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Extending the shelf life of packaged biltong

Biltong is an intermediate moisture ready-to-eat meat snack that originated in South Africa. Low water activity, increased solutes content and low pH help extend biltong’s shelf life. A Hamilton company, Safari Biltong, specialises in producing biltong. Its current product is manufactured to a food control plan (FCP) approved by the Ministry of Primary Industries. This FCP allows the biltong to be kept for a maximum of two weeks. The company wants to develop more markets and also to export biltong. This involves researching systems that would allow the product to retain the desirable quality and food safety for up to a year without using chemicals or preservatives. A good quality biltong has dark colouring (black to dark brown), no visible fungal growth, no bacterial populations that exceed allowable limits, water activity below 0.85, a pH around 5.3, little to no rancid flavours and a chewy consistency. Freshly made biltong was packaged using film with low water, oxygen and carbon dioxide transmission and sealed under full vacuum (VS), partial vacuum (PV) or partial vacuum with an oxygen scavenger (PVS) then stored at 35°C, 20°C and 4°C for 46 weeks. The water activity, pH, appearance and mould spore viability was monitored periodically. Sensory evaluations were also done using an untrained panel. A second, smaller trial investigated the effect of adding a proprietary natural antioxidant on storage quality and lipid oxidation. The national lockdown due to the Covid 19 pandemic prevented some data being collected during the trial. Water activity of biltong kept at the 35 and 20°C decreased during storage, especially in biltong kept at 35°C, where water activities decreased to as low as 0.4. The water activity of biltong stored at 4°C fluctuated around the initial value of 0.69 over the 46-week storage period. Storing under full vacuum was best for maintaining a higher water activity associated with biltong having an acceptable texture. During storage, none of the biltong had a water activity that exceeded the allowable limit of 0.85. Biltong maintained the best appearance and pH when kept at 4°C in full vacuum packs. Colour of fresh biltong is black, which fades to a light brown colour with deterioration. This occurred the most in biltong stored at 35oC, especially in the PV environment, which became unacceptable after 16 weeks. Biltong stored in a VS environment maintained colour best, becoming unacceptable after 42 weeks whilst biltong stored in the PVS environment was unacceptable after 24 weeks. Biltong stored at 20°C and 4°C remained acceptable throughout storage for all packaging environments, with the best colour being maintained in the VS environment. Bacteria were not isolated from the biltong during storage. No visible mould growth was observed on the packaged biltong during storage, other than one pack with a faulty seal. Viability of mould spores decreased during storage. Viable mould spores were not detected on biltong stored at 35°C after 9 weeks storage or after 15 weeks on biltong stored at 20°C. However, viable spores were isolated from biltong stored 4°C at the end of the 46 week trial. Sensory analysis after six weeks showed biltong stored at 35°C PV conditions was very unacceptable and that biltong stored at 4°C, regardless of packaging environment, was best. All biltong stored at 20°C was acceptable, with that stored in VS and PVS environments being preferred over biltong stored in the PV environment. Scores for sensory evaluations varied greatly and panellists could not discern differences between biltong stored in different environments. Including a proprietary rosemary extract in the marinade decreased the rate of lipid oxidation (measured as thiobarbituric acid reactive substances) and development of rancid flavours (measured using a sensory panel). Lipid oxidation, as expected, was highest in biltong stored at 35°C and lowest in biltong stored at 4°C. The greatest oxidation occurred in the VS environment and the least in the PV environment. Further trials on the effect of the packaging environment on lipid oxidation need to be done as data did not agree with that obtained for biltong with no added extract, which showed that oxidation was greater in the PV environment. Sensory data indicated that the quality of biltong containing the rosemary extract and packed under partial or full vacuum was still acceptable after 14 weeks at 20oC and 4oC. Adding an oxygen scavenger slightly improved quality. The acceptability of biltong stored at 35oC deteriorated quickly but this temperature could be used for accelerated storage of the effect of packaging environments and additives on biltong quality. Recommendations for further research are given, including further investigating factors that affect lipid oxidation, using a trained panel for sensory evaluations, investigating other packaging environments and storage temperatures, and investigating the reason for variation in water activity and pH measurements.
Type of thesis
Senekal, E. (2020). Extending the shelf life of packaged biltong (Thesis, Master of Science (Technology) (MSc(Tech))). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/14128
The University of Waikato
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