Comparative studies of ginger (<i>Zingiber officinale</i>) and black pepper (<i>Piper guinenses</i>) extracts at different concentrations on the microbial quality of soymilk and kunuzaki

Abstract

Extracts of two spices namely ginger (Zingiber officinale) and black pepper (Piper guinenses) were prepared in 0.4, 1.2, 2.4 and 3.6% concentrations. Soymilk and kunuzaki, 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 spoiled. On the first day, 0.4% ginger extract in soymilk and kunuzaki had a microbial load of 7.77 × 10^6b and 5.17 × 10^6b, respectively. 3.6% ginger extract in soymilk and kunzakki recorded 3.73 × 10^6b and 3.30 × 10⁶ each. 0.4% black pepper extract in soymilk had 6.273 × 10^6b and recorded 4.63 × 10^6b in kunuzaki. 3.6% black pepper extract in soymilk and kunuzaki had a microbial load of 3.20 × 10^6d and 2.90 × 10^6c, respectively. On the 3rd day, the microbial load increased for both ginger and black pepper extract. Ginger extract recorded 9.13 × 10^6b in soymilk and 5.60 × 10^6b in kunuzaki at 0.4% concentration. Black pepper extracts recorded 7.43 × 10^6b in soymilk and 3.27 × 10^6b in kunuzaki also at 0.4% extract. 3.6% black pepper extract recorded 4.10 × 10^6a in soymilk and 2.20 × 10^6c in kunuzaki. There was linear reduction of microbial load as spice concentration increases. Black pepper recorded lower microbial load, thus has more anti microbial activity and may be preferred to be used as national anti microbial preservatives to extend the shelf-life of food.

Keywords: Zingiber officinale, Piper guinenses, soymilk, kunzakki