3.2.3. Alpha-amylase inhibition
Figure 7A shows the α-amylase inhibitory effect of 3% husk emulsion
with 0, 5, 10, 15 and 20% w/w inulin addition at 5 mg/ml. Inhibitory
activity increased with increasing inulin concentration from 0% to
15%. The α-amylase inhibitory activity of the emulsion gel at 20%
inulin was not significantly different (p>0.05) from that
of 15% inulin concentration. The inhibitory activity of 3% husk
emulsion gel with 20% inulin at 5 mg/ml on α-amylase was 16.06 ±
3.03%.
(Place for figure 7)
Fig. 7 Inhibitory potency of (A) 3% psyllium husk emulsion in the
presence of different concentration of inulin at 200X dilution, and (B)
puree samples with incorporated 5% or 10% husk-20% inulin emulsion
gel against α-amylase (1 U/mL) activity at 1% starch concentration.
Different letters represent significant different at p<0.05.
The α-amylase inhibitory activity of puree samples (salmon, chicken,
chicken stew or beef) with 5% w/w and 10% w/w husk-20% inulin
emulsion gel (Fig. 7B), showed that all puree samples can delay
α-amylase activity. The inhibitory activity of puree samples with 10%
w/w replacement by the emulsion gel was higher than that of puree with
5% w/w replacement. Amongst the purees with 10% w/w replacement by
husk-20% inulin emulsion gel, the chicken stew had the highest amylase
inhibition (21.14%), followed by salmon and chicken (14.12 and 12.68%
inhibition, respectively). The beef had the lowest amylase inhibition of
7.93%. Guo et al. (2020) reported that the hydroxyl (-OH) and carboxyl
groups (-COOH) on the polysaccharides branched chain can interact with
the amino acid residues of digestive enzymes (α-amylase and
α-glucosidase), thus inhibiting their activity. In addition, Ahmed &
Urooj (2010) concluded that dietary fiber, such as wheat bran and
psyllium husk, can bind glucose, and thereby inhibit amylase activity.
Previous α-amylase inhibitory activity indicated that soluble fibers can
capsulate α-amylase and starch, thereby reducing starch accessibility to
the enzyme (Ou et al., 2001).
Our result indicates that incorporation of husk-20% inulin emulsion gel
will be beneficial to delay dietary starch breakdown in food product and
thereby maintain their consistency with addition of starch-based
thickener during oral digestion.