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|Autori: ||Luciano, Giuseppe|
|Titolo: ||Meat oxidative stability as affected by animal feeding system and dietary phenolic compounds|
|Abstract: ||Meat oxidative stability represents a major topic in meat science because of the importance of both colour and flavour in consumer's assessment of meat quality. Several findings showed that colour stability and lipid oxidation in meat are connected, with interactions existing between the oxidation of lipids and the oxidation of myoglobin. However, the exact mechanisms behind these relationships are still under debate. Several authors proposed that the direct interaction of secondary compounds of lipid oxidation with myoglobin can promote the oxidation of the latter, while other authors proposed that the consumption of oxygen by lipid oxidation could contribute to the oxidation of myoglobin. Several strategies can be implemented to improve meat oxidative stability and, among these, the diet of the animals represents an important approach. The present thesis was aimed at studying the effects of different feeding strategies on meat oxidative stability and was developed with four experiments.
Experiment One: with this experiment, the effect of feeding lambs with herbage- or concentrate-based diets on meat oxidative stability was studied. The results of the study showed unequivocally a beneficial effect of the herbage-based diet on all the major parameters of meat oxidative stability, with marked protective effects against lipid and myoglobin oxidation and, consequently, against meat discolouration.
Experiment Two: this experiment was designed to assess the effects of varying the proportion of concentrates and forages in the diets for cattle on the balance between pro-oxidant and antioxidant components in muscle and on the oxidative stability of the resultant meat. The results of the study interestingly showed that the diet can deeply modify the balance between pro- and antioxidants in muscle with a clear interaction between the dietary background of the animals and the oxidative stability of their meat. Indeed, it was demonstrated that meat with different levels of antioxidants can display similar oxidative stability because of the different levels of pro-oxidant components. Conversely, dietary strategies impairing the deposition of antioxidats in muscle can have deleterious effects on meat shelf life if the levels of pro-oxidants in muscle remain high. Moreover, it has been demonstated that herbage-based feeding systems improve meat colour stability compared to concentrate-based diets and, with respect to this issue, the positive effect on meat colour stability seems to be at some extent unrelated with lipid oxidation
Experiment Three: this experiment aimed at evaluating the possibility of using phenolic compounds in animal feeding to improve meat shelf life. It was demonstrated that feeding lambs with a concentrate-based diet enriched with a polyphenol-rich plant extract improved myoglobin oxidation and meat colour stability. Interestingly, no effect of dietary polyphenols was detected on meat lipid oxidation.
Experiment Four: this study was designed to better understand the protective effect of dietary phenolics on meat colour stability observed with the Experiment Three. The analysis of phenolic compounds and of the overall antioxidant status of the muscles from the same animals used in Experimen Three showed that dietary phenolics could be transferred from feeds to animal tissues where they could exert direct antioxidant activities. Moreover, meat from lambs fed the polyphenol-enriched diet showed higher resistance of myoglobin to induced oxidation, which confirms that phenolic compounds may exert positive effects on myoglobin stability with no involvemet of lipid oxidation.|
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