Abstract

The effect of processing methods on the chemical composition, proximate, mineral, vitamin and microbiological quality of vegetable drink extract of Irvingia gabonensis was studied. The processing methods included drying (shade and solar drying), blanching (at 0, 2, 4 and 6 min) as well as blanching and drying of the leaves. Aqueous extracts were obtained from the leaves and the analysis carried out using standard methods. The result showed that whereas some parameters analyzed varied with processing, others remained unaffected. The moisture, protein and fat content did not vary significantly (p<0.05) with treatments while shade drying increased ash content significantly. Shade drying also increased the phytochemicals from 17.50 to 72.50% for total phenol; 4.53 to 6.72% for flavonoids and 2.98 to 3.86% for alkaloid. It also reduced steroids and saponin significantly (p<0.05). Phytate content was non-significantly (p<0.05) reduced by shade and solar drying whereas the other processing methods increased it to the range of 5.38 to 14.33 mg/100 g. Six minutes blanching reduced oxalate from 8.15 to 7.25 mg/100 g and tannin content from 0.023 to 0.019 mg/100 g. Cyanide content of 0.03 mg/100 g was increased by all the processing methods though minimally by blanching and solar drying. Carotenoid content of 164.56 IU was reduced significantly (p<0.05) to the ranges of 92.83 to 151.90 IU for blanched and 16.88 to 59.07 IU for dried vegetable drink extracts. Vitamin A content of 987.34 IU was significantly (p>0.05) reduced by all the processing methods to the range of 101.27 to 632.91 IU. Vitamin C, on the other hand, was increased significantly (p<0.05) by all the drying methods. The rest of the vitamins and also minerals were inconsistent with the processing methods. Total plate count was negligible in blanched drink extracts while shade drying gave the highest count (1.30 × 10³ cfu/g). Total coliforms were reduced in all the drinks from the processed leaves. The mould count in the blanched drink extract remained relatively low, but increased mould counts occurred in drink extract from shade dried leaves.

Key words: Blanching, Irvingia gabonensis leaf, shade drying, solar drying, vegetable drink extract.