Page 241 - Natural Antioxidants, Applications in Foods of Animal Origin

220 Natural Antioxidants: Applications in Foods of Animal Origin
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Measuring Oxidative Stability of Fresh Rendered Lard During Storage

300
~ Reference
PV
§ 250
i .,
;§ 200 ---PV- Reference+ Nat. Ox.
Inhib .
.....
0 150 ...,._pA V Reference
-.::
E
~ 100 ---pAV Reference+ Nat. Ox.
gj Inhib.
~ 50 ---TOTO X Reference
0
0 (fresh) 2 .....,. TOTO X Reference+ Nat
Ox. Inhib.
Weeks Storage at !30°F (54.4°C) , Atmospheric Conditions
FIGURE 6.10 Data show an improvement in the storage stability of lard with natural
oxidation inhibitors (abbreviated as Nat Ox Inhib). PV or p-AV values alone would minimize
the importance of the added natural oxidation inhibitors.

TOTOX values (2PV + p-AV) provide more information because it
measured the current oxidative status (PV) and oxidation that had occurred
during processing (p-AV).

6.2.4 TBARS AND SENSORY EVALUATION

Volatile secondary oxidation products are most likely to be associated with
off aromas and off flavors in meat products. Malondialdehyde (MDA) is a
secondary oxidation product (from trienes) that at concentrations as low as
2–3 ppm produces off flavors and off aromas in value-added beef, pork, and
poultry products (Pearson & Dutson, 1985). The diagram of the reaction
shows that a prepared sample containing the secondary oxidation product
MDA (compounds in abundance in oxidized tri-ene and tetra-ene fatty acids)
reacts with thiobarbituric acid (TBA) to from a chromagen that absorbs
strongly at 532 nm (distillation method). However, some TBA reactive alde-
hydes absorb at 450 nm.
One mole of MDA reacts with two moles of TBA to form a chromagen
that absorbs strongly at 532 nm. TBA may react with other compounds
present; therefore data form this method are reported as TBARSs. The
concentration of thiobarbituric reactive substances or TBARSs (expressed
as TBARS or MDA kg of sample) is determined by developing a calibra-
–1
tion curve using appropriate concentration range (mg mL or μmoles mL )
–1
–1