Characterization of edible coatings consisting of pea starch, whey protein isolate, and Carnauba wax and their effects on oil rancidity and sensory properties of walnuts and pine nuts.
Edible coatings made of whey protein isolate (WPI), pea starch (PS), and their combinations with carnauba wax (CW) were prepared and characterized. WPI combined with CW formed stable emulsion while PS with CW formed unstable emulsion and both formulations produced non-homogeneous films. Addition of PS to WPI: CW combination at the ratio of 1:1:1, respectively, resulted in stable emulsion and homogenous films. The emulsion PS: WPI: CW (1:1:2) was stable and formed a continuous film but had less homogenous droplets size distribution when compared to 1:1:1 film. Combined films had a reduced tensile strength and elongation compared to single component films. WPI : CW (1:1) films had higher elastic modulus than the WPI films, but the modulus reduced by the addition of PS. All the coating formulations were effective in preventing oxidative and hydrolytic rancidity of walnuts and pine nuts stored at 25 °C throughout the storage (12 d) but were less effective at 50 °C. Increasing the concentration of CW from 1:1:1 to 1:1:2 in PS: WPI: CW formulation did not contribute in further prevention of oil rancidity at 25 °C. Using of PS: WPI: CW (1:1:1) coating on both nuts significantly (P < 0.05) improved their smoothness and taste but the PS: WPI: CW (1:1:2) coatings imparted unacceptable yellowish color on walnuts.


CONCLUSIONS
Edible coating of walnuts and pine nuts by whey protein isolate, pea starch, and carnauba wax reduced the oxidative and hydrolytic rancidity of the nuts and improved sensory characteristics.
Dept of Nutrition and Food Technology, Univ of Jordan, Amman 11942, Jordan. g.mehyar@ju.edu.jo
Ghadeer F
GF
Mehyar
Khalid
K
Al-Ismail
Jung H
JH
Han
Grace W
GW
Chee
D003116:Color; D003258:Consumer Behavior; D004655:Emulsions; D005511:Food Handling / Q000379:methods; D018857:Food Packaging / Q000379:methods; D005519:Food Preservation / Q000379:methods*; D031324:Juglans; D008894:Milk Proteins / Q000737:chemistry*; D009754:Nuts / Q000378:metabolism; D009821:Oils / Q000378:metabolism*; D010084:Oxidation-Reduction; D018532:Pisum sativum / Q000737:chemistry*; D028223:Pinus; D013213:Starch / Q000737:chemistry*; D013718:Tensile Strength; D014885:Waxes / Q000737:chemistry*; D000067816:Whey Proteins
D004655:Emulsions; D008894:Milk Proteins; D009821:Oils; D014885:Waxes; D000067816:Whey Proteins; D013213:Starch; C026344:carnauba wax