Page 38 - Natural Antioxidants, Applications in Foods of Animal Origin
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Mechanism of Oxidation in Foods of Animal Origin                17
  VetBooks.ir  1.4.7  PARTICLE SIZE REDUCTION AND TUMBLING




            Ladikos and Lougovois (1990) postulated that any process causing disruption
            of the muscle membrane system, such as grinding, cooking, and deboning,
            results in exposure of the labile lipid components to oxygen, and thus accel-
            erate development of oxidative rancidity. Destruction of the extremely well
            organized structure of living animal cells will bring together lipids, oxidation
            catalysts, and enzymes responsible for lipid oxidation. Pearson et al. (1977)
            suggested that chopping and emulsification are at least as likely to cause
            WOF as grinding or mincing of samples. Dawson and Gartner (1983) attrib-
            uted the high oxidative potential of mechanically deboned poultry to the
            extreme stress and aeration during the process and the compositional nature
            (bone marrow, heme, and lipids) of the product; TBA values increase most
            rapidly with decreasing particle sizes, as the latter are related to greater cell
            disruption. On the other hand, comminuted beef has a storage life similar to
            that of intact pork, despite the differences in fatty acid composition (Enser,
            1987).
               The mechanical force of tumbling can break the structure of the cell and
            organelle  membranes which could lead to an exposure of phospholipids
            to cellular prooxidants (e.g., iron and heme proteins) or free radicals. The
            tumbling process has also been found to promote lipid oxidation in beef
            bottom  round (Cheng  &  Ockerman,  2003). However, inhibition  of lipid
            oxidation by the citric acid marination could be due the removal of prooxi-
            dants such as heme proteins by the marination/tumbling procedure. Alter-
            nately, inhibition of lipid oxidation could be due to the presence of citric acid
            since these molecules are strong metal chelators (Ke et al., 2009).



            1.4.8  HIGH PRESSURE PROCESSING

            High pressure (HP) processing has been shown to initiate lipid oxidation in
            fresh meat, especially a threshold pressure around 500 MPa seems to exist,
            which can lead to reduced quality and shelf life (Bolumar et al., 2014). Two
            mechanisms have been proposed to explain the pressure-induced lipid oxida-
            tion: (a) increased accessibility of iron from hemoproteins and (b) membrane
            disruption. Several studies have observed that the addition of ethylenediami-
            netetraacetic acid (EDTA), which can chelate metal ions like iron, can be
            correlated with a reduction of the lipid oxidation in meat processed by HP,
            which suggests that transition metal ion catalysis is the major factor under-
            lying the increased lipid oxidation (Beltran et al., 2004; Ma et al., 2007).
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