Abstract
Traditional dried mutton (faroese: turt kjøt or skerpikjøt) has been a delicacy and a necessity on the Faroe Islands for centuries. The meat is cut in slices, put on buttered bread and drizzled with salt. It has its similarities with e.g. Iberian and Serrano ham, but one significant difference is that the dried mutton is not cured or pre-treated in any way prior to drying for preservation purposes. The aim of the present study was to investigate the microbiota by culture dependent techniques and the number of colony forming units on wind-dried mutton over a five month period.Four lamb carcasses were used as material. The lambs were slaughtered in primo October 2019. Two of the carcasses (K and L) were hung to ripen in a garage from day 0 (approx 15 oC). After four days they were transferred to a traditional wind ventilated drying storehouse (Faroese: Hjallur ) where the two other carcasses (A and B) had hung from day 0. All carcasses were dry and ready to eat in primo March 2020. The drying period is 4-6 months and the process is not controlled.
The samples were taken from the surface of the left thigh of four carcasses with a depth of 0.5 cm. The microbiota was investigated by culture-dependent methods which were steered by plating dilutions of the samples on seven different selective media for bacteria (VRBG, PCA, TSA, MRS and BA with added cycloheximide) and fungi (MYGP and MEA with added chlorampenicol and oxytetracycline). All samples were vacuum packed and frozen directly after
sampling. Therefore, one non-frozen control was taken parallel to one of the samplings in order to evaluate the effect of freezing on the viability of microorganisms in the meat. The non-frozen control indicated that the process of freezing and thawing seemed to have a greater effect in viability for eucaryotic cells than bacterial cells.
The findings show that the total Colony Forming Units (CFU/g) counted from PCA as well as TSA agar (bacterial counts) on day 1 was around 105. The counts peak after 12 weeks of ripening with counts of 108-109 CFU/g. The CFU/g from MEA and MYGP agar (fungal counts) were around 103 at day 1, and were increasing throughout the whole period with CFU/g values around 107-108 in primo March 2020.
Samples taken on the 27th of December, after 12 weeks of ripening, were chosen for random isolation of colonies and purification, as high bacterial counts were expected around this time. A total of 18 bacterial and nine eucaryotic species were isolated for sequencing by Sanger sequencing and phenotypic investigations. Five different fungal genera were identified, including
Debaryomyces, Penicillium, Mucor and Cladosporium. 70 out of 90 fungal isolates were identified as D. hansenii. 87 bacterial isolates were sequenced and revealed 12 different genera. 25 of the isolates were identified as E. coli while 35 were identified as Staphylococcus spp.. The Staphylococcus spp. consisted of 6 different species.
| Date of Award | 2020 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Supervisor | Petra Elisabeth Petersen (Supervisor), Jógvan Páll Fjallsbak (Supervisor), Pernille Johansen (Supervisor) & Lene Jespersen (Supervisor) |