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A Critical Control Point approach to beef eating quality

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A Critical Control Point approach to beef eating quality

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									Meat technology update
99/1 – February 1999
Reprinted November 2006



     A Critical Control Point approach to
              beef eating quality
The production of beef that satisfies or,     Tenderness/toughness
better still, exceeds the consumer’s
                                              The variation in tenderness/toughness
expectations with regard to eating quality    can be partitioned into the muscle-fibre
is central to the industry’s future.          and connective-tissue components. In
The purpose of this update is to provide      living muscle, the fibres are responsible
an overview of beef eating quality and        for contraction. The action of the
the critical control points in any            contraction is then transferred through
production pathway that can impact on         the connective tissue framework of the
quality.                                      muscle to the ligaments and tendons
                                              which attach to the skeleton. After death,
Eating quality                                muscle-fibre contraction and relaxation
Eating quality is determined by the           continues until the biochemical reactions
consumer’s perception of whether the          underpinning this process cease. At this
product was:                                  point, the fibres are irreversibly bound.
                                              This loss of extensibility is referred to as
1.    Tender or tough                         rigor. The degree of muscle-fibre
2.    Juicy or dry                            shortening that occurs after death is the
                                              most important factor governing overall
3.    Flavoursome or lacking in flavour       tenderness/toughness in cuts low in
      and free from taints.                   connective tissue (e.g. striploin). This, in
Most of the research effort has been          turn, is regulated by the rates of pH
dedicated to the improvement of beef          decline and cooling in the muscle. The
tenderness, as consumers have clearly         indicative relationships between pH and
said that the variation in tenderness/        temperature decline and the degree of
toughness is the major factor limiting        shortening are shown in Table 1.
eating quality. In the future, as the         Another process that impinges on the
variation in toughness is successfully        magnitude of muscle-fibre toughness is
reduced, it is anticipated that issues such   the enzymatic breakdown of some of the
as flavour will take on greater               muscle-fibre proteins, which occurs when
prominence.                                   meat is aged. This is referred to as
                                              proteolysis and is controlled by a number
                                              of enzyme systems. Of these, the
                                              calcium-dependent calpains and their
                                              inhibitor, calpastatin, and the lysosomal
                                              cathepsins are considered the most
                                              important.
TABLE 1: Indicative relationships between pH and temperature decline on post-mortem
         muscle-fibre contraction

             pH      Temperature    Percentage of                             Effect
                         °C          shortening#
     ≤6.0               12-20           10-20        Optimal for tenderness
     >6.0 (slow)       <12 (fast)       30-50        Extremely tough (cold shortened)
     <5.9 (fast)      >30 (slow)        20-30        Some loss in tenderness and possibly juiciness
                                                     (heat shortened)

# Relative to approximate resting length
The contribution of connective tissue to            Since complete coverage is not possible in
overall toughness depends on both its               this update, only a brief overview is given.
quantity and quality. The amount of                 More detailed discussion of pre-slaughter
connective tissue varies between muscles            management of cattle and post-slaughter best
and this is a reflection of muscle function. For    practice will be the subjects of future updates.
instance, muscles involved in movement
contain higher amounts of connective tissue         Pre-slaughter stress must be minimised
than muscles used to maintain posture.              during the marketing of animals to slaughter.
Connective tissue toughness occurs in               Stress results in losses in muscle glycogen.
proportion to the presence of heat-stable           Sustained stress and/or muscular activity
crosslinks within the connective tissue. Since      which results in the loss of >30% of the
the proportion of crosslinks increases with         glycogen reserves in a normal, healthy animal
age, so does the connective tissue toughness.       will result in meat with a higher ultimate pH
                                                    (≥5.9), increased toughness and reduced
Critical Control Points                             shelf life. This meat is typically referred to as
                                                    ‘dark, firm and dry’ (DFD).
To deliver beef of consistent eating quality, it
is important to recognise that tenderness can       There is new evidence which suggests that
be influenced at any point along the                acute stress immediately pre-slaughter or
production pathway right up to and including        stress of a more subtle nature could be
the final process of cooking. In view of this,      implicated in altering the rates of post-mortem
the Meat Standards Australia (MSA) system           pH decline and proteolysis. This area is
has targeted critical control points within         currently being investigated by the
production pathways and implemented                 Cooperative Research Centre (CRC) for the
specifications or practices which ensure that       Cattle and Beef Industry (Meat Quality) and
losses in eating quality are minimised.             positive results have been achieved already
                                                    by varying pre-slaughter management
The critical control points, key factors within
                                                    strategies.
each, and the association or effect they can
have on the intrinsic muscle attributes are         Post-slaughter best practice is targeted at
presented in Table 2.                               both minimising the degree of muscle-fibre
                                                    contraction and ensuring optimal activity of
Pre- and post-slaughter factors
                                                    the proteolytic enzymes. Minimising the
The management of the animals and their             degree of shortening can be achieved by
carcasses in the 24–48 hours immediately            ensuring the muscle enters rigor at an optimal
prior to and after death has the greatest           pH and temperature (refer Table 1) or by
influence on ultimate eating quality.               restricting the fibres from shortening by
Inappropriate management during this phase          stretching or restraining the muscle. The rate
can result in irreversible losses in eating         and extent of pH and temperature decline also
quality.                                            influences post-mortem proteolysis. However,
                                                    the nature of this relationship is less clear and
                                                    is the subject of current investigations.
    TABLE 2:       Critical control points and associations with muscle characteristics

     Critical           Factor          Tenderness                                                     Juiciness   Flavour
     Control
                                          Muscle     Ultimate   Rate of    Rate and     Connective
      Point
                                           fibre        pH        pH       extent of      tissue
                                        shortening   (normal    decline   proteolysis   contribution
                                                      ≤5.7)

