Yellow passion fruit (Passiflora edulis f. flavicarpa Deg.) oil refining extracted by mechanical pressing

Passion fruit belongs to the Passifloraceae family and is a native plant from tropical America, which comprises more than 500 species around the world. Among these, the yellow passion fruit (Passiflora edulis f. flavicarpa Degener) is widely cultivated and commercialized in Brazil, where it is presented in 95% of orchards [1,2,3]. 

Fruit juice and pulp industries produce thousands of tons of agro-industrial residues. During the processing of passion fruit juice, the main generated waste is composed of seeds and peels, which contains great amounts of fibres and oil. These type of raw material is applied in food, cosmetics and pharmaceutical industries as an alternative to reduce environmental impacts [4,5,6,7]. 

Food drying techniques result in mass and volume reductions as well as packaging and handling cost savings. They also minimize chemical and microbiological alterations during the final product storage [8]. Among various existing methods for drying, convective drying is one of the most used to remove moisture from a wide variety of biological materials, including grains and seeds [9]. This is due to the low cost of deployment, maintenance and ease of operation compared to other drying methods [10]. 

Passion fruit seeds present an excellent oil extraction percentage in the range between 18.5 and 28.3%, according to [3]. The oil also contains a huge amount of unsaturated fatty acids like oleic acid (C18:1), present in concentrations between 13.6 and 16.9%; and linoleic acid (C18:2), present in concentrations between 67.8 and 74.3%. These characteristics enable the use of passion fruit seed oil as a good source of food grade oils [3,11,12,13]. 

Crude vegetable oils, also named unrefined or unprocessed oils produced from vegetables, contain desirable compounds for human health like triacylglycerides (TAG), tocopherols (TCP) and phytosterols. However, they also present undesirable ones as free fat acids (FFA) and phospholipids [14]. The main purpose of oils extraction technologies is to separate proteins from fat obtaining a higher purity product using low cost processes which must avoid secondary chemical reactions [15,16]. 

In vegetable oils refinery industries, either by chemicals or physical procedures; blanching is a very important processing step where undesirable components are removed by the adsorption technique. Clays and adsorbents, like bentonite and activated carbon, are widely used once they present excellent adsorption characteristics and are able to remove phospholipids and minimize the increasing of free fat acids levels during blanching. Besides, the impurities removal allows the production of stable and clear oil; improves its sensory characteristics and oxidative stability [17, 18,19]. 

In the present study, we performed refinery of yellow passion fruit (Passiflora edulis) seeds oil extracted by mechanical pressing. The seeds were firstly dried and the best process conditions were chosen for the subsequent processing steps which were degumming, neutralization, clarification and filtration. The oil thermal performance was also analyzed using thermogravimetric (TGA) and differential scanning calorimetry (DSC) methods.