, hot water (165°F) is a very useful intervention to reduce pathogen loads. Maintenance of this temperature is necessary to ensure that effectiveness is maintained. Research has demonstrated that steam pasteurization in a commercial plant results in a 1–2 log reduction in aerobic plate counts.

None of the aforementioned approaches are 100% effective. The commonly accepted approach today is to use multiple sequential or layered interventions to reduce the risk of contamination of pathogens. Each firm and even each processing plant has unique approaches to achieve this reduced risk, but virtually all employ a multiple hurdle approach. A multiple hurdle approach takes advantage of additive effects of interventions to improve food safety. Fig. 7.5 demonstrates that when interventions are employed throughout the slaughter process, total plate counts, total coliforms, and total E. coli counts are all reduced.

Fig. 7.5

Fig. 7.5. Log value of total plate count (TPC), total coliform counts (TCC), and E. coli counts (ECC) on beef carcasses during beef processing.

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Strategies to limit meat wastage: Focus on meat discoloration

Ranjith Ramanathan , ... Gretchen G. Mafi , in Advances in Food and Nutrition Research, 2021

4.4 Microbial spoilage

Meat is an excellent nutrient medium for microbial growth. Contamination occurs during animal harvest, carcass fabrication, processing equipment, and/or through personal. Meat companies follow stringent meat hygienic practices such as antimicrobial washes or steam pasteurization to minimize the bacterial load. Bacterial counts (less than 3  log   CFU/mL) combined with good cold chain management has much less impact on product discoloration. Generally, some discoloration becomes visible at 6   log   CFU/mL, and bacterial counts greater than 7   log   CFU/mL can decrease red color and increase off-odors. For example, inoculating steaks with spoilage bacteria such as Pseudomonas caused rapid discoloration. The major impact of spoilage bacteria on color can be attributed to the oxygen-consuming property. Depending on the bacterial type, some are capable of utilizing heme from myoglobin and cause discoloration. Some bacteria have the capacity to produce NADH and convert metmyoglobin to deoxymyoglobin, which is sometimes referred to as color reversion.

Both aerobic and anaerobic bacterial growth can influence odor and slime on meat. Lactobacillus species can be problematic in vacuum packaged meat if proper hygienic practices are not followed. During storage, fluid flows out of meat, commonly called as drip loss, is an excellent medium for bacterial growth. Although drip loss is unavoidable, proper packaging and maintaining a cold chain can minimize bacterial growth. Recently studies have focused on the type of metabolites present in meat such as amino acids and its impact on bacterial growth. The use of a microbiome approach helps to characterize the different types of bacterial populations on the surface of the meat. Relative to creating the desired initial meat product color that has reasonable color stability, controlling other factors such as initial microbial loads on raw materials, plant sanitation, temperature control, and personal hygiene can also affect color stability.

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Physical decontamination strategies for meat

R.T. Bacon , in Improving the Safety of Fresh Meat, 2005

16.4.2 Pasteurizing

The process of steam pasteurization TM involves: (i) removal of water from tissue surfaces in order to reduce the steam barrier; (ii) exposing all carcass surfaces to 'saturated' steam; and (iii) cooling tissue surfaces in order to minimize the impact of heat on product color. Gill and Bryant (1997) randomly selected and sampled surfaces of 50 carcasses and determined microbiological counts both before and following exposure to a commercial steam pasteurization process. Mean and estimated arithmetic mean differences in aerobic plate counts before and after treatment application approximated 1.0 log CFU/100 cm2, while differences in corresponding total coliform and E. coli counts were greater than 2.0 log CFU/100 cm2. Total coliform and E. coli counts appeared to be reduced by an additional 1.0 log CFU/100 cm2 following the cooling process (Gill and Bryant, 1997). Phebus et al. (1997) exposed fecal slurry contaminated pre-rigor beef to a 15 second steam pasteurization process 20 minutes after inoculation. Microbiological analyses of excised tissues indicated that steam pasteurizing reduced E. coli O157:H7, S. Typhimurium, and L. monocytogenes counts by 3.5, 3.7, and 3.4 log CFU/cm2 (Phebus et al., 1997).

