Antimicrobial effects of butylated hydroxyanisole alone or in combination with potassium sorbate on quality changes in palm oil co-inoculated withAspergillus flavus andBacillus spp

Abstract

Palm oil was sterilised and subjected to different concentrations (0.2 to 1.0 g litre -1 ) of butylated hydroxyanisole (BHA) alone or in combination with potassium sorbate (KS) and co-inoculated with Aspergillus flavus and Bacillus species, the most prevalent organisms isolated from the palm oil. A dramatic increase of c3.43, 3.16 or 1.83 log 10 cfu ml -1 microbial populations occurred in control samples or those treated with 0.2 or 1.0g litre -1 of BHA alone respectively. On the contrary, populations lower by approximately 1.0-1.3 log 10 cfu ml -1 occurred in samples subjected to the combination treatment. Bi-phasic minima-extended-tag-phases were observed in the samples treated with BHA + KS. Mycelial growth was markedly inhibited in samples preserved with BHA + KS, being more apparent at concentrations of between 0.4 and 0.8 g litre -1 of BHA in combination with potassium sorbate. Similarly, significantly (P=0.05) lower free fatty acid content was observed in samples subjected to the combination treatment particularly at concentrations ranging from 0.6 litre -1 . Changes in pH were minimal suggesting less microbial activity, but significantly lower values occurred in samples treated with BHA alone after 14 days of ambient (30(±3)°C) storage. Better sensory qualities (less 'separation' i.e enhanced stability and aroma) were exhibited by samples preserved with the combination of BHA with KS. These various induced changes demonstrate the importance of concentration, residence time and synergism in relation to the effectiveness of antimicrobial agents. The benefits of the application of combination treatments have been shown and could be exploited by palm oil processors and importers. However, samples treated with the low concentrations are more likely to present potential hazards to consumers.