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.