Influence of microwave roasting on chemical composition, oxidative stability and fatty acid composition of flaxseed (Linum usitatissimum L.) oil

Authors: SURI, KANCHAN - Guru Nanak Dev University; SINGH, BALWINDER - Khalsa College; KAUR, AMRITPAL - Guru Nanak Dev University; Yadav, Madhav; SINGH, NARPINDER - Guru Nanak Dev University

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2020
Publication Date: 5/5/2020
Citation: Suri, K., Singh, B., Kaur, A., Yadav, M.P., Singh, N. 2020. Influence of microwave roasting on chemical composition, oxidative stability and fatty acid composition of flaxseed (Linum usitatissimum L.) oil. Food Chemistry. https://doi.org/10.1016/j.foodchem.2020.126974.
DOI: https://doi.org/10.1016/j.foodchem.2020.126974

Interpretive Summary: Flaxseed is an annual herb grown as fiber or oil crop due to its unique nutritional properties and health benefits. Flaxseed contains oil (37.1%), carbohydrates (28.9%), protein (20.3%), dietary fiber (4.8%), moisture (6.5%) and minerals (2.4%). It is rich in polyphenols and mucilage that are known for various bioactivities and beneficial intestinal function. Flaxseed oil is considered as a healthy oil due to its unsaturated fatty acid composition. It has gained popularity as a functional ingredient in a variety of foods due to consumer awareness of its beneficial effects. It is considered as an important ancient medicine due to its wide range of pharmacological, biological and therapeutic properties. It has several health benefits like lowering plasma low-density lipoproteins (LDL), reducing the risk of coronary heart diseases, inhibition of type-I and type-II diabetes and prevention of mammary and colon cancer. Studies have proven that roasting had a significant influence on the composition and quality characteristics of oils from different oilseed crops. Roasting treatment increases oil yield, facilitates the release of important oil constituents during the extraction process and significantly influences phenolic content and antioxidant activities of oils. The present study evaluated the influence of roasting of flaxseeds at different microwave power and radiation time on oil yields, chemical properties, pigment content, total phenolic content, radical scavenging activity, Maillard reaction products, oxidative stability index and fatty acid composition of flaxseed oil. Microwave roasting of flaxseeds significantly affected the quality characteristics of oil. In this study, we found that microwave roasting of flaxseeds at 540 W for 10 min improves oil yield, oxidative stability, pigment content, and other chemical properties. Incorporation or consumption of roasted flaxseed oils has a wide range of possible applications in the food and pharmaceutical industries. This study can be of great value to the US and Indian agricultural and food processing industries and also to flaxseed growers.

Technical Abstract: In this study, flaxseeds roasted at microwave (MW) powers of 180, 360 and 540 W for 5 and 10 min were evaluated for their influence on oil yield, chemical properties, carotenoid and chlorophyll contents, total phenolic content (TPC), radical scavenging activity (RSA), oxidative stability index (OSI), fatty acid composition (FAC) and Maillard reaction products (MRPs). MW roasting at 540 W for 10 min significantly increased the oil yield, TPC, OSI, RSA, a value, browning index, carotenoid and chlorophyll contents while decreased the L and b values of flaxseed oil (FSO). Maillard reaction products (5-hydroxymethylfurfural (2.89) were detected only in oil of flaxseeds roasted at 540 W for 10 min. The level of stearic, palmitic, oleic, linoleic and a-linolenic acids in FSO were slightly changed by increasing MW power and radiation time. FTIR spectra showed minor variation in peak intensities of oil from different MW roasted flaxseeds. MW roasting at 540 W for 10 min is recommended for improving quality and stability characteristics of FSO.