SHELF LIFE OF WHEY PROTEIN‐COATED PISTACHIO KERNEL (PISTACIA VERA L.)

Abstract

ABSTRACT Dried pistachio kernels were coated with whey protein concentrate (WPC)/glycerol (Gly) solutions. Accelerated rancidity tests of uncoated and coated nuts were performed. Lipid oxidation in pistachios results in “flavor‐fade” and off‐flavor development. WPC‐based coatings are excellent oxygen barriers and have the potential to be formed as coatings on pistachio kernels to extend their shelf life. Thus, I hypothesized that whey protein isolate films formed as coatings on pistachios would reduce the rate of peanut lipid oxidation. The objectives of this study were to determine coated and uncoated pistachio kernels' oxidation in pistachios stored at ambient conditions. Nine different formulations of WPC‐based coatings were used to coat the pistachios. Besides an uncoated pistachio kernel reference, controls were used to investigate the effects of other ingredients in the coating formulation. The pistachio samples were stored in duplicate at ambient conditions for up to 24 weeks and then analyzed peroxide value (PV) and sensory properties. The objective of this work was to evaluate how WPC/lipid‐based edible coatings affect the development of rancidity. Products resulting from lipid oxidation were measured by PV as an indicator of the formation of hydroperoxide, the primary initial product of lipid oxidation. The results indicate that the coated samples were oxidized significantly slower than the reference (uncoated pistachios); hence, the predicted shelf life is longer for the coated samples. The control samples also showed a delay in oxidation. The results also indicate that the WPC coatings, regardless of composition or thickness, provided a glossy appearance that made the coated nuts very distinctive from the uncoated nuts. In addition, coated nuts were slightly darker. PRACTICAL APPLICATIONSEdible films and coatings add value to their products, increase shelf life and/or reduce packaging. Applications of interest to the food industry include: coating oxygen‐sensitive foods such as nuts to extend shelf life and reduce packaging; coating nuts to prevent oil migration into surrounding food components (e.g., nuts in chocolate).