Soluble Nutrient Production During Fermentation of Three Melon Varieties in the Leaves of Musa spp, Thaumatococcus danielli and Carica papaya

Abstract

The amount of soluble nutrient production (soluble sugars and free amino acids) in three varieties of melon seeds, Citrullus colocynthis (A), Cucumis melo (B) and Cucumeropsis mannii (C) during fermentation in Musa spp (M), Thaumatococcus danielli (D) and Carica papaya (P) leaves were  investigated. Proximate compositions of the three varieties revealed that they were very rich in fat with variety C having the highest content  (55.93%) while it was the least rich in protein (24.42%). In contrast to the fat composition, carbohydrate content was the least in all three varieties with variety B having the highest (16.31%) and A the least (7.86%). Variety A, however, was the richest in protein (37.14%) while C had the lowest value (24.42%). Fermentation increased the amounts of free amino acids in all varieties of melon and in all leaf types. Varieties fermented in Musa spp leaf gave the highest amounts with C having 275 ± 19.6 mg/g dry weight, B and A having 240 ± 19.6 mg/g and 155±9.8 mg/g  respectively. Varieties fermented in Thaumatococcus danielli had higher retention levels of free amino acids than those fermented in Carica papaya. Fermentation however decreased the total soluble sugar levels in all three varieties of melon and in all leaf types. On the average, varieties fermented in Musa spp gave highest retention levels of soluble sugars with C (720 ± 29.3 mg/g dry weight), B (567 ± 13.72 mg/g), A (295±9.8 mg/g). Enzymatic activities (amylase, proteinase and lipase) increased throughout fermentation in all varieties of melon and in all leaf types, with proteinase being the highest as observed in variety B (10.33 ± 1.67, 10.00 ± 1.96 and 9.67±1.5 mg tyrosine/min) for all leaves. Amylase activity followed the same trend (0.252 ± 0.03, 0.236 ± 0.02 and 0.224 ± 0.02 mg maltose/min). Lipase activity was highest in variety A (0.53 ± 0.003 mg oleic acid/min) than in B and C (0.48 ± 0.02 and 0.49 ± 0.002 mg/g) respectively. Of the three types of leaves used in the fermentation process, Musa spp and Thaumatococcus danielli were observed to serve as better materials for fermentation while melon varieties C and B were better suited for fermentation into condiment.