Abstract
Novel vegetable proteins, like those extracted from abundant raw materials (grass) or agri-food by-products and waste streams (oilseed meals), are expected to be used as replacers for animal-derived proteins, due to higher production efficiency, reduced life cycle environmental impact and possibility to meet consumers' dietary or cultural preferences. Although having a versatile functionality (emulsifying, foaming, gelling, texturizing agents), application of proteins is limited since their properties highly depend on their structure and composition, environmental factors (pH, ionic strength, presence of other micro- and macro-molecules in food matrices) and isolation method and conditions. The objective of this article is to review the current techniques used to isolate the proteins from vegetable raw materials and comment on the influence of extraction method and conditions (pH, ionic strength, extraction media temperature, extraction time, etc.) on protein properties (yield, purity, appearance, solubility, denaturation degree, emulsification efficiency, etc.). The utilization of novel technologies such as ultrasound assisted extraction, electro-activation technique and approaches (enzyme-assisted extraction) to improve protein extraction yield or functionality was also discussed.
Highlights
Animal proteins have a competitive advantage over plant-based proteins in terms of their nutritional and functional properties, protein ingredient market is intensively seeking for alternative, underutilized sources of concentrated plant proteins in order to satisfy the demands of consumers with different ethnic, religious, dietary and moral preferences associated with consumption of animal-based products
Isoelectric precipitation technique more frequently leads to higher yields of extracted proteins than the micellization methods, which is documented for different protein isolates such are safflower (Paredes‐López and Ordorica‐Falomir, 1986), pigeon pea, cowpea (Mwasaru et al, 1999) and Lupinus campestris (RodríguezAmbriz et al, 2005)
Concerning the purity of extracted proteins, Mwasaru et al (1999) noticed that protein isolates of pigeon pea seed obtained by micellization procedure were of higher purity in comparison to protein isolates derived by isoelectric precipitation technique
Summary
Animal proteins have a competitive advantage over plant-based proteins in terms of their nutritional and functional properties, protein ingredient market is intensively seeking for alternative, underutilized sources of concentrated plant proteins in order to satisfy the demands of consumers with different ethnic, religious, dietary and moral preferences associated with consumption of animal-based products. According to available literature data, isolation technique based on isoelectric protein precipitation in most of the cases results in coloured proteins due to coextracted chlorophylls and polyphenols which are very often of unpleasant and bitter taste that is undesirable from the technological and consumers point of view (Xu and Diosady, 2002). Another approach is to achieve protein solubilisation using saline solutions followed by protein precipitation due to salt removal through ultrafiltration and diafiltration membranes. The role of novel processing technologies and application of non-conventional approaches in protein isolation was discussed
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