On the quality control of 'olive paste', a specialty based on olives and olive oil.

'Olive paste' is a preserved food gaining popularity as a gourmet product. Its quality depends on that of the major ingredients, table olives (green or black) and virgin olive oil, as well as on the changes occurring to the constituents of the latter during preparation and storage. In this view, our attention was focused on the characteristics of the lipid fraction (1.f.) of a great number of commercial products after a careful search in retail markets and the web. Ultraviolet absorbance values (K 232 , K 270 ) of the 1.f., a criterion set for edible and non-edible olive oil oxidative status due to paste heat treatment during pasteurization, could not support the label information regarding the quality of the oil used. On the contrary, the content of α-tocopherol (∼250 mg/kg 1.f. or ∼50 mg/kg paste) was a strong indication of good-quality major ingredients. Within each brand, consistency with labeling was checked through squalene (higher content in products containing higher amounts of olive oil) or β-carotene determination (higher levels in preparations containing red pepper). For green olive paste samples, the values of the ratio pheophytin a/pyropheophytin a may be used to monitor the shelf life of the product. The findings support routine quality control of the new product.