Effect of age on beef quality

Abstract

English: A systematic description of the physical composition, eating and nutritional quality characteristics of South African beef has not been attempted before. Beef carcasses (n = 156) representing three age groups (A, B and C) and the full spectrum in fatness within each age group, as obtained on the commercial market were used. Each carcass side was divided into 15 retail cuts. To ensure that the effect of animal age (as defined in the current South African classification system) was accurately reflected, the fat content of carcasses was used as covariant in all the statistical analyses. The physical composition (proportion of subcutaneous fat, meat and bone) was assessed and proximate analyses (percentage total moisture, fat, nitrogen and ash) were performed on the deboned tissue of each cut of the right sides of carcasses. Total fat and muscle content for each cut were subsequently calculated. The bone and meat content of the different cuts within the same carcass varied considerably. In general the relative meat content decreased and bone content increased in older animals (C-age). A large variation in compositional and chemical characteristics for the various cuts for the three age groups was observed. On average the fore and hind shins contained the lowest amount of chemical fat, followed by the fillet and thick flank. The collagen content and solubility of muscles of electrically stimulated (500 V) left sides of beef carcasses (n = 41) were determined. Cuts (n = 61 left sides of carcasses) were cooked according to an appropriate dry (prime rib, wing rib, loin, M semitendinosus in the silverside, rump, topside and fillet) or moist (M. gluteobiceps in the silverside, thick flank, chuck, brisket, neck, shoulder, thin flank and the hind and fore-shins) heat cooking method, at an oven temperature of l 60°C, to an internal temperature of 70°C. Cooking losses were determined and shear force resistance and proximate analyses (percentages total moisture, fat, nitrogen and ash) were performed. A trained, ten-member panel, using an eight-point scale evaluated sensory quality characteristics. Tenderness, residue, collagen solubility, flavour and initial impression of juiciness of all cuts decreased significantly and cooking losses and sustained juiciness increased (although not linearly) with increasing animal age. Animal age did not have a significant effect on the collagen content of muscles. Cuts cooked using a dry heat cooking method were juicier (both initial and sustained) than those cooked using a moist heat cooking method. Composite samples of three similar cuts from three different age groups were analysed on a double blind basis by various laboratories. The physical composition (proportion of subcutaneous fat, meat and bone) of each right side cut was assessed, while each left side cut was cooked prior to nutrient analyses. All cuts (subcutaneous fat plus meat; n = 270 for raw and n = 270 for cooked cuts) were analysed for proximate composition (moisture, protein, and fat), minerals (phosphorus, calcium, magnesium, potassium, sodium, copper, zinc, manganese and iron), water-soluble vitamins (thiamin, riboflavin, nicotinamide, pyridoxine, folic acid, cyanocobalamin, biotin and calcium pantothenate) and amino acids (including tryptophan and cystine ). Lysine and iron were higher and linoleic acid lower in the C-age group animals than in A- or 8-age animals for both raw and cooked cuts. The attributes that mostly discriminated between the different cuts within the same carcass were hydroxyproline, glycine and some minerals (phosphorus, potassium and magnesium). Meaningful recommendations concerning meat can now be made on valid South African data to include the full diversity of the population, i.e. the higher iron content in C-aged animals, that are probably more affordable to people most likely to suffer from iron deficiency anemia. Lean meat provides significant amounts of the dietary nutrients required in a healthy diet. The protein is of a high quality and quantity, and many essential vitamins (such as vitamin 8 12) and minerals (such as iron) are present in sufficient quantities. People that are more concerned about the eating quality attributes and are prepared to pay a premium can also be advised accordingly.

