The effect of honeybush (Cyclopia subternata) extract in dry-cured and fermented warthog salami with reduced added nitrate

Smit, Paula (2020-04)

Thesis (MScFoodSc)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: The aim of this study was to investigate the effect of incorporating honeybush (Cyclopia subternata) extract as a natural antioxidant in dry-cured and fermented salami. This is the first study attempting the addition of honeybush extract to a processed red meat product and is therefore regarded as baseline data for future research. The data forms part of a relevant research focus, being botanical extracts in meat exhibiting antimicrobial and/or antioxidant activity and could expand the knowledge surrounding the potential of a native South African extract intended for the food industry. The first research trial was regarded as a pilot study to familiarise with the skill of salami making and to better comprehend the technical challenges when incorporating honeybush extract to salami. For this purpose, a typical pork Italian salami was chosen as the model. A total of 68 pork salami were produced, which were subdivided into three treatments: Control= no added honeybush or nitrate; Nitrate= with added sodium nitrate (100 mg/kg) and ascorbic acid; and Honeybush= with 0.5% (w/w) added honeybush extract. After 35 days of controlled ripening, the honeybush treated salami had a higher water activity (aw= 0.928, p ≤ 0.01) compared with the control (aw= 0.923) and nitrate salami (aw= 0.924). This was also reflected in the higher moisture content of the honeybush treated salami (35.3%), compared to the control (33.5%; p ≤ 0.01). Final product salami pH (5.35-5.24) was not affected by treatment, however, salami with honeybush extract had less spontaneous outer surface mould growth or coverage at the end of ripening. The subsequent research trial entailed the use of warthog meat and pork fat to create salami with reduced added nitrate and increasing amounts of honeybush, where: Control= 0%; Treatment 1= 0.125%; Treatment 2= 0.25%; Treatment 3= 0.375%; and Treatment 4= 0.5% (w/w) of added honeybush extract. A total of 75 mg/kg of sodium nitrate (in the absence of nitrite) was added to all salami treatments. This addition of nitrate equalled a 70% reduction compared to the maximum permitted amount of added nitrate by the European Union (250 mg/kg) for non heat treated cured meat products (in the absence of added nitrite). After a 40-day ripening period, all salami sufficiently decreased in moisture (30.1%) and were well within the recommended aw for microbial safety (aw= 0.8333- 0.873), with T4 resulting in a significantly higher aw (0.873, p < 0.001). Although the highest honeybush addition (T4= 0.5% w/w of added honeybush) significantly lowered the salami pH (p= 0.004), the salami pH overall failed to decrease sufficiently after stuffing (with the typical low acidity salami pH reduction being between 5.0-5.3), resulting in a strangely high final product salami pH (6.71-7.46). It was hypothesised that this strangely high pH was ascribable to surface mould (Penicillium nalgiovense) growth on the small diameter (~ 33 mm) salami with the ability of utilising lactic acid, counteracting the acidifying effect of the added starter culture. Furthermore, the possible outgrowth of the starter culture lactic acid bacteria strains by background competing microflora (including Enterococcus faecium) presumably hindered a successful pH reduction. Positively, the retention of the red salami colour was best in salami with the highest honeybush inclusion levels (T3, CIE a*= 10.07 and T4, CIE a*= 10.18) after five and a half months of frozen storage (-20°C). The addition of honeybush (in a maximum concentration of 0.5%) did not significantly affect the proximate composition (moisture, protein and total lipid content) and texture attributes (hardness, chewiness and cohesiveness) of final product salami. Final product salami microbial analyses were conducted to gain insight regarding the food safety when incorporating such an extract to dry-cured and fermented game salami with reduced added sodium nitrate. All salami treatments (C, T1-T4) were free from major pathogens: Escherichia coli; Listeria monocytogenes; Salmonella spp.; and Staphylococcus aureus. Lactic acid bacteria were lowest in the control salami (6.57 log CFU/g) and increased with increasing honeybush concentration, with T3 and T4 resulting in the highest counts (> 7.0 log CFU/g). This finding corresponded with the lower pH of T4 salami. This study proved the feasibility of producing game salami with a high pH (6.71-7.46) free from major pathogens with a 70% reduction in added sodium nitrate (75 mg/kg) with the addition of a natural extract, honeybush. The honeybush addition presumably promoted the growth of wanted acidifying bacteria, with no effect with regard to bacterial proliferation inhibition. The aim of the final research chapter was to determine the effect of the honeybush extract on the fatty acid methyl ester (FAME) composition and volatile organic compound (VOC) profile of the warthog salami. Honeybush significantly affected the fatty acid composition (C12:0, C14:1, C20:1, C18:3n6, C18:3n3, C20:3n3, C20:4n6, C20:5n3 and subsequently also total n-3 polyunsaturated fatty acids (PUFA) and the n-6/n-3 PUFA ratio). Nonetheless, the overall FAME composition of the final product salami were comparable with European and American dry-cured and fermented sausages. The VOC results indicated that a honeybush addition of 0.5% to warthog salami may contribute to floral, sweet and spicy aromas due to the presence of (R/S)-linalool, terpinene-4-ol and α-terpineol in the final product salami. Positively, honeybush treated salami resulted in lower amounts of compounds related to rancidity compared to the control after a 40-day ripening period, including: hexanal; nonanal; 1-pentanol; 1-octen-3-ol; 2-pentylfyran; and undecane. Of these, hexanal and 1-octen-3-ol reduced the most significantly in T2, T3 and T4 salami (0.25%, 0.375% and 0.5% honeybush addition, respectively) compared to the control salami (p < 0.01). These results were indicative of the suppression of rancid volatile compounds originating from oleic (C18:1n9c) and linoleic (C18:2n6c) fatty acid oxidation suggesting that honeybush suppressed the formation of the above-mentioned VOCs linked to unwanted aromas in meat products.

AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die effek van ʼn natuurlike anti-oksidant, naamlik heuningbosekstrak (Cyclopia subternata), te toets in gedroogde, gekuurde en gefermenteerde wors (wat bekend staan as salami). Dit is die eerste studie wat poog om heuningbosekstrak in ʼn verwerkte rooisvleisproduk te inkorporeer en word daarom beskou as ʼn basis datastel vir toekomstige navorsers. Die data wat gegenereer is in die tesis vorm deel van ʼn relevante navorsingsonderwerp wat die gebruik van botaniese ekstrakte met antimikrobiese en/of anti-oksidant eienskappe in vleis behels. Hierdie data sal die begrip rondom die toepassingspotensiaal van so ʼn inheemse ekstrak vir die voedselbedryf verbreed. Die eerste navorsingsproef was beskou as ʼn loodstudie om vertroud te raak met die vaardighede wat benodig word vir salami produksie en om die tegniese uitdagings wat gepaard gaan met die byvoeging van heuningbosekstrak tot salami beter te verstaan. Vir hierdie doel was ʼn tipiese Italiaanse vark salami gekies as die studiemodel. ʼn Totaal van 68 salami’s was vervaardig wat bestaan het uit behandelinge: Kontrole= geen bygevoegde heuningbos of nitrate; Nitraat= met bygevoegde natriumnitraat (100 mg/kg) en askorbiensuur; en Heuningbos= met 0.5% (w/w) bygevoegde heuningbosekstrak. Na 35 gekontroleerde rypwordingsdae, het die heuningbos salami ʼn hoër wateraktiwiteit gehad (aw= 0.928, p ≤ 0.01) in vergelyking met die kontrole (aw= 0.923) en nitraat salami (aw= 0.924). Hierdie bevinding was ook gereflekteer in die hoër voginhoud van die heuningbos salami (35.3%) in vergelyking met die kontrole (33.5%, p ≤ 0.01). Die pH van die finale salami produk (pH= 5.24-5.35) was nie beïnvloed deur die heuningbosbehandeling nie. Die heuningbosbehandelde salami het wel minder suksesvolle spontane groei van muf op die buite-oppervlak gehad na die rypwordingstydperk. Die daaropvolgende navorsingsproef het die gebruik van vlakvarkvleis en varkvet ingesluit om salami te vervaardig met verminderde bygevoegde nitraat en toenemende hoeveelheid heuningbosekstrak, waar: Kontrole= 0%, Behandeling 1= 0.125%; Behandeling 2= 0.25%; Behandeling 3= 0.375%; en Behandeling 4= 0.5% (w/w) bygevoegde heuningbosekstrak behels het. Al die behandelinge het 0.75 mg/kg bygevoegde natriumnitraat bevat, sonder die byvoeging van nitriet. Hierdie byvoeging van nitraatsout was gelykstaande aan ʼn 70% vermindering in vergelyking met die maksimum toelaatbare hoeveelheid soos deur die Europese Unie gestipuleer (250 mg/kg) word vir gedroogde, bereide en gefermenteerde vleis wat nie onderhewig gemaak is aan ʼn hittebehandeling nie (in die afwesigheid van nitriet). Na ʼn 40-dag rypwordingsperiode het die voginhoud (30.1%) in al die salami genoegsaam afgeneem en was alle behandelinge binne die aanbevole minimum wateraktiwiteit (aw) vir mikrobiese veiligheid (aw= 0.8333-0.873). Behandeling 4 het ʼn betekenisvolle hoër aw-waarde gehad (0.873, p < 0.001). Alhoewel die hoogste heuningbos byvoeging (behandeling 4= 0.5% bygevoegde heuningbosekstrak) die salami pH aansienlik verlaag het (p = 0.004), het die salami pH in totaal nie voldoende gedaal tydens die fermentasietydperk nie. Dit het gelei tot ʼn eindproduk salami met ʼn onverwagte hoë pH (6.71-7.46). Die laasgenoemde verskynsel was toegeskryf aan die groei en metabolisme van die buite-oppervlak muf (Penisillium nalgiovense) op hierdie relatiewe klein deursnee salami (~ 33 mm) wat die bekende vermoë het om