Infrared drying as a potential alternative to convective drying for biltong production

Two infrared systems set at an intensity of 4777 W/m² with peak emission wavelengths of 2.5 and 3.5 μm were used to produce biltong by drying differently pre-treated meat. In addition to meat texture and colour, the microbial quality of the biltong produced was assessed by quantifying viable heterotrophic microorganisms using a most probable number (MPN) method and by verifying the presence of presumptive Escherichia coli in samples produced using infrared and conventional convective drying. The two infrared drying systems reduced the heterotrophic microbial burden from 5.11 log₁₀ MPN/g to 2.89 log₁₀ MPN/g (2.5 μm) and 3.42 log₁₀ MPN/g (3.5 μm), respectively. The infrared systems achieved an up to one log higher MPN/g reduction than the convective system. In biltong samples produced by short wavelength (2.5 μm) infrared drying, E. coli was not detectable. This study demonstrates that the use of short wavelength infrared drying is a potential alternative to conventional convective drying by improving the microbiological quality of biltong products while at the same time delivering products of satisfactory quality.