3.2.1. Total expressible fluid (TEF)
Figures 5A and B represent the results of TEF of different purees by
water bath, and microwave oven heating, respectively.
(Place for figure 5)
Fig.5. Effect of incorporation of 10% psyllium husk (PH) emulsion gel
with 0%, 10% and 20% inulin in puree samples (A) at 70℃ water bath
heating for 30 min, and (B) at microwave oven heating with power 700W
for 2 min and then centrifugation at 3750 g for 3 min. Different letters
represent significant different at p<0.05.
TEF of water bath-heated or microwave-heated pure puree (chicken,
salmon, chicken stew and beef without emulsion gel incorporation) was
significantly higher than that of puree with 10% w/w husk-0% inulin
emulsion gel incorporation. Water bath and microwave oven heating
methods were selected in this study because they are common household
heating methods. Increased inulin concentration in emulsion gel (from
0% to 20%) incorporation in the purees further reduced their TEF. So,
the puree with husk-20% inulin emulsion gel had the lowest TEF among
the same puree group. For example, within the chicken puree group
(Figure 3.7), the pure puree (no emulsion gel incorporation) had the
highest TEF (31.77% mean value), while the puree with 10% w/w replaced
by husk-20% inulin emulsion gel had the lowest TEF (17.22% mean
value). Microwave-heating method (Figure 3.8) produced similar result;
the puree with husk-20% inulin emulsion gel incorporation still had the
lowest TEF within the same puree group. TEF reduction with the inclusion
of husk emulsion gel may be due to ingredients in the emulsion gel
crosslinking with the polar groups of protein matrix. The cross-linking
can strengthen the puree three-dimensional network structure, leading to
stronger binding properties and smaller fluid release during heating
(Colmenero et al., 2005; Kumar, 2021). Previous study (Kumar, 2021) has
shown that inulin has water and fat retention capacity, which also help
TEF reduction.
In comparison to water bath heated-meat puree, the microwave-heated meat
puree had higher TEF, which agrees with Colmenero et al., (2005). This
may be due to the internal microwave heating creating higher center
temperature of the puree, and the high steam pressure driving more water
from within the sample to the surface (Wang et al., 2020).