Bacteria are adversely affecting the quality of around a quarter of the herbs used in cooking Spain, new research shows.

Twenty-six per cent of herbs and 20 per cent of spices used in the country are contaminated by a number of bacteria, researchers at the University of Valencia have found.

The first study of its kind in the country has led study authors to recommend better health and safety controls at Spanish markets, where these herbs tend to be sold.

Researchers published their findings in the journal Plant Foods for Human Nutrition, noting some herbs even carried traces of staphylococcus aureus.

They explained: "Herbs and spices are exposed to a wide variety of contaminants both before and after production, and can contain high levels of bacteria."

Those cooking meals for themselves at home are becoming increasingly concerned about the providence of ingredients they use in their home baking.

Katherine Darling of the Plunkett Foundation recently noted that there is a clear move towards people buying more local produce at the moment.

This may have seen more people asking questions about ingredients at their local cook shop, prior to making a purchase.