Preparation of protein isolate from different plant meal
Proteins are extracted by solubilizing in water and converted into powder using spray, freeze or vacuum drying. The process parameters involved in the extraction, purification and drying induce a certain degree of change in the protein structure and ultimately affect the techno-functionality and nutritional value of proteins.
The defatted meal was dispersed in alkaline waterto extract the protein. After that this slurry was centrifuged and the supernatant containing the dissolved protein was collected. This supernatant was further filtered through Whatman No. 1 filter paper to remove any insolubles. This filtrate was acidified to isoelectric point in order to precipitate the dissolved protein. The protein precipitate was recovered by centrifugation and washed with Milli-Q water. The precipitate was re-suspended in Milli-Q water at pH 7.0 and stirred for 10 min to solubilize the protein. This protein solution was dried using spray, freeze and vacuum drying.
Proteins, together with peptides, are one of the major groups of food components, and they are found in many different organisms of both vegetal and animal origin. Peptides are also obtained during technological processes such as fermentation and storage of foods. Moreover, many experiments involve enzymatic hydrolysis of proteins from food resources such as milk, meat, fish, eggs, or plants to produce a variety of peptides.
In the last decades increasing attention has been paid on oilseed as a valuable source of protein even though cereals predominate in providing both proteins and calories. There have been several reasons for that: oilseeds have two or four times higher protein content, they have higher nutritional quality and oil cake, a by-product of the oil extraction process is unused protein source with protein content range from 30% do 60%.
Cultivation of pumpkin (Cucurbita pepo) in the middle-south Europe region is wide-spread, primarily for oil production from seed. Oil extraction from pumpkin seeds yields a large amount of defatted pumpkin oil cake (PuOC), which contains a significant amount of protein, but it is usually used only as animal feed. Valorization of this by-product is of great importance from economical as well as environmental reasons. Recent studies showed that proteins derived from PuOC could be enzymatic modified for potential usage as food ingredients. Moreover, researches, carried out in our laboratory, showed that these proteins contain bioactive peptides which have antioxidants and antihypertensive effects. Additionally, many proteins from pumpkin seed evince pharmacological activities, responsible of the effect on prostatic diseases.
Proteins have great importance, they prominent functional roles in food preparation, processing, storage and consumption which contribute to the quality and sensory properties of food products and also have biological function when consumed (e.g. antioxidant, ACE-inhibition, opioid activities). Enzymatic modification of proteins is an attractive method to produce novel, tailored food components, with both functional and valuable health benefits.