Abstract
This study assessed the effects of different pretreatment methods on the proximate, mineral and
vitamin composition of “Nyama Asabo” (Diplazium esculentum) to identify methods that
maintain nutritional quality during processing. Fresh leaves (300 g each) were subjected to
oven drying at 60°C, steam blanching at 70°C for 2 minutes, hot water blanching at 70°C for
2 minutes and hot water blanching with 2.5% sodium bicarbonate at 70°C for 2 minutes, with
fresh leaves serving as control. Proximate composition included moisture, protein, fat, ash,
crude fiber, carbohydrate and energy, while mineral content comprised phosphorus,
potassium, iron, magnesium, sodium and calcium. Vitamins A, B1, B2, C and E were also
measured. Moisture decreased across all treatments, with oven-dried and steam-blanched
leaves retaining higher protein, carbohydrate and energy levels. Mineral content was best
preserved in steam-blanched samples, while sodium bicarbonate-assisted blanching showed
lower retention. Water-soluble vitamins declined under all treatments, but steam blanching
maintained higher levels of vitamins A, B1, B2, C and E. Heat and water exposure affected
nutrient retention, with minimal water contact reducing losses. The results indicate that steam
blanching effectively maintains macronutrient, mineral and vitamin content in Diplazium
esculentum, supporting its use in household and small-scale processing to improve dietary
quality. The researchers recommended that steam blanching should be used as the preferred
pretreatment to preserve nutrients. Hot water blanching and chemical-assisted treatments
should be minimized or optimized to reduce losses of water-soluble vitamins and minerals.
Oven drying can be applied selectively to concentrate macronutrients, with controlled
temperature to limit degradation of sensitive vitamins.