Browsing by Author "Muller, M."

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    Carcass and muscle yields of ostriches as influenced by genotype
    (South African Society for Animal Science, 2007) Hoffman, L. C.; Brand, M. M.; Muller, M.; Cloete, S. W. P. (Schalk Willem Petrus van der Merwe)
    ABSTRACT: Live, carcass, leg and muscle weight (kg) as well as dressing percentage were compared between South African Black (Struthio camelus var. domesticus) ostriches, purebred Zimbabwean Blue Neck (Struthio camelus australis) ostriches and the progeny of Zimbabwean Blue Neck males crossed with South African Black females, commercially slaughtered at 14 months of age. South African Black ostriches had the lowest live (84.9 kg) and carcass (43.3 kg) weights, compared to Zimbabwean Blue Necks (100.9 and 51.2 kg, respectively). In general, crossbred birds resembled Zimbabwean Blue Necks more closely for the quantitative meat traits. However, dressing percentage (51.1%) and yields of different carcass components (bone, leg) did not differ between genotypes. Six of the major muscles present in the ostrich leg (M. gastrocnemius, M. femorotibialis accessorius, M. iliotibialis cranialis, M. iliotibialis lateralis, M. iliofibularis and M. iliofemoralis) showed significant weight differences between genotypes, with South African Black ostriches yielding the lowest values.
  • Thumbnail Image
    Item
    Development of chemical-based reference standards for rooibos and honeybush aroma lexicons
    (Elsevier, 2019) Du Preez, B. V. P.; De Beer, D.; Moelich, E. I.; Muller, M.; Joubert, E.
    The honeybush sensory wheel was revised, using a large sample set (n = 585) comprising of the major commercial Cyclopia species, i.e. C. intermedia, C. subternata and C. genistoides. Only positive and negative aroma attributes were included in the wheel. Chemicals were identified to serve as reference standards for the honeybush (Cyclopia spp.) lexicon. Similarly, chemical-based reference standards were identified for the rooibos (Aspalathus linearis) lexicon. From a comprehensive literature search and gas chromatography–mass spectrometry analyses, chemicals were screened by an expert panel for their suitability in terms of typicality of the target aroma. Each chemical was evaluated in a ‘base tea’ and compared to a specific ‘reference tea’ exhibiting a high intensity of the target aroma. A total of 30 and 44 chemicals for rooibos and honeybush, respectively, were selected for validation by a trained panel. Descriptive sensory analysis was conducted to assign typicality and intensity scores for each chemical representing a target aroma attribute. Several chemicals were identified as suitable reference standards for the following aroma notes: isophorone (‘rooibos-woody’), maltyl isobutyrate (‘caramel’), cis-3-hexenol (‘green grass’), 4-oxoisophorone (‘seaweed’) and 2,4,6-trichloroanisole (‘musty/mouldy’) for rooibos; and 2-acetyl-5-methylfuran (‘woody’), levulinic acid (‘fynbos-sweet’), maltyl isobutyrate (‘caramel’), and 2-acetylpyrrole (‘nutty’) for honeybush.
  • Thumbnail Image
    Item
    The fatty acid composition of muscles and fat depots of ostriches as influenced genotype
    (South African Society for Animal Science, 2012) Hoffman, L. C.; Brand, M. M.; Cloete, S. W. P. (Schalk Willem Petrus van der Merwe); Muller, M.
    Three genotypes of ostrich (South African Black, Zimbabwean Blue Necks and crosses between Zimbabwean Blue Neck males x South African Black females) were used to investigate the influence of genotype on the fatty acid composition of the musculus gastrocnemius and musculus iliofibularis, and abdominal and breast fat depots. Total saturated fatty acids in both the m. gastrocnemius and m. iliofibularis were higher in crosses (36.4% and 35.9%) than in South African Black ostriches (32.9% and 30.4%), whereas mono-unsaturated fatty acids were highest in South African Black ostriches. Total polyunsaturated fatty acids in the m. gastrocnemius were lowest in South African Black ostriches (26.5%) compared with the Zimbabwean Blue Necks (33.2%). Neither the ratio of polyunsaturated to saturated (0.73 to 0.99) nor n-6 to n-3 (1.6 to 2.2) fatty acids were influenced by genotype, although the ratio of polyunsaturated to saturated fatty acids in Zimbabwean Blue Necks was higher in the m. gastrocnemius (0.99) than in the m. iliofibularis (0.73). Differences in individual fatty acids were prominent in the breast fat, and total saturated and mono-unsaturated fatty acids differed between genotypes in both breast and abdominal fat. Only the ratio of polyunsaturated to saturated fatty acids in the fat depots differed between South African Black (0.48) and Zimbabwean Blue Neck ostriches (0.42). The latter ratio was higher in the breast (0.50) than abdominal (0.42) fat in Zimbabwean Blue Necks. These results indicate that crossbreeding of different genotypes of ostriches reared under similar conditions does influence the overall fatty acid profiles of meat and fat.
