An Investigation of the Effects of the Addition of Pistachio Hul and Testa on the Oxidative Stability of Pistachio Butter

Pistachio butter is susceptible to autoxidation owing to its high content of unsaturated fatty acids.

In this research, the effects of pistachio hull and testa (0.0, 0.5, and 1.0%) on the oxidative stability of pistachio butter have been investigated. The peroxide value, oxidative stability (using the rancimat method at 110°C), and the refractive index (at 30°C) were evaluated after months 0, 2, and 4 from the storage time at 25°C.

The peroxide value of the samples increased with an increase in the storage time. The lowest peroxide value was related to the treatment containing 1.0% of hull and 1.0% of testa. Besides, in the oxidative stability test, the control sample and the treatment containing 1.0% of hull and 1.0% of testa showed the lowest and highest stability time against oxidation, respectively. The refractive index of the samples was determined within the range of 1.464-1.470. According to the results, there was a significant difference just between the control samples of month 0 and month 4, being an indicator of polymerization reactions. There was no significant difference among other treatments at different storage times.

Pistachio butter containing the combination of 1% of hull and 1% of testa showed higher oxidative stability after 4 months of storage.