melksuur te metaboliseer en sodoende die versuring van die melksuurbakterieë teen te werk. Dit, te same met die kompeterende groei van bakterieë in die vleis (insluitend Enterococcos faecium), kon die bygevoegde melksuurbakterieë onderdruk het. ʼn Belowende resultaat was die behoud van salami rooiheid (CIE a*) gepaardgaande met die byvoeging van heuningbosekstrak. Na vyf-en-‘n-half-maande se vriestydperk (-20ºC), het salami met die hoogste heuningbos toevoeging (T3, CIE a*= 10.07 en T4, CIE a*= 10.18) hul rooiheid die beste behou in vergelyking met die ander behandelinge met laer heuningbosekstrak inhoud. Die byvoeging van heuningbos (tot ʼn maksimum konsentrasie van 0.5% w/w) het nie die onmiddellike samestelling (vog, proteïen en lipied-inhoud) en tekstuureienskappe (hardheid, koubaarheid en sameklewing) van die finale vlakvark salami verander nie. Mikrobiese analise op die finale vlakvark salami was uitgevoer om die voedselveiligheidsaspek in ag te neem wanneer so ʼn tipe ekstrak in wildsalami gevoeg word met ʼn 70% vermindering in bygevoegde nitraat. Alle salami Behandeling C, T1-T4 was vry van patogene: Escherichia coli; Listeria monocytogenes; Salmonella spp.; en Staphylococcus aureus. Melksuurbakterieë was die laagste in die kontrole salami (6.57 log CFU/g) en het toegeneem met toenemende heuningbosekstrak met Behandeling T3 en T4-salami wat gevolglik die hoogste hoeveelheid gehad het (> 7.0 log CFU/g). Laasgenoemde bevinding stem ooreen met die laer pH van Behandeling-T4-salami. Hierdie studie het die moontlikheid bewys om wildsvleis salami (spesifiek vlakvarkvleis) met ʼn hoë pH (6.71-7.46), 70% verminderde bygevoegde nitraat (75 mg/kg) en met toenemende heuningbosekstrak konsentrasies te produseer wat vry is van getoetsde patogene. Die heuningbosekstrak byvoeging het ook die groei van verlangde melksuurbakterieë bevorder, met geen effek ten opsigte van bakteriese groei inhibisie nie. Die finale navorsingshoofstuk se doel was om die effek van heuningbosekstrak op die vetsuurmetielester samestelling en vlugtige organiese verbindings van die vlakvark salami te bepaal. Heuningbosekstrak het geselekteerde vetsure betekenisvol beïnvloed (C12:0, C14:1, C20:1, C18:3n6, C18:3n3, C20:3n3, C20:4n6, C20:5n3 en gevolglik ook die totale n-3 en n-6/n-3 verhouding). Die algemene vetsuursamestelling van al die finale produk vlakvark salami was egter steeds vergelykbaar met Europese en Amerikaanse gedroogde en gefermenteerde worse. Die resultate rakende die vlugtige komponente het aangedui dat heuningbos kan bydra tot ʼn soet, blomme en kruie aroma as gevolg van die teenwoordigheid van (R/S)-linalool, terpien-4-ol en α-terpineol in die finale salami produk. Verder het die heuningbosekstrak ʼn afname in ongewensde, galsterige aromas getoon in vergelyking met die kontrole salami na 40 rypwordingsdae, insluitend: heksanaal; nonanaal; 1-pentanol; 1-okten-3-ol; 2-pentielfuran; en undekaan. Van die laasgenoemde komponente, het al die heuningbosekstrak behandelde salami (T1-T4) betekenisvol minder heksanaal en 1-okten-3-ol inhoud gehad in vergelyking met die kontrole (p < 0.01). Hierdie resultate was ʼn aanduiding van die onderdrukking van galsterige komponente met ʼn oorsprong van oleïensuur (C18:1n9c) en linoleïensuur (C18:2n6c) oksidasie wat gevolglik daarop dui dat heuningbos die potensiaal toon om die rakleeftyd van salami met verminderde bygevoegde nitraat kan verleng.

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