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Whey-protein-coated peanuts assessed by sensory evaluation and headspace gas chromatography

S. Y. LEE1, T. A. Trezza, M. T. Satué-Gracia, E. N. Frankel, J. X. Guinard, and J. M. Krochta. (1) Food Science and Technology, University of California, Davis, Department of Food Science and Technology, Davis, CA 95616

Lipid oxidation is one of the main causes of deterioration in peanuts. For roasted peanuts, auto-oxidation is the major cause of lipid oxidation. Auto-oxidation is governed by many factors, such as light, aw, temperature, relative humidity, and O2 concentration in the environment. O2 concentration plays an important role in oxidation because it provides the driving force for O2 uptake. O2 uptake can be impeded by specialized packaging systems or an edible coating, which in turn will decrease the rate of lipid oxidation. In the present study, whey-protein-isolate (WPI)-based edible coatings were applied on roasted peanuts using a commercial coating process and evaluated for their O2 barrier properties using both sensory and instrumental methods.

The objectives of this study were (1) to develop a commercial coating method to apply WPI-coating on peanuts successfully, (2) to investigate the effects of WPI edible coatings on sensory properties of peanuts after storage, and (3) to correlate sensory attributes and instrumental measurements.

Four different formulations of WPI-coatings were used to coat the peanuts. A formulation without WPI was used to provide the control peanut samples. Uncoated peanuts were designated as the reference. The peanut samples were stored in duplicate at 40 °C, 50 °C and 60 °C for storage times of 0, 5, 15 and 45 d. The samples were evaluated by sensory evaluation using descriptive analysis and by instrumental analysis using static headspace gas chromatography (GC) analysis of hexanal.

Descriptive analysis results revealed that the rancid attribute which results from lipid oxidation was significantly lower for WPI-coated peanuts than the reference. This finding was also confirmed by static headspace GC analysis.

The results from this study strongly suggest that WPI-based edible coatings can be applied using a commercial process to provide a good O2 barrier for food products that are susceptible to lipid oxidation.