Nutsch et al. (1997) determined microbiological counts on 140 carcass sides – derived from fed and non-fed cattle – immediately before and after commercial steam pasteurizing, and following post-treatment chilling for 24 hours at 0 °C. Exposure to an 8 second commercial steam pasteurization process reduced pre-treatment aerobic plate counts associated with fed and non-fed carcass surfaces from 2.1 and 2.2 log CFU/cm2, respectively, to 1.0 and 0.8 log CFU/cm2. Enterobacteriaceae, total coliform, and biotype I E. coli counts were detected in 46, 38, and 16% of pre-treatment samples, respectively, while 3, 1, and 0% of samples yielded detectable counts following treatment application (Nutsch et al., 1997). Twenty-four hours following pasteurizing and chilling, aerobic plate counts on treated carcass surfaces were approximately 1.0 log CFU/cm2 lower than corresponding counts from non-pasteurized carcasses. The researchers reported that the steam pasteurization process significantly reduced microbiological population densities on carcass surfaces following 8 seconds of application regardless of cattle type (Nutsch et al., 1997).

Nutsch et al. (1998) determined the efficacy of commercial steam pasteurizationTM in reducing bacterial counts on beef carcass surfaces at each of five anatomical regions (inside round, loin, midline, brisket, and neck). Tissue surfaces associated with each region were sponge-swabbed (300 cm2) both before and after treatment application for 6.5 seconds. Pretreatment aerobic plate counts ranging from 3.4–4.5 log CFU/cm2 were significantly higher than corresponding post-treatment counts ranging from 2.6–3.3 log CFU/cm2. Reductions in total coliform and biotype I E. coli counts on carcass surfaces following steam pasteurizing ranged from 0.6– 1.8 and 0.4–0.7 log CFU/cm2, respectively. The researchers also reported significant treatment-dependent reductions in Enterobacteriaceae counts approximating those observed for total coliforms (Nutsch et al., 1998). Retzlaff et al. (2004) determined the impact of exposure time (0, 3, 6, 12, and 15 seconds) and chamber temperature (82.2, 87.8, 93.3, and 98.9 °C) on the efficacy of a steam pasteurization process in reducing bacterial counts on pre-rigor beef tissue. Temperatures of 82.2 and 87.8 °C were ineffective at all exposure times, while 93.3 °C reduced E. coli O157:H7, S. Typhimurium, and L. innocua counts by at least 1.0, 1.6, and 2.6 log CFU/cm2, respectively, following 6, 9, and 15 seconds of application. The researchers reported 98.9 °C superior to other chamber temperatures both in antimicrobial efficacy and consistency, as a 9 second exposure time reduced pathogen counts by greater than 3.5 log CFU/cm2 (Retzlaff et al., 2004).

Differences between reported quantitative reductions following steam pasteurizing may be due, at least in part, to higher pre-treatment microbiological population densities (> 5.0 log CFU/cm2) observed when artificially contaminating tissue surfaces (Gill and Bryant, 1997; Phebus et al., 1997; Retzlaff et al., 2004), compared to commensal microbiological counts observed on fresh carcass surfaces manufactured under commercial operating conditions (Nutsch et al., 1997, 1998). Similar to other non-discriminating decontamination strategies, antimicrobial efficacy of a steam pasteurization process is not dependent upon visually identifying gross contamination. Due to process automation, steam pasteurization also does not depend upon operator performance to thoroughly treat tissue surfaces and prevent cross- or recontamination by adhering to strict operational sanitation procedures. Further, condensable steam may be capable of uniformly heating entire surfaces including those of irregular shape that may prove challenging during application of other decontamination treatments.

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Emerging methods for post-packaging microbial decontamination of food

H. Neetoo , ... D.G. Hoover , in Microbial Decontamination in the Food Industry, 2012

23.10 Conclusion and future trends

Recalls, largely caused by the transference of pathogens such as L. monocytogenes into food products between the final processing step and packaging of perishable foods, have spurred interest in post-packaging decontamination. Improvements to existing designs and development of new technologies for thermal post-packaging applications have included hot water bath immersion, steam pasteurization, sous-vide processing, microwaving, and RF heating. Non-thermal post-packaging decontamination systems can include high hydrostatic pressure, irradiation, pulsed light technology and active packaging. One can expect continuing research into these technologies in tandem with advances in food packaging materials, given increasing consumer awareness of product safety linked to human health and the potential of economic losses associated with contaminated products. Since non-thermal methods do not incorporate additional exposure of packaged products to elevated temperatures which can further degrade sensory quality and nutrient content, one can easily envision post-packaging decontamination using a non-thermal method, such as HHP, becoming more commonplace in the food industry in order to assure enhanced food safety at a moderate cost.

