- Rapid Meat Cooling

Lee Gapper (FOOD MACHINERY COMPANY) COOLMEAT Consortium

Meat & Poultry SeminarCampden BRI, Chipping Campden,

Gloucestershire, UK21st March 2013

Challenges for the meat industry In order to minimise the growth of pathogens in the cooked meat

industry, strict EU guidelines demand that cooked meat joints including ham, turkey, chicken, pork and beef need to be cooled within tight time limits post cooking, whereby meat joints should not exceed 2.5 kg and 100 mm in thickness and should be chilled from 74 to 10ºC within 2.5 h after being removed from the cooking process.

Irrespective of the preparation methods and cooking procedures employed, rapid cooling of meat after cooking is vital for microbiological safety as well as for keeping sensory and nutritional quality.

Conventional methods for cooling cooked meat are time consuming and prevent manufacturers from meeting EU “cook-cool” guidelines, particularly in the case of large meat joints.

Vacuum cooling has been proven to dramatically reduce cooling times, but with negative effects on the flavour, texture and colour of the meat.

The COOLMEAT project aimed to develop an alternative method to provide cooked meat producers with an effective technique of improving the vacuum cooling process, while safeguarding the quality and safety of meat products.

Introduction to the COOLMEAT projectVacuum Cooling Principles Vacuum cooling is based on rapid evaporation of water on and within a product to obtain the cooling effect.In vacuum refrigeration, water vaporizes in a chamber under low pressure. For any product containing free water, if placed in a closed vessel where pressure is reduced through a vacuum pump, the vapour pressure difference between the water in the product and the surrounding atmosphere will cause water to evaporate. Since the product is in a closed system, the latent heat required for evaporation has to be furnished by itself through the conversion of sensible heat. Consequently, the product temperature is reduced.The temperature at which liquid starts to evaporate is called the liquid saturation temperature, and is dependent on the surrounding vapour pressure.

Fig. 1 - Illustration of the vacuum cooling process

Principles of the technique...

Cooling is mainly achieved by evaporation, not conduction

Size and weight are not as important as density and porosity

Principles of the technique...

Significantly faster than other cooling process Uniform temperature distribution Precise temperature control Process is very hygienic and

microbiologically safe Low energy consumption

Principles of the technique...

Advantages

and Disadvantages

Significantly higher cooling loss Batch process Product specific Undesirable effects on some

quality properties

Vacuum cooling of large cooked meat joints

Faster

Safe

Reduced yield

Increased firmness of product

advantages

drawbacks

A combined cooking & cooling procedure to produce very tender and juicy large cooked meat joints

Immersion cooking at 80oCCooling: IVC

log hams, average weight 3.8kg

Steam cooked till 72oC at core for 2 min

Cooling: IVC; Vacuum Cooling (VC); and Air Blast (AB)

Laboratory trials with IVC

Morcilla sausages:

Hams:

Results

Fig. 2 – COOLMEAT IVC prototype - Trials with “Botifarra”

Trials with COOLMEAT IVC

Fig. 3 – COOLMEAT IVC prototype –Trials with hams.

Trials with COOLMEAT IVC

Vacuum cooling (Final P = 6.5 mbar)

Immersion vacuum cooling (Final P = 6.5 mbar)

Air blast cooling (air velocity =1.8m/s, -3.0oC ≤ Tar ≤ 2.9oC,

Taverage=0.8oC)

Ham trials - Cooking and Cooling

Cooling Methods until core T <5oC

AB VC IVC

Ham trials - Results

ABIVCAB

IVC

IVCAB

Both VC and IVC could cool the hams down to <4oC

Cooling times: VC < IVC < ABCooling losses: IVC < AB < VC

Ham trials - Results

Cooling method

Cook loss(%)

Cool loss(%)

Total loss(%)

Cook rate(oC/min)

Cool rate(oC/min)

Cook time(hours)

Cool time(hours)

Total time

(hours)

VC 23.3% 9.7% 30.7% 0.28 1.03 3.3 1.0 4.3

AB 20.1% 5.5% 24.5% 0.35 0.21 3.5 5.5 9.0

IVC 20.6% 2.4% 22.4% 0.37 0.42 3.2 2.8 5.9

Hams cooled in COOLMEAT IVC

Morcilla IVC trials …

Linear pressure reduction rate: 75 mbar/min

Water temperature T 15oC, water level 2 cm above sausage surface

Final pressure set at 5 mbar; flash point set to 200mbar

Agitation 870 rpm; condenser temperature: -12oC

Immersion vacuum cooling conditions

Immersion for 10 min (Tw 17.7oC), then transfer to cold

room until T 5oC

5 > TCR > -2oC

Simulated industrial cooling conditions

Immersion cooling conditions Water bath, Tw 3oC

Morcilla IVC trials results

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 1500

10

20

30

40

50

60

70

CR IC IVC

time (min)

Tem

pera

ture

(oC)

Immersion Cooling (IC)

Simulated industrial Cooling (CR)

Immersion vacuum cooling (IVC)

Cooling time to 5oC min 49a 8 123b 7 34c 3

Total mass loss % 4.1a 1.4 6.0b 0.7 5.0c 0.6

Moisture content % 64.75a 0.95 64.26a 0.94 64.44a 0.97

Surface Colour (L*/ a*/ b*) 37.68a/ 11.04a/4.35ab 35.65b/11.25a/3.10a 37.49a/11.10a/3.55b

Internal Colour (L*/ a*/ b*) 35.38a/16.88a/3.72a 34.67a/17.58a/2.88a 34.46a/17.38a/2.65a

Morcilla IVC trials results

Note: different superscript letters indicate significant difference (P < 0.05).

