Chapter 26 - Cold pressed onion (Allium cepa L.) seed oil

Abstract

Onion (Allium cepa L.) is the second most important horticultural crop and a famous spice commodity widely grown all over the world. Onion seeds are also eaten, but their commercial availability is currently limited. The bioactive properties and characteristic flavor of onion have been attributed to its sulfur compounds, which are found in the volatile fraction (onion oil). Cold pressed onion seed oil is preferred by consumers because the cold processing increases the retention of flavor and beneficial phytochemicals. Research related to the cold processing of onion seed oil has highlighted its potential use as functional edible oil that is advantageous in the food, cosmetics, and nutraceutical industries. Cold pressed onion seed oil has high polyunsaturated fatty acid content, primarily contributed by linoleic acid (64%–65%). Cold pressed onion seed oil also contains a significantly higher amount of α-tocopherol (634mg/L). This level is higher than the commercial extra virgin peanut, olive, corn, and sunflower seed oils. Cold pressed onion seed oil is a preferred dietary source for total, α-, and γ-tocopherols, with significant levels of δ-tocopherol and natural phenolics. In addition to flavoring properties, cold pressed onion seed oil has been demonstrated to have antioxidant and antimicrobial properties due to the presences of bioactive compounds (tocopherols and phenolic). The green technology, bioactive compounds, functionality, and application of cold pressed onion seed oil are reviewed in this chapter to stimulate future research and impending applications.