Performance of egg white and hydroxypropylmethylcellulose mixtures on gelation and foaming

The aims of this research were: i) to investigate phase separation behavior of egg white (EW) and hydroxypropylmethylcellulose (HPMC) mixtures at pH 7 (EW natural pH) or 3 (below EW proteins isoelectric point); ii) to study the impact of this segregation on gelation and foaming properties of the mixed systems as compared to single EW. A sudden phase separation took place at pH 7, while at pH 3 occurred gradually and slowly. In confocal microscopy, fluorescence of EW and HPMC was found on the same locations, indicating complex formation. At pH 7 complexation was more pronounced and the complexes flocculated to form bigger particles bringing on the sudden macroscopic phase separation. At pH 3 the complexes were smaller and did not flocculate with time. The mixtures gelation temperature (T-gel) was similar to HPMC T-gel; however, the storage modulus (G') initially similar to that of HPMC was then dominated by the protein. A synergism between EW and HPMC regarding G' was found at both pHs, being this effect higher at pH 3. For textural properties, an improvement on hardness and springiness was found at pH 3. Regarding foaming properties, there was a synergistic effect on foam collapse at pH 3, while foam overrun slightly decreased and drainage did not show differences as compared to single EW. Thus, although depending on pH conditions, it is possible to improve gelation and foaming of EW by adding HPMC. Improvement was mostly found below the iso-electric point of EW. (C) 2015 Elsevier Ltd. All rights reserved.