Food Biochemistry and Food Processing (2 edition)

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300 Part 3: Meat, Poultry and Seafoods

3

2 Mixing

Addition

of buffer

and

enzyme

1

Muscle sample

from carcass

extraction

5 4

Enzyme extract

and substrate

added to

Incubation

and

lecture in

6

Computer

reaction buffer in

multiwell plates

spectrofluorimeter

recording

Figure 15.11.Example of application of biochemical-based

methods for evaluation of meat quality. A sample of the carcass

(1) is mixed with buffer (2) for enzyme extraction and

homogenization (3). Enzyme extracts are placed in the wells of a

multiwell plate and synthetic substrates, previously dissolved in

reaction buffer, are added (4). The released fluorescence, which is

proportional to the enzyme activity, is read by a multiwell plate

spectrofluorometer (5) and computer-recorded (6).

Biochemical Assay Techniques

Biochemical assay methodologies are based on biochemical

compounds that can be used as markers of meat quality. The

mode of operation is essentially schematized in Figure 15.11.

Some of the most promising techniques include assay of pro-

teolytic muscle enzymes and use of peptides as biochemical

markers.

The assay of certain proteolytic muscle enzymes such as cal-

pain I, alanyl aminopeptidase, or dipeptidylpeptidase IV at just 2

hours postmortem, has shown good ability to predict the water-

holding capacity of the meat (Toldr ́a and Flores 2000). Modified

assay procedures, based on the use of synthetic fluorescent sub-

strates, have been developed to allow relatively fast and simple

measurements of enzyme activity with enough sensitivity.

Some peptides have been proposed as biochemical markers

for meat tenderness, which is particularly important in beef.

These are peptides with molecular masses ranging from 1282 to

5712 kDa, generated from sarcoplasmic and myofibrillar pro-

teins (Stoeva et al. 2000). The isolation and identification of

these peptides are tedious and time consuming, but once the

full sequence is known, Enzyme-linked immunosorbent assay

(ELISA) test kits can be developed, and this would allow rapid

assay and online detection at the slaughterhouse.

BIOACTIVE COMPOUNDS

It is well known that meat contains a large amount of proteins

with high biological value. However, in recent years, the bioac-

tivities of certain compounds that are present in meat, even

though in minor amounts, have received increased attention be-

cause they may have an important nutritional role.

CLA is a group of isomers of octadecadienoic acid that is

abundant in the fat of ruminants like cattle and sheep. The con-

tent may change depending on the breed, feed, and age. CLA has

been reported to reduce the risk for certain types of cancer like

the colorectal cancer as well as having other activities like an-

tiartherioesclerotic, antioxidative, and also playing certain role

in controlling obesity (Arihara and Motoko 2010).

Some of these substances are small peptides, which are present

in meat. Dipeptides carnosine and anserine are present in meat

although their content varies depending on the animal species

and the type of muscle metabolism (Aristoy et al. 2004, Aristoy

and Toldr ́a 2004, Mora et al. 2008). Both peptides have shown

good resistance to proteases and a good antioxidant activity.

Other bioactive peptides are derived from meat proteins after di-

gestion. These peptides exert an antihypertensive effect through

the inhibitory action on the angiotensin I converting enzyme. So,

several bioactive peptides have been identified and sequenced

after simulated in vitro gastrointestinal digestion of pork meat

proteins (Escudero et al. 2010a, 2010b).

In summary, there are many biochemical and chemical re-

actions of interest in raw meats that contribute to important

changes in meat and affect its quality. Most of these changes, as

described in this chapter, have an important role in defining the

aptitude of the meat as raw material for further processing.

REFERENCES

Abouelkaram S et al. 2000. Effects of muscle texture on ultrasonic

measurements.Food Chem69: 447–455.

Arihara K, Motoko O. 2010. Functional meat products. In: F Toldr ́a

(ed.)Handbook of Meat Processing. Wiley-Blackwell, Ames, IA,

pp. 423–439.

Aristoy MC, Toldra F. 1998. Concentration of free amino acids and ́

dipeptides in porcine skeletal muscles with different oxidative

patterns.Meat Sci50: 327–332.

Aristoy MC, Toldr ́a F. 2004. Histidine dipeptides HPLC-based test

for the detection of mammalian origin proteins in feeds for rumi-

nants.Meat Sci67: 211–217.

Aristoy MC et al. 2004. A simple, fast and reliable methodology

for the analysis of histidine dipeptides as markers of the presence

of animal origin proteins in feeds for ruminants.Food Chem94:

485–491

Armero E et al. 1999a. Effect of the terminal sire and sex on

pork muscle cathepsin (B, B+L and H), cysteine proteinase

inhibitors and lipolytic enzyme activities.Meat Sci51: 185–

189.

Armero E et al. 1999b. Effects of pig sire types and sex on carcass

traits, meat quality and sensory quality of dry-cured ham.JSci

Food Agric79: 1147–1154.

Armero E et al. 2002. Lipid composition of pork muscle as affected

by sire genetic type.J Food Biochem26: 91–102.

Bandman E. 1987. Chemistry of animal tissues. Part 1-Proteins.

In: JF Price, BS Schweigert (eds.)The Science of Meat and

Meat Products. Food and Nutrition Press, Inc, Trumbull, CT,

pp. 61–102.

Basset O et al. 1999. Texture image analysis: application to the

classification of bovine muscles from meat slice images.Optical

Eng38: 1956–1959.