Challenge test – C. perfringens

Aim: Document that the IVC-process is fast enough to ensure no

microbiological growth during chilling

Methods Inoculate ham (±nitrite) with Clostridium perfringens Measure the temperature/time during cooling Measure growth of Clostridium perfringens during three different

cooling sessions (IVC, cook/chill, chill room)

Results: Challenge test – C. perfringens

Temperature during cooling hams (core temperature):

  Cook/chill cabinet IVC-prototype Chill room at 5°C

No of measurements

3 hams 6 hams 2 hams

70°C to 10°C 322 ±25 minutes 178 ±5 minutes 675 ±14 minutes

50°C to 10°C 257 ±16 minutes 165 ±5 minutes 628 ±81 minutes

Results: Challenge test – C. perfringens

Number of C. perfringens in hams (n=6) after heat treatment and cooling

Measured number (log cfu/g)Mean of 6 hams

Cook/chill cabinet

IVC-prototype Chill room at 5°C

Ham, 0 ppm nitrite (A) 3.4 ±0.2(No growth)

2.9 ±0.3(No growth)

5.2 ±0.4(Growth)

Ham, 150 ppm nitrite (B) 2.0 ±0.3(No growth)

2.4 ±0.5(No growth)

1.9 ±0.4(No growth)

Conclusion: Challenge test – C. perfringens Growth in hams without nitrite during slow cooling in chill room (10-

11 hours from 50°C to 10°C) No growth during cooling of ham added 150 ppm nitrite (3, 4 or 11

hours from 50°C to 10°C Addition of 150 ppm nitrite increased the reduction of C. perfringens

(spores) during heat treatment (72°C). No growth of C. perfringens was observed in hams with and

without nitrite during cooling in the IVC-prototype.

The fast cooling in the IVC chamber improves the safety of large pieces of meat added low amounts of preservatives.

Sensory evaluation

Aim: to investigate whether the immersion vacuum cooling led to dry meat?

The professional panel of assessors performed the evaluation of texture attributes.

Horseshoe gammon bombs

Compare traditional cooling with IVC(9 hams pr. treatment – 18 in total)

Two muscles

Nine assessors

Accredited profile analysis

Focus on texture :Juiciness and tenderness

Results for sensory analysis - silverside

No difference!

Same result for top round

A reduced cooling time in conjunction with energy savings as result of lower process times . In terms of the cooling time, results with hams, both at laboratory and prototype scale, showed that although cooling times for IVC were higher than vacuum cooling as expected, they were approximately 40-50% shorter than air blast, which is the usual cooling method used in industry for this type of products. Tests with “morcillas” or products alike were performed only at laboratory scale. Reductions in the cooling time of approximately 70% were obtained at laboratory level when “morcillas” were immersion vacuum cooled and compared to the traditional method used in industry.

The COOLMEAT technology reduces the weight loss of vacuum cooling technology by at least 50%. The weight loss of immersion vacuum cooled hams is about 4 to 5%, while for vacuum cooled samples weight loss ranges from 10 to 12%. Thus, cool loss is remarkably lower than for vacuum cooling, and certainly still lower than for air blast (about 6%).

Overall Conclusions

Product quality of the cooked-cooled meat product - The overall results showed no significant differences between ham samples immersion vacuum cooled and samples cooled in a chilling room (air) for any of the texture attributes studied (e.g. firmness, juiciness, tenderness, stringy, crumble, chewing time). In addition, and with respect to the vitamin content, thiamine in particular, no difference was observed between the two cooling methods used. Thus, with COOLMEAT is possible to obtain a product of comparable quality properties to those cooled by the traditional method (air blast).

The COOLMEAT IVC prototype is implemented with a precise control of the pressure reduction, so to avoid sudden and uncontrolled boiling and reduce the free space on top of the solution containing the cooked meat product to be cooled. This characteristic will differentiate the COOLMEAT system with respect to vacuum coolers commercially available, which lack this type of control.

COOLMEAT is an affordable technology that allows simple installation and integration into existing meat plants. This feature would aid a successful marketing strategy of COOLMEAT.

Cost efficiency and price - The COOLMEAT system would be marketable at a cost in the region of €27,500 -30,000. There is no equivalent equipment available in the market, but an approximate estimation could be done if the basic structure is a simple commercial available unit, a vacuum cooler, to which it is added the control system and complementary accessories to be operated as immersion vacuum cooler.

Thanks for the attention!