Abstract Peanut butter, a popular food spread, is prone to rancidity caused by lipid oxidation, which leads to quality degradation and undesirable flavors. With increasing consumer preference for natural substitutes over synthetic antioxidants, this study explores the use of peanut skin extracts (PSE), both encapsulated and non-encapsulated, as natural antioxidants in peanut butter. The study evaluates the impact of PSE on oxidative stability and sensory attributes of peanut butter during a 24-week storage period. Findings revealed that PSE did not significantly enhance oxidative stability and introduced undesirable flavors, highlighting challenges in applying natural antioxidants to food products.
Introduction
Oxidation of lipids is a major factor in the quality decline of peanut butter, resulting in rancidity and off-flavors. Synthetic antioxidants are typically used to combat these effects, but there is growing interest in natural alternatives due to health and environmental concerns. Peanut skins, a byproduct of the peanut industry, are rich in polyphenols, which have antioxidant properties. This study aims to evaluate the effectiveness of peanut skin extracts (PSE) as natural antioxidants in unstabilized peanut butter and examines their effects on the product’s oxidative stability and sensory characteristics during storage.
Methodology
Materials: The study utilized jumbo runner peanuts, with some roasted with skins and others blanched to remove the skins. Peanut skin extracts were obtained from a commercial supplier and tested in both encapsulated (blended with maltodextrin) and non-encapsulated forms.
Sample Preparation: Peanut butter samples were prepared with varying concentrations of PSE and stored under controlled temperature and humidity conditions for 24 weeks.
Quality Parameters: Various quality metrics were assessed, including moisture content, color, free fatty acids (FFA), peroxide value (PV), fatty acid profile, and hexanal, a volatile marker of lipid oxidation. Sensory evaluations were performed by a trained panel to monitor flavor changes over the storage period.
Results
The inclusion of PSE, regardless of its form or concentration, did not significantly improve the oxidative stability of the peanut butter. Some samples with PSE showed a slight reduction in peroxide values, but free fatty acid levels increased, indicating continued lipid oxidation. Hexanal levels, which are associated with oxidation, remained unchanged with the addition of PSE.
Sensory evaluations indicated a decline in roasted peanut flavor across all samples over time, a typical outcome during storage. However, the addition of PSE introduced distinct off-flavors, negatively affecting the sensory appeal of the peanut butter.
Discussion
1. Limitations of Natural Antioxidants: Although peanut skin extracts have demonstrated antioxidant activity in laboratory settings, their effectiveness in complex food systems like peanut butter is limited due to the interactions and conditions during processing.
2. Impact on Flavor: The incorporation of PSE led to the development of off-flavors, which limits its practical application in peanut butter products.
3. Optimization of Formulation: The study did not include stabilizers such as high oleic peanuts or nitrogen flushing, which are common in commercial peanut butter production to reduce oxidation. Future research could explore these methods to enhance the efficacy of PSE.
4. Future Research Directions: Additional research is needed to explore different extraction techniques, the combination of PSE with other natural antioxidants, or changes to the peanut butter formulation to improve the potential of peanut skins as functional ingredients.
Conclusion
Peanut skin extracts did not effectively act as natural antioxidants in unstabilized peanut butter, as they did not significantly improve oxidative stability and introduced undesirable flavors. This study highlights the difficulties of using natural antioxidants in food products and emphasizes the need for further research to optimize their use.
Source
Mohebpour, D. & Dean, L. & Dean, L. & Harding, R. & Hendrix, K., (2023) “Effects of Peanut Skin Extracts on the Shelf Life of Unstabilized Peanut Butter”, Peanut Science 50(1), p.8-21. doi:
