Insect infestation of biltong, a salted dried meat product consumed in Botswana

Abstract

A survey of home and commercial biltong in Botswana showed that hidden infestation by insects undetected before storage affects the quality of biltong. Seventy-nine (79) samples; made up of sixty-one (61) commercial biltong (cb) and eighteen (18) home biltong (hb) were stored under ambient laboratory conditions (temperature range 25 to 30 °C, relative humidity range 45 – 70%) for a period of 3, 6 and 12 months duration; during which samples were examined for hidden infestation. At the end of 3, 6 and 12 months, insect infestation of all the samples was 8.9%, 17.7% and 68.4%, respectively. The incidence of species after 3 months was: Dermestes maculatus (5.1%), Stegobium paniceum (2.5%), Tribolium confusum (2.5%), Calliphora sp. (2.5%), Oryzaephilus surinamensis (1.3%), and Liposcelis sp. (1.3%). Species predominance in the infested samples was: Liposcelis sp. (44.5%)(cb); S. paniceum (20%(cb); D. maculatus (16%)(hb); Acarus siro (15.5%)(cb); Calliphora sp. (2%)(c/hb); T. confusum (1)(cb) and O. surinamensis (1)(cb). After 6 months, D. maculatus was the predominant species (96.6%), caused 72.1% wt. loss, and average feeding residue of 102.9g. It completely destroyed the food product. The weight loss caused by the remaining infesting species was less than 1% i.e. Crematogaster sp. (0.24%), Plodia interpunctella (0.62%), Necrobia rufipes (0.05%) and S. paniceum (0.03%); causing damage to the food product. The incidence of the species in all the samples was: D. maculatus (7.6%)(cb/hb); Crematogaster sp. (7.6%)(cb/hb); P. interpunctella (7.6%)(cb/hb); N. rufipes (2.5%)(hb); S. paniceum (1.3)(cb) and Bracon hebetor (1.3)(hb). The total average number of insects in all samples was 229. After 12 months of storage, incidence of the species present was: P. interpunctella (40%)(cb/hb); T. confusum (20%)(cb); D. maculatus (12.9%)(cb/hb); Crematogaster sp. (11.7%)(cb); S. paniceum (7.1%)(cb); Lasioderma serricorne (4.7%)(cb/hb); Callosobruchus maculatus (2.4%)(cb) and O. surinamensis (1.2%)(hb). The predominant species were: S. paniceum (49.8%), P. interpunctella (14.1%), T. confusum (13.5%), Crematogaster sp. (12.1%), L. serricorne (5.4%), D. maculatus (4.4%), C. maculatus (0.6%) and O. surinamensis (0.07%). Even though S. paniceum was the predominant species in commercial biltong, P. interpunctella had the highest per cent incidence in both commercial and home biltong samples. The total insect counts in infested samples were 200 (3 months), 1144 (6 months) and 1452 (12 months); indicating increase in insect numbers with longer storage period. Symptoms of biltong damage over the period have been given. Hidden infestation undetected during storage of biltong could create infestation problem.