Sunday 10 July 2016

Physicochemical properties, rheological behavior and morphology of pectin-pea protein isolate mixtures and conjugates in aqueous system and oil in water emulsion

Published Date

May 2016, Vol.56:405–416, doi:10.1016/j.foodhyd.2015.12.033

Title

Physicochemical properties, rheological behavior and morphology of pectin-pea protein isolate mixtures and conjugates in aqueous system and oil in water emulsion

Author

Sahar Tamnak^a

Hamed Mirhosseini^a,^,

Chin Ping Tan^a

Hasanah Mohd Ghazali^b

Kharidah Muhammad^b

aDepartment of Food Technology, Malaysia
bDepartment of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia

Received 21 August 2015. Revised 22 December 2015. Accepted 30 December 2015. Available online 4 January 2016.

Highlights

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The single emulsion containing native pea protein isolate was totally unstable even in the fresh form.
•
The long incubation (48 h) resulted in the formation of a hybrid polymer with lower solubility than pectin.
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Pectin-PPI conjugate (3:1 w/w) incubated for 48 h at 60 °C provided the most desirable functional properties.
•
O/W emulsion stabilized by pectin–protein conjugate (3:1, 48 h) was highly stable after one-month storage.
•
Stability index of native pectin-stabilized emulsions was enhanced by conjugation from 43.03% to 94.86%.

Abstract

The application of pectin as an emulsifier in oil-in-water (O/W) emulsion does not guarantee its stability for a long time. In fact, pectin is not an effective emulsifier because of its hydrophilic structure. On the other hand, pea protein isolate (PPI) does not also have a proper emulsifying activity because of its hydrophobic structure. The main objective of this study was to investigate the effects of mixing and conjugation processes on the emulsifying activity and other properties of pectin and PPI in oil-in-water (O/W) emulsion and aqueous system. The conjugation variables were pectin to PPI ratio (i.e. 1:1, 2:1, 3:1, 1:2 and 1:0 w/w) and incubation time (i.e. 0, 6, 27 and 48 h). The native pectin was used as a control for a comparison purpose. The current study revealed that the long incubation (48 h at 60 °C) resulted in the formation of a strong linkage between pectin and PPI. As a result, a hybrid conjugated polymer was formed. This hybrid polymer had the lower solubility and higher emulsifying activity than the native pectin and PPI alone. After one-month storage, the emulsion containing pectin-PPI conjugate (3:1 w/w with 48 h incubation) was the most stable sample with the smallest droplet size (1.863 μm) among all prepared emulsions. This emulsion had the highest negative zeta-potential (−49.97 mV) and stability (83.33%) among all samples. This study revealed that mixing and conjugation of pectin and PPI led to improve the emulsifying activity of both polymers.