Egyptian goose (Alopochen aegyptiacus) : sensory, biochemical and physical meat quality as affected by gender, diet and ageing

Thesis (PhD(Food Sc))--Stellenbosch University, 2014.ENGLISH ABSTRACT: In Southern Africa, the hunting of wildfowl species has increased considerably in the past few years. Crop farmers incur major financial losses due to the feeding activities of Egyptian geese (Alopochen aegyptiacus); consequently a large number of geese are hunted in an attempt to reduce the damage caused. With the current absence of scientific information baseline research investigating the meat quality of this species is essential. The sensory profile of Egyptian goose meat was found to be very distinct in relation to the characteristics of other well-known fowl species. It has very strong game aroma and flavour attributes with a prominent metallic aftertaste. The intense aroma and flavour notes were linked to the substantially higher iron content, as well as the high overall polyunsaturated fatty acid content as revealed by chemical profiling. The trained sensory panel also found the meat to be very tough (high shear force) compared to the other species. To identify the factors which may affect the overall consistency of the meat quality, the influence of three main effects namely; season (grain vs. non-grain diet), gender and portion was investigated. This revealed that season had the largest effect and harvesting periods should therefore be considered. The main issue is the higher intramuscular fat (IMF) content in winter (July), as well as the substantial difference in the fatty acid profiles of the two seasons. The forage vs. grain based diets during certain periods of the year leads to variation in the content of key fatty acids in the meat i.e. oleic acid, linoleic acid and α-linolenic acid. In winter, the meat had a characteristic, prominent game and metallic aroma while the summer (November) profile was governed by “sweet-oily-duck” and beef-like sensory notes. The fatty acid differences also result in variation between the omega 6 to omega 3 ratios of the seasons; the portions from winter are within the recommendations (ratio<5) and those from summer not. Regarding gender, the females had a lower carcass yield but higher IMF content. The female breast portion was also more tender (lower shear force). In attempting to elucidate the toughness of the meat, possible causes have been proposed. The pH decline in the pectoralis muscle occurs quite rapidly and it is possible that the high rigor temperature (>20 °C) may contribute to the increased toughness. Regardless of the proteolytic enzyme activity during the rigor period, the meat is still tough at 36 h post mortem and the proteolytic contribution may be overshadowed by the background toughness, i.e. the connective tissue content and fibre structure. The latter was confirmed when the breast portions were aged for 14 days and no change (decline) in the shear force values was observed even though myofibrillar degradation did occur (during ageing). Given the lack of a decline in the shear force, the aging of Egyptian goose meat as a means of improving the overall toughness cannot be proposed without further research. The study in its entirety provides substantial proof that the commercial utilisation of Egyptian goose meat is feasible.AFRIKAANSE OPSOMMING: Die jag van wildsvoël spesies in Suider-Afrika het aansienlik toegeneem in die laaste paar jaar. Graanboere lei jaarliks groot finansiële verliese as gevolg van die voedingsgedrag van kolganse (Alopochen aegyptiacus). Gevolglik word ‘n groot hoeveelheid ganse elke jaar geoes om sodoende die skade te verminder. Met die huidige tekort aan wetenskaplike inligting is grondslag navorsing rakende die vleiskwaliteit van hierdie wildsvoël spesie noodsaaklik. Die sensoriese profiel van kolgansvleis is baie uniek in vergelyking met die vleis van ander bekende voël spesies. Dit word gekenmerk deur die sterk wildagtige aroma en geur tesame met ‘n baie prominente metaal nasmaak. Hierdie intense aroma en geur hou verband met ‘n baie hoër yster-inhoud, asook ‘n hoë poli-onversadigde vetsuur profiel soos uitgewys deur die chemiese karakteriserings studie. Die opgeleide sensoriese proepaneel het ook die vleis van hierdie voël spesie beskou as baie taai in vergelyking met die vleis van ander spesies. Ten einde te bepaal watter faktore die algehele variasie in vleiskwaliteit sal beïnvloed, is drie hoofeffekte naamlik, seisoen (graan teenoor nie-graan dieet), geslag en porsie ondersoek. Die verskeie studies het uitgewys dat seisoen die grootste invloed het en daarom sal die periodes waarin ganse geoes word in ag geneem moet word. Die hoër intramuskulêre vetinhoud in winter (Julie), asook die aansienlike verskil in die vetsuur profiele van die twee seisoene is die vernaamste verskille. Die weiding (hoofsaaklik gras) teenoor graan diëte wat gevolg word in sekere dele van die jaar lei tot variasie in die inhoud van belangrike vetsure (oliensuur, linoleïensuur en α-linoleensuur) in die vleis. In die winter het die vleis die kenmerkende en prominente wild geur en metaalagtige nasmaak getoon terwyl die profiel in die somer (November) hoofsaaklik bestaan het uit “soet-olierige-eend” en beesvleis geure. Die vetsuur verskille lei ook tot ‘n verskil in die omega-6 tot omega-3 verhouding van die seisoene; in die winter is die porsies binne die aanbevole voedingsvereistes (20 °C) waartydens rigor mortis plaasvind, kan bydrae tot die taaiheid. Ongeag die werking van die proteolitiese ensieme tydens die rigor periode was die vleis steeds taai 36 uur na dood, daarom was die proteolitiese bydrae moontlik oorskadu deur die agtergrond-taaiheid, dit wil sê die bindweefsel inhoud en vesel struktuur. Laasgenoemde is bevestig toe die borsspiere verouder is vir ‘n tydperk van 14 dae. Geen verandering (afname) in die instrumentele taaiheid is waargeneem nie, selfs al het miofibrillêre afbraak plaasgevind. Aangesien daar geen afname in instrumentele taaiheid opgemerk is nie kan veroudering van kolgansvleis, met die doel om die taaiheid te verbeter, nie aanbeveel word voor verdere navorsing nie. In geheel voorsien hierdie studie beduidende motivering rakende die moontlike kommersiële aanwending van kolgansvleis

