Comparative studies on the effect of processing methods on the nutritional value of Basella alba, Talinum triangulare, Celosia argentea, Amaranthus hybridus and Gnetum africanum leaves

The nutritional composition of vegetables is adversely affected by the method of processing for storage or preservation. This study was designed to determine the effect of blanching, boiling, and drying on the nutritional composition of selected vegetables using standard analytical methods. Proximate analysis was carried out on the fresh and processed leaf samples. Results obtained revealed that all the vegetables analyzed contained an appreciable amount of moisture, ash, protein, fiber, carbohydrate, β-carotene, and vitamins. Results also showed that all the processing methods employed significantly reduced (p < 0.05) the nutritional compositions of the vegetables studied. However, drying under the shade retained more nutrients compared to the other processing methods. Drying significantly increased (p < 0.05) the carbohydrate and protein contents of all the leaves (79.92 % & 7.51 % respectively in Basella alba, 66.74 % & 12.09 % respectively in Amaranthus hybridus, 82.56 % & 10.07 % respectively in Celosia argentea, 70.77 % & 13.05 % respectively in Gnetum africanum and 89.12 % & 4.70 % respectively in Talinum triangulare) compared to blanching, boiling and the control. Thus, from the three processing methods studied, drying was the most effective processing method that retained nutrients and is, therefore, a good preservation method for the vegetables.