Preparation and Characterization of Bigels from Psyllium Husk Seed Hydrogel–Beeswax Oleogel: As a Fat Replacer in Cakes

This study used PHP
(psyllium husk seed powder) and BW
(beeswax)
to create a hydrogel and Oleogel for bigel production. The resulting
bigels were utilized as a fat replacement in cake composition. Bigel
manufacturing employed 5 and 10% PHP hydrogels and 7.5% BW Oleogel
at various HG/OG ratios. Visual appearance results indicated that
gelation was verified by inverting the samples in plastic tubes, which
exhibited no flow under gravity. Also, the samples became bright yellow
as the Oleogel proportion increased. Microscopy revealed that the
bigel with a hydrogel/Oleogel volume ratio of 75:25 formed bicontinuous
structures. Fourier transform infrared spectroscopy (FTIR) spectra
of the Oleogel, hydrogels, and bigels showed no new peaks identified
in the bigel samples with different fractions of Oleogel. The bigel
samples showed that the G′ values were higher
than the G″ values, indicating that the samples
showed viscoelastic solid behavior. An increase in the Oleogel ratio
in bigel samples led to improved viscoelasticity. The hydrogel ratio
exhibited the highest thermal stability and a greater G′ value than the Oleogel, particularly at 5%-75 PHP and 10%-75
PHP across different temperatures. In addition, the hardness and chewiness
values of bigel samples increased with hydrogel concentrations. The
bigel stability result showed that the 10%-25 PHP had the lowest accelerated
percolation rate, suggesting it was the most stable sample and retained
more liquid. Cake samples created with palm oil, 5%-25 PHP, and 10%-25
PHP had a crumb structure with fine air cells evenly distributed.
10%-25 PHP and 5%-25 PHP cake samples showed the highest hardness
values and no significant change with the control palm cakes (p 0.05).
Furthermore, based on the ΔE value, 5%-50 PHP
and 10%-25 PHP cakes had the least color change in the crust and the
crumb of the cake. The 10%-25 PHP cake samples would be a better choice
as they could be considered an alternative to palm oil in cake in
terms of visual appearance, textural properties, and color properties.