Vol. 8, Issue 4 (2020)

Methodology: The vegetable leaves and potato tuber were cooked in boiling water for 40 minutes to determine their β-carotene and riboflavin content, and 45 minutes for ascorbic acid content. Furthermore, portions of the samples were refrigerated for a period of 3 days and 7 days, and their β-carotene and ascorbic acid content assessed. Determinations were done using standard AOAC methods and methods reported by previous researchers.

Results: The amount of β-carotene in untreated samples ranged between 1,200 mg/100g in potato to 17,310 mg/100g in water leaf and between 504.00 mg/100g to 10,729 mg/100g in the same samples respectively after boiling for 40 minutes. The riboflavin content ranged between 3.80 mg/100g to 130.00 mg/100g in pumpkin and onions respectively. After boiling for 40 minutes, this dropped to within a range of 2.00 mg/100g to 74 mg/100g in both samples respectively. The ascorbic acid content was generally below that of β-carotene but higher than riboflavin and ranged between 504 mg/100g to 10,729 mg/100g and 39 mg/100g to 180 mg/100g before and after boiling for 45 minutes respectively. The β-carotene in cabbage was least affected by heat treatment with a percentage loss of 21.30% whereas ascorbic acid in onions was most affected at 82.21%. Refrigeration also showed marked impact on the vitamin content with the β-carotene and ascorbic acid content completely lost in lettuce after refrigeration for 7 days, whereas it showed no impact on the β-carotene content of cabbage after 3 days. The ascorbic acid content of garden egg was reduced by 80.01% upon refrigeration for 7 days while the β-carotene and ascorbic acid contents of lettuce were completely lost after the same duration of time. Generally, the contents of the vitamins decreased with increasing refrigeration time.