Afrikaans: Daar is nog nie tot op hede gepoog om die fisiese samestelling, eet- en voedingskwaliteitseienskappe van Suid Afrikaanse beesvleis sistematies te beskryf nie. Snitte (n = 15) van beeskarkasse (n = 156) soos in die kommersiele mark beskikbaar, van drie ouderdomsgroepe (A, B en C) en verteenwoordigend van die volle variasie vetheid binne elke ouderdomsgroep is ontleed. Orn te verseker dat die effek van ouderdom van die dier akkuraat (soos in die huidige Suid Afrikaanse klassifikasiestelsel beskryf) weerspieel word, is chemiese vetinhoud van die karkas as kovariant in alle statistiese analises gebruik. Die fisiese samestelling (relatiewe hoeveelhede onderhuidse vet, vleis en been) is bepaal en chemiese analiese (persentasie totale vog, vet, stikstof en as) is op die ontbeende weefsel van elke snit van die regtersye uitgevoer. Totale vet- en spierinhoud is vervolgens vir elke snit bereken. Soos verwag het die been- en spierinhoud tussen die verskillende snitte in dieselfde karkas aansienlik gevarieer. In die algemeen het die vleisinhoud afgeneem en die beeninhoud toegeneem in ouer diere (C ouderdom). 'n Groot variasie in die samestelling en chemiese inhoud vir die verskillende snitte van die drie ouderdomsgroepe is waargeneem. Die voor- en agterskenkels het die laagste hoeveelheid chemiese vet bevat, gevolg deur die filet en diklies. Totale kollageeninhoud en -oplosbaarheid van spiere van elektries gestimuleerde (500 V) beeskarkasse (n = 41) is bepaal. Snitte (n = 61 karkasse) is volgens 'n geskikte droe- (primarib, voorrib, lende, M semitendinosus in die dy, kruis, binneboud en filet) of klamhittegaarmaakmetode (M. gluteobiceps in die dy, diklies, dikrib, nek, skouer, dunlies en voor- en agterskenkels) by 'n oondtemperatuur van 160°C, tot 'n interne temperatuur van 70°C gaargemaak. Gaarmaakverliese, snyweerstand en chemiese analiese (percentasie totale vog, vet, stikstof en as) is bepaal. Sintuiglike kwaliteitseienskappe is deur 'n opgeleide paneel bestaande uit tien lede, met 'n agtpuntskaal uitgevoer. Sagtheid, residu, kollageenoplosbaarheid, geur en inisiele indruk van sappigheid van alle snitte het betekenisvol (alhoewel nie-linier) afgeneem en gaarmaakverliese en voortgesette sappigheid het verhoog met toenemende ouderdom. Ouderdom van die dier het nie 'n betekenisvolle effek op die kollageeninhoud van spiere gehad nie. Snitte wat volgens 'n droehittegaarmaakmetode voorberei is, was meer sappig (inisiele en voortgesette) as die wat volgens 'n klamhittegaarmaakmetode voorberei is. Saamgestelde monsters van die ooreenstemmende snitte van elke ouderdomsgroep, is op 'n dubbelblinde basis deur verskillende laboratoriums ontleed. Die fisiese samestelling (relatiewe hoeveelhede onderhuidse vet, vleis en been) van elke regterkantste snit is bepaal, terwyl elke linkerkantste snit gaargemaak is voor voedingswaarde analises. Die volgende bepalings is op alle snitte (onderhuidese vet en vleis, n = 270 vir rou en n = 270 vir gaar) uitgevoer: chemiese analiese (% totale vog, vet en stikstof), minerale (fosfor, kalsium, magnesium, kalium, natrium, koper, sink, mangaan en yster), water-oplosbare vitamienes (tiamien, riboflavien, nikotienamied, piridoksien, foliensuur, cyanokobalamien, biotien en kalsiumpantonaat) en aminosure (insluitend triptofaan en sistien). Lisien en yster was hoer en linole'fensuur laer in C ouderdom diere as in A of B vir beide rou- en gaarsnitte. Die eienskappe wat die meeste tussen die verskillende snitte in dieselfde karkas onderskei het was hidroksieprolien, glisien en sommige minerale (fosfor, kaluim en magnesium). Sinvolle aanbevelings kan nou op geldige Suid Afrikaanse data gedoen word vir die totale verskeidenheid van die Suid Afrikaanse bevolking, bv. die C ouderdom diere met 'n hoer ysterinhoud is meer bekostigbaar vir persone wat aan ystertekort ly. Maervleis voorsien betekenisvolle hoeveelhede voedingstowwe wat in 'n gesonde dieet benodig word. Die prote'fne is van 'n hoe kwaliteit en kwantiteit, asook baie van die essensiele vitamienes en minerale (soos yster) is in genoegsame hoeveelhede teenwoordig. Persone wat meer bekommerd is oor die eetkwaliteitseienskappe en wat daarvoor 'n premium sal betaal, kan ook van advies voorsien word. Digitised