No cases of food poisoning have ever been reported after consuming tempeh (Ko Swan & Hesseltine, 1979). However, there is still a risk due to the potential growth of moulds and pathogenic bacteria (Table 2), and the production of mycotoxins and bacterial toxins. Pathogenic bacteria do not grow well in acidified substrates and even if they can grow, they are normally controlled by LAB (Table 2). The only bacterial toxin reported in tempeh hitherto is produced by Pseudomonas cocovenenans in tempeh bongkrek made from coconut grits or presscake (Ko Swan & Kelholt, 1981; Steinkraus et al., 1983). Some fungal taxa closely related to R. oligosporus produce toxins (Jennessen et al., 2005), and misidentification could potentially lead to the use of a toxin-producing strain for tempeh fermentation.
Inoculated Bacillus subtilis, Staphylococcus aureus and Escherichia coli did not grow during barley tempeh fermentation (Swanberg, unpublished), which might be due to the low pH under well-controlled fermentation conditions, as well as to competition from the fast growing R. oligosporus.
Table 4. Yeasts observed in tempeh
Species (number of isolates) Origin Reference
Trichosporon beigelii (34) The Netherlands (Samson et al., 1987)
Clavispora (Candida) lusitaniae (17)
Candida altosa (13)
Candida intermedia (11)
Yarrowia lipolytica (7)
Lodderomyces elongisporus (6)
Rhodotorula mucilaginosa (6)
Candida sake (3)
Hansenula fabian (3)
Candida tropicales (2)
Candida parapsilosis (2)
Pichia membranaefaciens (2)
Rhodotorula rubra (2)
Candida rugosa (1)
Candida curvata (1)
Hansenula anomala (1)
Trichosporon spp. Malaysia (Steinkraus et al., 1983)
Trichosporonpullulans Indonesia (Steinkraus et al., 1983)
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