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

Abstract

Two infrared systems set at an intensity of 4777 W/m<sup>2</sup> with peak emission wavelengths of 2.5 and 3.5 μm were used to produce <em>biltong</em> by drying differently pre-treated meat. In addition to meat texture and colour, the microbial quality of the <em>biltong</em> produced was assessed by quantifying viable heterotrophic microorganisms using a most probable number (MPN) method and by verifying the presence of presumptive <em>Escherichia coli</em> in samples produced using infrared and conventional convective drying. The two infrared drying systems reduced the heterotrophic microbial burden from 5.11 log<sub>10</sub> MPN/g to 2.89 log<sub>10</sub> MPN/g (2.5 μm) and 3.42 log<sub>10</sub> MPN/g (3.5 μm), respectively. The infrared systems achieved an up to one log higher MPN/g reduction than the convective system. In <em>biltong</em> samples produced by short wavelength (2.5 μm) infrared drying, <em>E. coli</em> 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 <em>biltong</em> products while at the same time delivering products of satisfactory quality.