Quantitative Changes of Ascorbic acid and Beta carotene in African nightshade (Solanum nigrum) and Spider plant (Cleome gynandra) due to traditional cooking methods used in western Kenya
*Anne A. Musotsi1 , Anselimo Makokha2 , Mary O. Abukutsa-Onyango3, and Sheila M. Kilonzi4
1-Masinde Muliro University of Science and Technology, P.O Box 190-50100, Kakamega-Kenya; E-mail: aswanianne@gmail.com
2-Jomo Kenyatta University of Agriculture and Technology, P.O Box 62000-00200, City Square, Nairobi; E-mail: anmakokha@gmail.com
3-Jomo Kenyatta University of Agriculture and Technology, P.O Box 62000-00200, City Square, Nairobi; E-mail: abukutsa.mary@gmail.com
4-Karatina University, P.O Box 1957-10101, Karatina; E-mail: skilonzi@gmail.com
ABSTRACT
African nightshade (Solanum nigrum) and Spider plant (Cleome gynandra) are among African leafy
vegetables (ALVs) that are consumed in Kenya. Studies were conducted to establish the traditional
cooking methods for ALVs and to determine quantitative changes in ascorbic acid and beta
carotene on cooking the two ALVs. Results revealed that the cooking methods had distinct steps.
The amount of time and water for cooking were unspecified. Ascorbic acid decreased from
28.2mg/100g to 1.8mg/100g in Spider plant (93.6% loss) and from 19.5mg/100g to 5.8mg/100g in
African nightshade (70% loss). Beta carotene decreased from 2.1mg/100g to 0.1mg/100g in Spider
plant (94.4% loss) and from 1.8mg/100g to 0.9mg/100g (50.6% loss) in African nightshade. All
results were significant (P˂ 0.001). The study concludes that there are existing methods of cooking
ALVs. For the two ALVs, cooking led to drastic losses of ascorbic acid and beta carotene. Losses
from the African nightshade were generally lower than from the Spider plant for the same nutrient,
under similar processing conditions. The study recommends procedural changes in processing
methods so as to conserve the two nutrients.
KEYWORDS: ALVs, cooking, Beta carotene, Vitamin C