2.2. Moisture determination
Moisture in fresh samples was determined according to the
method of AOAC (2005, 990.19) in which 1–2 g of homogenised
sample was dried in an oven at 100 5 8C until constant weight.
Moisture content as g per 100 g sample was then calculated from the
weight loss.
2.3. Inulin-type fructans and fructo-olisaccharides determination
Following the AOAC (2005, 997.08), total sugars, fructan and
FOS were extracted with hot water. Inulin-type fructans and FOS in
a portion of the hot water extract were hydrolysed by inulinase.
Both hot water extracted and enzyme hydrolysed fractions were
derivatised by oxymation and silylation reaction. Individual sugars
were then determined by high-temperature gas chromatography
(Joye and Hoebregs, 2000).
2.3.1. Extraction of sugars and inulin
Freeze-dried samples (1–5 g), containing about 1 g of inulin-type fructans, were weighed into a 100 mL screw cap bottle and
extracted with about 40 mL of hot water (about 60 8C). The pH of
solution was adjusted to 6.5–8.0 with 0.05 M KOH or 0.05 M HCl.
Final volume was made up to 50 mL with deionised water. The
mixture was incubated at 85 2 8C in shaking water-bath for
15 min.
2.3.2. Analysis of sugars in the hot water extract
Extracted sample solution (3–5 g) in Section 2.3.1 was weighed
directly into a 25 mL volumetric flask which contained 0.01 g of
rhamnose as an internal standard and then diluted to 25 mL with
deionised water. The solution was used for the derivatisation step.