Meat quality of raw and processed guinea fowl (Numeda meleagris)
Thesis (MSc (Consumer Science)--Stellenbosch University, 2008.
The purpose of this study was to investigate the chemical composition mineral and cholesterol content of the different cuts (breast, drumstick and thigh) of raw guinea fowl meat. The study also aimed at establishing the effect of cooking method on guinea fowl quality attributes by investigating the effect of different cooking methods on the chemical composition and sensory attributes of the different cuts. The effect of injecting a brine solution on the chemical composition and sensory attributes were also investigated. There were no differences in terms of moisture content of the various cuts raw guinea fowl meat The breast had significantly higher protein content when compared to drumstick and thigh (P<0.05). The fat content was similar for all the cuts (P>0.05). Whilst the drumstick had significantly the lowest value for ash content when compared to the thigh. Saturated fatty acids (SFAs) and total unsaturated fatty acids (TUFAs) were not different (P>0.05) in all the cuts. Drumstick had significantly higher monounsaturated fatty acids compared to other cuts (P<0.05), and it had the highest polyunsaturated fatty acids (P<0.05). The breast had the lowest (P<0.05) n-6 fatty acid value (44.25) and had relatively the lowest Polyunsaturated:Saturated (P:S) fatty acid ratio of 1.74 when compared to the other cuts. High n-6:n-3 ratios, ranging from 7.05 to 16.58, were also found in all the cuts. Cholesterol was lowest (P<0.05) in the breast. Seventeen amino acids were found, including the eight of the nine essential amino acids. Significant differences were found in amino acid values for the different cuts. Values of iron were significantly higher in the drumstick and thigh cuts (P<0.05), whilst drumstick had the highest zinc content of all the cuts (P<0.05). On investigating the effect of three cooking methods (baking-bag, foil-wrap, open-roasting at 140ºC for 65 minutes) on the chemical composition, the open-roasting method produced higher moisture content (P<0.05) consistently for all cuts, with the breast having the highest and the drumstick the lowest (P<0.05). The moisture content of the baking-bag method on the other hand was consistently the lowest (P>0.05). This effect was significant for the breast, which had lost the most moisture (P<0.05). The baking-bag method consistently resulted in a higher protein content, which is attributed to the higher moisture loss (P<0.05) in comparison with the other methods, resulting in a more concentrated product. With regard to the fat content no effect resulting from the cooking methods could be observed (P>0.05), but the cuts’ natural fat content was reflected especially in the open–roasting method (P<0.05) giving further support to the understanding that the open-roasting method indeed made the least inroads on the chemical composition of guinea fowl meat under these restraints: controlled for cooking time and temperature, internal temperature not controlled. All the cuts cooked according to all the methods, had the favourable >0.4 Polyunsaturated:Saturated fatty acids (P:S) ratio, ranging from 0.91 to 1.42 between cuts and treatments. The n-6:n-3 ratio was below the recommended beneficial value, namely <4:1, in all the cuts irrespective of all the cooking methods, ranging from 2.47 to 3.08. The study of the effect of the three cooking methods (baking-bag, foil-wrap and open-roast) on the sensory attributes of the breast meat revealed that aroma-intensity of the three cooking treatments did not differ significantly (P>0.05). Foil-wrap produced a more tender and juicier product (P<0.05), while, when using the baking-bag method, values for flavour decreased (P<0.05). It is proposed that a higher internal temperature (which was not controlled) was attained when using the baking-bag method (temperature and time controlled) resulting in loss of volatile flavour components. The effect of the three cooking methods (baking-bag, foil-wrap and open-roast) on the proximate composition (moisture, protein, fat and ash) of raw and cooked breast meat was investigated. As anticipated raw breast meat had higher moisture content (74.55%, P<0.05) than the cooked cuts, with open-roasting showing the highest (68.55%) value and foil-wrap close second (68.12%). These values differed significantly from the baking-bag method (66.06%, P<0.05). An investigation on the effect of brine infusion on the sensory attributes and chemical composition (proximate and fatty acid composition, and mineral content) of breast meat, baked in foil-wrap, was carried out using descriptive sensory analysis with the injected breast and the control as variable. There were no significant differences (P>0.05) between the injected and the control samples for any of the sensory attributes of aroma, tenderness, initial juiciness, sustained juiciness and flavour. Judge:treatment variations were observed for all the attributes, and samples differed for all attributes except for aroma. It is proposed that the use of the hand injector could not effectively distribute the brine solution, hence the recommendation to repeat the experiment using an electronic multineedle-injector. No effect was observed for the proximate composition (P>0.05). Further research pertaining to cooking methods of meat of free-range guinea fowl is recommended to address certain issues that have been highlighted.