Heat stability of oil-in-water emulsions formed with intact or hydrolysed whey proteins: influence of polysaccharides |
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| Affiliation: | 1. Top Institute Food and Nutrition, P.O. Box 557, 6700 AN Wageningen, The Netherlands;2. NIZO Food Research B.V., P.O. Box 20, 6710 BA Ede, The Netherlands;3. Physics and Physical Chemistry of Foods, Department of Agrotechnology and Food Sciences, Wageningen University, Bornse Weilanden 9, 6700 AA Wageningen, The Netherlands;1. College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, PR China;2. School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand;1. State Key Laboratory of Food Science and Technology, Nanchang University, No. 235 Nanjing East Road, Nanchang 330047, Jiangxi, China;2. Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA;1. Department of Chemistry, Western Kentucky University, Bowling Green, KY, USA;2. Food Processing and Technology Program, Western Kentucky University, Bowling Green, KY, USA;1. Petroleum Engineering Program, Department of Ocean Engineering, Indian Institute of Technology Madras, Chennai 600 036, India;2. School of Petroleum Technology, Pandit Deendayal Petroleum University, Gandhinagar 382007, India;3. Department of Energy Resources Engineering, Inha University, Incheon 402-751, South Korea |
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| Abstract: | The heat stability of emulsions (4 wt% corn oil) formed with whey protein isolate (WPI) or extensively hydrolysed whey protein (WPH) products and containing xanthan gum or guar gum was examined after a retort treatment at 121 °C for 16 min. At neutral pH and low ionic strength, emulsions stabilized with both 0.5 and 4 wt% WPI (intact whey protein) were stable against retorting. The amount of β-lactoglobulin (β-lg) at the droplet surface increased during retorting, especially in the emulsion containing 4 wt% protein, whereas the amount of adsorbed α-lactalbumin (α-la) decreased markedly. Addition of xanthan gum or guar gum caused depletion flocculation of the emulsion droplets, but this flocculation did not lead to their aggregation during heating. In contrast, the droplet size of emulsions formed with WPH increased during heat treatment, indicating that coalescence had occurred. The coalescence during heating was enhanced considerably with increasing concentration of polysaccharide in the emulsions, up to 0.12% and 0.2% for xanthan gum and guar gum, respectively; whey peptides in the WPH emulsions formed weaker and looser, mobile interfacial structures than those formed with intact whey proteins. Consequently, the lack of electrostatic and steric repulsion resulted in the coalescence of flocculated droplets during retort treatment. At higher levels of xanthan gum or guar gum addition, the extent of coalescence decreased gradually, apparently because of the high viscosity of the aqueous phase. |
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