Profiling of traditional South African biltong in terms of processing, physicochemical properties and microbial stability during storage

Jones, Maxine Sylvia (2017-03)

Thesis (PhD (Food Sc))--Stellenbosch, 2017.

Thesis

ENGLISH SUMMARY: In South Africa, there are no processing guidelines for biltong production and therefore the industry uses different processing parameters which results in variation in the product. The same process was used throughout this study and drying was done using constant parameters – temperature 25 ± 2°C, relative humidity 30 ± 5%, air velocity 2 ± 0.2 m/s. An initial study investigating the influence of vinegar addition during the production of beef biltong showed that vinegar addition does not influence its drying kinetics. The biltong reached a 50% weight loss after 66 hours and a 65% weight loss after 96 hours. The use of different meat muscles (topside, semimembranosus and silverside, biceps femoris), beef with subcutaneous fat and gemsbok (Oryx gazelle) showed differences (p ≤ 0.05) in drying rates when dried to a targeted weight loss of 65%. The two lean beef muscles both dried in 96 hours. The gemsbok topside took only 78 hours with a drying pattern similar to the lean beef topside. The fatty beef topside took 118 hours to dry. The microbiological profile of beef biltong over a three month shelf-life storage were studied. Final weight loss during drying and packaging method (modified atmospheric packaging and vacuum packaging) did not have an effect (p > 0.05) on the microbiological profile. Total viable counts and coliforms were only reduced in biltong with vinegar added. After drying, yeasts and moulds were already present at high levels (~ 2.5 log cfu.g-1) but not visible. After six weeks, yeasts and moulds became visible. Staphylococcus aureus was present at less than 20 log cfu.g-1 while Listeria monocytogenes, Salmonella spp. and Escherichia coli were not present during the three month storage period. Yeast and mould growth on biltong is a problem and therefore a challenge study was included. Beef biltong produced without and with vinegar and dried to a 50% or 65% weight loss were inoculated with yeasts and moulds. No yeast and mould growth was seen on biltong with vinegar but 1.8 – 2.5 log cfu.g-1 was detected after 34 days. Biltong without vinegar showed yeast and mould growth after 10 days with levels of 2.8 – 3.1 log cfu.g-1. Saccharomyces spp. (yeast) and Aspergillus spp., Fusarium spp. and Penicillium spp. (moulds) were the most common yeast and moulds. A small-scale study using ultrasound in the salting step of beef biltong processing showed that ultrasonic-brining did not have an effect on either the salting or drying kinetics contrary to what was expected. Throughout the study the physicochemical properties of the beef biltong gave consistent results. An approximate 50% and 65% weight loss produced biltong with a moisture content of 50% and 30%, respectively and water activity of 0.74 – 0.78 and 0.81 and 0.86, respectively. Weight loss or the addition of vinegar did not play a role in the salt content (dry basis). Beef biltong without vinegar had a pH 5.56 – 5.75 while the addition of vinegar to biltong lowered the pH of biltong to 4.89 – 4.93. It is recommended that the biltong industry should standardise their drying parameters to avoid variation in quality and for a more microbial stable product. Vinegar could be added as it has an effect on the yeast and mould growth. Biltong with water activity ranging from 0.74 to 0.83 does not have a shelf-life of more than three months when using modified atmosphere packaging or vacuum packaging. The data generated in this study serves as a base-line for future studies focused on optimising and standardising the drying procedures applicable to biltong.

