IntroductionSilky Fowl (Gallus gallus domesticus), originating from China, is a very unusual chicken with distinct characteristics: silky feathers, black-colored bones, and dark bluish skin. Silky fowl is characterized by melanin deposits on the surface of many organs, such as the skin, comb, bone, internal digestive organs, lung, brain and skeletal muscle, and has pigment granules in practically all of its tissues (Nozaki and Makita, 1998).According to traditional Chinese medicine, Silky Fowl meat is beneficial for women's diseases, while the eggs are beneficial for lung diseases (Akishinonomiya et al., 1994). It is likely that these traditions are one of the reasons people, even those outside China, expect pharmacological effects from Silky Fowl meat or eggs. Tian et al. (2007) reported that the carnosine content in Silky Fowl meat was 1.8-fold higher than that in White Plymouth Rock. However, the content of anserine, a dipeptide with antioxidant properties related to carnosine, in Silky Fowl meat has not yet been investigated.The involvement of oxygen radicals in accelerated aging and the incidence of cancer is known, and dietary prevention of these effects is considered important. Carnosine (β-alanyl-L-histidine) and its metabolic derivative anserine (β-alanyl-1-methyl-Lhistidine) are histidine-containing dipeptides, and are present in high concentrations in chicken breast muscle. Both dipeptides play beneficial roles in a number of physiological functions, as antioxidants (Yanai et al., 2004; Koide et al., 2007), and as antifatigue (Harada et al., 2002a) and anti-glycation (Hipkiss and Brownson, 2000) agents.Silky Fowl meat is used in traditional Chinese medicine; however, there remains insufficient scientific evidence as to its properties and effects. Its black appearance might deter ordinary consumers from using it as a food. Revealing the functionality and antioxidant dipeptide contents of Silky Fowl meat is thus important S. Kojima et al. 622 for the potential health benefits of this natural food to be realized.Further, both dipeptides are water-soluble components, and are therefore easily extracted (Takai et al., 1993). Thus, it is expected that Silky Fowl could contribute to prepared foods in a form more acceptable to consumers, such as soup.In this paper, we describe the content of histidine-containing dipeptides in the skeletal muscles and meat extracts of Silky Fowl, and evaluate the antioxidant activity in the meat extracts. We compare the values in breast and thigh muscles and their extracts with those of four other species of chicken.
Materials and MethodsRaw materials White-feathered Silky Fowls were bred and reared by the Tokyo Metropolitan Agriculture and ForestryResearch Center (Tokyo, Japan). Five females (79 weeks of age)were placed in individual wire-floored cages, and fed a commercial formula feed (JA Higashinihon Kumiai Shiryou, Ltd., Gumma, Japan; crude protein (CP) 17%, metabolizable energy (ME) 3.18Mcal/kg) for the last stage of broiler production. The birds had free access...
