3.1 Qualitative Analysis
The total number of volatile compounds found in sea buckthorn juice varies according to published data [8-12] and this study reports the highest number of compounds found so far, but there is an annual variation. In 2011, a total of 74, 89, 72 volatile compounds were extracted from 3 varieties (Hergo, wild and Frugana) of sea buckthorn berries (figure 1 and 2, table 1). A significant decline in the number of volatiles was seen in the 2012 harvest with only 17, 39, 9, 20 volatile compounds extracted in four varieties of berries (Hergo, wild, Frugana, Askola), (figure 3, and table 1). A rise in the volatiles was seen in 2013 and the four varieties of berries (Hergo, wild, Frugana, Askola) had 80,78,52,46 volatile compounds.
Despite the significant differences in the number of volatiles extracted during three harvesting seasons, there was an agreement in the most abundant volatiles which were ethyl esters (ethyl hexanoate, ethyl octanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, ethyl benzoate) and 3-methylbutyl esters (3-methylbutyl-2-methylbutanoate, 3-methylbutyl-3-methyl butanoate, 3-methylbutyl hexanoate, and 3-methyl-butyl benzoate). Thus a typical sea buckthorn juice sample will generate a similar fingerprint of volatiles regardless of variety, (figure 2 and 3). However, contradictory results were seen in 2012 Hergo whereby all the abundant 3-methylbutyl esters were all absent and 3-methylbutyl-2-methylbutanoate, 3-methylbutyl-3-methyl butanoate were absent in 2013 samples. In 2012 Frugana ethyl 2-methylbutanoate 3-methylbutanoate, ethyl benzoate, ethyl decanoate were absent and both in 2012/13 ethyl dodecanoate was absent. Biosynthetic differences in the volatile profile were more noticeable in compounds that were <1.0% abundance.
Other ethyl esters were found in all varieties of sea buckthorn juice such as ethyl 3-hydroxy-3-methyl butanoate was present in 2011/13 for wild variety and Frugana, only in 2011 for Hergo and in 2013 for Askola. Ethyl 2-hydroxy-3-methylbutanoate was found only in the wild variety during three harvesting collection and ethyl nonanoate was only found in 2011 and 2013 Hergo. Ethyl heptanoate was found in 2011 and 2013 for wild variety and Frugana, whilst it was identified during 2011-2013 in Hergo.
All three varieties of sea buckthorn juice contained aromatic esters at low abundance and the major compositional difference was that only the 2011 wild variety had ethyl phenyl 3-methylbutanoate, ethyl phenyl 2-methylbutanoate, 2-methyl propyl benzoate and propyl propanoate present, whereas only 2011 Frugana have propyl benzoate, which was absent in the 2011 Hergo variety. Ethyl phenyl acetate was found in Hergo Frugana and wild material, but was absent in Askola. Other minor aliphatic and aromatic esters were also found in sea buckthorn juice as reported in table.1.
Unbranched free fatty acids (acetic, hexanoic and octanoic acids) were only found in 2011 Hergo variety and...