The effect of rearing system and cooking method on the carnosine and anserine content of poultry and game meat

8 Poultry meat has been shown to be a rich source of carnosine and anserine (CRC) but 9 little is known of the effects of bird species and the system under which it is reared have 10 on the concentrations of CRC. Retail samples of breast meat from conventional chicken, 11 free range chicken and pheasant, and breast meat from wild caught pheasant were 12 procured and subjected to five different cooking methods: frying, grilling, boiling, 13 microwaving and roasting. CRC were greater in uncooked pheasant than chicken (P< 14 0.05) and greater in free range than conventionally reared chicken (P<0.05). There were 15 no differences in CRC between retail and wild caught pheasant. Cooking method affected 16 CRC content; boiling and microwaving resulted in lower CRC contents than grilling, 17 roasting or frying (P < 0.05). Pheasant is a richer source of CRC than conventionally 18 reared chicken, although free range chicken produces meat of similar CRC content to 19 pheasant.


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Carnosine and anserine are dipeptides of the amino acids -alanine and histidine and are 25 found in the muscles of a number of different vertebrates (Kohen et al., 1988). Carnosine 26 is more abundant in mammalian tissues, whereas anserine, the methylated form of 27 carnosine, is found in greater concentrations in the muscles of avian species (Wolf & 28 Wilson, 1935;Amend et al., 1979). Both carnosine and anserine have been shown to 29 serve a number of important physiological functions; these include inhibition of glycation 30 (Hipkiss et al., 1998), pH buffering in muscles (Davey, 1960;Harris et al., 1998) as well 31 as a role in antioxidant protection (Boldyrev et al., 1993, Chan et al., 1994. 32 Both carnosine and anserine can be synthesised in the human body from β-alanine and 33 histidine, but an alternative source is the exogenous supply of these dipeptides from the ). The rate of clearance of anserine when incorporated into a food (meat) appears to 41 be slower than when the anserine is consumed as a supplement (Kubomara et al., 2009), 42 and this may have some advantages with regard to the utilisation of this compound, and 43 its physiological efficacy. 44 Poultry meat has been shown to be a richer source of anserine when compared with other 45 meat sources (Peiretti et al., 2011;Rymer, 2012) and abundance varies with muscle type.

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Exercise has been reported to influence muscle fibre type, as prolonged, vigorous training 47 has been shown to result in an increase in the abundance of type II muscle fibres (Harris 48 et al., 2012). Type II muscle fibres can be prone to fatigue and as such contain greater 49 concentrations of carnosine related compounds (CRC) (Sewell et al., 1992;Dunnett et al., 50 1997). Therefore it is hypothesised that meat producing animals which are more active 51 may contain higher concentrations of these dipeptides within their muscle tissues than 52 those which are reared more intensively. Free range chickens may therefore have a higher 53 concentration of CRC in their flight (breast) muscles than conventionally reared chickens.

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Game birds are likely to have even more active flight muscles, and it is hypothesised that 55 the breast meat of pheasants would be a richer source of CRC than either conventionally 56 reared or free range chicken.

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Meat, particularly poultry meat, should be cooked through thoroughly prior to eating.

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Cooking has been shown to reduce the CRC content of meat (Purchas et al., 2004;59 Bauchart et al., 2006;Peiretti et al., 2011) with reductions being lower in grilled samples 60 when compared with those which had been boiled (Peiretti et al., 2011). If poultry meat 61 were to be marketed as a source of CRC, this effect of cooking would have repercussions 62 on the value of the meat as a CRC source, and so does need to be confirmed.

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The aim of this study was to determine whether the CRC content of a more active avian 64 species (pheasant) was greater than that of chicken, and whether the way in which the 65 bird was reared affected its CRC content. The study also aimed to determine whether 66 different cooking methods affected the CRC content of the meat from these different

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It is also interesting to note that the ratio of carnosine to anserine was very similar between 159 the two species. The carnosine:anserine ratio has been reported to be species specific and 160 that it could be used to determine the species of origin of meat products (Plowman and 161 Close, 1988;Abe and Okuma, 1995). The carnosine:anserine ratio in chicken has been 162 reported to range between 0.28 and 0.81 whilst that of turkey has been shown to be lower 163 at 0.18 to 0.27 (Plowman and Close, 1988). The carnosine:anserine ratio did not 164 differentiate between the two species in this study, and might suggest that the 165 physiological anatomy of these two species is similar.  (Table 2). Compared with the uncooked meat, the anserine 171 (P=0.013) and total CRC (P=0.042) content was increased when the meat was grilled, 172 roasted or fried; if the meat was microwaved this also increased total CRC content.  However, if the difference in CRC content between uncooked and cooked samples is 182 calculated then estimated CRC losses (Table 3)  in the current study and as such it is not possible to confirm this hypothesis.

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CRC losses associated with grilling, frying or roasting in the current study were markedly 199 lower than those seen with boiling or microwaving, accounting for approximately 5% of 200 the CRC content of the uncooked sample (Table 3). CRC losses reported in other studies 201 have shown that losses associated with grilling and broiling are lower than those seen in 202 boiling, although the losses reported for grilling are notably greater than those seen in the 203 current study (Peiretti et al., 2012). This difference in findings between studies may also 204 reflect differences in grilling technique.

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Breast meat from birds that have had access to range (and therefore more exercise) is a 207 richer source of anserine and CRC than that of conventionally reared chicken, but there 208 is no significant difference between free range chicken and retail pheasant, or retail