    On-farm     Breed                                              ?                                                  ?*
                Environment/nutrition                                          ?                                           *

                Age/weight at                                      ?           ?                                       *

                slaughter

    Pre-        Method of marketing                                ?           ?
    slaughter   Time off feed                                      ?           ?
                Lairage management                                 ?           ?                                      ?
                Weather conditions
                (extremes)

    Slaughter   Stunning
                Electrical inputs#                                                                                    ?
                Method of carcass
                hanging
                Duration prior to
                chilling
                Rate of chilling

    Process-    Ageing                                                                        ?
    ing         Cooking method/
                duration



#         ‘Electrical inputs’ includes electrical stimulation, immobilisation, and stiffening during hide pulling
*         The association between on-farm factors and flavour is primarily related to the amount, distribution and com-
          position of fat within the meat
          Some influence
          Moderate influence
          High influence
?         No conclusive evidence, but intuitively, it is reasonable to suggest an association.


With respect to minimising muscle-fibre                            3.      Effective chiller management (achieve
shortening, the processor has three basic                                  a moderate rate of cooling; however,
options:                                                                   this is not always practical from a food
                                                                           safety point of view).
1.      Apply electrical inputs such as
        stimulation in conjunction with rapid                      The full benefits of either electrical inputs or
        chilling, immobilisation which may be                      alternative hanging treatments will be
        carried out after stunning, and stiffening                 realised only when they are used in
        during downward hide pulling. These                        conjunction with fast chilling rates. Electrical
        inputs accelerate pH decline and must                      stimulation may not always be appropriate
        be carefully monitored.                                    for heavy carcasses.
2.      Use alternative carcass hanging
        treatments (prevents the myofibrils from                   On-farm factors
        contracting), e.g.
                                                                   The primary on-farm factors include:
          •      Tenderstretch (refer Meat
                 Technology Update 98/2)                           1.     Breed

          •      Tendercut®                                        2.     Weight and age at slaughter
3.   Nutrition/production system.                  vacuum-packaged cuts at storage
                                                   temperatures of 0-2°C, improves meat
Of all the critical control points, the on-farm    tenderness. The magnitude and rate of
factors have provoked, and continue to             improvement will depend on the post-
provoke, the greatest amount of                    slaughter management of the carcasses,
controversy. Unfortunately, much of the            the storage temperature and the ageing
debate has been unnecessary, as the                duration. For example, tenderness
magnitude of any effect has often been             improvements following ageing will be
overestimated because the post-slaughter           smaller in magnitude following effective
conditions were not controlled. For example,       electrical stimulation and/or tenderstretching
differences in weight and fatness, which           compared with normally hung, non-
typically occur between breeds (e.g. early         stimulated beef. The longer beef is aged,
versus late maturing breeds), and different        the larger the improvement; however, the
finishing systems (e.g. feedlot versus             majority of change occurs within the first
pasture finishing) will give rise to differences   seven days after slaughter. Ageing meat at
in carcass cooling rates. In the absence of        higher temperatures will also increase the
electrical inputs or alternative hanging           rate of improvement; this may, however,
treatments and when rapid chilling is used,        also compromise shelf life, flavour and
these differences in cooling rates will cause      weep.
variation in the degree of muscle-fibre
contraction and thus, tenderness.                  Cooking is the final act in the process and it
                                                   can have the largest effect on eating quality.
CRC and MSA results have demonstrated              Over-cooking or mismatching of the cut with
that, once the post-slaughter variation in         the appropriate cooking method can result
eating quality has been controlled, any            in significant consumer dissatisfaction.
breed effect is quite small. That said, there      Consumer education is one way in which
are noticeable breed effects in tenderness         the chance of failure in the household can
and these are most evident when the Bos            be avoided. Against this, however, is the
indicus content exceeds 75%. The exact             issue of ‘convenience culture’ which
reasons for this are linked to a number of         distinguishes the modern-day consumer.
intrinsic muscle factors; however, reduced         Consumers not only lack the traditional
proteolysis (i.e. ageing potential) has been       meat preparation skills but, more
demonstrated as a primary mechanism.               importantly, they lack the time to prepare
                                                   meals. Unfortunately, it is unlikely that this
The age of an animal at slaughter is               will change in the near future.
particularly important in the context of
connective tissue toughness. Currently,            This represents an opportunity for the
MSA require that all eligible cattle are less      Australian beef industry through the
than 30 months of age. MSA have also               application of value adding. The adoption of
developed a specification, defined as              value adding technologies will enable the
‘weight at maturity’ (WAM), which is a crude       production of a wide range of pre-prepared,
estimate of the growth rate/path.                  flavour-enhanced, ready-to-eat beef meal
                                                   solutions. Benefits associated with this
With regard to beef flavour, on-farm factors       approach include the delivery of:
are also important. Decisions that influence
either the feed type (e.g. pasture species         1.   Consistent eating quality
and grain ration content) and/or carcass
fatness (amount and composition) impact            2.   Convenient beef products which match
on beef flavour.                                        the tastes and health requirements of
                                                        consumers
Other processing factors
                                                   3.   Ultimately, more competitive beef
Ageing meat, either ‘on the bone’ or as                 products.
  This concept underpins the next stage
  for MSA, which aims at grading and
  labelling cuts in ways which reflect
  their end use. This not only expands
  the application of MSA to more than
  just the high value primal cuts (e.g.
  striploin, cube roll, tenderloin and
  rump), but it will ultimately obviate the
  need for some of the current pathway
  specifications, particularly the on-farm
  factors. For example, issues such as
  breed and growth history are not likely
  to have a large effect if the primal cut
  is to be minced, blended, flavour
  enhanced and pre-cooked prior to
  retailing.




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