Interest is growing in plant-derived food additives as replacements to synthetic antioxidants like butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT) to slow down the oxidative deterioration of food.
In the new study, published in the journal Food Chemistry (Vol. 97, pp. 122-129), extracts of nine difference herbs and spices were tested for their antioxidant activity and phenol content, compounds shown to be potent antioxidants.
Extracts were obtained for basil, laurel, parsley, juniper, aniseed, fennel, cumin, cardamom and ginger.
To make the extracts suitable as food additives, the hydrodistillation method was used to remove the essential oils from the herbs and spices that carry the intrinsic flavour.
"The extraction yields range from 88 milligrams per gram (mg/g) of plant material for cardamom to 422 mg/g plant material for juniper. No significant association could be found between the extraction yields and the total phenols," reported lead author Iris Hinneburg from the University of Helsinki.
The extraction of the active compounds was not straightforward for herbs and spices. Parsley leaves produced a jelly-like substance, and cardamom led to filtrations problems. These problems, the researchers proposed, were the cause of the low extraction yields for these herbs.
The highest concentrations of phenols were found in basil (147 mg/g) and laurel (92 mg/g).
Perhaps unsurprisingly, given the phenol concentrations, the greatest antioxidant activities were for basil and laurel, for all of the assays except the iron chelation assay.
"The good correlation between the results form total phenols analysis and the antioxidative assays has been previously reported it is important to characterise the extracts by a variety of antioxidant assays," confirmed Hinneburg.
"One gram of laurel extract was as effective as about 212 mg of Trolox (a water-soluble vitamin E analogue) in the prevention of lipid peroxidation. Basil extract offers the same protection as 177 mg trolox," reported Hinneburg.The researchers said that optimisation of the extraction process could possibly increase the trolox comparison ratios.
"As the extracts are better soluble in aqueous media than are the synthetic antioxidants, they offer a promising alternative as food ingredients with antioxidant activity," the researchers concluded.