Backfat quality of South African pigs: a meat processing perspective

Abstract

English: Fat quality of backfat from 2107 baconer pig carcasses, sampled at a major South African pig abattoir, were evaluated to obtain an overview of the backfat quality of South African pigs. Extracted fat was used to determine iodine and refraction index values as well as fatty acid profiles of these samples. Significant differences (P < 0.001) in terms of backfat quality were observed between the different classification groups. Improved fat quality was associated with increased backfat thickness and decreased lean meat content, caused by an increase in the total saturated and mono-unsaturated fatty acid contents and a decrease in the total unsaturated and polyunsaturated fatty acid contents as well as double bond and peroxidizability indexes. The Pand 0 classification groups (with backfat thickness measurements less than 17 mm) could not conform to the international standards proposed for backfat of good technological quality. The C, U and S groups (with backfat measurements of 23 to more than 32 mm) possessed backfat with good technological qualities. The R group had borderline fat quality. A high linoleic acid content, leading to a high dienoic fatty acid content, in turn influencing the total polyunsaturated fatty acid content, is the main cause of soft fat with poor technological quality. Correlation analyses and statistical techniques were employed to acquire equations to describe the relationships between iodine value and international fat quality parameters. Sy substituting the international fat quality criteria into the equations it became clear that pigs had to have an iodine value of 60 to comply with most of these criteria, which was unrealistic. The French system predicts fat quality by utilizing backfat thickness and lean meat content. It was proposed, through modification of this system, that South African pig carcasses with a backfat thickness of more than 17.8 mm and a lean meat content of less than 66.8% would have the potential to deliver backfat with good technological properties in terms of iodine value. If these new criteria were applied, the Pand 0 classification groups did not possess good quality fat. The probability of selecting a pig with an iodine value < 70 (indicating good fat quality) from the R group would then be > 55%. In the S group, > 77% of the pigs conformed to these new criteria. Pigs with poor fat quality may escape detection, but the risk of selecting a pig with poor fat quality from these groups is reduced. These values are applicable to either method of carcass evaluation (HGP or Intrascape) employed in South Africa. The method developed in this study therefore provides the South African meat industry with a cost-effective method to improve the probability of selecting pig carcasses with good fat quality. Soars had much better omega-6 to omega-3 ratios, lower slaughter weights and extractable fat contents compared to barrows and gilts combined. A significant seasonal trend in the backfat iodine values was observed. Setter fat quality was detected in mid-summer than in mid-winter. This seasonal effect was so large that improvement of winter backfat quality would cause the overall fat quality to improve. This could possibly be achieved by including feed ingredients rich in saturated fatty acids in the winter rations of pigs because fatty acid composition of the feed is reflected in the backfat of pigs. Large variation in fat quality existed between pigs within the same group originating from different suppliers. Within the P classification group, pigs with both highly acceptable and highly unacceptable iodine values were observed. Feeding, breeding, environmental and/or management differences between the suppliers could account for this. Fat quality influences the consumer, supplier as well as the meat technologist.

Afrikaans: Die rugvet van 2107 spekvarke is byeen van die grootste vark abattoirs in Suid-Afrika bemonster. Die kwaliteit van hierdie monsters is geëvalueer ten einde 'n oorsig van Suid-Afrikaanse varke, in terme van rugvetkwaliteit, te verkry. Geëkstraheerde vet is gebruik om die jodium- sowel as refraksie-indeks waardes asook die vetsuurprofiele van hierdie varke te bepaal. Die rugvetkwaliteit van die verskillende klassifikasiegroepe het betekenisvol (P < 0.001) van mekaar verskil. Namate rugvetdikte toegeneem en maervleis inhoud afgeneem het, het die vetkwaliteit verbeter. Hierdie verbeterde vetkwaliteit kan toegeskryf word aan die toename in die totale versadigde en mono-onversadigde vetsuurinhoude, maar ook die afname in die totale onversadigde, poli-onversadigde vetsuurinhoude, sowel as die dubbelbindings- en peroksideerbaarheids indekse. Die P en 0 klassifikasiegroepe (met rugvetdiktes onder 17 mm) kon nie aan die internasionaal gespesifiseerde standaarde, wat vereis word vir rugvet met goeie tegnologiese kwaliteit, voldoen nie. Daarenteen het die C, U en S groepe (met rugvetdiktes vanaf 23 tot meer as 32 mm) vet van goeie tegnologiese waarde besit. Die R groep was 'n grensgeval. Die hoofoorsaak van sagte vet van swak tegnologiese waarde is 'n hoë linoleïensuur inhoud wat 'n hoë dienoësuur inhoud veroorsaak, wat op sy beurt weer lei tot 'n verhoogde konsentrasie poli-onversadige vetsure. Korrelasie analises en statistiese tegnieke is gebruik om vergelykings te verkry wat die verhoudings tussen jodiumwaarde en die internasionale vetkwaliteitsparameters kon beskryf. Internasionale vetkwaliteitskriteria is in hierdie vergelykings ingestel en daar is bevind dat Suid-Afrikaanse varke oor 'n jodiumwaarde van 60 sou moes beskik om aan hierdie vereistes te voldoen, wat totaalonrealisties sou wees. Rugvetdikte asook maervleis inhoud word in die Franse klassifikasiesisteem van vetkwaliteitsvoorspelling gebruik. Met die nodige aanpassing van hierdie sisteem, is gevind dat Suid-Afrikaanse varkkarkasse met 'n rugvetdikte van meer as 17.8 mm en maervleis inhoud van minder as 66.8% oor die potensiaal beskik om rugvet van goeie gehalte, in terme van 'n jodiumwaarde, te lewer. Indien hierdie nuwe kriteria toegepas word, sou dit beteken dat varke in die P en 0 klassifikasiegroepe nie oor rugvet met goeie tegnologiese kwaliteit beskik nie. Die waarskynlikheid om 'n vark met 'n jodiumwaarde < 70 (wat dui op goeie vetkwaliteit) uit die R groep te kies was> 55%. In die S groep het> 77% van die karkasse voldoen aan die nuwe vetkwaltieitskriteria. Hoewel die moontlikheid steeds bestaan dat 'n varkkarkas met swak vetkwaliteit sou kon deurglip, verlaag dit die risiko om 'n varkkarkas met swak vetkwaliteit te selekteer. Hierdie nuwe kriteria kan toegepas word op metings van beide die Intraskoop en Hennesey graderings sondeerder. Die metode wat ontwikkel is gedurende hierdie studie verskaf dus aan die Suid-Afrikaanse vleisindustrie 'n koste-effeketiewe metode om die waarskynlikheid te verhoog om varke met goeie vetkwaliteit vanuit verskillende klassifikasiegroepe te selekteer. Bere het aansienlik beter omega-6 tot omega-3 vetsuurverhoudings, laer slaggewigte en ekstraheerbare vetinhoude, in vergelyking met burge en sóe gekombineerd, gehad. Jodiumwaardes van die rugvet het 'n betekenisvolle seisoenale neiging getoon. Gedurende die middel-somermaande was die vetkwaliteit beter as gedurende die middel-wintermaande. Indien 'n verbetering in die vetkwaliteit gedurende die winter bewerkstellig kon word, sou dit 'n verbetering in die totale vetkwaliteit teweeg bring. Die vetsuursamestelling van die rugvet van varke weerspieêl die vetsuursamestelling van die voer. Rugvetkwaliteit sou verbeter kon word indien meer versadigde vette gedurende die wintermaande by voere gevoeg word. Daar was groot variasie in vetkwaliteit tussen varke binne dieselfde groep wat van verskillende leweransiers afkomstig was. Varke met beide hoogs aanvaarbare en hoogs onaanvaarbare jodiumwaardes is binne die P klassifikasiegroep gevind. Voedings-, ras, omgewings- en/of bestuursverskille tussen die leweransiers kan hiervoor aanspreeklik wees. Vetkwaliteit beïnvloed dus die verbruiker, leweransier asook die vleistegnoloog.