Aroma components in Vangueria infausta L. : Characterization of components using GC_MS and aroma loss during drying

This study focuses on the fruit of the African medlar (Vangueria infausta L., family
Rubiaceae).
The investigation included the development of an extraction procedure of volatile components
from the fruit matrix, a purification step, separation, identification and quantification.
Initial experiments showed that some components, especially sugars, degrads during the
heating in the GC analysis, producing furfural, hydroxylmethylfurfural (HMF) and other
volatiles. These compounds are obtained together with the native aroma components of the
fruit making the analyses difficult.
We developed a procedure using a hydrophobic column with capability to retain the
hydrophobic aroma components and eliminating sugars that may disturb the analyses.
The volatile components found in pulp is primarily: Hexanoic acid (30000-4000 μg/g, DM),
octanoic acid (2000-200 μg/g, DM), ethyl hexanoate (400-40 μg/g, DM), ethyl octanoate
(200-10 μg/g, DM), methyl hexanoate (60-8 μg/g, DM) and methyl octanoate (70-9 μg/g,
DM). Based on the odor activity values (OAV) it can conclude that the odor of the fruit is
mainly originated by ethyl hexanoate and ethyl octanoate. Fruity, sweet, floral and slight fatty
are the most attributes that mark the aroma profile of studied fruit. The experiment was
repeated using samples collected in different occasion (2010-2013).
During food processing and preservation of food especially fruits many attributes are affected
including volatile components that are important attribute affecting palatability and consumer
interest of food. The finding is that the principal aroma components of pulp are well preserved
during the initial phase of drying (down to about a relative water activity 0.65). However, the
aroma components are lost after a more extensive drying. A possible explanation of the
volatilization is sugar crystallization that is to occur below a relative humidity of around 0.70
during the drying process.
The results highlighted, in somehow, the potential of Vangueria infausta as wild fruits to
include in industrial food products. However, more studies are needed to improve the
retention of volatile during drying. Encapsulation of these volatiles could help to sustainable
utilization of diversity wild fruits growing in Mozambique.