Exopolisacaridos

Food Hydrocolloids 23 (2009) 1299–1304

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Food Hydrocolloids
journal homepage: www.elsevier.com/locate/foodhyd

Effect of protein supplementation on the rheological characteristics of milk permeates fermented with exopolysaccharide-producing Lactococcus lactis subsp. cremoris
´ I. Ayala-Hernandez a, A.N. Hassan b, H.D. Goff a, M. Corredig a, *
a bFood Science Department, University of Guelph, Guelph, Ontario N1G 2W1, Canada Dairy Science Department, South Dakota State University, Brookings, SD 57007, USA

a r t i c l e i n f o
Article history: Received 30 December 2007 Accepted 12 November 2008 Keywords: Whey proteins Exopolysaccharides Lactococcus lactis subsp. cremoris Milk permeate Protein–exopolysaccharide interactions

a b st r a c t
This research studied the effect of addition of whey proteins on the rheological properties of ultrafiltration permeate fermented with the exopolysaccharide (EPS)-producing strain Lactococcus lactis subsp. cremoris JFR1. Milk permeates containing 8% solids and various levels of added whey proteins (0, 2, 4, 6 and 8%) were fermented for 12 h at 30  C. The rheological properties of thefermented samples were then evaluated and compared to controls fermented with a non-EPS producing strain. Scanning electron microscopy was also employed to confirm the existence of interactions between whey protein aggregates and EPS. The presence of EPS considerably increased the viscosity and viscoelastic properties of the media, especially in samples containing >2% whey protein added. The resultsobtained demonstrate the importance of EPS–protein interactions in structure formation and may help explain the viscosifying mechanism of EPS in fermented dairy products. Production of highly viscous material could potentially be employed in the future as a novel fiber-rich functional ingredient in dairy products. Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction Exopolysaccharides (EPS)are defined as long chain polysaccharides secreted by microbial cells (Laws, Gu, & Marshall, 2001). They are commonly associated with the ‘slimy’ or ‘ropy’ characteristic of some acidified milk products. Exopolysaccharides produced by some strains of lactic acid bacteria (LAB) have been found to improve textural properties and increase water retention in fermented dairy products (Cerning,Bouillanne, Desmazeaud, & Landon, 1986; Ruas-Madiedo, Tuinier, Kanning, & Zoon, 2002). The presence of EPS seems to contribute to texture, mouthfeel, taste perception and stability of the final products (Folkenberg, Dejmek, Skriver, & Ipsen, 2005; Girard & Schaffer-Lequart, 2007a; Hassan, Frank, Schmidt, & Shalabi, 1996). In addition to processing functionality, the consumption of EPS has been associatedwith health benefits (Dal Bello, Walter, Hertela, & Hammesa, 2001; Kitazawa et al., 1998; Korakli, Ganzle, & Vogel, 2002). Therefore, the development of EPS produced by LAB as a functional ingredient in foods has great potential. The yield of EPS produced by different LAB is generally quite low. It has been reported to vary widely from 50 to 2700 mg/L (Macedo,

* Corresponding author. Tel.: þ519824 4120x56101; fax: þ519 824 6631. E-mail address: mcorredi@uoguelph.ca (M. Corredig). 0268-005X/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodhyd.2008.11.004

Lacroix, Gardner, & Champagne, 2002). Several attempts have been made to control the fermentation conditions to increase EPS production (Grobben et al., 1998; Macedo et al., 2002), but there are stillmany unresolved questions. Because of their low production yields, very few studies have been carried out on the application of EPS produced by LAB as a functional ingredient, and most research has focused on the structuring effect of the polysaccharide in situ, mainly for the manufacture of cheese and yogurt (Folkenberg et al., 2005; Hassan, Frank, & Elsoda, 2003; Hassan et al., 1996). In these...