Effect of pre-emulsified soy oil with soy protein isolate in frankfurters: A physical-chemical and Raman spectroscopy study

• Energy and fat were decreased by substituting backfat with pre-emulsified soy oils.
• Low-fat frankfurters were proven to have higher cooking yield and better texture.
• More hydrophobic interactions were formed by pre-emulsified soy oils.
• Protein structure was affected by pork backfat and pre-emulsified soy oils.

In this study, the changes of protein structure, proximate composition and physico-chemical attributes of frankfurters (1% NaCl) with pre-emulsified soy oil used in the beating processing were investigated. Three samples were prepared: C, with pork backfat; T1, with pre-emulsified soy oil (soy protein isolate (SPI): soy: water was 1:10:10); T2, with pre-emulsified soy oil (SPI: soy: water was 1:5:5). The energy and fat content decreased while the protein content, L∗ value, cooking yield and textural properties of frankfurters increased when substituting backfat with pre-emulsified soy oils. The microstructure of C showed a spongy appearance with numerous cavities, then T1 and T2 showed more cavity formation and SPI dispersed around the oil globules. There were significantly (p < 0.05) affected the secondary and tertiary structures of protein, an increase of β-sheet, β-turn and random coil content accompanied by a decrease of α-helices content, and formed more hydrophobic interactions were found. However, there was no significantly (p > 0.05) changes for the secondary structures of protein in T1 and T2. The results showed that replaced pork backfat with pre-emulsified soy oil enabled to produce low-salt and low-fat frankfurters.