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Combining physical and chemical decontamination interventions for meat

I. Geornaras , J.N. Sofos , in Improving the Safety of Fresh Meat, 2005

21.4.4 Trimming, steam-vacuuming, water washing, and/or decontamination treatments

As already indicated, US slaughter facilities are utilizing knife-trimming or steam-vacuuming of < 2.5 cm diameter areas to comply with the zero-tolerance policy for visible physical contamination (Sofos and Smith, 1998; Sofos et al., 1999a; Gill, 2004; Koutsoumanis et al., 2005). In slaughter facilities, knife-trimming is usually followed by water washing after USDA-FSIS inspection, which in most cases does not result in any major additional microbial reductions (Table 21-1) (Gorman et al., 1995b; Prasai et al., 1995; Reagan et al., 1996; Phebus et al., 1997). Phebus et al. (1997), however, reported 4.7–5.0 log CFU/cm2 reductions of inoculated (approximately 5 log CFU/cm2) pathogens (E. coli O157:H7, Salmonella Typhimurium, and L. monocytogenes) after knife-trimming and water washing, compared to reductions of 0.8–1.3 log CFU/cm2 and 2.5–3.1 log CFU/cm2 after water washing and knife-trimming alone, respectively (Table 21-1). As indicated by the authors, extensive care had been taken in their trimming procedures and freshly sanitized instruments were used to avoid cross-contamination of the underlying tissue. In commercial practice, however, the effectiveness of knife-trimming and level of cross-contamination depends on the skill and training of the employee, and the sanitary status of the trimming instruments (Prasai et al., 1995).

Table 21-1. Comparison of log cycle reductions in aerobic plate counts and/or inoculated microorganisms (log CFU/cm2) on beef carcass surface samples, as a result of knife-trimming or water washing alone, and/or knife-trimming followed by water washing

Log cycle reductions in aerobic plate counts Log cycle reductions in inoculated microorganism(s) Reference
Knife-trimming Water washing Knife-trimming + water washing Knife-trimming Water washing Knife-trimming + water washing
2.5 1.5–2.1 (35 °C, 2.76–20.68 bar, 12 s) 2.3 (water washing: 35 °C, 20.68 bar, 12 s) 2.0 1.5–2.3 (35 °C, 2.76–20.68 bar, 12 s) 2.3 (water washing: 35 °C, 20.68 bar, 12 s) Gorman et al. 1995b
3.0 0.3 a 0.9 ND b ND ND Prasai et al. 1995 c
1.3 1.0 (28-42 °C, 410–2758 kPa, 18–39 s) 1.9 ND ND ND Reagan et al. (1996) c
ND ND ND 2.5–3.1 0.8–1.3 (35 °C, 38–40 psi, 23 s) 4.7–5.0 Phebus et al. 1997
a
Water washing details not provided.
b
ND = not done.
c
In-plant studies carried out in one (Prasai et al., 1995) and six (Reagan et al., 1996) beef processing facilities.

A number of researchers (Gorman et al., 1995b, Kochevar et al., 1997b; Phebus et al., 1997; Castillo et al., 1998b ) have compared the effectiveness of knife-trimming and/or water washing, alone and in combination with one or two sequential decontamination treatments (e.g., hot water, lactic acid, hot water + lactic acid, lactic acid + hot water, steam pasteurization, lactic acid + steam pasteurization) to reduce microbial contamination on beef and lamb carcasses. In all cases, knife-trimming or water washing alone produced smaller reductions than the single or sequential sanitizing treatments. This is not surprising since knife-trimming and water washing are regarded mostly as cleaning treatments and not processes that decontaminate and enhance the safety of the product. Furthermore, knife-trimming is used for small areas of visible contamination, unlike decontamination treatments that are applied to entire carcasses where contamination may be present, but is not visible ( Gill et al., 1996; Castillo et al., 2002).