AFRIKAANSE OPSOMMING: Daar is geen wetlike prosesseringsriglyne vir die produksie van biltong in Suid Afrika nie en dus maak die industrie gebruik van verskillende prosesseringsparameters wat lei tot variasie in die produk. Dieselfde proses en die droging was uitgevoer in hierdie studie volgens konstante parameters – temperatuur 25 ± 2°C, relatiewe humiditeit 30 ± 5%, lugspoed 2 ± 0.2 m/s. ‘n Aanvanklike ondersoek het bepaal dat die byvoeg van asyn gedurende die produksie van beesbiltong nie die droogkinetika van die biltong beïnvloed nie. Die biltong het ‘n gewigsverlies van 50% na 66 uur en 65% na 96 uur gehad. Verskillende vleis spiere (binneboud, semimembranosus en dy, biceps femoris), bees met onderhuidse vet en gemsbok (Oryx gazelle), gedroog tot ‘n teikengewigverlies van 65% het verskille (p ≤ 0.05) gehad in terme van droogtempo en -tyd. Die twee verskillende maer beesspiere was droog na 96 uur. Die gemsbokbinneboud was droog na slegs 78 uur en het dieselfde droogpatroon as die maer beesbinneboud gevolg. Die vetryke beesbinneboud het 118 uur geneem om te droog. Die mikrobiese profiel van die beesbiltong oor ‘n stoorperiode van drie maande is ondersoek. Die finale gewigsverlies en verpakkingsmetode (modified atmospheric packaging en vakuumverpakking) het nie die mikrobiese profiel geaffekteer nie (p > 0.05). Die totale lewensvatbare tellings en coliforms was laer in die biltong waar asyn bygevoeg is. Gisse en swamme was reeds teen höe vlakke (~ 2.5 log cfu.g-1) na droging teenwoordig maar was nie sigbaar met die blote oog nie. Beide gisse en swamme was na ses weke met die blote oog sigbaar. Gedurende die stoorperiode was Staphylococcus aureus teenwoordig by vlakke minder as 20 log cfu.g-1 terwyl Listeria monocytogenes, Salmonella spp. en Escherichia coli nie teenwoordig was nie. Die groei van gisse en swamme op biltong is ‘n probleem en daarom is ‘n uitdagingsstudie (challenge study) ingesluit. Biltong geproduseer met en sonder asyn, gedroog tot 50% en 65% gewigsverlies was geïnokuleer met gisse en swamme. Daar was geen sigbare groei van gisse en swamme op die biltong met asyn nie, maar na 34 dae is wel groeivlakke van 1.8 – 2.5 log cfu.g-1 gevind. Gisse en swamme het op die biltong sonder asyn na 10 dae teen vlakke van 2.8 – 3.1 log cfu.g-1 gegroei. Die algemeenste gisse en swamme op die biltong was Saccharomyces spp. (gis) en Aspergillus spp., Fusarium spp. en Penicillium spp. (swamme). ‘n Kleinskaalse studie op die gebruik van ultraklank gedurende die soutproses van beesbiltong het getoon dat die metode geen effek op die sout of droogkinetika van die biltong gehad het nie, wat teenstrydig was met die verwagte resultate. Die fisiochemiese eienskappe van die beesbiltong het deurgaans in die studie konstante resultate gelewer. Biltong met ‘n gewigsverlies van 50% en 65% het biltong met ‘n voginhoud van onderskeidelik 50% en 30% geproduseer, met ‘n wateraktiwiteit van onderskeidelik 0.74 – 0.78 en 0.81 en 0.86. Die gewigsverlies of byvoeging van asyn het nie ‘n rol gespeel ten opsigte van die totale soutinhoud nie (gebaseer op droëbasis). Die beesbiltong sonder asyn het ‘n pH van 5.56 – 5.75 gehad terwyl die biltong met asyn bygevoeg ‘n laer pH van 4.89 – 4.93 gehad het. Dit word aanbeveel dat die biltongindustrie drogingsparameters standardiseer om sodoende ‘n groot variasie in die eindproduk te vermy en ‘n meer mikrobies stabiele produk te verseker. Asyn kan bygevoeg word omdat dit die groei van gisse en swamme beïnvloed. Biltong met ‘n wateraktiwiteit van 0.74 to 0.83 het nie ‘n rakleeftyd van meer as drie maande nie ongeag die verpakkingsmetode (modified atmosphere packaging of vakuumverpakking). Die data van hierdie studie kan gebruik word as ‘n basispunt vir toekomstige studies wat fokus op die optimisering en standardisering van die droogmetodes wat gebruik word in die maak van biltong.

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