  • Thumbnail Image
    Item
    The growth and carcass and meat characteristics of pigs raised in a free-range or conventional housing system
    (South African Society for Animal Science, 2003) Hoffman, L. C.; Styger, E.; Muller, M.; Brand, T. S.
    The growth performance and the carcass and physical and chemical characteristics of the meat of 24 Landrace X Large White pigs were compared when reared under a free-range or a conventional housing system. The free-range pigs had lower feed intakes and slower growth rates than the conventionally housed pigs. The free-range pigs also had a lower P2 fat depth and therefore yielded a carcass with a higher percentage lean meat. Housing systems had no effect on the weight distribution of the commercial cuts (as a percentage of cold carcass weight). The meat from the free-range pigs was slightly more reddish in colour, but apart from that housing systems had no effect on the water-holding capacity (WHC) of the meat, its initial pH (PH 45) or its final pH (pH24). The meat from the free-range pigs had the same shear force (WBS) values as those of the conventionally housed pigs. Housing systems had an influence on the fatty acid composition. Stearic acid (C18:0) was significantly lower in the meat of the free-range pigs than that of the conventionally housed pigs while linoleic acid (C18:2n-6) and polyunsaturated fatty acid (PUFA) concentrations were significantly higher. However, the moisture, fat, protein and ash contents as well as the mineral composition in the meat were unaffected by housing systems. It could be concluded that pigs raised in a conventional housing system produced meat with similar quality characteristics to that of pigs raised in a free-range housing system.
  • Thumbnail Image
    Item
    Live weight and reproduction performance of Zimbabwean blue and South African black ostriches
    (South African Society for Animal Science, 2008) Cloete, S. W. P. (Schalk Willem Petrus van der Merwe); Brand, M. M.; Hoffman, L. C.; Muller, M.
    Data obtained from a pair-mated ostrich flock located at Oudtshoorn in South Africa were used to derive line differences for live weight and reproduction performance in sexually mature ostriches of the Zimbabwean Blue (ZB) and South African Black (SAB) strains during 2003 to 2006. At the commencement of breeding ZB breeding stock were, on average, between 9 and 13% heavier than SAB contemporaries. At the cessation of breeding the superiority of ZB birds was reduced to between 4 and 8%, expressed relative to SAB breeding stock. Live weight at the commencement of breeding was complicated by an interaction between sire line and year. The interaction resulted from no line differences between SAB and ZB males in 2003, contrasted to marked differences in subsequent years. Egg production was affected by dam line, but not by the line of the sire or the interaction between dam line and sire line. Egg production of SAB females was almost twice that of ZB contemporaries, at respectively 43.3 and 23.3 eggs per season. The number of infertile eggs was not affected by any of the independent variables considered. The number of shell deaths was affected by both sire line and dam line. Overall, SAB females sustained lower levels of shell deaths than ZB females, while the eggs produced by mates of SAB males had higher shell deaths than mates of ZB males. Chick production was affected by dam line; the effects of sire line and the dam line x sire line interaction being non significant. Overall, SAB females produced more than double the number of chicks produced by their ZB contemporaries, at respectively 23.1 and 10.6 chicks per season. Both egg production and chick production were affected by a dam line x year interaction. No dam line difference was observed during 2003, whereas SAB females clearly outperformed ZB females in subsequent years. Further studies on the ostrich bloodlines and their crosses are needed to devise a selection and crossbreeding strategy for improving production and profitability in the industry.
  • Thumbnail Image
    Item
    Study on applicability of adhesive forces for micro-material handling in production technology
    (Stellenbosch : Stellenbosch University, Department of Industrial Engineering, 2011-09) Neugebauer, R.; Koriath, H-J.; Van der Merwe, A. F.; Muller, M.; Matope, S.
    Micro-material handling and micro-assembly becomes increasingly important in largevolume manufacturing of products like sensors in automotive applications. Smaller dimensions of the micro-objects lead to problems with regard to the reliability of the manufacturing process because adhesive forces become predominant over gravity for objects whose dimensions are in the micro-range. In contrast to the common approach of minimizing those adhesive forces, this paper focuses on the use of the three main adhesive forces, van-der-Waals, electrostatic and surface tension forces, as gripping principles. These forces are compared to conventional vacuum grippers with regard to gripping forces and complexity of application. Modelling of the forces is executed for separation distances in the range of 1x10-12 m - 1x10-3 m. Even though vacuum forces dominate in magnitude over others within the whole range, there are several disadvantages of using them. On the other hand adhesive forces are advantageous in that they require little amount of energy and they do not mechanically strain the micro-parts being handled.
  • No Thumbnail Available
    Item
    The relationships between consumer liking, sensory and chemical attributes of Vitis venifera L. cv. Pinotage wines elaborated with different Oenococcus oeni starter cultures
    (JOHN WILEY & SONS LTD, THE ATRIUM, SOUTHERN GATE, CHICHESTER, ENGLAND, WSUSSEX, PO19 8SQ, 2013) Malherbe, S.; Menichelli, E.; Du Toit, M.; Tredoux, A. G. J.; Muller, M.; Naes, T.; Nieuwoudt, Helene