Investigation of the chemical composition and nutritional value of smoothhound shark (Mustelus mustelus) meat

[摘要] ENGLISH ABSTRACT:The aim of this study was to determine the proximate composition of five individual body sites ofthe Mustelus mustelus shark in order to evaluate the cross carcass variation of the individualproximate components (moisture, protein, lipid, ash) of the meat. This variation was determined inorder to find a representative sample of the edible part of the shark (fillet and body flap). Secondly,this sample representing the entire shark fillet was used to investigate the endogenous factors(gender, size and life cycle stage) and their effects on the individual proximate components andother meat components (amino acids, fatty acids, minerals, histamine and mercury contents).Finally, all this data was combined to describe the average chemical composition and nutritionalvalue of M. mustelus meat.None of the proximate components showed any variation between the different filletpositions. This indicated that the fillet is homogenous and samples for chemical analyses can betaken anywhere on the fillet as representative of the entire fillet.It was found that all three main effects (gender, size and life cycle stage) did not have majorinfluences on most of the components of the chemical composition of M. mustelus meat analysed.Higher fatty acid levels (SFA, MUFA and PUFA) were observed in large females than in largemales as well as in non-pregnant large females compared to pregnant large females. According tostatistical analysis, large males had higher total mercury levels than large females. The onlycomponent affected by size variation was the fatty acids, showing a trend to decrease in quantitybefore maturity was reached. Variation due to life cycle stages was mostly evident in the fatty acidcomponent with some small effects on two mineral components, aluminium and copper, which hadslightly higher levels in pregnant large females than in non-pregnant large females.M. mustelus meat has an average proximate composition of 75% moisture, 23% protein,1.6% lipids and 1.4% ash (weight per wet weight). The protein is, however, an over-estimation ofthe true protein value as the meat contains significant amounts of non-protein nitrogen (NPN) inthe form of urea which contributes to the N concentration. M. mustelus meat is a good source ofsome essential amino acids, especially lysine and threonine (78% of the daily requirements for anadult in a 100g portion), but low in minerals. The meat has a healthy lipid content with a good ratio(>0.45) of PUFA:SFA (0.83) as well as a healthy (<4) n-6:n-3 fatty acid ratio of 0.39. The histaminecontent was very low or not detectable but some samples contained total mercury values abovethe maximum safe limit.Although further research is needed for some meat components, these results are avaluable contribution to the new South African Food Composition Tables being compiled.

[发布机构] Stellenbosch University