Effect of Rosemary Leaf Essential Oil Addition on Chemical Properties of Raw Milk During Storge

• Rusell Ali Hashem Al-Jashami Adnan Wahhab Habeeb

  Author

The aim was to extract essential oil from rosemary leaves and use it to improve the properties of raw milk and extend the shelf life of raw milk during low-temperature storage. This study provided a detailed evaluation of the chemical composition of rosemary (Salvia rosmarinus) leaf essential oil, providing important baseline data for its structural integrity, biochemical stability, and functional efficacy.

The extracted essential oil showed excellent physical and chemical quality indicators, along with strong antioxidant activity, with a total oil production of a significant 39.20%, with a relative density of 0.86 g/cm³. The Acid value of essential oil was set at 1.22 mg KOH/g, with a corresponding free fatty acid ratio of 0.65%. Furthermore, the initial peroxide value was recorded at a low level of 4.75 mmEq/ kg oil, indicating the absence of extensive early oxidation in oil samples. The essential oil showed strong antioxidant activity, manifested in a high ascorbic acid content of 20.40% and a high radical-scavenging activity free radical removal activity of 6.70 mmEO₂/kg oil.

Rosemary oil demonstrated a clear dose-dependent antioxidant activity to inhibit lipid peroxidation and oxidative damage in raw milk during extended cold storage. For DPPH, the 1.00% concentration produced the highest antioxidant capacity, with an average mean inhibition of 51.73% and a significant peak of 68.40% on the first day of storage. At the same time, the untreated control sample rapidly deteriorated from its initial state to a mean inhibition of only 2.10% on the eighth day. Fat oxidation was suppressed, measured via the peroxide (PV) value, effectively through 1.00% processing, which maintained a significantly lower PV of 1.36 mEq/ kg milk even on the last day of storage. However, the control group experienced a rapid oxidative acceleration, reaching 5.42 mEq/kg milk on the eighth day, indicating an advanced stage of spoilage. Similarly, the value of thiobarbituric acid (TBA)), which measures oxidation byproducts such as malondialdehyde (MDA) responsible for rancidation, were severely limited by extracts. The 1.00% essential oil treatment restricted the TBA value to only 0.50 mg malondialdehyde/kg milk on day eight, while the untreated control group increased to of 2.20 mg malondialdehyde/kg milk, well above acceptable sensory and regulatory thresholds.

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