The Preservative Effects of Aframomum melegueta and Piper guineensis Extracts on Microbial Load of Hibiscus sabdariffa and Sorghum bicolour Liquors

Abstract

Aims: The preservative effects of hot sterile water extracts of Aframomum melegueta and Piper guineensis on the shelf life of Hibiscus sabdariffa (H. sabdariffa) and Sorghum bicolor (S. bicolor) liquors were investigated. Study Design: Factorial design was used for this study. Place and Duration of Study: The study was carried out in Chemistry, Food Processing, Sensory and Microbiology Laboratories of the Department of Food Science and Technology, Federal University of Technology, Akure, Ondo State, Nigeria, between September, 2012 and December, 2013. Methodology: Dried H. sabdariffa calyx and S. bicolor stem sheath were cleaned by removing extraneous materials, milled and sieved separately. Extracts of the two spices, namely A. melegueta and P. guineensis were prepared in 0.5%, 1.0%, 1.5% and 2.0% concentrations respectively making a total of 5 samples with the control for each liquor. H. sabdariffa calyx and S. bicolor stem liquors were treated respectively with the different concentrations (0.5,1.0,1.5 and 2.0%) of spice extracts in 1000 mls (1 litre) of each liquor respectively and stored at ambient temperature (28±2ºC) for 4 days. The microbial loads were determined daily until the samples were adjudged spoilt through offensive smell and characteristic odour with observable changes in colour from bright red to black. Results: On the first day, there was no observable bacteria growth and no Coliform count throughout the period of storage. This is an indication that the liquors were prepared under hygienic condition. Microbes were however observed for samples treated with A. melegueta and P. guineensis extracts on the second day. At 0.5% inclusion, A. melegueta extract in H. sabdariffa calyx and Sorghum bicolor liquors had microbial loads of 3.70 x102 and 4.42 x102 cfu/mL respectively while 0.5% P. guineensis extract in H. sabdariffa calyx and Sorghum bicolor liquors recorded 3.20 and 3.54 x102 cfu/mL. At 1.5%, A. melegueta extract in H. sabdariffa calyx and S. bicolor liquors had microbial loads of 3.20 and 4.00x102 cfu/mL respectively. At 1.5%, P. guineensis extract in H. sabdariffa calyx and S. bicolor liquors had microbial loads of 1.70 and 3.18 x102 cfu/mL respectively. On the fourth day, the microbial load for 1.5% A. melegueta extract in H. sabdariffa calyx and S. bicolor liquors were 3.50 and 3.80x102 cfu/mL respectively. The 1.5% P. guineensis extract in H. sabdariffa calyx and S. bicolor liquors recorded 2.82 and 3.20 x102 cfu/mL respectively. Results showed that the Control samples had higher microbial loads than the spiced (treated) samples indicating some preservative effects of the spices on both liquors. Furthermore, the result showed that P. guineensis had a better preservative action than A. melegueta. Likewise, the preservatives were found to have better control on microbial growth in H. sabdariffa than in S. bicolor. Conclusion: The preservative effects of Aframomum melegueta and Piper guineensis extracts on microbial load of Hibiscus sabdariffa and Sorghum bicolor liquors showed that A. melegueta had lower antimicrobial activity than P. guineensis, thus P. guineensis may be preferred as a natural antimicrobial (preservative) to extend the shelf life of foods.