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2006 IFT Poster Presentation (PDF)
Presentation Number: 054C-02
Ascorbic acid-containing whey protein film-coatings for control of peanut oxidation
S. MIN and J.M. Krochta, Dept. of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616 U.S.A.
Justification:
The low oxygen permeability of whey protein films can potentially be complemented by incorporation of ascorbic acid (AA). However, activity of AA in whey protein films has not been demonstrated.
Objectives:
The objectives were to evaluate the effects of whey protein isolate (WPI) coatings incorporating AA on lipid oxidation of roasted peanuts and to study the effects of the incorporation of AA on film properties.
Methods:
The film-coating forming solution was prepared with 10% WPI, 10% glycerol, and 0.2 M AA. Coated peanuts, with and without AA, and non-coated peanuts (control) were stored at 50 °C and 21% relative humidity (RH). Peanut lipid oxidation was determined by measuring peroxide value, thiobarbituric acid reactive substance values (TBARS), and free radical scavenging activity. Tensile properties, oxygen permeability (OP), and color (Hunter Lab) of AA-WPI film were compared to those of plain WPI film (control).
Results:
Peroxide values of controls, WPI-coated peanuts, and AA-WPI-coated peanuts after 14 d storage were 21, 14, and 9 milliequivalent peroxide/kg, respectively. The TBARS of AA-WPI-coated peanuts was 52% smaller than that of non-coated peanuts. Initial free radical scavenging activity of AA-WPI-coated peanuts was reduced by 55% during the 14 d storage. No significant differences in elastic modulus and tensile strength of control and AA-WPI films were observed. However, the incorporation of ascorbic acid reduced % elongation at break (E) by 26%. The OP of the AA-WPI film (76.5 cm3×mm/m2×d×kPa) was significantly smaller than that in the control (238.8 cm3×mm/m2×d×kPa). Whiteness and yellowness were not changed by the incorporation of AA, but redness increased.
Significance:
Lipid oxidation in roasted peanuts was significantly retarded by the AA-WPI coating, indicating potential for increasing shelf life of the peanuts. The OP and E of the WPI film were significantly reduced by the incorporation of AA, indicating an anti-plasticizer effect of the AA.