title: The impact of anthocyanin-rich red raspberry extract (ARRE) on the properties of edible soy protein isolate (SPI) films.
abstract: To modify the properties of edible soy protein isolate (SPI) films, 0.5% anthocyanin-rich red raspberry (Rubus strigosus) extract (ARRE) (0.5 g raspberry powder in 95% ethyl alcohol/water/85% lactic acid [80:19:1. v/v/v]) was incorporated into film-forming solutions. ARRE resulted in an SPI film having significantly enhanced tensile strength (P < 0.05) and % elongation at break (P < 0.05), as well as increased water swelling ratio (P < 0.05) and in vitro pepsin digestibility (P < 0.05). The resultant films also showed significantly decreased water solubility and water vapor permeability (P < 0.05). In addition, ARRE increased darkness, redness, and yellowness film appearance as evidenced by a lower L* (P < 0.05), greater positive a* (P < 0.05), and a higher b* (P < 0.05) than the control film. Scanning electron microscopy images revealed that extract-added films had denser and more compact cross-section microstructure. Fourier transform infrared spectra illustrated that ARRE-created hydrogen bonding involved conformational changes of soy protein without destroying its backbone structure. SDS-PAGE electrophoretograms revealed that the extract induced intermolecular interaction of the soy protein monomers. Natural plant extracts would be a promising ingredient to make SPI films with different physicochemical properties and applications.
  
  
  CONCLUSIONS
  This study characterizes the potential physicochemical changes of SPI film with incorporated raspberry extract. Upon the above modification, the resultant film was found to enhance the applications of pure SPI film in food packaging. For example, SPI-ARRE film could prolong the usage life of SPI film due to increased strength, or could be useful as a desiccant (drying agent) such as a water-absorbing sheet for preserving dried foods due to its increased hydrophilic surface and water-swelling ratio. SPI-ARRE film could also be alternately used as a food wrap with unique color.
authors.affiliation: Department of Food Science, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Sunan
authors.initials: S
authors.lastname: Wang
authors.forename: Massimo
authors.initials: M
authors.lastname: Marcone
authors.forename: Shai
authors.initials: S
authors.lastname: Barbut
authors.forename: Loong-Tak
authors.initials: LT
authors.lastname: Lim
mesh_terms: D000872:Anthocyanins / Q000032:analysis*; D055598:Chemical Phenomena; D004063:Digestion; D004548:Elasticity; D018857:Food Packaging; D005638:Fruit / Q000737:chemistry*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D055595:Mechanical Phenomena; D008855:Microscopy, Electron, Scanning; D010434:Pepsin A / Q000378:metabolism; D010539:Permeability; D010858:Pigmentation; D010936:Plant Extracts / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D027824:Rosaceae / Q000737:chemistry*; D030262:Soybean Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D013499:Surface Properties; D013718:Tensile Strength; D014867:Water / Q000032:analysis / Q000737:chemistry
chemical_list: D000872:Anthocyanins; D010936:Plant Extracts; D030262:Soybean Proteins; D014867:Water; D010434:Pepsin A