# Applications of Plant Polymer-Based Solid Foams: Current Trends in the Food Industry
## 2 Food Industry Applications
### Plant Polymer-Based Foams as Edible Materials
#### 2.1.6 Plant Polymer-Based Egg Protein Replacers
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**Plant Polymer**} & \multicolumn{1}{c}{**Study**} & \multicolumn{1}{c}{**Type of Foam**} & \multicolumn{1}{c}{**Foam Characteristics**} & \multicolumn{1}{c}{**Polymer Characteristics**} \\ \hline \multirow{6}{*}{Oca Starch} & & & Foams with addition of fibers & Oca starch has a phosphorus content \(\sim\)60\% lower than \\  & & & showed a less compact structure & potato starch. Its amylose \\  & & & and with distribution no & content is approximately 21\% \\  & & & homogenous of poreswhen & (lower than that of maize and potato starches). Amylopectin \\  & & & compared to the control. The fiber & & \\  & & sugarcane bagasse & distribution through the cellulose matrix was dissimilar for both SB & is similar to that of potato \\  & & (SB) and & & matrix was dissimilar for both SB & amylopectin, with some \\  & & & and AP fiber. Trays with SB fiber & differences in the length of its \\  & & fiber (AP) [64] & & had larger cells arranged in a thinner layer than those with AP & internal chain and amount of \\  & & & fiber. Both exhibited the typical sandwich structure & fingerprint B-chains. Oca \\  & & & fiber. Both exhibited the typical sandwich structure & starch granules had a volume \\  & & & sandwich structure & moment mean size of 34.5 μm \\  & & & & and B-type polymorph [65] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cont. area of air cells was reduced by the presence of lentil protein but the number of air cells per unit area increased; thus, the height of angel food cakes with lentil protein remained very close to that of the control formulations [42]. Likewise, yellow cake prepared from a mixture of soy protein isolate and 1% mono- or diglycerides that replaced eggs as a foaming agent yielded a similar specific volume, specific gravity, firmness, and moisture content [41]. The authors of this study presented a detailed explanation of cake structure based on an analysis of the relationship between SPI secondary structure and different additives. \(\beta\)-sheet structures were dominant among the secondary structures in all control and eggless groups. The content of these structures increased after the addition of SPI, suggesting an increase in the intermolecular interactions in gliadins. On the other hand, adding Xanthan gum into the cakes with SPI and soy lecithin reduced the \(\beta\)-sheets significantly and converted them to random coils and helical structures. This might be attributed to the slightly charged property of soy lecithin, as it binds to proteins via hydrophobic interactions and the remaining phosphate groups repel each other to loosen the molecules, leading to weakened intermolecular interactions arising from \(\beta\)-sheets and looser molecules being converted into coils. Gliadin is rich in proline; therefore, the \(\beta\)-turn conformation could be more highly favored. They also proposed a schematic model for the gluten formed in the presence of SPI. The model was based on the structural analyses of gliadin and glutenin after the addition of the protein and additives. Analysis of starch suggested the existence of new cross-linking with ester bonds, while an SPI analysis showed the presence of dominant gliadin aggregates in the size range of 100-200 nm and glutenin networking structures containing fewer but larger porosities. These results provide enough support to suggest using SPI in combination with 1% mono- and diglycerides (MDG) as a substitute foaming agent for eggs in cakes.