The fatty acid, amino acid, and mineral composition of Egyptian goose meat as affected by season, gender, and portion

With the current absence of scientific information on the nutritive aspects it is essential to investigate the fatty acid, mineral, and amino acid composition of Egyptian geese as well as the factors of influence. The forage vs. grain based diets of Egyptian geese during certain periods of the yr leads to variation in the content of the key fatty acids such as oleic acid, linoleic acid, and α-linolenic acid. The differences in these fatty acids results in variation between the n-6/n-3 ratios of the seasons; the portions from winter (July) are within the recommendations (rati

The influence of post-mortem conditioning on the tenderness of Egyptian goose (Alopochen aegyptiacus) breast meat (M. pectoralis major)

BACKGROUND: Egyptian goose breast meat has been found to be very tough compared to the meat of other well-known fowl species. In attempting to clarify the toughness of the meat, the physical and biochemical changes during post-mortem conditioning (14 days) was investigated. RESULTS: Although there was increased cathepsin (B, B & L and H) activity, together with a decrease (P ≤ 0.05) in myofibrillar fragmentation lengths (32-25 μm) with conditioning, no change (decline) in shear force values was observed. The higher (P ≤ 0.05) shear force of the male breast portions may be linked to the higher (P ≤ 0.05) concentrations of total and insoluble collagen. CONCLUSIONS: No significant change (decline) in shear force values was observed. Conditioning of Egyptian goose meat as a means of improving the overall toughness cannot therefore not be proposed. The higher shear force and lower sensory tenderness of the male breast portions, as previously observed, may be linked to higher concentrations of total and insoluble collagen

Gamebirds : a sustainable food source in Southern Africa

Publication of this article was funded by the Stellenbosch University Open Access Fund.The original publication is available at http://www.springer.com/life+sciences/agriculture/journal/12571In order to alleviate the current food security situation the world is faced with, it is essential to investigate meat sources which have the potential to be used in a sustainable manner. This review provides substantial arguments to prove the viability of sport hunted wildfowl as a food source in Southern Africa. However, before the use of wildfowl meat can be realised, there are certain challenges to overcome in order to ensure meat of the best possible quality reaches the consumer. Important aspects to consider regarding the eating quality of wildfowl meat are identified and include the physical activity of the different portions and muscle fibre types, diet, breeding, age and gender as well as the post mortem handling/ageing of the meat. The safety issues involved in producing gamebird meat i.e. shot contamination (microbial or lead), are also discussed. Other areas that warrant scientific research include investigating the intrinsic and extrinsic factors that may have an influence on the ultimate meat quality and exploring possible techniques of improving the eating quality of wildfowl meat. The insights these investigations will provide have the potential to increase the commercial viability, directly or indirectly, of African wildfowl meat and thus contribute to food security.Stellenbosch UniversityPublishers' Versio

The influence of season on the sensory profile of Egyptian goose (Alopochen aegyptiacus) meat