Steam-vacuuming systems are approved by the USDA-FSIS and are used throughout the US meat industry as an alternative to knife-trimming to remove visible contamination that is < 2.5 cm in diameter. Laboratory (Phebus et al., 1997) and in-plant (Kochevar et al., 1997a) evaluations have found comparable reductions of bacterial contamination after steam-vacuuming and knife-trimming. However, after an in-plant study, Dorsa (1997) concluded that steam-vacuuming could out-perform knife-trimming in reducing bacterial populations from < 2.5 cm diameter contaminated areas. Several researchers have also investigated steam-vacuuming in combination with other treatments for reducing bacterial contamination on carcass surfaces (Dorsa et al., 1996, 1997a; Phebus et al., 1997; Castillo et al., 1999a). Dorsa et al. (1996) found that steam-vacuuming followed by double water spray washing (72 °C contact surface temperature, 20 psi followed by 30 °C, 125 psi; 12 seconds) of fecally contaminated beef carcass short plates resulted in reductions (3.1 log CFU/cm2) that were not different from those achieved by steam-vacuuming (3.0 log CFU/cm2) or water washing (2.7 log CFU/cm2) alone. Similarly, reductions of inoculated E. coli O157:H7, Salmonella Typhimurium or L. monocytogenes (ca. 5 log CFU/cm2) on cutaneus truncii surfaces were similar for steam-vacuuming alone (3.1–3.4 log CFU/cm2), steam-vacuuming followed by water (35 °C) washing (3.5–3.6 log CFU/cm2), and steam-vacuuming followed by water washing and steam pasteurization (3.8–4.2 log CFU/cm2) (Phebus et al., 1997). However, when a 2% lactic acid solution (54 °C, 22 seconds) was applied prior to steam pasteurization, an additional 1-log reduction was achieved (Phebus et al., 1997).

In an additional study, when fecally contaminated carcass surfaces were treated by steam-vacuuming followed by hot water (82 °C at carcass surface, 5 seconds), 2% lactic acid (55 °C, 11 seconds), or hot water and lactic acid sprays, reductions in aerobic plate counts for the combination treatments ranged from 3.5–4.4 log10 CFU/cm2, while the reduction attained by steam-vacuuming alone was 2.7 log10 CFU/cm2 (Castillo et al., 1999a). The combination treatments were also found to effectively reduce contamination dispersed outside the inoculated area as a result of steam-vacuuming. Based on these results, it appears that steam-vacuuming is effective in reducing microbial and visible contamination from small areas; however, the effectiveness of these hand-held pieces of equipment again depends on the training and diligence of the employee and the operational status of the equipment (Sofos and Smith, 1998).

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SLAUGHTER-LINE OPERATION | Cattle

D.R. Woerner , ... K.E. Belk , in Encyclopedia of Meat Sciences (Second Edition), 2014

Final Carcass Decontamination Interventions

Just before initiation of chilling procedures, carcasses generally are subjected to a sequence of several 'final intervention' decontamination technologies designed to address the possible presence of pathogens on carcass surfaces ('multiple hurdles' systems). Synergistic or additive effects are obtained when combinations of two or more decontamination systems are used in sequence. As a rule, all carcasses are washed with large volumes of ambient-temperature water. Most plants also incorporate a thermal or steam pasteurization system designed to apply water at temperatures in excess of 82  °C, as well as spray cabinets that apply organic acids (e.g., lactic acid and acetic acid) or other chemical decontaminates to the surfaces of carcasses. Lactic acid and acetic acid are the most commonly applied organic acids in practice, both of which are approved by FDA and the Codex Alimentarius Commission as direct food additives. The Food and Agriculture Organization of the United Nations and the World Health Organization has specifically approved lactic acid and acetic acid as a food additive in all meat products (Codex Alimentarius Commission in 2006). Among the many available chemical decontaminates used as interventions, lactic acid sprays (concentrations ranging from 2.5 to 5% of solution) are one of the most consistently effective interventions against pathogenic microorganisms on the surface of beef carcasses. Until recently, the European Commission has refused to allow the use of chemical applications (e.g., lactic acid) onto carcass surfaces as interventions because of a philosophy that required prevention of contamination of live animals. However, that philosophy has now changed, and beginning in 2013, voluntary use of some interventions will become possible.

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