Comparative Studies of Ginger (<i>Zingiber officinale</i>) and West African Black Pepper (<i>Piper guineense</i>) Extracts at Different Concentrations on the Microbial Quality of Soymilk and <i>Kunun-zaki</i>

Abstract

Extracts of two spices, namely ginger (Zingiber officinale) and black pepper (Piper guineense) were prepared in 0.4%, 1.2%, 2.4% and 3.6% concentrations. Soymilk and kunun-zaki were treated respectively with the different concentrations and stored at ambient temperature for 5 days. The microbial load and identification were determined every day of storage
until samples were adjudged spoilt. On the first day, 0.4% ginger extract in soymilk and kunun-zaki had a microbial load of 7.77 x 106b and 5.17 x 106b respectively. 3.6% ginger extract in soymilk and kunun-zaki recorded 3.73 x 106b and 3.30 x 106 each. 0.4% black pepper extract in soymilk had 6.273 x 106b and recorded 4.63 x 106b in kunun-zaki. 3.6% black pepper extract in soymilk and kunun-zaki had a microbial load of 3.20 x 106d and 2.90 x 106c respectively. On the third day the microbial load
increased for both ginger and black pepper extract. Ginger extract recorded 9.13 x 106b in soymilk and 5.60 x 106b in kunun-zaki at 0.4% concentration. Black pepper extracts recorded 7.43 x 106b in soymilk and 3.27 x 106b in kunun-zaki also at 0.4% extract. 3.6% black pepper extract recorded 4.10 x 106a in soymilk and 2.20 x 106c in kunun-zaki. There was linear reduction of microbial load as spice concentration increased. Black pepper recorded lower microbial load, thus having more antimicrobial activity and may be preferred to be used as natural antimicrobial  preservatives to extend the shelf-life of food.

Keywords: Ginger, black pepper, extracts, soymilk, kunun-zaki.