The feeding activities of Egyptian geese are becoming a problem for crop farmers in South Africa. Their grain-based diet during the harvesting season compared to the diet during the rest of the year may have an influence on the meat quality, especially the sensory profile. Descriptive sensory analysis, physical measurements, and the proximate composition were used to investigate these effects. Season was a major influential factor with the meat from summer associating with sweet-oily-duck and beef attributes in contrast to the strong association towards the game, metallic, and fish attributes of the winter meat. This is due to the difference in the main fatty acids; winter was higher (P ≤ 0.05) in polyunsaturated fatty acids (PUFA) (C18:3 n-3) and summer higher (P ≤ 0.05) in monounsaturated fatty acid (C18:1 n-9). This study established that season has a significant effect on the sensory profile of Egyptian goose meat and should be considered regarding the utilization and consumption

Aspects of the nutritional value of cooked Egyptian goose (Alopochen aegyptiacus) meat compared with other well-known fowl species

There is no scientific research regarding Egyptian goose (Alopochen aegyptiacus) meat; therefore, a chemical analysis to establish the nutritional characteristics of the breast portion is described. Meat from guineafowl, Pekin duck, ostrich, and broiler chicken were used as a reference. The high intramuscular fat content of Egyptian goose meat (5.6 g/100 g) may be linked to the fact that this species relies on fat for heat insulation and buoyancy. Egyptian goose meat is very high in polyunsaturated fatty acids (39.7%). The polyunsaturated fatty acid/saturated fatty acid ratio is within the recommendations (>0.4), although the n- 6/n-3 ratio is higher than the suggested value of 5. The high Fe content of 7.5 mg/100 g is the differentiating factor within the mineral compositions and is related to the physical activity endured by the breast muscle of Egyptian geese. This study provides new insight into the nutritional characteristics of a meat species providing crucial information that is, as of yet, not available in the literature

Proximate and fatty acid composition of zebra (Equus quagga burchellii) muscle and subcutaneous fat

BACKGROUND: The meat from African game species is healthy, naturally produced and increasingly popular with consumers. Among these species, zebra (Equus quagga burchellii) are growing in number in South Africa, with the meat from surplus animals holding potential to contribute to food security and economic stability. Despite being consumed locally and globally, little information exists on the composition of zebra meat. This study aimed to determine the proximate composition of zebra meat as well as the fatty acid composition of the intramuscular (IMF) and subcutaneous (SCF) fat.RESULTS: Zebra longissimus lumborum muscle was shown to have a high mean protein content (22.29 g per 100 g) and low mean fat content (1.47 g per 100 g). High proportions of polyunsaturated fatty acids (PUFAs) were found in the IMF (41.15%) and SCF (37.71%), mainly comprising α-linolenic (C18:3n-3) and linoleic (C18:2n-6) acids. Furthermore, the IMF and SCF had favourable PUFA/saturated fatty acid ratios (>0.4) and omega-6/omega-3 ratios

Post mortem rigor development in the Egyptian goose (Alopochen aegyptiacus) breast muscle (pectoralis): factors which may affect the tenderness

BACKGROUND: Baseline research on the toughness of Egyptian goose meat is required. This study therefore investigates the post mortem pH and temperature decline (15 min-4 h 15 min post mortem) in the pectoralis muscle (breast portion) of this gamebird species. It also explores the enzyme activity of the Ca-dependent protease (calpain system) and the lysosomal cathepsins during the rigor mortis period. RESULTS: No differences were found for any of the variables between genders. The pH decline in the pectoralis muscle occurs quite rapidly (c = -0.806; ultimate pH ∼5.86) compared with other species and it is speculated that the high rigor temperature (>20 °C) may contribute to the increased toughness. No calpain I was found in Egyptian goose meat and the μ/m-calpain activity remained constant during the rigor period, while a decrease in calpastatin activity was observed. The cathepsin B, B & L and H activity increased over the rigor period. CONCLUSION: Further research into the connective tissue content and myofibrillar breakdown during aging is required in order to know if the proteolytic enzymes do in actual fact contribute to tenderisation

The effect of dietary energy content on quality characteristics of Boer goat meat

The palatability and chemical composition of Longissimus lumborum muscles from 24 Boer goat castrates (eight goats per treatment), finished on diets varying in energy content (9.7, 10.2 and 10.6 MJ ME/kg feed), were evaluated by a trained sensory panel on a line scale ranging from low to high intensity for aroma, flavour and texture attributes. Physical measurements as well as proximate analysis were performed for each sample. No differences (P > 0.05) were found between the dietary treatments for any of the attributes analysed. Lamb flavour and aroma were the most prominent attributes, while only low levels of goat-like flavours were detected. Juiciness and tenderness had a strong correlation (r = 0.864) and were rated to be moderate. The findings suggest that energy density of feedlot diets can be varied to still produce chevon with uniform meat quality characteristics